23rd International Conference on Radionuclide Metrology and its Applications - ICRM 2023

Mar 26, 2023, 4:00 PM → Mar 31, 2023, 7:30 PM Europe/Bucharest

The 23rd International Conference on Radionuclide Metrology and its Applications (ICRM 2023) will be held during 27-31 March 2023, in the city of Bucharest, Romania.
We kindly invite you to participate to this important scientific event.
The conference is organized by the International Committee for Radionuclide Metrology (ICRM) and the Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering (IFIN-HH).

Abstract-information-ICRM-2023.pdf

Abstract_Template_ICRM2023.docx

Book-Abstracts_Final.pdf

LLMT-WG-SESSION-agenda.pdf

Sunday, March 26

1 Bucharest City Tour

A guided Bucharest city tour is organized for the participants to the ICRM 2023 conference, following the last minute cancellation of the visit to the Parliament Palace in Bucharest (2-4 Izvor Street, Bucharest). Two buses will go on the city tour, leaving from H. Radisson Blu, at 16:00 h local time.
Please, confirm by e-mail to the organizers of ICRM 2023, until 22 March 2023, that you will go to this visit.

2 Registration and Informal Reception

Registration and informal reception for the ICRM 2023 participants, at the conference venue - Hotel Radisson Blu (mezzanine floor) in Bucharest, 63-81 Street Calea Victoriei.

Monday, March 27

3 Registration and Poster mounting

Opening Session: Welcome by Dr. Nicolae Marius Marginean (Director General of IFIN-HH) and Dr. Brian Zimmerman (ICRM President), and first Invited Talk by Dr. Maria Sahagia (IFIN-HH)

Opening of the conference and first invited talk

Convener: Aurelian Luca (IFIN-HH)

4 Welcome, by the Director of IFIN-HH and ICRM President

5 Herceg-Novi Summer School, the starting point in the history of the International Committee of Radionuclide Metrology (Invited Talk)

Invited talk

Speaker: Maria Sahagia (IFIN-HH)

Aspects of international metrology: 2 Oral and 3 Poster contributions

International collaboration in the field of radionuclide metrology

Conveners: Carine Michotte (BIPM), Lisa Karam (NIST)

6 CCRI(II)-P1.Co-60 Pilot Study - Validation of the Extended International Reference System (ESIR) for medium and high energy beta emitting radionuclides

Since 1976, the International Bureau of Weights and Measures (BIPM) operates the International Reference System (SIR) which provides international comparisons of radioactivity standards. This system is based on a re-entrant ionization chamber and a specific approach to provide robust comparison values over decades [1]. Although the system has proven its worth for many gamma-emitting radionuclides, it is not optimized for comparing pure beta emitters and some electron-capture nuclides without gamma-ray emissions.
As a result, there has been a long-standing desire to supplement the system to allow comparisons for these types of radionuclides. This extension of the SIR is referred to as the extended SIR (ESIR) and has been under active development since 2018 [2]. It is based on Liquid Scintillation (LS) counting combined with the Triple to Double Coincidence Ratio (TDCR) method [3]. Here, the TDCR approach is used to compensate for potential slight changes of the counting efficiency without using reference sources. Moreover, an extended TDCR methodology can account for a potential asymmetry of the 3 photomultiplier tubes (PMT) involved in the system. The validity of a new approach to compensate for counting efficiency and PMT asymmetry variations has been demonstrated in preliminary studies simulating long-term instabilities via neutral density filters [4].
In this work, we report on a validation of the new ESIR system. To this end, 60Co was selected as it can be measured in both systems, the established SIR and the new ESIR. A total of 13 laboratories took part in the pilot study, CCRI(II)-P1.Co-60, by sending 1 or 2 ampoules with an activity between 280 kBq and 2.16 MBq of 60Co standardized solution. The preparation of the liquid scintillation samples (10 per submitted solution) and the TDCR measurements (10 per LS vial) were carried out following the same procedures that would have been employed in a real comparison exercise. A good agreement between the two systems has been observed for almost all the laboratory submissions. The ESIR has demonstrated its capability to provide robust degrees of equivalence for radionuclides emitting medium/high-energy charged particles, with a high precision (relative standard uncertainty less than 10-3). A few discrepant values have been investigated in more detail, by analysing the results from different standardization methods and additional feedback from the participating laboratories. The study reveals that discrepancies are likely due to the presence of radioactive impurities with low energy emissions that are not detected in the conventional SIR system.
[1] Rytz A 1978 Environment International 1 15-18
[2] Coulon R et al. 2022 Journal of Radioanalytical and Nuclear Chemistry
[3] Broda R 2003 Applied Radiation and Isotopes 58 585–94
[4] Coulon R et al. 2020 Metrologia 57 035009

Speaker: Romain Coulon (BIPM)

7 AMBIENT HUMIDITY, THE OVERLOOKED INFLUENCER OF RADIOACTIVITY MEASUREMENTS

Authors: S. Pommé (JRC), K. Pelczar (JRC), I. Kajan (PSI), L. Verheyen (SCK CEN), et al.

Science-based decision making crucially depends on the quality of the metrology from which it derives its information. Measurements with incomplete uncertainty budgets can lead to a misinterpretation about the phenomena under investigation, sometimes with fundamental implication in science and policy making. One of the most persistent misunderstandings in radionuclide metrology is the assertion that cyclic variations in measured decay rates are caused by decays induced by space weather phenomena, in particular by neutrinos emitted from the sun or dark matter. Some authors are adamant in their claims that the observed violations of the exponential-decay law cannot be attributed to environmental conditions in the laboratory. However, using historical weather data available on meteorological websites, a link with terrestrial weather could be established for many infamous experiments.
Whereas temperature and radon decays are among the expected influencers of nuclear counting, it was found that ambient humidity is often the overlooked culprit. The ambient air humidity easily enters ventilated rooms, also in temperature-controlled laboratories, and affects the air density and the behaviour of detectors and their electronics. In this work, an overview is given of radioactivity measurement series that show a correlation with humidity. The accuracy of the most precise radioactivity measurements would benefit from a correction for humidity effects and an appropriate uncertainty estimate to avoid erroneous interpretations. For example, it would be beneficial to counteract the high error propagation factor of such environmental influences on half-life measurement results. It is a well-established fact that published half-life uncertainties are sometimes underestimated by one or two orders of magnitude because the authors fail to make a distinction between random statistical count rate variations and slowly varying instabilities of the measurement conditions.

Speaker: Dr Stefaan Pomme (JRC, Belgium)

8 Traceability of radionuclides in the environment: the status of primary radioactivity standards

Authors: Romain M Coulon 1, Roselyne Ameon 2, Steven Bell 3, Maurice Cox 3, Mikael Hult 4, Peter Ivanov 3, Simon Jerome 5, Stefaan Pommé 4, Benoit Sabot 6, Steven M Judge 1*
1. Bureau International des Poids et Mesures, Pavillon de Breteuil, 92312 Sèvres Cedex, France; 2. ALGADE, Avenue du Brugeaud, 87250 Bessines-sur-Gartempe, France; 3. National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW, United Kingdom; 4. JRC-Geel Retieseweg 111, 2440 Geel, Belgium; 5. Norges miljø- og biovitenskapelige universitet, Universitetstunet 3, 1433 Ås, Norge; 6. Université Paris-Saclay, CEA, List, Laboratoire National Henri Becquerel (LNE-LNHB), F-91120 Palaiseau, France
* retired

To protect nature and human health, the presence of artificial and natural radionuclides in the environment must be monitored. Specific measurement techniques such as gamma-ray spectrometry and liquid scintillation counting are widely deployed in monitoring laboratories around the world. In addition to the specific challenges of environmental measurements, such as the measurement of low activity levels, sample homogeneities and sampling uncertainty, metrological traceability is key to ensuring the comparability of the measurements performed worldwide.
To obtain an overview of the standardisation capabilities of NMIs for the production of primary standards for radionuclides in the environment, a survey was carried out on the basis of literature references and inter-laboratory key comparison data. The areas covered by the study are calibration radionuclides, releases from nuclear power plants, waste from nuclear decommissioning, radionuclides from nuclear weapons or from terrorist attacks, and naturally occurring materials.
The outcome of this study is a priority list of radionuclides where metrological traceability needs to be improved. Recommendations are given for how such improvement could take place, for example, by developing new standardisation techniques, extending measurement range, improving sample purity or homogeneity, or by establishing comparison or proficiency exercises.

Speaker: Romain Coulon (BIPM)

9 Activity determination of 65 Zn

Authors: 1. Christian Balpardo (LMR-CNEA, Argentina), 2. Eliana Depaoli (LMR-CNEA, Argentina), 3. Mario Rossi (LMR-CNEA, Argentina), 4. Pablo Arenillas (LMR-CNEA, Argentina), 5. Clara Ferrari (LMR-CNEA, Argentina).

Several absolute methods were employed for standardization the 65Zn solution received within the context of the CCRI(II)-K2.Zn-65 comparison: a 4 Pi gamma integral counting system with a NaI(Tl) well-type detector and a digital interface, a digital KX-gamma coincidence with two NaI(Tl) scintillation crystals of different characteristics and a sum-peak method using a HPGe planar detector with extended energy range. Five punctual sources was prepared with this nuclide that decays by electron capture to the 1115 keV excited level and by electron capture and beta plus emission to the ground state level of 65Cu. Activity standards of 65Zn are frequently used for ionization chambers calibration.

Speaker: Mr Christian Balpardo (Radioisotope Metrology Laboratory, National Atomic Energy Commission, Argentina)

10 Transfer of developed pre-selection and free release technology to decommissioning industries

Authors (affiliation): Arūnas Gudelis 1, Petr Kovar 2, Jiri Suran 2, Virginia Peyres 3, Jose Carlos Saez Vergara 3, Lukas Skala 4, Tomas Grisa 4
1 FTMC, Lithuania; 2 CMI, Czech Republic; 3 CIEMAT, Spain; 4 NUVIA, Czech Republic

The first generation of nuclear power plants and reprocessing facilities is coming to the end of their working lives. The aim of the decommissioning process is to clear the site, while minimising the risk to the public and the environment from the hazardous waste arising. Two of essential steps in decommissioning process are pre-selection of wastes either to repository, or potential free release to the environment, and free release measurement. These needs are supported by the EU Council Directive 2011/70/EURATOM, where necessity of the development of new measurement techniques is stated to improve safe and effective management of radioactive wastes.
The overall aim of JRP 16ENV09 'MetroDecom II – In-situ metrology for decommissioning nuclear facilities' was to provide the metrology for decommissioning nuclear facilities. The project addressed the needs to achieve traceability to primary standards of activity of radionuclides and to validate the calculation methods used for activity determination of radionuclides occurring in wastes either stored in radioactive waste repositories or free released to the environment.
Within the JRP 16ENV09 project, pre-selection and free release measurement facility was constructed, and operational, measurement, calibration and evaluation software prepared.
In accordance with the EMPIR 2020 SIP Call scope a new project 20SIP02 has been proposed that takes into consideration the needs related to outputs of the MetroDecom II. It provides results which enable 1) transferring the new technology and knowledge to a commercial business and 2) bringing the developed facility to wide international market and adoption by wide community of end-users. The results of the 20SIP02 project are:
• Report on the modification of pre-selection and free release measurement facility for different types of nuclear facilities, and national and European legislations.
• Detail description of pre-selection and free release measurement facility for each interested end-user, identified during the project, taken into account the required throughput, types of wastes, radionuclides of interest, pre-selection and free release criteria, and legislative requirements.

Speaker: Dr Arunas Gudelis (Center for Physical Sciences and Technology (FTMC), Savanorių Ave. 231, 02300, Vilnius, Lithuania)

10:20 AM Coffee Break

Quality assurance and proficiency tests: 3 Oral and 8 Poster contributions

Quality assurance and proficiency tests

Conveners: Denis Glavič-Cindro (Jožef Stefam Institute), Michel Bruggeman (SCK CEN)

11 An overview of 20 years of accreditation in gamma-ray spectrometry laboratory at Jožef Stefan Institute

Authors: 1. Denis Glavič-Cindro (Jožef Stefan Institute), 2. Matjaž Korun (Jožef Stefan Institute), 3. Toni Petrovič (Jožef Stefan Institute) 4. Branko Vodenik (Jožef Stefan Institute) 5. Benjamin Zorko (Jožef Stefan Institute)

The Laboratory for radioactivity measurements (LMR) at Jožef Stefan Institute, Slovenia, was established in 1981. Since then, the measurements with high-resolution gamma-ray spectrometry of activities in samples from the living and working environment, food and feeding stuff, chemicals, building and raw materials, etc., are carried out, initially mainly for the purpose of environmental radioactivity monitoring of the Krško NPP.
From the very beginning, laboratory management has realized the need to implement a quality assurance system to ensure a constant quality of measurement results and comparability at the global level. In parallel, the need for uniform quality assurance systems also emerged in other areas, so standards on quality assurance started to develop in the late Eighties. In LMR, we started to implement a quality system according to the SIST EN ISO/IEC 17025:2017 standard in 1999 and gained accreditation by Slovenian Accreditation in March 2003.
In general, the quality system does not mean only increased paperwork; a cleverly implemented quality system also reduces repetitions, improves traceability and is the basis for better performance and more consistent quality of work. We will present and discuss the lessons learned and the laboratory achievements gained in the last 20 years of accreditation, emphasizing metrological improvements. The most important metrological benefits are assuring traceability to SI units and its regular checks using certified reference materials, a detailed determination of uncertainty budget based on the GUM and evaluation of characteristic limits (decision threshold, detection limit and limits of the coverage interval) according to ISO 11929:2019 standard. Furthermore, sets of measurements to ensure the validity of results are conducted regularly, as well we participate in different schemes of intercomparison measurements and proficiency tests. The most important confirmation of the quality on the metrological level in LMR is the EURAMET nomination of the Laboratory as the designated institute in the ionizing radiation (radioactivity) field.
All results of these measurements and tests are statistically evaluated. These results are the basis for continuous improvement of laboratory performance. During the presentation, practical examples will be presented and discussed.

Speaker: Denis Glavič-Cindro (Jožef Stefam Institute)

12 Cross-validation of standardisation techniques at ANSTO using Cobalt-60 and subsequent learnings from the presence of non-gamma emitting impurities

Two newly implemented primary standardisation techniques (4π(LS)-γ live-timed anti-coincidence and 4π(HPPC)-4πγ) were cross-validated against their respective established laboratory methods (4π(LS)-γ coincidence and analogue 4π(PC)-γ), using Cobalt-60. ANSTO has also recently developed a more robust ionisation chamber measurement and analysis strategy that traces current measurements to the national standard for direct current, thereby reducing reliance on ageing 226Ra reference sources. This measurement campaign was utilised to confirm and document best practice for both the new and established techniques, which contributed towards efforts to formalise the laboratory's quality assurance system and obtain ISO 17025 accreditation. 60Co was selected because of its simple decay scheme which allows highly accurate standardisation, its long half-life facilitating submission to the SIR, and its availability. However, the initial solution used provided inconsistent results.
Preliminary results indicated a 2% discrepancy between the secondary standard ionisation chamber, previously calibrated for 60Co by intercomparison, and the primary measurements, which agreed to within standard uncertainties. As HPGe spectroscopy confirmed that the solution did not contain any gamma emitting impurities, it was hypothesised that low energy electron or X-ray emitters may be responsible for the discrepancy. The ionisation chamber would not be sensitive to these low energy emissions, whereas the LS and PC detectors would be. Radiochemical and inductively coupled plasma mass spectrometry (ICP-MS) analyses are currently underway to identify any impurities. These methods and results will be presented.
In addition, a new 60Co solution was produced by neutron activation of 99.995% pure cobalt metal in ANSTO's OPAL reactor. Standardisation of this solution by the four different primary detection systems provided results that agree to within standard uncertainties, providing validation for the newly implemented techniques. Pertinent details on the production, dissolution and standardisation, including detailed uncertainty budgets, will be presented. Standard ampoules of both solutions were submitted to the BIPM; the new solution for participation in the BIPM.RI(II)-K1.Co-60 key comparison, and both solutions for participation in the CCRI(II)-P1.Co-60 pilot study for extension of the SIR to beta-emitters (ESIR). The original solution will most likely contribute information on the impact of difficult to measure radionuclidic impurities on the ESIR.

Speaker: Dr Freda van Wyngaardt (ANSTO, Australia)

13 Calibration of novel transfer standards with new 222Rn emanation sources

Authors: T. J. Ballé 1, S. Röttger 1, F. Mertes 2, P. P. S. Otáhal 3, P. Kovar 4, A. Röttger 1

Affiliation:
1: Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany
2: Bundesamt für Strahlenschutz (BfS), Ingolstädter Landstraße 1, 85764 Oberschleißheim, Germany
3: National Institute for Nuclear, Biological and Chemical protection (SUJCHBO, v.v.i), 262 31 Milin, Czech Republic
4: Czech Metrological Institute (CMI), Regional Branch Prague, Radiová la, 102 00 Prague, Czech Republic

The alpha-decay chain of 222Rn results to the highest dose contribution from natural radiation and by this exposure to the highest natural risk for developing lung cancer. Therefore, precise and quality assured measurements of 222Rn are of great importance and EU member states are required to implement 222Rn mitigation measures according to the European Council Directive 2013/59/EURATOM.
The outdoor 222Rn activity concentration (typically in the range of 1 Bq·m-3 to 100 Bq·m-3) can be used to improve the identification of radon priority areas, where countermeasures are most needed. Despite an enlarging network of 222Rn activity concentration measurements across Europe, traceability to SI at the outdoor level is still lacking.
The EMPIR project 19ENV01 traceRadon addressed this issue and has developed several new 222Rn emanation sources and transfer standards, to be used as primary and secondary calibration standards to calibrate reference instruments at the environmental level with uncertainties below 10 % for k = 1.
In this talk the novel 222Rn emanation sources as well as their implementation as calibration standards for transfer standards will be presented.

Corresponding author e-mail address: Tanita.balle@ptb.de
Proposed session: Quality assurance and uncertainty evaluation in radioactivity measurements or Low-level measurement techniques
Proposed presentation type: Oral

Speaker: Mrs Tanita J. Balle (PTB, Germany)

14 A National Inter-Laboratory Comparison for The Activity Measurement of 152Eu Source in Indonesia

Authors (affiliation): Hermawan Candra 1, Susilo Widodo 2, Gatot Wurdiyanto 2
1 National Research and Innovation Agency (BRIN), Indonesia
2 Research Center for Safety, Metrology, and Nuclear Quality Technology, Indonesia

Research Center for Safety, Metrology, and Nuclear Quality Technology (PRTKMMN)-National Research and Innovation Agency (BRIN) had coordinated a national inter-laboratory comparison of 152Eu source activity measurements in Indonesia. The aim of this inter-laboratory comparison was to investigate the abilities of laboratories monitoring, to obtain information on the quality of radionuclide activity measurements , to determine equipment performance and to improve the quality of radioactivity metrology in Indonesia. Twenty four radioactivity laboratories participated in these comparisons. The measurement results were evaluated using percentage differences of relative deviations (%), value of activity concentration ratio (R) and value of equality or activity measurement proportionality between Standardization Radionuclide Laboratory PRTKMMN and participant laboratories in Indonesia (En numbers criteria). The majority of the result were considered to be satisfactory because there were within the acceptable limits.

Speaker: Mr Gatot Wurdiyanto (BRIN, Indonesia)

15 Performance evaluation of radon monitors at IFIN-HH, Romania

Authors (affiliation): Ioana Lalau 1,2, Aurelian Luca 1, Claudia Olaru 1, Constantin Teodorescu 1, Mihail-Razvan Ioan 1
1 Horia Hulubei National Institute of Physics and Nuclear Engineering (IFIN-HH), Romania,
2 University of Bucharest, Faculty of Physics, Romania

Uranium decay series represent one of the most significant sources of naturally occurring radioactivity. Starting from 238U, the series decay consecutively by alpha emission into one of its daughters, 226Ra which decays into 222Rn a colorless, odorless and chemically inert radioactive gas.
Therefore, high concentrations of 222Rn can be found in dwellings, caves and other closed areas which require a careful monitoring of radon activity concentration, as lung cancer can occur when people are exposed to high levels of radon concentration. Accurate indoor determination of the radon 222Rn activity concentration in air is necessary in order to implement the European Council Directive No. 2013/59/EURATOM. The Romanian National Commission for Nuclear Activities Control (CNCAN) designated several Romanian testing laboratories for measurements of radon activity and/or radon activity concentration in air. Calibration of the equipment used by these laboratories is essential for assessing with high precision, the indoor levels of radon activity concentration. Starting from 2022, for the first time in Romania, the calibration of various radon monitors received from customers was performed at Horia Hulubei National Institute of Physics and Nuclear Engineering (IFIN-HH) by the Ionizing Radiation Metrology Laboratory (LMRI), designated by CNCAN as a calibration laboratory. The calibration was performed with the radon gas activity standards produced by LMRI and the radon chamber of IFIN-HH (1 m3 volume) and its accessories.
The method used to extract radon with an activity value suitable for the monitor calibration based on a 226Ra source (Pylon type, 250 kBq activity) is described. The radon is transferred in the radon chamber, which is then closed. A homogeneous radon atmosphere in the radon chamber is assured by two fans. Then, the calibration process starts, following the radon activity concentration decay,
measured with both the reference monitor and the customers monitor. The calibration range is (100 - 10,000) Bq/m3.
The purpose of the study was to analyze the radon monitors responses and their uncertainties, and finally compare their performance with the standard radon
monitor AlphaGuard in order to improve the calibration process in the future. Measurements results and the uncertainty budgets are presented in the paper.
A few recommendations for customers are provided. A new working procedure for the calibration of the systems using solid state nuclear track detectors will be developed and implemented in the near future by LMRI.

Speaker: Ioana Lalau (IFIN-HH, DRMR/LMRI and University of Bucharest, Faculty of Physics, Romania)

16 Proficiency Test for Low and Intermediate Level Radio-assay Laboratories in Taiwan for one decade

Authors (affiliation): 1.Wan-Tzu Hung (INER, Taiwan), 2. Wei-Han Chu (INER, Taiwan), 3.Ming-Chen Yuan (INER, Taiwan)

The Institute of Nuclear Energy Research (INER) is recognized by the Taiwan Accreditation Foundation (TAF)as the main organizer for low and intermediate activity level proficiency tests. The INER is requested to conduct this proficiency test at least every three years, therefore, this research reviewed the results of the summary reports from 2013 to 2021. The test items of the proficiency test are 7 in total according to the TAF test item category. These items include gamma nuclides analysis, tritium nuclides analysis, total beta nuclides analysis, strontium 90 analysis, mixed gamma nuclides analysis, mixed strontium 89/90 nuclides analysis and mixed iron 55/59 nuclides analysis. In 2021, in response to the difficult-to-measure nuclides that may be derived from the decommissioning of nuclear power plants, INER went for the first implementation of the project for mixed nuclides analysis projects which addded the items of Ni-63, Tc-99 and Am-241.Besides, it was not only the year for the most numerous nuclear species to be tested, but it also had the greatest number of testing items for this proficiency test within a decade.
Generally,the actual blank matrix is used and prepared for adding radioactive sources that can be traced back to the national ionizing radiation standard. Each participating laboratory could select the test samples for the analysis and comparison according to their own needs. The specific activity of each sample was about 0.5 kBq/g to 10 kBq/g. While the laboratory performing the blinded test, for each group of test categories, the analysis was to be repeated for 2 to 5 times.
Requirements for passing the test in accordinance with TAF criteria (TAF-CNLA-T10(3)) : (1) Ratio: The ratio between the measurement value of the proficiency test executing agency and its measurement standard uncertainty is called the resolution. Whether the test results are recognized relies on the activity of the radioactive species. The ratio of the laboratory's test value and the test value of the proficiency test executing agency, in accordance with the corresponding resolution, if the ratio falls within the limit value, the measurement ratio of the test laboratory is qualified; (2) ξ(zeta score): It is defined as subject to the ratio of the deviation between the test value of the test laboratory and the test value of the proficiency test executing agency and the combined standard uncertainty, if ξ<3,it then passed the zeta score evaluation; (3) The measurement standard uncertainty of the test value for the tested laboratory and the proficiency test executing agency should be less than 10%, it should be evaluated according to the methods described in ISO/IEC Guide 98-3. The participating laboratories will pass the proficiency test only if they meet all requirements above.

Speaker: Ms Wan-Tzu Hung (Health Physics Division, Institute of Nuclear Energy Research, Taiwan)

P86-Proficiency Test for Low and Intermediate Level Radio-assay Labs.docx

17 Inter-laboratory comparison of radionuclide in food in Taiwan

Authors (affiliation): 1. Wei-Han Chu (INER,Taiwan) 2. Wan-Tzu Hung (INER,Taiwan) 3. Ming-Chen Yuan (INER,Taiwan).

"Food safety" has been a major issue in Taiwan. Since the events of the Fukushima Daiichi nuclear disaster happening on March 11, 2011, the matter of man-made radioactive substances in food and food safety have soon caught Taiwanese attention. Undoubtedly, the correct detection for the content of radioactive substances in food has become the primary aim for ensuring food radiation safety. At present, there are eight food radiation testing laboratories in Taiwan that comply with ISO-17025 (the domestic equivalent document is CNS-17025) and are certified by the Taiwan Accreditation Foundation (TAF). According to the method of Announcement No. 1051900834 (MOHWO0015.00), the eight laboratories mainly perform the food detection for nuclear species like I-131 (iodine-131), Cs-134 (cesium-134) and Cs-137 (cesium-137).
The organizer (National Radiation Standard Laboratory) produced a set of reference samples that were traceable to the national measurement standards and passed them to the food radiation testing laboratories participating in this proficiency test. The test results were as follows:
1. The first stage of measurement
a. All samples with low specific activity could be detected in the first stage measurement.
b. For some small-amount specific activity samples, the measurement system could not determine the nuclear species in the first stage of measurement, but the existence of nuclear species could be judged by naked-eye observation.
2. The second stage of measurement
a. Among the total 228 measurement results, around 99% of them of had the deviation within 20%.
b. The average measurement uncertainty (k=1) is about 6.8%, and the average ratio to the reference value is 1.020±0.079 (k=1).
The competent authority used the test results to review the suitability of the presently announced methods, or as a reference for future revisions of the test methods. In the meantime, the test results are also shared with participating laboratories as a basis for their technical improvement to have high accuracy and consistency during the tests. Through the proficiency test carried out by this study, there should have been a comprehensive understanding of the applicability of the current testing methods. Besides, the technical capabilities of food radiation testing of the joined laboratories and the consistency of testing results will also play an important role in ensuring food safety for Taiwanese people.

Speaker: Mr Wei-Han Chu (Health Physics Division, Institute of Nuclear Energy Research, Taiwan)

P87-ILC-in-Taiwan.docx

18 Quality assurance key point for environmental measurements using various techniques: Intercomparisons

Authors (affiliation): Ileana RADULESCU (IFIN-HH, Romania), Antonio Andrei SOFRON (IFIN-HH, Romania), Ciprian Augustin PARLOAGA (IFIN-HH, Romania), Annette RÖTTGER (PTB, Germany), Stefan RÖTTGER (PTB, Germany), Viacheslav MOROSH (PTB, Germany), Marta FUENTE (LSCE-IPSL, France).

The intercomparison exercises and proficiency tests are very important for the laboratories for which the main activities are environmental radioactivity measurements. These tests are the most used methods to assess the accuracy of the analytical data produced. In the same time, is representing a requirement for the laboratories which have ISO 17025 and quality assurance system implemented. Gross alpha-beta, gamma and radon measurements are worldwide applied techniques to measure and to analyze, both the natural and artificial isotopes, either in situ or in the labs.
This paper presents the results from few types of intercomparison exercises organized by the IAEA, and for radon within an international collaboration such as the traceRadon project.
Feedback from the final IAEA reports for gamma, alpha and beta measurements demonstrated that more than 100 reported results, 94 passed all test acceptance criteria, leading to an acceptance rate of almost 90 %. The failed results served as the basis for an analysis to apply corrections in the laboratory's measurement capabilities and to optimize their procedures.
In the case of radon measurements, solid state nuclear track detectors (SSNTD) were first exposed to an know radon concentration at the PTB climate chamber facility for calibration, and subsequently, the integral radon exposure of the SSNTD determined at an Atmospheric Monitoring Network Station (AMNS) was compare to the radon activity concentration estimated from the integral values and the average radon activity concentration measured by active monitoring devices. In operational services, the sensitivity and accuracy of the SSNTD readings are key factors, and must be properly estimated to provide correct exposure from radon.
In general, the overall results of the intercomparison exercises and proficiency tests point out the reliability and traceability of the systems used. Participating in intercomparison tests is one of the methods of evaluating the accuracy and precision of analytical data produced by laboratories.

Speaker: Mrs Ileana Radulescu (Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering, Romania)

19 Application of High-sensitivity Radon Monitor on Walk-in Type Radon Calibration Chamber at KRISS

Authors (affiliation): Hyun Su Lee 1, Min Ji Han 1,2, Sanghoon Hwang (corresponding author) 1,2, Byoung-Chul Kim 1, Jong-Man Lee 1,2, and Kyoung Beom Lee 1,2.
1 Korea Research Institute of Standards and Science (KRISS), Daejeon, 34113, Republic of Korea
2 University of Science and Technology (UST), Daejeon, 34113, Republic of Korea.

A recent increase of public concerns on radon exposure in Republic of Korea has made a great demand on radon measurement service and radon detectors as well. In a consequence of increased radon detector usage, demands on radon detector calibration has been increased. As a national metrology institute of Korea, Korea Research Institute of Standards and Science (KRISS) developed a radon calibration chamber for large-scale calibration (H.S. Lee et al.). The walk-in type chamber made of insulation panel has interior volume of 17.3 m3 and the ambient condition can be controlled in ranges of 0 ℃ – 60 ℃ for temperature and 20% – 90% for relative humidity. Radon from Ra-226 source was flown in a constant rate, and radon concentration in the chamber was maintained by equilibrium of generation, decay, and leakage of radon. To provide a calibration of radon detector with smaller uncertainty, even for low radon concentration, we developed new radon monitor based on the KRISS high-sensitivity radon monitor (S.H. Hwang et al. and M.J. Han et al.). New radon monitor based on electrostatic collection and alpha spectrometer is composed of four radon cells with a digital data acquisition system, Flash-ADC. New radon monitor was demonstrated in the walk-in type radon calibration chamber at various ambient condition and radon concentration. Effects of ambient condition on measurement and achievable calibration uncertainty will be discussed.

Reference
Lee, H.S., Hwang, S.H., Kim, B.C., Lee, J.M., Lee. K.B., 2022. Development of Walk-in Type Radon Calibration Chamber at KRISS. Journal of the Korean Physical Society, in-press.
Hwang, S.H., Han, M.J., Seon, Y.G., Lee, J.M., Lee, K.B., 2020. Development of a high-sensitivity radon monitor for a radon calibration system at KRISS. Appl. Radiat. Isot. 164:109228.
Han, M.J., Hwang, S.H., Heo, D.H., Kim, B.C., Lee, J.M., Lee, K.B., Seon, Y.G., 2021. Development of a mobile radon calibration system at KRISS. Journal of Radioanalytical and Nuclear Chemistry, 330, 571-576.

Speakers: Dr Hyun Su Lee (Korea Research Institute of Standards and Science, South Korea), Dr Sanghoon Hwang (KRISS, UST, Republic of Korea)

20 Development of a KRISS radon detector for the active ventilation system for radon reduction

Authors (affiliation): 1. Sanghoonn Hwang (KRISS, Republic of Korea), 2. Min Ji Han (KRISS, Republic of Korea), 3. B.C. Kim (KRISS, Republic of Korea), 4. J.Man Lee (KRISS, Republic of Korea), 5.D.H. Heo (KRISS, Republic of Korea), 6. K. B Lee (KRISS, Republic of Korea).

Recently, Radon (Rn-222) and Thoron (Rn-220) made an issue in Republic of Korea, since the mattresses from domestic manufactures release the radon at levels that exceed safety standards, which is 1 mSv per year for the radiation dose of the general public by processed products. Radon emanation found in several living goods, such as a natural latex, a mask, a sanitary pad, a health care instrument, construction materials and so on. Most types of the radon mitigation use the ventilation outside. This method causes some loss of the heat capacitance or air-conditioned air, which increase the operation cost of the air-conditioning system. Korea Research Institute of Standards and Science (KRISS) is developing a new concept of an active radon reduction system by an interworking technology with a highly sensitive radon monitor system and a ventilation system. We employ an electrostatic radon detection method and the radon detector counts an alpha emitting from the radon daughters (Po-218, Po-214, Po-216 and Po-212 from Rn-222 and Rn-220) with a silicon photo-diode. KRISS is developing a highly sensitive radon detectors, KRISS Rn-mini and Rn-trio, with a micro controller and own developed signal processing circuit. The electric field has been optimized by the 3D electric field calculation by finite element method. The mock-up model of the radon collection cell has been fabricated by the 3D printer and the sensitivity is found to be (31.0 ± 0.6) min^{-1}/(kBq/m^{3}) for the KRISS Rn-mini and (61.3 ± 1.1) min^{-1}/(kBq/m^{3}) for the KRISS Rn-trio. In this presentation, the development of the KRISS radon detector will be discussed.

Speaker: Dr Sanghoon Hwang (KRISS, Republic of Korea)

21 IARMA: review of the first ten years and challenges for a next decade

Interlaboratory comparisons and proficiency tests (PT) are an increasingly popular necessity used by laboratories as an external, independent confirmation of the quality of their results. How to find and choose the most appropriate PT, how can the laboratory influence the provider of PTs? And, vice versa: is providing the samples with a known true value and issuing the evaluation report to the laboratory the only task of the organizer? Can the provider of PT do more for the labs and how? These questions will be answered on the case of IARMA, rather new and small provider of PT tests.
IARMA (International Atomic Reference Material Agency) was established in 2012. The first release of PT samples occured in 2013. The first set of samples was devoted to gamma spectometry laboratories, consisted of three water samples and the sample of soil. 18 participants from 16 states participated on the first ERAD (Environmental RADioactivity). In 2014, tritium ETRIT (Environmental TRITium) was organized, with the set of eight water samples and 25 participants from 16 states. The program was enlarged in 2015 by EGROSS (Environmental GROSS alpha and beta emittors), with 6 water samples in the set. From 2016 on, all three PT tests regularly appear on the worldwide scene. In average, around 70 sets of samples are released yearly. ECARB (Environmental CARBon) joined as a last one in 2020.

Up to now, 148 different samples were prepared and sent in 2876 replicates, 45% of those samples were tap water, 9% ground water, 11% sea water and 5% of other matrices such as hay, seaweed, soil and mushrooms. All together, 7701 results were received and evaluated in the individual reports with short response time, followed by Summary report, with information about the sample matrices, sample preparation, homogeneity and stability tests, as well as assessments of bias, trueness, precision, uncertainty estimations, z-score. Beside regular numerical evaluations, the additional goals were analysed and discussed in each Summary report, such as Metod‘s Minimum Detection Limit, Blank (background) verification, Bias and uncertainty of the measurements results, Repeatability on duplicate samples, False positive / negative.
The interaction with customers is very important and valuable. PTs should be designed in a way that match with customer's needs. On the other side, the statistical evaluation of PT provider might help to individual laboratories in the decision making process about the most appropriate method for their needs and also in the process of method validation.
The resume of statistical analyses of results will be presented, as well as lessons learned during 10 years and vision and challenges which will guide IARMA in the next decade.

Speaker: Dr Jasmina Kožar Logar (Jožef Stefan Institute, Jamova cesta 39, SI-1000 Ljubljana, Slovenia)

12:10 PM Lunch Break, Conference Group Photo and Visit at the Romanian Athenaeum (at 13:30 h)

Radionuclide metrology in life sciences: 2 Oral and 8 Poster contributions, ICRM WG Meeting

Radionuclide metrology in life sciences

Conveners: Jeffrey Cessna (NIST), Brian Zimmerman (NIST)

22 Development of a portable device for primary measurement of radiopharmaceuticals volume activity

Authors: B. Sabot 1, F. Ogheard 2, P. Cassette 1, M. Hamel 3, P. Gervais 4, C. Fréchou 1, X. Mougeot 1, M. Tbatou 1
Affiliations: 1 CEA/LNE-LNHB, France, 2 LNE-CETIAT, France, 3 CEA/LCAE, France, 4 CEA/SHFJ, France

Radiopharmaceuticals (RPMs) used for diagnostic or therapeutic purposes are produced most often in the form of colloidal radioactive solutions. On-site measurement of their activity is mainly carried out using dose calibrator. This type of device requires prior calibration for each measured sample geometry (vials, syringes, etc.). In practice, these dose calibrators are first calibrated on-site by a secondary laboratory equipped with a transfer instrument that has been previously calibrated.
In the latter case, performing these experiments for very short-lived radionuclides is more than complicated for various reasons on the top of which radioprotection and transportation from the manufacturer to the NMI. The subject of this development is therefore to propose an alternative solution where the primary calibration is performed at the RPM production site. Such a solution is intended to meet a direct need for the calibration of measuring devices for short-lived RPMs, but will also limit the transport of sources that becomes more and more complicated due to regulation rules.
A transportable instrument has thus been developed allowing both the precise measurement of a volume of solution sampled in the order of µL and the measurement of the activity of this same drop of solution. A device using a quartz capillary with a diameter of 1 mm was developed. This system allows the sampling of a drop of radiopharmaceutical solution directly from penicillin type vial. The volume of this drop is of about 1 µL and is measured by image processing with a relative standard uncertainty of less than 1%. This capillary was coupled to a compact TDCR measuring device using a plastic scintillator specifically designed and shaped to optimise the measurement geometry.
We will present the design of this new device and the methods used for the measurement and calculations. The first measurement results, performed in Orsay Hospital, on the two RPMs [11C]PIB (10 MBq/mL) and [18F]FDG (80 MBq/mL) in solutions ready for injection, will be presented. We measured the volume activity on a single drop of solution with a relative standard uncertainty of 2% within only 5 min of experimentation. On top of that, these measurements can be controlled remotely and limit the dose received by the user. To validate these first measurements, we performed a transfer of the drop in the capillary to a liquid scintillation vial for standard TDCR. The results are consistent within their standard uncertainties. The possibilities offered by this new device are important for the metrological traceability of RPM as it allows the standardization of the volume activity directly on a very small sample of a high-activity vial of RPM. This vial can then be used to create all the geometries necessary for the calibration of the dose calibrator in the RPM producer laboratory. However, this type of measurement is not applicable in every case and the current limitations will be discussed.

Speaker: Dr Benoit Sabot (CEA/LNE-LNHB, France)

23 From Primary Standards to Primary Care; Metrology in nuclear medicine imaging

Authors: Andrew J Fenwick 1,2, Andrew P. Robinson 1, Ana Denis Bacelar 1, Kelley Ferreira 1, Daniel Deidda 1, Warda Heetun 1, Chris Marshall 2,3, Stephen Paisey 2,3, Wil Evans 2,3
Affiliation: 1 National Physical Laboratory, Teddington, UK, 2 Cardiff University School of Medicine, Cardiff, UK, 3 Wales Research and Diagnostic PET Imaging Centre, Cardiff, Wales

Positron emission tomography (PET) is a powerful diagnostic tool in the field of nuclear medicine. The use of novel radioisotopes has significantly increased in recent years and there has been an international drive for new standards of radioactivity for radionuclides such as 89Zr. To accurately quantify radioactivity distributions in PET images it is necessary to calibrate imaging equipment and perform verification measurements. This paper evaluates the quantitative accuracy of PET imaging systems used for activity measurement of 89Zr and how to link these systems to primary standards of radioactivity.
A methodology was developed for creating traceable imaging objects to be used for calibration and verification measurements in PET imaging. Uncertainties were estimated for each stage of the measurement chain and combined where appropriate to give overall uncertainty budgets. The results show that traceable imaging measurements are achievable in both preclinical and clinical PET systems, but uncertainty assessment is challenging when dealing with proprietary acquisition and reconstruction algorithms. Future work is also discussed, and it is hoped these projects will further develop the metrology required for traceable PET imaging in the clinical environment and open the door to a new era of accuracy and precision and harmonisation in PET activity quantification.

Speaker: Andrew Fenwick (National Physical Laboratory, Teddington, United Kingdom)

24 Radiobioassay strategies of radiation workers in various field for internal contamination and on-site screening procedure study

Effective doses for occupational exposure of workers are estimated as internal and external doses. To properly manage protection for workers, internal contamination and exposure must be well controlled. Radiation workers may be exposed to radioactive materials in their work environment, so exposure must be continuously monitored. In Korea, thermoluminescent dosimeters (TLDs) are designated as legal dosimeters. However, dosimeters are normally used only for external exposure control. Applications for internal dose monitoring are difficult. There are several methods of detecting internal contamination, depending on the radionuclides. Gamma emitting radionuclides can be monitored using a whole body counting system (WBC) and alpha/beta nuclides are measured by analyzing excreta samples. Special analyzes should be performed after contamination above the threshold has been identified.
In this study, the screening conditions for measuring the internal contamination during work were studied. An on-site internal contamination screening vehicle named mobile radiobioassay laboratory (MRL) is used for this project. Screening conditions for urinalysis and WBC system were studied in this process to effectively monitor the contamination of workers.
Radiation workers were classified into military, education, research, and medical institutions. Field measurements consist of work records, whole body counts, urine collection and questionnaires for laboratory analysis. Based on the questionnaire, gamma and beta emitting radionuclides were selected capable of internal exposure. Gamma emitting radionuclides were monitored using the WBC of the MRL system. A separate pretreatment procedure was used for liquid scintillation counting (LSC) of tritium in urine samples. Other alpha/beta nuclides were screened using the LSC system. The critical level for internal contamination was derived taking into account the public dose limit of 1 and 0.1 mSv. Measurement time was determined in consideration of MDA, and actual measurement results and range of variation were investigated in some areas.

Speaker: Dr Seokwon Yoon (KRISS, Korea)

25 Dissemination of Canada’s National Standards for Radionuclide Metrology

Calibration of detector systems, traceable to the International System of Units (SI), is at the heart of any reliable measurement. For Nuclear Medicine applications, the knowledge of the amount of substance available in diagnostic or therapeutic radiopharmaceuticals can have a direct effect on patient outcomes. The National Research Council (NRC) of Canada is Canada’s National Metrological Institute and is charged with developing, maintaining and disseminating Canada’s standards for radioactivity. This work will describe the dissemination of three radionuclides standards: 99Mo, 177Lu and 90Y, in 2020 and 2021. Due to the short-lived nature of many radionuclides used in nuclear medicine, the standards for many -emitting isotopes are disseminated through the use of the NRC Secondary Standard of Ionizing Radiation Chamber System (SSIRCS)[1]. This is a collection of
Ionization Chambers (IC) which have been calibrated using artifacts standardized by primary methods directly traceable to the SI.
The SSIRCS has been calibrated for many radionuclides in two primary calibration
geometries; a 5ml serum vial and a 5ml flame sealed ampoule. If the calibration of the requested isotope has already been established, a standard can quickly be prepared by the end user or by the NRC and then exchanged. Measurements in the remote detection system (e.g. IC or -spectrometer system) and the SSIRCS provide all the necessary information to the end user to calibrate their detectors. This was how a recent (2021) standard for 99Mo was carried out.
The request for a traceable standard of 177Lu required more work because the end-user geometry was not a standard geometry maintained by NRC. Moreover, at the time of the request, the SSIRCS had not been calibrated for this isotope. In this case, the end user sent a dose of the 177Lu radioisotope in their calibration geometry to NRC. The dissemination of the standard was performed by certifying the activity concentration of the master volume provided to the NRC.
Calibration geometries are central to the dissemination of the standards. Occasionally, a geometry can be rather unique, as in the case of a glass sphere 90Y product that required standardization. The approach taken here was to prepare a mock artifact with cold glass spheres surrounded by a standardized 90Y solution.
The standard uncertainty with which standards of 99Mo, 177Lu and 90Y were provided by NRC were 1%, 0.5% and 0.3% respectively. Since the method by which this standard is disseminated varies according to the requirements of the end user, NRC has developed a range of techniques to address common nuclear medical isotopes.

References
[1] Galea R and Gameil K., Appl Radiat Isot. 109 (2015) 254-256.

Speaker: Raphael Galea (National Research Council of Canada)

26 A Review of the Accuracy of Radionuclide Calibrators in UK Hospitals

To assess the measurement capabilities of UK hospitals for commonly used radionuclides, and to identify any key areas of improvement, data has been collected during the routine calibration of hospital radionuclide calibrators. The calibration service operated by the NPL involves hospitals measuring a radioactive source in their calibrator before shipping it to the NPL for standardisation. The sources are calibrated using a secondary standard ionisation chamber with verification and purity measurements performed by gamma spectrometry. The results are returned to hospitals in the form of a calibration certificate and adjustments may be made if their measurement falls outside of acceptable limits (typically ±2 % for gamma emitters and ±5 % for pure beta emitters). This work was designed to complement the ongoing comparison exercises undertaken by NPL over the last decades.
Prior to receiving the calibration certificate, hospitals were asked to provide the make and model of calibrator, the dial setting used, the measured activity, measurement uncertainty and reference time. Once received at the NPL the sources sent were measured on two commercially available calibrators, using the manufacturer supplied settings for each radionuclide. Data was grouped by radionuclide and geometry to account for the different dial settings or calibration factors in use. The results show that even for routinely used and relatively simple to measure radionuclides such as 99mTc, differences of up to 15 % are observed. Results also show that geometry can have a significant effect on measurement accuracy when non geometry specific dial settings are used.

Speaker: Ms Emma Bendall (National Physical Laboratory, United Kingdom)

27 The NPL secondary standard radionuclide calibrator; Design information and calibration factors

The provision and dissemination of radioactivity standards within the UK is largely dependent on the suite of ionisation chambers maintained at the NPL. These chambers are vital for underpinning work in the medical, industrial, low level and nuclear data fields. The NPL provides ongoing support for the commercially available secondary standard radionuclide calibrator (SSRC), currently marketed as the Fidelis, and previously available as the Vinten 671/271, ISOCAL IV or NPL-CRC. This system is based on the NPL designed IG-42 chamber which is marketed and constructed by Centronic Ltd. Several monte-carlo models have been developed for this system by the international community to allow estimation of dial settings for novel geometries and radionuclides. This ionisation chamber is used throughout the world both by industry and national metrology institutes (or designated institutes) to demonstrate traceability to NPL and the international community. The NPL also maintains a fleet of other commercially available radionuclide calibrators to provide indicative dial settings during standardisations of novel radionuclides and to investigate measurement problems that may be encountered in the clinical environment.
The design and material composition details of the NPL SSRC are presented to support those developing Monte Carlo models. A brief discussion regarding common pitfalls and advice on developing a Monte Carlo model has been included. A detailed description of the production methodology and comparison measurements to the master chamber at the NPL is presented. A description of common geometries used including material composition and designs for dedicated holders is introduced. An updated list of calibration factors for the NPL SSRC and dial settings for the NPL maintained Capintec and Atomlab radionuclide calibrators are included in the publication.

Speaker: Dr Andrew J. Fenwick (National Physical Laboratory, Teddington, United Kingdom)

28 Application of the national standard of radionuclide activity for calibration of activity meters in Lithuanian hospitals

The variety of radiopharmaceuticals used in nuclear medicine and amount of procedures are constantly growing. The activity of radiopharmaceuticals, which are administered for diagnostic and therapeutic purposes, strongly depends on the accuracy of the measuring equipment. According to international recommendations the dosimetry instrumentation should be traceable to a Secondary Standards Laboratory. The activity meters are not absolute assay systems, this equipment should be calibrated directly or indirectly, using standard reference sources traceable to absolute assay systems. The measurements of radionuclides with an activity meter are susceptible to geometrical influences and the container type, for radionuclides that emit beta-radiation or low-energy X-ray, gamma-photons. In this study the accuracy evaluation of activity meters was performed from 2016 to 2021.
The measurements of sixteen activity meter calibrators that are used in four Lithuanian hospitals that provide nuclear medicine procedures with diagnostics and therapeutic radiopharmaceuticals were compared with the readings of the secondary standard chamber Capintec CRC-15R (4π γ ionization chamber), No. 158488 brought to hospitals by the Ionizing Radiation Metrology Laboratory of the FTMC which is the National Metrology Institute (NMI) in Lithuania. The portable ionization chamber Capintec CRC-15R is used in parallel with a stationary ionization chamber Fidelis No. 06048, calibrated by National Physical Laboratory.
Data of 151 activity meter readings of activity of diagnostic, therapeutic and calibration radionuclides in different sources and geometries were analyzed. For calibration sources, the results of 78% activity meters were within the ± 5% tolerance level, while for the therapy sources 60% of the measuring equipment were within the acceptance level (± 5%), and for diagnostic sources about 90% of activity meters were within the ± 10% tolerance level.

Speaker: Mr Kirill Skovorodko (Center for Physical Sciences and Technology (FTMC), Lithuania)

29 Facilitating direct Traceability to the Primary Standard for Australian Nuclear Medicine Departments

The Radionuclide Metrology (RM) group at ANSTO maintains the Primary Standard for Activity of Radionuclides for Australia. To support measurement accuracy in nuclear medicine, RM develops primary standards for radioisotopes significant for their role in patient imaging and treatment. In particular, Tc-99m, I-131 and Lu-177, which are produced using the Open Pool Australian Lightwater (OPAL) reactor and make up the majority of nuclear medicine procedures in Australia. Primary Standards have been developed for these radionuclides by applying the 4πβ-γ coincidence method. International measurement traceability was established by participation in key comparisons, specifically APMP.RI(II)-K2.I-131, CCRI(II)-K2.Lu-177 and BIPM-RI(II)-K4.Tc-99m.

To enable the dissemination of Primary Standards, RM maintains a Secondary Standard Ionisation Chamber (SSIC) for which radionuclide-specific calibration factors are developed during primary standard campaigns. In addition to the widely used measurement geometry of 3.6 mL in a glass ampoule, RM develops calibration factors for measurement geometries routinely used in clinical settings. Applying sources prepared in these geometries for calibration provides more relevant instrument settings than simply adopting the manufacturer's specification.

ANSTO developed the Australian Nuclear Medicine Traceability Program (ANMTP) in consultation with the Australian and New Zealand Society of Nuclear Medicine. Following a successful pilot in 2014, ANSTO have provided opportunity for Nuclear Medicine Departments to access the Australian Standard in the same measurement geometries used for distribution of radiopharmaceuticals. The program is run in October-December each year and includes on-site measurements of Certified Reference Materials in Hospital dose calibrators. Results are recorded using a custom-designed tablet application, allowing measurements to be time stamped and discrepancies calculated in real time. There is then the opportunity for the instrument calibration factor(s) (or dial setting) to be adjusted to minimise any discrepancy. Results are subsequently reported to clients. ANSTO has successfully executed eight of these measurement campaigns, with a ninth planned for late 2022. Thirty-nine departments have gained access to the Australian Standard through this program, from six States and Territories.

The consistent manner in which data is collected allows trends to be identified year on year. Where drift is identified for an instrument, departments are provided with an awareness of the behaviour of their instrument. For older instruments, this is of particular importance as manufacturers will routinely decline to support models which are no longer produced.

Acknowledgements:
1.We acknowledge the contribution of B Caruana, who worked to set up this program.
2.L Mo and L Bignell developed the Lu-177 and I-131 primary standards.

Speaker: Ms Christine M.B. Keevers (ANSTO, Australia)

30 Standardisation and half-life of 177Lu

Authors (affiliation): Virginia Peyrés 1, Miguel Roteta 1, Marcos Mejuto 1, Nuria Navarro 1, Eduardo Romero 2
1 Laboratorio de Metrología de Radiaciones Ionizantes, CIEMAT, SPAIN;
2 Unidad de Aplicaciones Biomédicas y Farmacocinética, CIEMAT, SPAIN.

177Lu is the first nuclide approved by the US Food and Drug Administration for peptide receptor radionuclide therapy. It decays by beta minus emission (4 branches) to 177Hf. In the deexcitation process, 6 gamma lines are emitted with energies between 71 and 321 keV. This paper describes the standardization and half-life determination of this nuclide.
Its half-life has been determined by following the decay rate with two measurement systems:
A well-type ionization chamber IG11 with digital registering of the ionization current for time intervals up to 5 half-lives.
An extended-range coaxial HPGe detector from CANBERRA with a digital acquisition system configured to periodically register the spectrum area in an energy region from 40 to 400 keV.
The combination of six results gives a preliminary value of T1/2= 6.643 (4) d, very similar to the DDEP recommended value of 6.647 (4) d.
This radionuclide has also been standardised by three techniques: Liquid scintillation counting (LSC) with Triple to Double Coincidence ratio (TDCR) method (using a custom built system and a commercial TDCR counter); 4πγ counting with a large NaI (Tl) well detector (17.8 × 17.8 cm.) and coincidence techniques.

Speaker: Dr Virginia Peyres (CIEMAT, Espana)

31 National Programme for the Reliability of Ionising Radiation Measurements based on Inter-Laboratory Comparisons (ILC) n°2 on Radiopharmaceutical Activities

Authors: Lucrezia Spagnuolo 1,*, Marco Capogni 1, Aldo Fazio 1 and Pierino De Felice 1
Affiliation: 1 Istituto Nazionale di Metrologia delle Radiazioni Ionizzanti (INMRI)-ENEA, C.R. Casaccia - Via Anguillarese 301 I-00123 Roma

The Italian National Institute of Ionizing Radiation Metrology (INMRI) belonging to ENEA and located in the Casaccia Research Centre near Rome, has organized in 2022 a National Program for the promotion of the reliability of ionizing radiation measurements based on six Inter-Laboratory Comparisons (ILCs). The Program is funded by the Ministry of Economic Development (Ministero dello Sviluppo Economico, MiSE) as part of the initiatives and studies on controls on measuring instruments, in contexts of particular relevance for consumers with implications for health and safety.
In particular, the ILC n. 2 concerns the measurement of activity of short-lived radionu-clides of interest in nuclear medicine by means of activimeters (usually named “dose calibrators”). Precise and accurate measurements of the activity of such kind of ra-dionuclides is a deeply felt need in the country (and in the world), considering the nu-merous nuclear medicine centres that use radiopharmaceuticals for diagnostics and ther-apy and the numerous medical applications of radiopharmaceuticals.

The current legal and technical legislation requires that the instrumentation necessary to determine the activity and radiochemical purity of the radiopharmaceutical must be adequately shielded from the influence of environmental radiation and appropriately ca-librated. In addition, the activity of radiopharmaceuticals is required to be known with an uncertainty less than 10%.
To date, ENEA-INMRI has met numerous requests for calibration of activimiters, com-ing from individual production centers or from nuclear medicine centers in the country. However, a national inter-comparison (ILC) in this area has not yet been carried out.
Therefore, this ILC was necessary to ensure, for all the laboratories involved, the tra-ceability at national and international level to a common reference standard, for each radionuclide covered by the ILC, developed and maintained at ENEA-INMRI. In this way it will be possible to realize, for the laboratories concerned, the technical-scientific conditions to achieve adequate levels of accuracy and reliability in this kind of mea-surements.
The ILC n. 2 is focused on the verification of the preparation and measurement capabili-ties of a given short-lived radioactive source by each Participant Laboratory.
In particular, the physical quantity covered by the intercomparison is the activity, meas-ured in Bq, of the Tc-99m, F-18 and Lu-177 radionuclides. Each Participant Laboratory was left completely autonomy to participate in the intercomparison with one or more radionuclides among the previous three.
The analysis of the results is based on the comparison of the values of the measures, provided by each Participant Laboratory, with the reference value of the same measu-rand, provided by ENEA-INMRI.

Speaker: Dr Lucrezia Spagnuolo (Istituto Nazionale di Metrologia delle Radiazioni Ionizzanti (INMRI)-ENEA C.R. Casaccia - Via Anguillarese 301 I-00123 Roma, Italy)

32 ICRM WG Meeting: Radionuclide Metrology in Life Sciences (RMLS)

Speakers: Brian Zimmerman (NIST), Jeffrey Cessna (NIST)

Alpha-particle and beta-particle spectrometry: 2 Oral contributions

Spectrometry of alpha and beta particles

Conveners: Stefaan Pommé (JRC), Xavier Mougeot (CEA-LNHB)

33 Experimental measurements for the intensities of the long-range alpha-particles from 212Po

Among the radiations from 212Bi sources, Rutherford and Woods noted in 1916 a few particles whose range is markedly more than the 8.6 cm range of the well-known 8.78437-MeV alpha-particle emissions from 212Po to 208Pb. A small fraction of the excited 212Po nuclei will undergo alpha decay directly from an excited level, due to the partial half-life for alpha decay is comparable with that for gamma decay. The energies and relative intensities of these long-range alpha-particle groups of 212Po were summarized by Rytz (1953). Scarce revisions of these data have been found in the bibliography (Emery and Kane, 1960). But even in the most recent compilations (Nichols, 2011) relative intensities (including uncertainties) have been only poorly estimated.
New measurements have been made of these long-range alpha particles in our laboratory and, with the tabulated energy-emission values, relative intensities have been calculated being their uncertainties experimentally estimated for the first time. The measurements were performed by alpha-particle spectrometry with a low-resolution silicon detector inside a vacuum chamber. The source used was a 232U (in equilibrium with its daughters) collimated disc, 20 mm2 active area, made by electrodeposition, and provided by CIEMAT. A PIPS detector from Canberra, with 50 mm2 active area, was used, and 65 mm for the source-to-detector distance. Due to the short life of the 212Po levels, coincidence summing is produced between the emitted alpha particles and the beta particles coming from the 212Bi ground level, making difficult the analysis of the region above 8.78437 MeV, where the long-range particles are expected (Martín Sánchez et al., 1990). To avoid these interferences, measurements including a magnet between source and detector were also performed. Results show that the values reached for the relative intensities of the long-range alpha-particles of 212Po agree with the tabulated values, but this is the first time estimating experimentally their uncertainties.

G. T. Emery, W. R. Kane, 1960. Gamma-ray intensities in the Thorium active deposit. Phys. Rev. 118, 755.
A. Martín Sánchez, F. Vera Tomé, C. J. Bland. Recent measurements of 228Th activity by alpha-beta coincidence counting. Nucl. Instrum. Methods Phys. Res. A 295, 273.
Nichols, A. L., 2011. 212Bi-Comments on evaluation of decay data. LNE-LNHB/CEA Table de Radionuclèides.
A. Rytz, 1953. J. Recherches Centre Natl. Recherche Sci., Labs. Bellevue (Paris) 25, 254.

Speaker: Prof. Alejandro Martin Sanchez (University of Extremadura, España)

34 Atomic exchange correction in forbidden unique beta transitions

The extended international reference system (ESIR) is being developed by the BIPM. The objective is to create a specific instrument for comparing primary standards of almost pure alpha and beta emitters and low-energy electron capture decaying radionuclides, for which gamma emission is inexistent or extremely low. The measuring device is based on the liquid scintillation counting technique with the triple-to-double coincidence ratio (TDCR) method and a 0.1% standard uncertainty is aimed at. The CIEMAT/NIST method is also commonly used in radionuclide metrology when carrying out liquid scintillation activity measurements. Both methods necessitate precise knowledge of the beta spectrum to compute the efficiency. Recent studies have demonstrated that not using an accurate description of the very low-energy part of the spectrum, where atomic effects play a major role, can lead to an underestimation of the activity of a fraction of a percent and even more in some cases. In addition, observed discrepancies between the activities determined with these two methods are resolved when using such accurate beta spectra.
However, the available modelling of the atomic exchange effect applies only to allowed transitions. In this case, the angular momentum carried away by the beta particles limits the exchange process to atomic electrons in s_1/2 and p_1/2 orbitals. In relation to the ESIR, it is necessary to ensure the same level of accuracy for the beta spectra from forbidden transitions. The beta particles can then be emitted with higher angular momenta and exchange becomes possible with atomic electrons in other orbitals. In the present work, the formalism of the exchange effect has been extended to forbidden unique transitions. The correction associated to a specific angular momentum is demonstrated to act on the corresponding component with identical angular momentum in the shape factor. Consequently, overlaps of continuum and bound relativistic electron wave functions have to be calculated for all the possible angular momenta at each beta particle kinetic energy. Theoretical predictions for different transitions of interest are presented.
The computational burden to determine the exchange correction is significant, typically tens of minutes on a recent workstation for a single beta spectrum with fine energy binning. In order to make these predictions available in a simple manner through the BetaShape code, extensive tabulation of the exchange correction factors has been considered. However, the atomic screening correction in BetaShape had also to be revised because the analytical correction in the current version is not as accurate as the exchange correction. Full numerical computation of the screening effect on the parameters that enter in the definition of the spectrum shape has thus been performed. For both atomic corrections, tables have been generated up to Z=120 considering an exponential energy grid in order to ensure sufficient precision at very low energy. For the exchange effect, all atomic orbitals have been considered and a numerical precision of at least 0.001% has been ensured. For the screening effect in beta plus and beta minus transitions, the Fermi function and the lambda_k parameters have been tabulated up to 30 MeV and lambda_7 corresponding to a sixth forbidden unique transition. Interpolation within these tables allows the fast and precise inclusion of these atomic effects in the beta spectra provided by the BetaShape code.

Speaker: Dr Xavier Mougeot (Université Paris-Saclay, CEA, List, Laboratoire National Henri Becquerel (LNE-LNHB), 91120, Palaiseau, France)

4:30 PM Coffee Break

Alpha-particle and beta-particle spectrometry: 2 Oral contributions and ICRM Alpha-particle Spectrometry WG Meeting

Spectrometry of alpha and beta particles

Conveners: Stefaan Pommé (JRC), Xavier Mougeot (CEA-LNHB)

35 False Alarm Reduction in Measurement of Artificial Radionuclide Using a Radioactive Aerosol Monitor

Authors (affiliation): 1. Hiroki Hashimoto (Hirosaki Univ., Japan), 2. Ryohei Yamada (Hirosaki Univ., Japan), 3. Kouichi Sasaki (JNFL, Japan), 4. Kanna Yamaguchi (JNFL, Japan), 5. Yasutaka Omori (Hirosaki Univ., Japan), 6. Masahiro Hosoda (Hirosaki Univ., Japan), 7. Shinji Tokonami (Hirosaki Univ., Japan).

Early detection of the abnormal release of artificial radionuclides from nuclear facilities requires discriminative measurements of natural and artificial radionuclides. Currently, there are measuring instruments with discrimination functions, but false alarm events have been reported. Thus, a reliable detection system with as few false alarms as possible is required. Since false alarms may occur when judgments are made based on only one method, we are constructing some discriminative methods and developing a system that combines them to detect the abnormal release of artificial radionuclides quickly. In this study, we examined two discriminative methods as a system component.
Discriminative methods were developed based on the aerosol monitor using a silicon semiconductor detector. The first method is based on the counting ratio in the region of interest (ROI). In this method, the ROI for plutonium and the ROI for 218Po and 212Bi, which are decay products of 222Rn, were set. The counting ratio within these ROIs was evaluated in the presence of only natural radionuclides. Artificial radionuclides were considered to have been detected when the counting ratio exceeded 3σ of this ratio. The mean and standard deviation of the counting ratio were evaluated to be 0.45 ± 0.55 using the radioactive aerosol chamber at Hirosaki University. Although no change in this ratio was observed at several concentrations in the chamber, a significant variation in the ratio was observed under the environment due to a few counts. A one-month measurement in September 2021 in Rokkasho Village, Aomori Prefecture, Japan, the mean and standard deviation of the ratio were evaluated to be 0.54 ± 0.28, and the number of times above the 3σ range (0 - 1.38) was 1.6% of the total.
The second method uses the relationship between 214Po counts and gross alpha counts. Taking advantage of the fact that previous studies have shown a correlation between gross alpha counts and alpha-beta coincidence counts from 214Bi and 214Po, 214Po counts were directly obtained and correlated with gross alpha counts. As a result, a strong positive correlation was found between them, and a regression equation was obtained. Based on the regression equation, gross alpha counts based on 214Po were calculated and subtracted from the measured gross alpha counts to reduce the influence of natural radionuclides. However, since they could not be removed entirely, any deviation from these 3σ values was considered to detect artificial radionuclides. As a result, the number of times above the 3σ range was 0.57% of the total.
The timing at which the two methods exceeded the reference values was different. This finding implies that applying a combination of these two methods can reduce the false alarm rate.

Speaker: Mr Hiroki HASHIMOTO (Graduate School of Health Sciences, Hirosaki University, Japan)

36 Ultraviolet imaging of alpha sources via radioluminescence

Authors (affiliation): 1. Maksym Luchkov (PTB, Germany), 2. Claudia Olaru (IFIN-HH, Romania), 3. Annika Klose (LUH-IRS, Germany), 4. Ioana Lalau (IFIN-HH, Romania), 5. Andrei Antohe (IFIN-HH, Romania), 6. Mastaneh Zadehrafi (IFIN-HH, Romania), 7. Clemens Walther (LUH-IRS, Germany), 8. Mihail-Razvan Ioan (IFIN-HH, Romania), 9. Faton Krasniqi (PTB, Germany)

The optical detection of alpha sources presents solid advantages over conventional close range particle detection in terms of operational safety and source localization. In the framework of the EMPIR project "RemoteALPHA", two large diameter radioluminescence scanning systems were developed and tested against a variety of alpha emitting sources. Considering the working distance of 2 m, the scan resolution of 2 mm can be reached, with the detection limit as low as 4 kBq at 1 s pixel integration time.
The UV image is obtained through the mechanical movement of an optical system with the help of two goniometric stages, giving the scan defined in pitch and yaw angles. This scan is then superimposed on the depth camera RGBD image (having color and depth values) to outline the source shape and location.
This work presents the application of the developed radioluminescence sensing devices and UV imaging techniques to the detection of low activity alpha sources: pitchblende minerals, contaminated environmental samples, and nuclear materials. The measurements were performed in darkness with a source-detector distance of 2 m. Surface activities as low as 80 Bq cm-2 are reported [1].
The proposed measurement approach allows unsupervised alpha source localization and contamination mapping from a safe distance, which can be adapted to support decommissioning activities at nuclear installations, management of nuclear materials, and other tasks concerning the handling of alpha emitting radionuclides.

[1] Klose, A., Luchkov M. et al. On the way to remote sensing of alpha radiation: radioluminescence of pitchblende samples, Journal of Radioanalytical and Nuclear Chemistry (2022); https://doi.org/10.1007/s10967-022-08540-6.

Speaker: Mr Maksym Luchkov (Physikalisch-Technische Bundesanstalt (PTB), Germany)

37 ICRM WG Meeting: Alpha-particle Spectrometry

Speaker: Stefaan Pommé (JRC)

38 END of CONFERENCE DAY 1

Conference organisation announcements

Speaker: Aurelian Luca (IFIN-HH)

Tuesday, March 28

39 The discovery of radioactivity: The French-Polish connection; invited talk presented by Dr. Mark A. Kellett (Université Paris-Saclay, CEA, List, Laboratoire National Henri Becquerel, France)

Invited talk

Speaker: Mark Kellett (CEA\LNE-LNHB)

40 Controlling the driver of ionizing radiations beams at ELI-NP: metrology at the High Power Laser System; invited talk presented by Dr. Daniel Ursescu (IFIN-HH/ELI-NP)

Invited talk

Speaker: Dr Daniel Ursescu (IFIN-HH/ELI-NP)

Alpha-particle and beta-particle spectrometry: ICRM Beta-particle Spectrometry WG Meeting

Spectrometry of alpha and beta particles

Convener: Xavier Mougeot (CEA-LNHB)

Radionuclide metrology techniques: 11 Poster contributions

Radionuclide metrology techniques

Conveners: Christophe BOBIN (LNE-LNHB), Ryan Fitzgerald (NIST)

41 Ongoing research at NPL for Radioactive Gas Metrology

Presented is a poster with an overview of ongoing research projects at NPL
related to Radioactive Gas Metrology. Included are projects focused on the
development of (i) an IR laser spectroscopy technique for measuring 14CO2, and
(ii) a beta-gamma coincidence technique for measuring radioxenon and
radiokrypton. The first project is related to monitoring the ratio of 14C to
12/13C in the atmosphere as a tracer for greenhouse gases. The second project is
related to monitoring the condition/health of stored or in-reactor nuclear fuel.
Both projects are underpinned by NPL's Primary Gas Counting capability. An
update on modernisation of this facility will be included.

Speaker: Dr Steven Bell (NPL, UK)

42 PRIMARY STANDARDIZATION AND MONTE CARLO MODELLING OF (243Am + 239Pu) BY MEANS OF A 4-PI (PC)- GAMMA COINCIDENCE COUNTING SYSTEM

The procedure followed by the Nuclear Metrology Laboratory (LMN) at the Nuclear and Energy Research Institute (IPEN-CNEN/SP), in São Paulo, Brazil, for the primary standardization of a (243Am + 239Pu) solution is described. 243Am decays almost 100% by alpha transitions (with a very small branch, 10-9 %, of spontaneous fission), to 239Np with a Q value of 5438.8 keV, and a half-life of 7367 years. Most of the decay (86.74 %) populates the excited level of 239Np, with energy of 74.66 keV. The alpha decay is followed by a beta decay from 239Np to 239Pu, with a Q value of 722.5 keV, and a half-life of 2.356 days, populating mainly the excited levels of 228.18 keV (38.6 %) and 277.59 keV (34.8 %) of 239Pu. The measurements were carried out in a 4-pi (PC)-gamma coincidence counting system, composed by a gas-flow proportional counter filled with P-10 mixture and coupled to a 76.2 x 76.2 mm NaI(Tl) crystal. The standardization was accomplished by dropping known aliquots of the solution on Collodion films (20 micro g.cm-2), previously coated with thin gold layers (10 micro g.cm-2) on both sides. The efficiency was varied by placing Collodion films over and under the sources. The counting was performed by an electronic system composed of discriminators, gates and a TAC (Time to Amplitude Converter) module, yielding a time spectrum in a MCA (Multichannel Analyser). In this time spectrum the peaks corresponding to alpha, beta, gamma, alpha-gamma coincidences and beta-gamma coincidences were identified and provided the Nalpha, Nbeta, and Nc alpha+beta counts, to be used in the coincidence equations, for two gamma gates: one at 75 keV, corresponding to alpha decay and another one at (228+278) keV, corresponding to beta decay. The measurements were performed at two plateaus: one for alpha particles at 1.45 kV and another one for alpha+beta particles at 2.05 kV. The extrapolation curves were compared with Monte Carlo calculations, applying the code MCNP6, that considered all aspects of the counting system, including the radioactive source and absorbers details. Code Esquema, used in previous works, was improved and applied in order to calculate the alpha, beta, gamma and coincidence spectra, taking into account the decay scheme information. This provided an independent comparison with the experimental results. Cox-Isham formalism was applied to experimental data and all partial uncertainties were considered, applying the covariance analysis methodology.

Speaker: Dr Mauro S. Dias (IPEN-CNEN/SP, Brazil)

43 Primary standardization of I-125 in aqueous form using a gamma well counter

The radionuclide iodine-125 (I-125) is an important agent in radiation therapy of various cancers, especially for brachytherapy. Reliable and safe application of I-125 activity require primary standardization as the foundation of traceability. The I-125 decay scheme, proceeding primarily through emission of two photons in coincidence, lends itself to primary standardization through coincidence methods. Often, the sum-peak method is used as it can be accomplished using a single detector, or two detectors operated as one without the need of complicated coincidence logic. However, to date at NIST, this method was limited to evaporated point sources both to mitigate photon attenuation and geometric variability effects.

The need for evaporated sources presents a challenge due to the volatility of iodine. Adapting this method to aqueous samples would improve the safety and accessibility of this method but requires consideration of geometric effects.
In this work we present sum-peak counting for an aqueous solution in a flame-sealed ampoule, counted in a commercial NaI(Tl) well counter along with thorough Monte Carlo modelling. Five ampoules were prepared, with activities spanning a factor of two, all gravimetrically linked to a NIST SRM, which had been standardized by the evaporated point-source method. The ampoules were measured in two different ampoule holders (PTFE and nylon) on two occasions. The highest total count rate was 22000 s-1 on the first occasion and 500 s-1 on the second occasion. Activities were calculated using the formulism of J.S. Eldridge and P. Crowther (Nucleonics 22 56, 1964), with updated nuclear decay data. Extrapolations of calculated activity at zero count rate were adopted as nominal values that differed between PTFE and nylon by 0.80 % and 0.08 % and differed from the SRM certificate by (0.24 ± 0.81) % and (0.69 ± 0.20) %, for the high and low activity measurements respectively, thus agreeing with the SRM within its stated uncertainty due to the extrapolation (1.1 %).

In addition, significant Monte Carlo simulation studies were carried out to analyze the effect of sample holder material (air, PTFE, nylon, aluminum), sample holder geometry (cylinder or cup), solution volume (0.01 mL to 5.0 mL), and pileup (0 or 5 %) on the resulting extrapolated activity. Further, the underlying physics was studied by simulating I-125 decay with varied decay parameters to understand the relative importance of multiple assumptions of the method. It was found that an important assumption involves variation of efficiency over the source volume, similar to the requirement for beta-gamma coincidence (C. Bobin, Metrologia 44 S27, 2007). From this understanding, the "ideal" geometry is described as well as a practical geometry such that a standard 5 mL ampoule source can be measured accurately without applying corrections. Alternatively, other geometries could be used with corrections tabulated from the Monte Carlo model results.

Speaker: Ryan Fitzgerald (NIST)

44 Activity determination of 113Sn by LS methods

Authors (affiliation): 1. Justyna Marganiec-Gałązka (POLATOM, Poland), 2. Ewa Kołakowska (POLATOM, Poland), 3. Edyta Lech (POLATOM, Poland), 4. Anna Listkowska (POLATOM, Poland), 5. Paweł Saganowski (POLATOM, Poland), 6. Zbigniew Tymiński (POLATOM, Poland), 7. Tomasz Ziemek (POLATOM, Poland)

Tin-113 decays by electron capture to three excited levels of In-113: 1029.73 keV - 0.00103%, 646.833 keV - 2.21%, and the metastable excited state of 391.699keV - 97.79%. The transitions depopulating the first and second levels are partially converted, with a total conversion coefficient 0.540 and 0.0464, respectively. The recommended half-life of Sn-113 is 115.09 (3) d, and the recommended half-life of In-113m is 1.6579 (38) h. After a sufficiently long period of time, the activity ratio of In-113m and Sn-113 stabilizes at 1.0006 level (Helmer, 2002). Tin-113 is an important isotope for the calibration of γ-spectrometry systems. It is used as a constituent of gamma-ray emitter mixtures, but also as a quasi-monoenergetic gamma emitter (391.698 keV), due to its relatively simple decay scheme.

In this work, the activity concentration of a Sn-113 solution was measured by two methods: liquid scintillation counting applying the CIEMAT-NIST method, and the 4πβ(LS)–γ coincidence counting. An accurate activity determination of this nuclide is not trivial. Due to the long half-life of the main excited state, it is not possible to apply the coincidence between the effects of electron capture process and the γ radiation. However, the conversion electrons and X-rays after conversion from the K shell are coincident, and can be used for this purpose. In this case the knowledge of some nuclear parameters is required, and the standardization by this method cannot be strictly considered as an absolute procedure.

The result of both methods were found to be in good agreement. The relative uncertainties of results from the CIEMAT-NIST and the 4πβ(LS)–γ coincidence counting methods were 0.4% and 0.6%, respectively.

References
Helmer, R.G., 2002. 113Sn. In: Bé M., et al. (Eds.), Table of Radionuclides. CnEA-ISBN 2 7272 0200 8. Website: http://www.nucleide.org/DDEP_WG/Nuclides/Sn-113_tables.pdf.

Speaker: Dr Justyna Marganiec-Gałązka (National Centre for Nuclear Research, Radioisotope Centre POLATOM, Poland)

45 Primary Internal Gas Counting at NRC

Radioactive noble gases and tritium are emitted from nuclear reactors when electricity is produced, accidents occur and as the result of nuclear weapons testing or use and hence are of great interest to the nuclear forensics communities. In addition, some radioactive noble gases serve critical medical functions, as is the case of Xe-133 in the diagnostic imaging for certain lung cancers. The accepted method by which radioactive noble gases have been standardized in terms of primary activity concentration is through the use of a length-compensated proportional counter (LCPC). The National Research Council (NRC) of Canada is developing a new primary method for radioactive noble gas counting using an LCPC. The NRC system consists of three stainless tubes, vertically mounted and serially connected, each with an inner diameter of 25 mm and lengths of (152, 254 and 381) mm. A stainless steel wire with a diameter of 0.0254 mm is located at the centre of each tube forming the three proportional counters. Activity concentration of the contained gas is determined from the differences in count rates for each pair of counters, an approach that eliminates end effects since the tubes are nominally identical. Two counters are in principle sufficient, and the third provides a measure of redundancy to permit the detection of potential malfunctions.
Operationally, the radioactive gas under study, Xe-133, is mixed with a counting gas (i.e., P10) and homogenously expanded in the three proportional counters, which are initially evacuated. As the counting is carried out, accurate knowledge of the absolute chamber volumes, pressures and temperatures is needed to accurately determine the activity concentration of the radioactive gas sample. A programmable high-voltage power supply is used to generate the biases fed to the proportional counters. The acquisition of the signals from the counters is done via three independent charge-sensitive preamplifiers, immediately followed by digitization and pulse shaping on parallel channels.
In terms of design features, a circulation fan and mixing chamber are incorporated into the gas handling system and permit the counting measurements to be performed in either a dynamic gas flow or a static state. Different methods for sample introduction have been incorporated into the system (e.g., digital gas regulators, quick-connect manifold, casse-ampoule) and a ballast tank has been included to mitigate emergency evacuation occurrences. A turbo pump that vents to the outside of the building is used for routine evacuation of the gas handling system.
The system has been tested and its overall performance evaluated with Xe-133. The determined activity concentrations obtained from the three pairs of counters were consistent to within 0.3 %. The mean absolute value of the activity concentration was found to be in line with expectations based on Xe-133 supplier-provided information (pressurized bottle volume and total activity).

Speaker: Dr James Renaud (National Research Council Canada)

46 Commissioning and validation of a high-pressure proportional counting system at ANSTO

Authors: 1. M.L. Smith, 2. W.M. van Wyngaardt, 3. A.H.H. Bowan, 4. C.M.B. Keevers, 5. M. Zarifi and 6. E.L. Clark (all from ANSTO)

Radionuclides have been standardized by 4π(PC)-γ coincidence counting at ANSTO using an atmospheric pressure proportional counter (PC) with conventional analogue electronics since the 1970s. The ANSTO Radionuclide Metrology (RM) group extended this capability by purchasing a High-Pressure Proportional Counting (HPPC) system from the National Physical Laboratory (NPL, UK). This system, which is operated with a NaI(Tl) well detector, has benefits of energy discrimination in the beta channel and can also be applied for 4π-γ counting and 4πβ-γ sum counting.
The instrument consists of a 2 inch diameter HPPC that can be inserted into a 5 inch well-type NaI(Tl) detector. The proportional counter is used with P-10 or methane counting gas and is capable of pressures up to 10 atmospheres at low gas flow rates. The HPPC, pressure control system, shielding and table were manufactured by NPL as a duplicate of their system and will provide a unique opportunity for collaboration between the laboratories.
Two data acquisition systems are being used with the HPPC. The first is a well-established computer based Digital Coincidence Counting (DCC) system that was originally developed in collaboration with the NPL, and is still utilised by both laboratories. The second employs an off-the-shelf CAEN-6720B Pulse-shape discriminator in combination with coincidence data analysis scripts that have been developed using C++ and Python as an update or alternative to DCC software.
In this work, we will show the validation of the HPPC system against our existing atmospheric proportional counter using Co-60, Tc-99m, and I-123. The newer data acquisition system and software will be compared in view of the eventual replacement of the aging DCC system hardware.

Speaker: Dr Michael L. Smith (ANSTO, Australia)

47 Standardization of Cd-109 by two methods at IFIN-HH

In 1988 LMRI from IFIN-HH carried out the first measurements of Cd-109 standardization within an international comparison organized by BIPM. The measurements were performed using the 4π(PC)ce-NaI(Tl)X coincidence counting and Ge(Li) γ-ray spectrometer.
This paper presents the results obtained by LMRI, IFIN-HH of Cd-109 standardization using two methods within the scope of an international comparison, CCRI(II)-K2.Cd-109, 2021-2022. The 4π(LS)ce and HPGe γ-ray spectrometer counting methods were used to determine the activity of the Cd-109. The spectra containing the Auger electrons and conversion electrons was measured using a liquid scintillation analyzer, TRICARB 4910TR type. The measured spectrum was fitted by Gaussian peaks using ORIGIN in order to set a threshold between the Auger electron peak and the conversion electron peak. The transfer of the HPGe detection efficiency was performed by MC simulations using Gespecor software. The activities of Cd-109 determined by the two methods are in good agreement with a relative difference less than 1.5%.

Speaker: Dr Andrei Antohe (IFIN-HH, Romania)

48 Activity standardization of 64Cu by 4πβ(LS)-γ coincidence and TDCR counting method

Authors (affiliation): 1. Agung Agusbudiman (UST, South Korea), 2. Kyoung Beom Lee (KRISS, South Korea), 3. Jong Man Lee (KRISS, South Korea), 4. Sang Hoon Hwang (KRISS, South Korea), 5. Byoung Chul Kim (KRISS, South Korea).

The copper-64 (64Cu) is one of the important radiopharmaceuticals used in nuclear medicine. The nature of its decay through three different modes, β+, β-, and electron capture, makes this radionuclide useful for both imaging and radionuclide therapy purposes. On the other hand, this decay scheme makes the activity standardization of 64Cu become challenging. We present the activity standardization of 64Cu performed at the Korea Research Institute of Standards and Science (KRISS). The standardization was mainly performed based on the 4πβ(LS)-γ coincidence counting method with the TDCR counting method used for confirmatory measurement purposes. Two analysis techniques were used in the activity determination by the coincidence counting method. The first technique uses the general extrapolation method based on coincidence events between the electron capture radiations and the low-probability of 1346 keV gamma radiations. This technique requires an ad-hoc correction to be applied to the extrapolated value because the detection efficiencies of beta plus and beta minus electrons are not able to be extrapolated to 100 % with the extrapolation range of electron capture radiations. The second technique uses two-dimensional extrapolation, which adds the contribution of coincidence events between the positron and the 511 keV annihilation gamma radiations to the first analysis; thus, no correction is required for the extrapolated value. The 4πβ(LS)-γ coincidence system was used in the experiments with a digital sampling technique that allowed us to perform both analysis techniques based on a single measurement data. For the TDCR method, an in-house code is developed based on the KLM shell model to calculate the efficiency for all 64Cu decay paths. The energy transfer probability in the liquid scintillator was calculated using the PENELOPE simulation code (version 2018). We compared the three results of activity value and investigated the measurement comparability between the results, and found that they still agree within the uncertainty range.

Speaker: Mr Agung Agusbudiman (University of Science and Technology (UST), South Korea)

49 α-γ digital anti-coincidence spectroscopy and its application to activity measurement of 225Ac

Authors (affiliation): 1. Ken-ich Mori (Kindai Univ., Japan), 2. Takahiro Yamada (Kindai Univ., Japan), 3. Yasushi Sato (NMIJ/AIST, Japan), 4. Kotaro Nagatsu (QST, Japan), 5. Hidetoshi Kikunaga (Tohoku Univ., Japan).

Recently, 225Ac has been proposed for Targeted Alpha Therapy. In such medical applications and studies, quantitative activity measurements for evaluating the accumulation of radioactivity in tissues and dosimetry are indispensable. However, because α emitters including 225Ac have complex decay chains, conventional coincidence counting techniques are difficult to apply in a straightforward manner. Liquid scintillation counting (LSC) techniques have been successfully applied to the standardization by several authors. In the measurement of 225Ac using LSC techniques, however, the detection efficiency of α-rays emitted from the decay of a short-lived progeny, 213Po is significantly reduced due to 213Po decay during the dead time generated by its parent nuclide 213Bi β-ray detection. We found that this problem can be solved by sandwiching a source between two ultra-thin plastic scintillator (PS) sheets as only α signals can be selected under the presence of both α and β nuclides. Thus, α-rays emitted from 213Po can be detected with high detection efficiency. In this study, carrier-free 225Ac solutions were produced via the 226Ra(p, 2n)225Ac reaction in the NIRS-AVF-930 cyclotron or chemically separated from 229Th. 225Ac solution was directly dropped onto a 20 µm ultra-thin PS sheet. The source was then covered with an identical PS sheet after drying. To determine individual α-counting efficiency, 4πα-γ anti-coincidence spectrometry techniques were adapted with a 4πα-γ detector configuration composed of a sandwich-type PS sheets detector and a Ge detector. A list-mode MCA (16bit ADC, 40 ns/bit resolution timestamp) which treats shaping amplifier output signals from both α- and γ-channels. A high-speed digitizer (1GHz ADC for a PS, 62.5 MHz for a Ge-detector), which could directly accept pre-amplifier output signals from both channels, was used. The system records pulse height information along with a time stamp for every recorded event and software was developed to generate the coincidence/anti-coincidence spectra or time spectra. In the study, the supplied voltage to the photomultiplier tube (PMT) was adjust appropriately to avoid β contribution on the PS sheets. To validate the detection of α-particles from 213Po, a series of measurements of γ-α/β time difference spectra was conducted with varying voltages supplied to the PMT. The time-difference spectra were obtained as histograms of time-differences from the detection of 440 keV γ-rays due to 213Po γ-rays being emitted promptly after 213Bi β decay. Consequently, most of the time differences were distributed within 1 μs with a higher voltage supply to the PMT. The results demonstrated that few α-particles from 213Po were detected due to the detection of β-rays of 213Bi. However, with a lower voltage supply, the time-difference distribution could be fitted with an exponential function, and a half-life of 3.67±0.12 μs was obtained. This showed that 213Po induced α-rays were detected with minimal β-rays interference. The α efficiencies determined as 1- nanti/nγ were 0.971 and 0.987 for 221Fr and 213Po, respectively. Finally, the activity concentration of 225Ac calculated using the determined α-efficiency was consistent with the results obtained using the Ciemat/Nist-method by NMIJ within their uncertainties.

Speaker: Dr Takahiro Yamada (Kindai University, Japan)

50 COMPARISON OF CALIBRATION FACTORS FOR VINTEN IONIZATION CHAMBER SIMULATED USING FOUR MONTE CARLO METHODS

Monte Carlo (MC) simulations are a useful tool in benchmarking a range of calibration services, from confirming ionization chamber calibration factors to aiding the development of novel calibration systems. Different MC programs can be more tuned towards different applications and user populations. However, due to the difference in the underlying physics and transport mechanisms, different MC programs can produce different results. Modelling a similar geometry in various MC programs can increase confidence in the results and encourage their utility.
Here, the Vinten 671 ionization chamber (VIC) was modelled using four MC programs: EGSnrc, EGS++, Penelope, and TOPAS. VICs with well-characterized response relationships are deployed at several national measurement institutes (NMIs). Modelling the VIC can serve as a benchmarking tool for MC programs to determine the validity of the simulation output in the energy range of the radioisotope studied. Calibration coefficients for many radionuclides have been measured, modeled, and compared between institutes.
VIC models were constructed based on a CT scan of the VIC at the National Institute of Standards and Technology (NIST) and parameters in the literature [1]. Radioisotopes were modeled as distributed aqueous sources in 5 mL borosilicate flame-sealed ampoules; 12 radionuclides with various decay emissions were assessed as well as 14 monoenergetic photon sources. To compare the response of the nuclides, the energy deposited in the simulated VIC nitrogen gas volume was observed and used to calculate the calibration coefficient. These values were compared to experimental values from the literature and the percent error was assessed. The error per nuclide was added in quadrature (the 'sum of square errors', SSE) as a comparison between models.
Of the nuclides assessed, 10 agreed with published values within 2%; 5 agreed within 1%. The largest disagreement was observed for Pb-212, which had a 1-4% error for all models. The best agreement was observed for Ba-133, which had a 0.05-0.2% error for all models. Overall, all models were within an SSE of 5%. Over the photon energy range from 0.2 to 2.02 MV, the relative response of all models agreed from 0.2 to 5%.
This study provides the geometry and decay data used so that others may develop and benchmark their own implementations of these VIC models.

[1] Townson et al., 2018. ARI 134.

Speaker: Ms Brittany Broder (National Institute of Standards and Technology (NIST), United States of America (USA))

51 Digital coincidence counting system with 4πβ(PPC)-γ for the standardization of Co-60

Authors (affiliation): 1. Minji Han (KRISS, South Korea, UST, South Korea), 2. Sanghoon Hwang (KRISS, South Korea, UST, South Korea), 3. A. Agusbudiman (KRISS, South Korea, UST, South Korea, BATAN, Indonesia), 4. J.M. Lee (KRISS, South Korea, UST, South Korea), 5. K.B. Lee (KRISS, South Korea, UST, South Korea), 6. B.C. Kim (KRISS, South Korea), 7. D.H. Heo (KRISS, South Korea).

Korea Research Institute of Standards and Science (KRISS) has developed beta-gamma coincidence system with 4πβ(LS)-γ, 4πβ(PPC)-γ and 4πβ(3PM-LS)-γ. Recently, 4πβ(LS)-γ(LaBr3) coincidence system has developed with a digital DAQ system based on the Flash-ADC (FADC). The 4πβ(LS)-γ(LaBr3) coincidence system showed good performance for long half-life nuclide with the 60Co pilot experiment, and the potential for use as a primary system. The digital DAQ system has been used in the BIPM.RI(II)-K4 (SIRTI) as the short half-life nuclei since the high count rates compared with an analog DAQ. In this presentation, a 4πβ(PPC)-γ(NaI) with digital DAQ is introduced. A Co-60 source on the thin film has been measured to optimize the high voltage and the operating ionizing gas pressure. The pilot experiment with the Co-60 source has been performed. The maximum efficiency with the Co-60 source is found to be 94.8 %, it has higher efficiency compared with 92 % of LS system. The activity is estimated to be (3375.78 ± 58.10) Bq and the activity is good agreement with the reference ionizing chamber. In this presentation, preliminary results of the 4πβ(PPC)-γ(NaI) will be discussed.

Speaker: Ms Minji Han (Korea Research Institute of Standard and Science, University of Science and Technology, South Korea)

10:50 AM Coffee Break

Radionuclide metrology techniques: 4 Oral contributions

Radionuclide metrology techniques

Conveners: Christophe BOBIN (LNE-LNHB), Ryan Fitzgerald (NIST)

52 A bilateral comparison between LNHB and PTB to determine the activity concentration of the same 125I solution

Due to a constant demand for standards of the radionuclide 125I, LNHB and PTB decided to verify their calibration capabilities by means of a bilateral comparison to determine the activity concentration of the same 125I solution. As electron-capture radionuclide with a rather high atomic number, 125I must be regarded as difficult to measure. The situation is partly exacerbated by the fact that some established standardisation methods, like photon-photon coincidence counting, can no longer be applied due to the unavailability of appropriate equipment and expertise.
On the other hand, the liquid scintillation counting (LSC) methods have been further developed in recent years and today even allow the standardization of 125I. Both participating metrology institutes have used their custom-built triple-to-double-coincidence ratio (TDCR) counters to measure aliquots of the same 125I solution, that was provided by LNHB. The activity concentrations are in excellent agreement even though the ways to analyse the data and to compute counting efficiencies were completely independent. The results also agree with the outcome of 4π-γ counting that was carried out at LNHB.
In both laboratories, the measurements were complemented by measurements with several ionization chambers serving as important tools for secondary standardization. Eventually, PTB could also apply an LSC-based secondary standardization method. The results of all secondary standardization methods are slightly higher than those from the TDCR measurement, but still in very good agreement. The secondary standardization techniques allow us to establish a link to the comparison CCRI(II)-K2.I-125 organized in 2004. Even if this link is fraught with some uncertainty, it allows us to draw some important conclusions. We find a good agreement between the TDCR results and the key comparison reference value of the 2004 comparison. Moreover, the results make it possible to evaluate calibration factors for the ionization chambers which are usually the working horses for routine activity determinations in metrology institutes.

Speaker: Karsten Kossert (Physikalisch-Technische Bundesanstalt)

53 Implementation of digital selective sampling method (SESAM) on a 4πβ(PC)-γ(NaI) system

The selective sampling method (SESAM) was proposed by Müller from the BIPM, as an alternative to the β-γ coincidence counting. The SESAM does not need to introduce a coincidence resolving time during which accidental coincidences could be recorded. Correcting of these accidental coincidences is the trickiest part of β-γ coincidence counting. Compare to coincidence or anticoincidence approaches, the principle of the SESAM is simple and does not require sophisticated corrections. However, since its invention, the SESAM has not been widely used due to the too long dwell time of the commercially available MCA. In recent years, high-frequency digitizers have appeared on the market, enabling the SESAM to be implemented digitally. For the first time, digital SESAM was implemented on a primary measurement system consisting of a proportional counter (PC) for the beta channel and a NaI(Tl) scintillator (NaI) for the gamma channel, named by the acronym 4πβ(PC)-γ(NaI). The signal processing is performed by a CAEN DT5730 digitizer. The shaped analog signals from PC and NaI detectors are sent as inputs to the digitizer. The digitizer processes the digitized pulse signals from the detectors using the DPP-QDC real-time firmware embedded in the FPGA. The output data formed by the {timestamp, energy} doublet of each pulse is stored in list-mode files (CSV format). Dedicated software (D-SESAM) has been developed for offline implementation of digital SESAM. D-SESAM consists of three modules, namely “software-based circuits module”, “dead time and background correction module” and “efficiency extrapolation module”. The "software based circuit module" performs an extendable dead-time on the beta channel, a delay time on the gamma channel and builds the time distribution between gamma and beta events. The β efficiency (ε) can be easily derived from the time distribution spectrum using the ratio of the counts of the region of interest preceding the beta event (g) and the region of interest following the beta event (G), such as ε=1-g/G. The “dead time and background correction module” is used to perform the dead-time and background corrections on the counts (g and G) involved in the calculation of the β efficiency, and to correct counting losses caused by dead time in the β channel. The “efficiency extrapolation module” is applied to measure and correct the γ sensitivity in the β channel. To demonstrate the performance of the 4πβ(PC)-γ(NaI) digital SESAM, the technique was applied to a standard solution of Co-60 standardized using the conventional 4πβ(PC)-γ coincidence counting method. The result from SESAM is in good agreement with the one obtained by 4πβ(PC)-γ coincidence counting, with a relative deviation of 0.3%. The digital version of SESAM, through the use of a digitizer, overcomes the limitations that existed in analogue architectures and brings this primary calibration approach back to the fore. Corresponding author e-mail address: liuhr@nim.ac.cn

Speaker: Haoran LIU (National Institute of Metrology)

54 Standardization of Tc-99m by digitizer-based 4πce(LS)-γ coincidence counting

Technetium-99m, the short-lived metastable nuclear isomer of Tc-99 is one of the most relevant medical radionuclides world-wide, due to its extensive use in medical imaging and functional studies of various organs. Nevertheless, from a metrological point of view, the absolute standardization of Tc-99m is far from straightforward due to its short half-life and its low energy conversion electron spectrum. Recently, our working group at PTB successfully realized an absolute activity standardization of a Tc-99m solution by means of digital coincidence counting in the frame of a key comparison involving the International Reference System’s Transfer Instrument (SIR-TI) organized by BIPM. The solution was obtained from a commercial Mo-99/Tc-99m generator and standardized by detecting the 140.5 keV gamma radiation from the decay of Tc-99m in coincidence with the preceding emission of conversion electrons with energies around 2 keV. In order to maximize the detection efficiency for these low energy electrons, the measurements were performed using a custom-built liquid scintillation counter equipped with a CeBr3 inorganic scintillator as dedicated gamma detector. Furthermore, the light yield of the scintillation cocktail was optimized by using a 13:2 mixture of Ultima Gold F und Ultima Gold LLT scintillators. By simply changing the ratio of the two scintillators, or by addition of small amounts of a chemical quenching agent, detection efficiency for conversion electrons could be varied. The activity of the solution was obtained by the efficiency extrapolation technique. The overall uncertainty was less than 0.8% (k = 1). To validate the results of this novel approach, an independent standardization of the same Tc-99m solution was also carried out using a proportional counter based conventional coincidence setup. The samples were prepared by drop deposition on thin polyvinyl chloroacetate (VYNS) films. In this case, the efficiency variation was achieved by adding droplets of a colloidal silica solution (LUDOX) on the top of the samples. The obtained activity was consistent with the one derived by the liquid scintillation-based approach, although, its uncertainty was higher due to the lower overall detection efficiency for conversion electrons.

Speaker: Dr Marcell Takacs (PTB, Germany)

55 Comparative study of digital electronic systems available at IRA primary laboratory

Authors: 1. M. Teresa Durán (IRA, Switzerland) 2. Youcef Nedjadi (IRA, Switzerland) 3. Frédéric Juget (IRA, Switzerland) 4. CLaude Bailat (IRA, Switzerland)

Digital electronic systems for primary activity measurement methods are gaining ground in the reference laboratories all over the radionuclide metrology community. A wide range of alternatives is available on the market and the choice is not always easy as it depends on the circumstances, needs and capacities of each laboratory. In our case, IRA primary laboratory started in the transition to digital systems with a National Instruments system with very high performances that had to be programmed and tailored to our applications from the very beginning by the users. The continuation of this project was to complement and back up this system with the purchase of plug-and-play digitizers by CAEN. A comparative study of both system's approaches is presented in this work as a paradigm of the digital scene in radionuclide metrology laboratories. Different tests were carried out to evaluate and compare performance parameters such as: signal-to-noise ratio (SNR) at different energies, gamma energy resolution, time measurement accuracy and resolution and counting efficiency. The activity measurement of Co-60 and Ba-133 sources was performed by β-γ digital coincidence counting using both devices in parallel and the resulting activities are compared to demonstrate the overall performances.

Speaker: Dr Teresa Duran (Institute of Radiation Physics, Switzerland)

12:40 PM Lunch Break

56 OPTIONAL: Visit to IFIN-HH (Ionizing Radiation Metrology Laboratory, ELI-NP), with Coffee Break included

Radionuclide metrology techniques: 3 Oral contributions

Radionuclide metrology techniques

Conveners: Ryan Fitzgerald (NIST), Christophe BOBIN (LNE-LNHB)

57 Standardization of Rn-222 concentration using the multi-electrode proportional counter

Authors: 1. Rio Furukawa (NMIJ, Japan), 2. Miroslaw Janik (NIRS, Japan), 3. Satoshi Kodaira (NIRS, Japan), 4. Seiya Manabe (NMIJ, Japan), 5. Tetsuro Matsumoto (NMIJ, Japan), 6. Chihiro Shimodan (NMIJ, Japan), 7. Yasushi Sato (NMIJ, Japan), 8. Hideki Harano (NMIJ, Japan).

Radon (Rn-222) and its progeny is regarded as the largest contributor to an effective dose for the public globally. A variety of radon monitoring devices has been developed worldwide. The exact calibration of these devices is required. In Japan, a primary radon standard had not been developed. The National Metrology Institute of Japan (NMIJ) has been developing radon standard using the multi-electrode proportional counter (MEPC). The MEPC is a cylinder type detector and its length is 30 cm and its radius is 3.5 cm. The anode wire is arranged in the center of the cylinder and consists of tungsten with a thickness is 50 µm. P-10 gas (nominally argon 90% and methane 10%) is used as the counting gas. Six ring electrodes have been concentrically embedded in the inner sides of the flanges at a distance of 0.5 cm from each other. Electric voltages are applied to these rings to compensate for the field distortions normally occurring at the counter ends. The voltages are calculated by the finite element method. The alpha spectrometry of radon and its short half-life progenies (Po-218 and Po-214) by the MEPC was carried out at the QST NIRS radon facility. And the energy resolution was enough for separating 3 peaks. The applied anode voltage was 1100 V which was in the plateau region. Radon is a gas and fills the MEPC uniformly. However, its short half-life progenies are metal ions and are presumed to be attached to inside walls. With the geometrical condition, the counting efficiency η for radon and its short half-life progenies is approximated as 0.5. The counting efficiency η was calculated by the Monte Carlo particle transport simulation codes Particle and Heavy Ion Transport code System (Sato et al., 2018). η was smaller than the prior research (Busch, 2002). It seems to be reasonable because MEPC manufactured in this study is bigger than the prior research. In this study, the uncertainty will be evaluated.

<References>
Sato, T. Iwamoto, Y. Hashimoto, S. Ogawa, T. Furuta, T. Abe, S. Kai, T. Tsai, P.-E. Matsuda, N. Iwase, H. Shigyo, N. Sihver, L. Niita, K, J. Nucl. Sci. Technol. 55 (2018) 684.
Busch, H. Greupner, U. Keyser, Nucl. Instr. and Meth. A 481 (2002) 330.

Speaker: Ms Rio Furukawa (National Metrology Institute of Japan (NMIJ), Japan)

58 A Calibration procedure of beta-gamma coincidence measurements using four radioxenon spikes

Authors: Boxue Liu, Richard Britton, Seokryung Yoon, Ashley Vaughan Davies, Nikolaus Hermanspahn, Gohla Herbert, Jonathan Bare, Peter Jansson, Martin Kalinowski
Affiliation: CTBTO, Vienna, Austria
The current address is Swedish Defence Research Agency, Stockholm, Sweden

The accurate measurement of radioxenon isotopes plays an important role in the radionuclide component of the International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). There are four isotopes relevant to the CTBT verification regime, 133Xe, 133mXe, 131mXe and 135Xe. Ratios of four radioxenon isotopes can be used to discriminate nuclear explosion sources from releases of nuclear facilities such as medical isotope production as well as to determine the time of detonation under an assumed scenario. The determination of the concentrations of these isotopes relies on a robust calibration method. This paper outlines a calibration method based on four radioxenon spikes. For the beta/gamma coincidence spectrum analysis of the four radioxenon isotopes, the gross number of counts in a Region of Interest (ROI) includes contributions from the radionuclide associated with that ROI, the detector background, interference contributions from other radionuclides (including radon), and the activity from previous samples remaining in the detector cell. The net numbers of counts in ROIs and their associated uncertainties are estimated by the net count calculation (NCC) method. An alternative approach is the regression analysis, such as, the least squares fitting of ROI counts, enabling the deconvolution of X-ray contributions from the different radioxenon isotopes and radon. A combined calibration procedure between the NCC method and least squares fitting is investigated, which could also be used in the maximum likelihood fitting of ROI counts. For this method, spike measurements of four xenon isotopes are performed. The output of the beta-gamma detector system can be read out as three measurement channels: beta-gamma coincidences, beta singles and gamma singles. All three channels detect the same number of radioactive decays but differ in the number of detected emissions in 4π measurement geometry. The detection efficiencies are absolutely determined by comparison among the numbers of the ROI counts from three measurement channels, without the need for a reference value of radioxenon activity. The efficiency of 30 keV X-rays is determined by the 131mXe spike first, then applied to the other radioxenon spikes for determining the gamma efficiencies of associated ROIs. One of the key challenges is to estimate the uncertainty of the net number of counts, particularly considering correlations between beta-gamma coincidences and beta/gamma singles. In this work, the activity values of radioxenon standard sources, e.g., radioxenon spikes, are estimated based on the NCC method first, and then used for calibration of the regression analysis method.

Speaker: Mr Boxue LIU (CTBTO, Austria)

59 The standardisation of 125I and 109Cd using gamma-X coincidences via the National Nuclear Array

Authors (affiliation): 1. Robert Shearman (NPL, UK), 2. Séan M. Collins (NPL, UK / University of Surrey, UK), 3. John D. Keightley (NPL, UK).

Cadmium-109 is one of the most challenging radionuclides to standardise; the pure electron capture decay from the ground state (I pi = 5/2+; T1/2 = 461.9 a) populates one delayed (I pi = 7/2+; T1/2 = 39.7 s) state only, followed by an 88.0 keV gamma ray (T = 26.3). The temporal decoupling between the atomic rearrangements and the gamma transition makes conventional coincidence counting measurements problematic, often requiring some analogous tracer radionuclide. One common tracer is 125I, the ground state of which decays similarly (I pi = 5/2+, T1/2 = 59.388 d), but to a less-delayed state (I pi = 3/2+; T1/2 = 1.48 ns) followed by a 35.5 keV gamma ray (T = 14.08). Although 125I is simpler to standardise, and has been via numerous techniques [1], due to their differences in chemistry it is by no means an ideal tracer in liquid form for 109Cd.
Previously, the National Nuclear Array (NaNA) at the National Physical Laboratory (NPL) has been used to perform a primary standardisation of 60Co by the gamma-gamma coincidence technique[2]. NaNA has recently undergone an upgrade, now composed of up to twenty 1" by 2" CeBr3 scintillation crystals coupled with Hamamatsu photo-multiplier tubes. The current configuration has a maximum angular efficiency of 22.5 % and 33 angles between detector pairs. This upgrade reduces the internal radioactive background and allows for less uncertain peak areas in the low- and mid- energy regime, compared to the previously used LaBr3 detectors.
In this work, sources of 125I were dropped deposited onto thin films before adding drops of AgNO3, to stop the iodine escaping and left to dry before being mounted in source holders. Gamma-X coincidence measurements were made of numerous sources at several distances, and the calculation of the single and coincidence in-gate count rates in all detector pairs allowed for the determination of the efficiency of detection. These values were then used to extrapolate and derive the source activity following formulae as described in previous literature [1,3]. Following this, "sandwich" sources were made containing 125I and 109Cd, in which the activity of the 109Cd was calculated via the tracer method [3].

[1] Pommé S, Altzitzoglou T, Van Ammel R, Sibbens G. Standardisation of 125I using seven techniques for radioactivity measurement. Nucl. Instrum. Methods Phys. Res. A: Accel. Spectrom. Detect. Assoc. Equip. 2005;544(3):584-592.
[2] Collins SM, Shearman R, Keightley JD, Regan PH. Investigation of γ-γ coincidence counting using the National Nuclear Array (NANA) as a primary standard. Appl. Radiat. Isotopes. 2018;134:290-296.
[3] Schrader H. Photon–photon coincidences for activity determination: I-125 and other radionuclides. Appl. Radiat. Isotopes. 2006;64(10):1179-1185.

Speaker: Dr Robert Shearman (National Physical Laboratory (NPL), United Kingdom)

3:10 PM Coffee Break

Radionuclide metrology techniques: 1 Oral contribution and ICRM WG Meeting

Radionuclide metrology techniques

Conveners: Ryan Fitzgerald (NIST), Christophe BOBIN (LNE-LNHB)

60 Application of inductively coupled plasma tandem mass spectrometry for re-measuring the half life of long lived radionuclides

Authors (affiliation): Emma Braysher (NPL, UK), Heather Thompkins (NPL, UK), Saskia Burke (NPL, UK), Hibaaq Mohamud (NPL, UK), Frankie Falksohn (NPL, UK).

A number of long-lived radionuclides suffer from half-life measurements that are outdated, have inconsistencies in the values obtained and/or limitations with regards to the uncertainty budget. When used in combination with absolute counting techniques, inductively coupled plasma mass spectrometry (ICP-MS) is a potentially powerful metrological tool for providing updated and precise half-life measurements. This work shows the development of a consistent approach to measurement of the number of atoms using ICP-MS/MS for the first time for this purpose to contribute to updated, precise half-life measurement of long-lived radionuclides. ICP-MS/MS has unique interference removal capabilities, the advantages of which have been demonstrated for improved sample throughput for nuclear decommissioning and environmental monitoring applications. However, this technique also has the potential to enable half-life measurement for usually difficult to measure radionuclides.
Results are shown for several radionuclides (32Si, 36Cl, 93Zr, 238U and 239Pu), each with a range of isobaric, tailing and polyatomic interferences that must be removed using offline chemical and/or ICP-MS/MS separation. In all cases, ICP-MS/MS measurement was performed using a series of isotope dilutions using standardised solutions. The importance of suitable isotopic ratio reference materials for correcting the instrument mass bias is also highlighted for each radionuclide. Instrument setup is a key consideration, including the sample introduction system and the use of the collision-reaction cell for optimising interference removal without compromising sensitivity. The optimised setup for each radionuclide was used to derive the number of atoms, which is combined with the absolute activity values to obtain a remeasured half-life value.
The advantages and limitations of ICP-MS/MS compared to alternative instrument designs (specifically multi-collector ICP-MS) is discussed, as well as further radionuclides of interest that could benefit from ICP-MS to contribute to update half-life measurements.

Speaker: Dr Ben Russell (National Physical Laboratory, United Kingdom)

61 ICRM WG Meeting: Radionuclide Metrology Techniques (RMT)

Speakers: Ryan Fitzgerald (NIST), Christophe BOBIN (LNE-LNHB)

62 END of CONFERENCE DAY 2

Speaker: Aurelian Luca (IFIN-HH)

Wednesday, March 29

63 50 years of progress in gamma-ray spectrometry; Invited talk presented by Prof. Dr. Octavian Sima (University of Bucharest and IFIN-HH, Romania)

Speaker: Octavian Sima (University of Bucharest & IFIN-HH Bucharest)

Gamma-ray spectrometry: 2 Oral and 10 Poster contributions

Gamma-ray spectrometry

Conveners: Marie-Christine Lépy (CEA-LNE-LNHB), Octavian Sima (University of Bucharest & IFIN-HH Bucharest)

64 Radionuclide-free efficiency calibration of an HPGe detector using monochromatic photon beams measured with a cryogenic radiometer

The efficiency calibration of spectrometers is traditionally based on the measurement of radioactive sources calibrated in activity and whose emission intensities are known. However, in the energy range below 60 keV, there is a lack of reliable tabulated emission intensities and some inconsistencies have been highlighted [1]. Furthermore, if one aims to improve the measurement of emission probabilities, this approach implies the use of the same parameters that one intends to measure. The solution to these limitations is the use of photon fluxes whose intensity has been determined in an absolute way by another technique. Here we present the calibration of a high-purity germanium (HPGe) detector in the energy range from 3 keV to 60 keV through a procedure that involves the following sequence of steps: First, the intensity of a monochromatic photon beam was measured by means of a cryogenic electrical-substitution radiometer BOLUX (BOLometer for Use in the field of X-rays) [2]. Cryogenic detectors are based on the measurement of the temperature rise experienced by an absorber when the radiation interacts with it. In particular, in electrical-substitution radiometers, the amount of incident energy is determined by finding the electrical power that must be dissipated in the material to get the same temperature increase than that obtained during the photonic heating. Second, these well-determined photon beams have been employed for the calibration of different photodiodes in terms of current induced per unit optical power (efficiency) at different photon energies. Finally, for each energy step, the efficiency calibration of an energy-dispersive spectrometer based on an HPGe detector was obtained by comparison with the primarily-calibrated photodiodes. The calibration measurements were performed at two different beamlines (Métrologie and PUMA) of the SOLEIL synchrotron facility, and different photodiodes were used to cover the energy range of interest. The experimental approach and efficiency results will be detailed. The final application of this study is the use of the radionuclide-free calibrated spectrometer to determine new values of absolute X-ray emission intensities for radionuclides, starting with 109Cd and 152Eu. [1] Applied Radiation and Isotopes, Volume 134, April 2018, Pages 131-136 [2] Presented at EXRS2022, submitted to X-Ray Spectrometry

Speaker: Dr Victor H. Elvira (CEA, France)

65 Verification of gamma-ray spectrometry analysis software for the computation of characteristic limits according to ISO 11929

Authors: 1. M.W. van Rooy (NMISA, South Africa), 2. M. Herranz (UPV/EHU, SPAIN),
3. R. Idoeta (UPV/EHU, SPAIN), 4. L. Verheyen (SCK CEN, Belgium), 5. M. Bruggeman (SCK CEN, Belgium), 6. M. Lepy (LNE-LNHB, France), 7. S. Pierre (LNE-LNHB, France), 8. P. Saganowski (NCNR RC POLATOM, Poland), 9. A. Luca (IFIN-HH, Romania)

Metrologically sound analyses of radioactivity of samples requires that the measurement method is fit for purpose and validated. One of the parameters to consider in the validation, especially when dealing with low-level radioactivity analysis, is the detection limit of the method or for a specific measurement condition of the method. In 2010, with an update in 2019, the concepts of the computation of detection limits and characteristic limits for measurements of ionizing radiation have been published in the ISO 11929 standard. Since most laboratories rely on commercial software to perform gamma-ray spectrometry analyses, verification of this software with respect to the computation of characteristic limits may be required to obtain the proof of compatibility with the ISO standard. Moreover, a verification is useful in order to know and understand the conditions (e.g. critical settings) used in the software to calculate the result. To help the community of radioactivity analysis laboratories, the Gamma-ray spectrometry working group of ICRM started an exercise to investigate the problem of verification of characteristic limits in gamma-ray spectrometry. For that purpose, well defined gamma-ray spectra together with specific instructions fixing key parameters in the computation of detection limits were sent to several laboratories for analysis, evaluation and reporting. The results obtained by different participating laboratories were then compared and were also verified by manual computation. It was observed that different results were obtained by different software packages and that generally no consistent values are directly obtained even when fixing the key parameters. The main causes of the differences in results could be explained by considering the specific approaches and conditions used in the software.

This paper will report on the results obtained in the exercise and will highlight and discuss the impact of important parameter settings of the different software packages. Guidance will be provided on how best to set these parameters to obtain consistent values between software packages used to calculate the decision threshold and detection limit of a specific spectrum.

Speaker: Michel Bruggeman (SCK CEN)

66 Unmanned Long Range Helicopter System for Radiological Emergency HPGe Spectrometry

Following a nuclear or radiological event, radiation protection authorities and other decision-makers need rapid and credible information about the affected areas based on reliable radiological data. However, the potentially large areas and risks to people in the vicinity pose difficult measurement challenges.
Therefore, European joint research project “Metrology for Mobile Detection of Ionising Radiation Following a Nuclear or Radiological Incident” (Preparedness) in the frameworkof the European Metrology Programme for Innovation and Research (EMPIR) has developed new measurement techniques and traceable calibration methods for determining ground surface activity.
One of the major outcomes of the Preparedness project is the development of unmanned airborne spectrometric system equipped with a high-purity germanium (HPGe) detector. Considering accident conditions, the system must be reliable and heavy-duty. Therefore, an unmanned helicopter with sufficient payload and flying range is used as a carrier. Spectrometric system enables fast and safe identification of released radionuclides and thus the level of technology disruption and the determination of accident zones with specific conditions. The system will support timely and effective measures to protect the population and the environment from the effects of ionising radiation.
The paper describes adaptation of the HPGe detector for airborne use, testing its performance using standard sources and Monte Carlo modelling. Data collected during the initial flight tests are presented and compared to the Monte Carlo simulations. The data obtained was used to calculate minimum detectable activity for several radionuclide sources and different flight altitudes.The results of various flight exercises are presented, including the IAEA Technical Meeting on the Use of Uncrewed Aerial Systems for Radiation Detection and Surveillance.
This project has received funding from the EMPIR programme co-financed by the Participating States and from the European Union’s Horizon 2020 research and innovation programme.

Speaker: Dr Jiri Suran (CMI, Czech Republic)

2023-03 ICRM poster.pdf

67 Gamma-ray interrogation of some neutron source using MCNP

Neutron sources have been in use for quite some time, and the need for accurate account for nuclear material especially Plutonium and Uranium is necessary for IAEA safety and safeguards. Following recent events there has been special need to know how much Plutonium or Americium are present in old sources that are scattered around the world in the form of Pu-Be neutron sources. Isotopic content is of great and important information for further certification and accountancy of nuclear material.
Most of these sources lack in the source description the amount of active material present not to mention isotopic contents, one way of doing this is by gamma-ray interrogation. One such a neutron source Pu-Be type was characterized by experimental measurements at ELI-NP at National Institute for R&D in Physics and Nuclear Engineering (IFIN-HH).
In our present work we use Gold and Nickel around Pu-Be, and two other neutron sources for comparison reasons Am-Be, 252Cf. We aim to use neutron activation analysis to accurately get the neutron flux from the amount of gamma-rays induced by the activation.
Gold has been used as a monitor for neutron sources successfully before and its being used in previous experimental measurements as neutron flux monitor, Nickel is being used as a comparison purpose.
The experiment will further look into establishing a way to calibrate detectors for higher energies expected to come from Variable Gamma – Ray Source at ELI-NP.

Speaker: Mr Ciprian Cosar (University of Bucharest, Faculty of Physics)

68 A Novel Method of Fast Computing of the Full-Energy Peak Efficiency for Cylindrical Sources Using Coaxial High-Purity Germanium Detectors

The computation of the FEP efficiency is widely used because the relative method of measurement has severe restrictions. The MC simulation of photon transport is the reference method of computing the FEP efficiency but it is rather complicate, time consuming and requires skilled people for determining optimal detector parameters.Hence, it is not convenient its use for many different source configurations and therefore simpler and faster methods must be developed.
In this work a novel deterministic method for fast computing of the FEP efficiency for cylindrical sources emitting photons in the range of 60-2000 keVusing coaxial HPGe detectors is described in detail. It has a sound theoretical basis being based on thefollowing integral equation(Stanga and Gurau, 2021)
ε_ps (μ_s,E)=1/V ∫_V▒〖F_ap (μ_s,E,r ⃗ ) ε_pp^o (E,r ⃗ )dV (1) 〗
where ε_ps (μ_s,E) is the FEP efficiency for a given sample.F_ap (μ_s,E,r ⃗ )is the attenuation factor for a point source embedded in the volume sample at the position r ⃗and ε_pp^o (E,r ⃗ ) is the FEP efficiency response of the detector. To apply Eq. (1), a gridding technique was used for computing ε_pp^o (E) (Venkataraman et al., 2005). Grids were created inside of a right circular cylinder placed on the detector end cap and having radius r (cm)[0, 20] and height h (cm)[0, 30]. This space can accommodate almost all samples measured by gamma spectrometry (GS) laboratories.A grid-based interpolation was employed to compute ε_pp^o (E) at any values of r, h and E using its computed values in grid points.It was shown that F_ap can be approximated with sufficient accuracyby the mean value of the transmission factor of photons through the sample (Stanga and Gurau, 2021) for values of the linear attenuation coefficient in the range 0.0-1.0 cm-1. Moreover,ε_ps (μ_s,E)values can be accurately computed because the computed values of F_ap have large errors (e.g. 10 %) only for small ε_pp^o (E,r ⃗ ) values.The attenuation factor was computed using MC integration and ε_ps (μ_s,E) was computed by numerical integration of the integral from Eq. (1) using mid-point rule.The method described above was implemented as a Matlabcode.
The methodwas applied in practice usinga GS system equipped with a p-type coaxial HPGe detector model B20214, and LabSOCS code. For this detector, the values of ε_pp^o (E) in grid points were computed by means of Gespecor code.Theε_ps (μ_s,E)values were computed for ten cylindrical samples (five water samples and five aluminum samples) and different photon energies using this novel method, Gespecor and LabSOCS codes. The discrepancies were smaller than 3 % and 5 % for water and aluminum samples, respectively. The activity of a cylindrical water sample containing 137Cs was measured using the value of ε_ps provided by this novel method. The measured and certified values of the activity agreed within the uncertainty.
Stanga D. and Gurau D., (2021). Applied Radiation and Isotopes, 172.
Venkataraman, R., et al., (2005). J. Radioanal. Nucl. Chem., 264.

Speaker: Doru Stanga (IFIN-HH (Romania))

69 Calibrating GESPECOR Model of Computing the Full-Energy Peak Efficiency of Coaxial High-Purity Germanium Detectors by Monte Carlo Simulation

Monte Carlo (MC) simulation models implemented as computer codes are widely used for computing the full-energy peak (FEP) efficiency of gamma spectrometry (GS) systems. Their calibration is an important step in obtaining the traceability of GS measurements that employ computed values of the FEP efficiency. The input of MC models consist of model variables (e.g. photon energy) X=〖(x_1,....,x_d)〗^T and model parameters (e.g. crystal radius) θ=〖(θ_1,....,θ_m)〗^T. The design points for measurements are {X_1,...X_n }, and measured responses are Y={y_1,..,y_n }. Because computer models are always imperfect, a commonly used statistical model is y_i=y_m (X_i,θ^ )+δ(X_i )+e_i, where y_m (X,θ^) is the model output, δ(X_i) is the discrepancy function that accounts for the difference between the model and the GS system, θ^ contains optimal model parameters, e_i is y_i error. (Kennedy and O'Hagan, 2001).The goal of the model calibration is to estimate θ^ and δ(X) so that the model outputs match the measured responses.
The calibration of MC models is known as detector characterization. Previous studies showed that the discrepancy function is small for these models in the photon energy range of 60-2000 keV. In this case, it was proved that the least squares calibration is consistent and efficient (Tuo and Wu, 2015). MC codes are computationally expensive and therefore surrogate models must be built. A linear surrogate model was developed using the first order Taylor approximation of the Gespecor FEP efficiency. A nonlinear surrogate model was developed for large intervals of the detector parameters, which well approximates the Gespecor FEP efficiency using grid-based interpolation.
In this work a methodology for calibrating the Gespecor model is described and applied in practice using a GS system equipped with a p-type coaxial HPGe detector model B20214. The geometrical model of the model contains fifteen parameters but many of them are either known accurately or insensitive. Consequently, five parameters (crystal radius and length, face and side dead-layer thickness, side holder thickness) were taken as free parameters. Firstly, a set of values of the FEP efficiency of the B20214 detector was determined experimentally for different point source positions and different photon energies. Secondly, the optimal parameters for the detector B20214 were computed making use of the data obtained in the first step and employing linear and nonlinear least squares methods and surrogate models mentioned above.
The optimal model for the p-type HPGe detector B20214 was verified in the energy range of 60-2000 keV by measuring the FEP efficiency for point and cylindrical sources located at different positions above the end cap. The discrepancies between measured and computed values were smaller than 3 % for point sources and 5 % for cylindrical sources.

Kennedy, M. C. and O'Hagan, A, 2001. Journal of the Royal Statistical Society B, 63.
Tuo R. and Wu C.F.J., 2015. The Annals of Statistics, 45.

Speaker: Dr Doru Stanga (IFIN-HH (Romania))

70 Measuring mass attenuation coefficients for materials with unknown composition by performing transmission measurements with a HPGe detector for X-rays and low-energy gamma rays

In gamma-ray spectrometry the analysis of low-energy gamma-emitting nuclides like 210Pb, 129I needs special attention because the gamma attenuation in the sample depends on the specific element composition of the sample material. Hence, a material- or sample-specific self-attenuation correction is necessary. For that purpose, attenuation correction procedures have been developed in the past that rely on transmission measurements. The Cutshall (Cutshall, 1983) correction method is probably the best-known and most used but it suffers from measurement bias. Moreover, attenuation correction procedures relying on efficiency transfer require the mass attenuation coefficients to be known and hence need a different approach. Practice shows that attenuation coefficients at low gamma-ray energy of unknown sample materials are not easily obtained by transmission measurements with a parallel beam of gamma-rays and they generally suffer different experimental limitations. We propose non-collimated transmission measurements using gamma-rays of an 241Am and 133Ba source to determine attenuation coefficients at the different energies emitted by the source. The measurement principle relies on setting up a set of calibration curves for the attenuation data for each of the gamma-ray energies of the source. These calibration curves are specific for the detector and the sample geometry used. They are relating the count rate of the transmitted gamma-rays through the known sample relative to the count rate measured for the water sample to the attenuation coefficients for this material relative to that of water. For all materials used to set up these calibration curves, and for all considered energies, the mass attenuation coefficients are taken from the XCOM database (Berger, 2010). Measurements were done on an extended range HPGe detector, and the energies used range from 21.16 keV until 302.9 keV. Mass attenuation coefficients ranged from 0.7 to 33 cm²/g at 21.16 keV. The counting geometry used to set up the calibration curves for the transmission uses a source positioned on top of a cylindrical container (h 23 mm x70 mm) resulting in a fan beam of gamma-rays towards the detector. The apparent mass density of the materials used for the calibration is used to compute the linear attenuation coefficient. By measuring, the count rates for transmission relative to water of an unknown sample at the different source energies and by accounting for the apparent density of the unknown sample material, the mass attenuation coefficients relative to that of water can be determined directly from the calibration curves. The attenuation data obtained in this way allow interpolation between the data points to obtain the attenuation also at other energies. The procedure is easily tested by comparing measured attenuation data for materials of known composition with their attenuation data read from XCOM. For routine analyses with this method, the measured attenuation data are transcribed to a sample-specific material file to be used by the efficiency transfer software. We use EFFTRAN (Vidmar, 2005) for efficiency transfer. The paper will outline the set-up of the different calibration curves used to determine the attenuation data at low gamma-ray energy and will illustrate how the procedure can be used in combination with efficiency transfer by EFFTRAN. Uncertainty propagation from the transmission measurement and the calibration curves towards activity determination in samples with unknown composition will be outlined. The fact that this method does not yield information on absorption edges will also be discussed in view of its general applicability to the analysis of low-energy gamma emitters in environmental and NORM samples. References Berger, M. H. (2010). XCOM: Photon Cross Section Database. NIST STandard Reference Database, na. Retrieved from http://www.nist.gov/pml/data/xcom/ Cutshall, N. (1983). Direct analysis of 210Pb in sediment samples: Self-absorption corrections. Nucl.Instrum.Methods, 206, 309-312. Vidmar, T. (2005). EFFTRAN A Monte Carlo efficiency tranfer code for gamma-ray spectrometry. Nucl. instrum. Methods, 550, 603-608.

Speaker: Michel Bruggeman (SCK CEN)

P18-GS-Determination of mass attenuation coëfficient with transmission measurements.docx

71 Self-attenuation in the low-energy range: an experimental study on Pb-210

Authors: M.-C. Lépy 1, L. Chambon 1, B. Sabot 1, M. Anagnostakis 2, A. De Vismes 3, R. Galea 4, R. Idoeta 5, P. Jodlowski 6, K. Karfopoulos 7, A. Meyer 3, I. Mitsios 2, V. Peyres 8, P. Saganowski 9, N. Salpadimos 7, M.I. Savva 10, O. Sima 11, T.T. Thanh 12, R. Townson 4, Z. Tymiński 9, T. Vasilopoulou 10, L. Verheyen 13, T. Vidmar 13
Affiliations: 1: LNHB, 2: NTUA, 3: IRSN, 4: NRC, 5: UPV/EHU, 6: AGH UST, 7: EEEA, 8: CIEMAT, 9: POLATOM, 10: NCSR "Demokritos", 11: U. Bucharest, 12: VNUHCM, 13: SCK -CEN.

Quantitative analysis of environmental samples generally involves volume source with low radioactivity and an unknown composition of the sample matrix. Unless an efficiency calibration with the same geometry and matrix is available, it is necessary to correct the raw counting rates for self-attenuation effects in order to obtain the correct sample activity. This can be achieved either experimentally or by means of calculation based on mass attenuation coefficients that can be directly measured or taken from tabulated absorption data. The self-attenuation effect is more pronounced when the energy of the emitted photons is low. This is the case with 210Pb, which is a low-energy gamma emitting radionuclide (46.54 keV) suffering strong absorption in the sample matrix and whose concentration in the environment must be regularly monitored according to public health regulations.
Within the framework of the GSWG, twelve laboratories agreed to carry out measurements with matrices containing 210Pb and to compare their approaches to the determination of self-attenuation correction factors in order to draft practical recommendations for users.
With this aim, the Laboratoire National Henri Becquerel (LNHB) prepared two different sets of three samples, each packed in cylindrical containers with known activities of Pb-210 and Cs-137, according to the preparation procedure using standard solutions. The sample filled with resin was meant to be considered as a standard source by the participants and could be used for the efficiency calibration of the detectors. The goal of the exercise was to determine the activity of the two radionuclides included in the other two samples, with unknown matrices. This required the participants to establish the self-attenuation correction factors between the calibration and the measurement matrices. Inactive matrices were also provided so that participants could experimentally determine the attenuation coefficients and use them for calculating the self-absorption correction factors.
We will present the different approaches and results obtained by the participants and give some general recommendations on the correct treatment of self-attenuation effects in the low-energy range.

Speaker: Marie-Christine Lépy (CEA-LNE-LNHB)

72 Calculation of detection limits with the LSQ method in gamma-ray spectrometry using interpolation

The detection limit (DL) is the smallest value of the measurand which can be detected with a predefined probability. In terms of the indication, which is in gamma-ray spectrometry the number of counts in a peak occurring at an energy where the analyte radiates, the indication corresponding to the DL, np#, is the solution of the equation [1]
(np#- np)2=k1-β2[ur2(W)+u2(np= np#)] , ()
where np denotes the indication corresponding to the decision threshold (DT), u(np#) and ur(W) are the uncertainty of the indication corresponding to the DL and the relative uncertainty of the factor converting the indication to the observed value of the measurand, respectively and k1-β is the quantile of the normal distribution corresponding to the probability β for making the error of the second kind. By approximating u(np) with a quadratic function of np it is possible to calculate np#.
Since the DT is calculated from the spectrum in the absence of the indication, i. e. from the indication background, to arrive at the DL, the indication must be stripped off from the measured spectrum
n0i=ni-pi·np,
where np denotes the observed value of the indication, ni and n0i are the channel contents of the measured and the reduced spectrum respectively and pi describes the shape of the indication. The matrix elements of the variance-covariance matrix of the reduced spectrum, are
U0ij= ni·δij+pi·pj·u2(np),
where u(np) denotes the uncertainty of the indication observed.
By the LSQ method the variance of the indication is given by the corresponding diagonal matrix element of the variance-covariance matrix of the results, given as
Un=(P2T·U0-1·P2)-1,
where P2 denotes the two-column matrix holding in one column the shape of the indication normalized to unity, pi, and in the second column the indication background n0i. Then the matrix element Un11 holds the square of the null-indication uncertainty u(np=0).
To arrive at the uncertainty at an arbitrary value of the indication, np~, the matrix U0 is modified to
Uij= U0ij+pi·pj·np~.
It should be observed that adding-up an indication to the spectrum introduces an additional correlation among channel contents, although np~ itself is uncertainty free. By calculating the matrix Uij with e. g. np~=k1-α·u(np=0) and e. g. np~ =(k1-α+ k1-β)·u(np=0), the parameters of the quadratic parabola can be determined. By inserting the parabola into the Eq. (), the equation can be solved on np#, the indication corresponding to the DL.
The procedure described will be illustrated with the DLs as functions of the indication calculated for isolated indications and indications overlapping with close peaks. The results will be compared with results obtained with other methods.

Reference:
[1] M. Korun et al., Calculation of the decision threshold and detection limit in high-resolution gamma-ray spectrometry, Nucl. Instr. and Meth. A 1014 (2021) 165686.

Speaker: Toni Petrovic (“Jožef Stefan” Institute)

73 Surface activity determination in metallic waste samples by using HPGe and CeBr3 detectors and MCNP modelling of γ-spectra

Authors (affiliation): 1. Rita Plukienė (FTMC), 2. Elena Lagzdina (FTMC), 3. Darius Germanas (FTMC), 4. Kristina Mikalauskienė (FTMC), 5. Marina Konstantinova (FTMC), 6. Artūras Plukis (FTMC), 7. Arūnas Gudelis (FTMC), 8. Vidmantas Remeikis (FTMC)

One of important tasks for smooth and successful nuclear power plant (NPP) decommissioning process is optimization of nuclear facility metallic radioactive waste (MRW) management by applying grouping and separation of MRW. In order to reduce the amount of MRW to be disposed of in final repositories the efficient characterization, decontamination and/or melting processes should be applied. Modelling tools (MCNP6, SCALE6.2) are usually used for obtaining activation of materials in the reactor core for characterization and separation of waste streams of high activation, intermediate, low activation metal waste and also non-activated materials for which only surface contamination is relevant. For efficient characterization of very low-level metallic waste the determination of surface contamination part is needed by simple nondestructive γ-spectrometry measurement or combination of dose rate/γ-spectrometry measurement application. The aim of this work is to investigate the γ-spectra of 60Co (activation) and 137Cs (surface contamination) sources in different shielding geometries and from the shape/intensity and peak/Compton ratio of γ-spectra analysis identify surface and volume activity by using different HPGe and CeBr3 detectors.
The measurements of the same known-home-made different geometry metallic waste laboratory samples with 60Co and 137Cs sources have been performed using HPGe semiconductor and CeBr3 scintillation detectors. MCNP6 modelling of both detectors and different sample geometries of the experiments are carried out for comparison reasons. The coincidence-summing effect was taken into account. Detectors were efficiency calibrated using reference materials traceable to NMI. The GammaVision software (v. 6.06) was applied for spectra acquisition and analysis. A good consistency (discrepancies not more than 3%) of experimental and modelled results has been obtained during comparison of measured and modelled γ-spectra of laboratory samples with HPGe, on the contrary, not so good agreement was obtained for CeBr3 detector (discrepancies up to 15%). This was associated, probably, with CeBr3 detector measured γ-spectrum thermal dependence which is not taken into account in the modelling case. The analysis of experimental measurement and modelling of the 60Co and 137Cs source samples has shown, that there is peak/Compton ratio dependence for different thickness iron shield laboratory samples. MCNP modelling of different source cases: planar source shielded with different metal plates and volume source have revealed, that surface contamination 137Cs source can be distinguished if compared with a reference source case by using modelling and measurement techniques from the shape/intensity and peak/Compton ratio of γ-spectra analysis. This allows investigating of γ-spectra of surface contaminated and volume activated different geometry metallic waste samples. Some recommendations for application of different spectrometers for surface activity determination in metallic contaminated samples are proposed.

Speaker: Dr Arunas Gudelis (Center for Physical Sciences and Technology (FTMC), Savanorių Ave. 231, 02300, Vilnius, Lithuania)

74 Initial Gamma spectroscopy of ITER materials irradiated in the JET D-T neutron environment

Authors (affiliation): Callum L. Grove (UKAEA, UK), Chantal R. Nobs (UKAEA, UK), Lee W. Packer (UKAEA, UK), Nicola Fonnesu (ENEA, Italy), Ewa Łaszyńska (IPPLM, Poland), Jerzy W. Mietelski (IFJ, Poland), Mario Pillon (ENEA, Italy), Marilia I. Savva (NCSRD, Greece), Ion E. Stamatelatos (NCSRD, Greece), Anthony Turner (UKAEA, UK), Theodora Vasilopoulou (NCSRD, Greece), Rosaria Villari (ENEA, Italy), Andrej Zohar (JSI, Slovenia) and JET contributors.

As part of the EUROfusion Preparations for ITER Operations (PrIO) programme, with the 'ACT' sub-project, 11 real materials used in the main components of the International Thermonuclear Experimental Reactor (ITER) tokamak and 4 different dosimetry foil materials have been irradiated within the Joint European Torus (JET) tokamak neutron environment during the operations with deuterium and tritium undertaken in 2021 (DTE2 campaign). A total of 68 ITER material foils and 13 dosimetry foils were placed in a long-term irradiation station (LTIS) assembly close to the JET vacuum vessel. These irradiated foils were extracted and distributed to several labs across Europe for gamma spectroscopy measurements. The goal of this analysis was to identify and accurately assess the activity of nuclides present. This work presents the latest gamma spectrometry results of the foils measured by the RADLab, UKAEA.
The dosimetry foils materials include Titanium, Cobalt, Iron, and Yttrium. The selection of these foil materials was based on known dosimetry reactions present in nuclear data to characterise the irradiation received at the location of the LTIS. The irradiated ITER foils consist of materials used in the ITER fusion device currently under construction, which include: stainless steels from the in-wall shield, vacuum vessel and toroidal field plates, EUROFER 97-3 steel, Alloy 660, CuCrZr, Al-Bronze, XM-19, Tungsten, and Inconel 718. The data obtained from these irradiated ITER materials provide insight into the neutron-induced radionuclides that ITER will generate in the nuclear phase. The activity measurement results from UKAEA are presented and compared with initial simulated predictions from neutron transport and nuclear inventory calculations.

Speaker: Dr Callum Grove (UKAEA, United Kingdom)

75 Machine learning approach to the fast screening analysis of atmospheric radioactive aerosols

Authors: Miroslav Hýža 1, Lenka Dragounová 1, Mahulena Kořistková 1
Affiliation: 1 National Radiation Protection Institute (NRPI), Czech Republic

For atmospheric radioactivity monitoring, the emphasis is on two conflicting requirements: sensitivity, and timeliness of reported results. This paper describes a sensitive method for quick screening measurements of aerosol filters, using a HPGe detector and accounting to high and variable natural background.
During a routine monitoring regime, filters from a high volume sampler (900m3/h) are being exchanged in intervals of several days. The withdrawn filters are then set aside for several hours prior to the laboratory measurement to let the 222Rn/220Rn daughters to decay. Not doing so significantly reduces the sensitivity of the measurements.
Delaying the measurement by several hours has an effect especially on the activities of 214Pb and 214Bi with half-lives of 26.9 min and 19.8 min. Thoron decay products 212Pb, 212Bi and 208Tl decay on the filter with a half-life of 10.6 h, which is not as significant considering the approx. 8-hour deadline for result reporting. This delay before placing the filter on a detector can therefore take up a significant part of the total time available for analysis.
For this reason, the possibility of exploiting also the time reserved for the decay of daughter radionuclides was investigated. Experimental measurements were performed using a 100% HPGe detector (FWHM 2 keV) whose dead time with a fresh filter reached up to 25 %. The high natural background is also very variable – affected by the concentration ratios of 222Rn/220Rn decay products (DP) in the air, and the sampling time.
The proposed method is based on the precise and reliable DP background subtraction, using a full-spectrum analysis instead of the classical peak search algorithm. Our approach is based on several machine-learning algorithms - mainly the Principle Component Regression (PCR) and Autoencoder neural network, which fully exploit the autocorrelation structure of HPGe spectra.
Apart from the higher sensitivity, a major feature of this method is the ability to deal efficiently with spectral interferences, i.e. 137Cs (661.6 keV) and 214Bi (661.1 keV, γ=0.054 %), or with the contributions of β+ active radionuclides to the 511 keV annihilation peak.

Speaker: Dr Miroslav Hýža (National Radiation Protection Institute (NRPI), Czech Republic )

10:25 AM Coffee Break

Gamma-ray spectrometry: 2 Oral contributions, ICRM WG meeting

Gamma-ray spectrometry

Conveners: Marie-Christine Lépy (CEA-LNE-LNHB), Octavian Sima (University of Bucharest & IFIN-HH Bucharest)

76 A benchmark for Monte Carlo simulations in Gamma-ray spectrometry – Part II: True coincidence summing correction factors

Authors: M.-C. Lépy 1, C. Thiam 1, M. Anagnostakis 2, C. Cosar 3, A. De Blas del Oyo 4, H. Dikmen 5, M.A. Duch 4, R. Galea 6, M.L. Ganea 3, M. Hult 7, S. Hurtado 8, K. Karfopoulos 9, A. Luca 3, G. Lutter 7, I. Mitsios 2, H. Persson 9, C. Potiriadis 10, S. Röttger 11, N. Salpadimos 10 M.I. Savva 12, O. Sima 3,13, T.T. Thanh 14, R. Townson 6, A. Vargas 4, T. Vasilopoulou 12, L. Verheyen 15, T. Vidmar 15
Affiliations: 1 LNHB, France, 2 NTUA, Greece, 3 IFIN-HH, Romania, 4 UPC, Spain, 5 TENMAK, Turkey, 6 NRC, Canada, 7 JRC-Geel, Belgium, 8 U-Sevilla, Spain, 9 Mirion Technologies, Inc, USA, 10 EEEA, Greece, 11 PTB, Germany, 12 NCSR “Demokritos”, Greece, 13 U. Bucharest, Romania, 14 VNUHCM, Vietnam, 15 SCK-CEN, Belgium.

Monte Carlo simulations are now widely used in gamma-ray spectrometry to calculate either the detection efficiency or the true coincidence summing correction factors. However, running the calculations is not always easy for new users, and errors in defining the geometry files for the Monte Carlo computer codes, as well as misinterpretations of their outputs, often lead to incorrect results. Within the ICRM Gamma-ray Spectrometry Working Group (GSWG), an action had been initiated to prepare sample geometry files for the commonly used Monte Carlo software for selected calculation cases in order to provide a benchmark for new users. The first part of this action was devoted to the calculation of detection efficiencies [1]. A further step focuses on coincidence summing corrections. In this second part, the same simulated measurement setups were considered as for the calculation of efficiencies and the relatedgeometry description files for the different Monte Carlo codes had already been made available on the ICRM GSWG webpage [2]. The resulting coincidence summing correction factors for the eight simulated setups concerned radionuclides with characteristic decay schemes: 60Co and 134Cs are beta minus emitters, 133Ba decays by electron capture accompanied by intense X-ray emission, while 22Na decays by both electron capture and beta plus emission, the latter leading to the emission of annihilation photons.Seven different computer codes (EFFTRAN, EGSnrc, EGS4, GEANT, GESPECOR, MCNP and PENELOPE) were considered in this exercise and 20 series of results were collected from the participants and analysed.Initially discrepancies were observedbetween the results of different users of the same code, especially for 133Ba and the N-type detector model, which emphasized the important role of proper treatment of X-rays in the calculations. A comparative analysis of the decay data tables used by the different codes showed that they are not a major source of deviations between the results. The importance of the peak area determination procedures(subtraction of the background) was highlighted. Further calculations with harmonized simulation conditions were conducted to reach better agreement between the participants. The results of this collaborative work make possible a derivation of practical recommendations for the training of new users, in order to avoid typical simulation errors. The benchmark results (correction factors) will be made available and discussed on the ICRM GSWG webpage, along with practical recommendation for their use.

[1] Applied Radiation and Isotopes, Volume 154, December 2019, 108850
[2] http://www.lnhb.fr/icrm_gs_wg/icrm_gs_wg_benchmarks/

Speaker: Marie-Christine Lépy (CEA-LNE-LNHB)

77 Uncertainty and covariance matrix of the coincidence summing correction factors due to decay data uncertainties

Coincidence-summing effects play a significant role in present-day gamma ray spectrometry. The evaluation of the corresponding correction factors (FC) and of the associated uncertainties is an important issue for the Gamma-Ray Spectrometry Working Group (GSWG) of the ICRM, being the subject of several intercomparisons.

In this work the uncertainties and the covariance matrix of the FC values due to the uncertainties of the decay data parameters were evaluated for the main emissions Ei of Co-60, Y-88, Ba-133, Cs-134 and Eu-152. Other contributions to FC uncertainty, due to measurement conditions and radiation transport, were switched off by preparing in advance (Monte Carlo) the required set of joint detection probabilities of all the relevant cascading photons. The effect of the decay data uncertainties was evaluated by constructing sets of decay schemes for the same nuclide, with different values of the parameters, sampled from distributions based on the values V and uncertainties s listed in the decay data base (DDEP). Typically normal distributions N(V,s) were used, but in the case when a parameter is listed as <V in the data base, a linear distribution in (0,V) was considered. When unphysical values were sampled, the sampling was repeated. For a sampled decay scheme, the set of FC(Ei) values for the Ei emissions was computed by combining the decay scheme data with the corresponding joint detection probabilities. The evaluation of FC(Ei) was done for each decay scheme generated. Finally, the distribution of the set of FC values was constructed and summarized by the best estimate and standard deviation of FC(Ei) for each Ei and by the covariance of FC(Ei) and FC(Ej). The procedure was applied for a set of samples and detectors, including the cases considered in the recent GSWG intercomparison [1]. Generally, the uncertainties are very small, but in specific cases (e.g. 79 and 160 keV of Ba-133 for a point source measured with a n-type detector) can as high as 5%.

The bias resulting from neglecting the angular correlations, as well as the uncertainty associated with the uncertainties of the mixing ratios, were also evaluated.

[1]. M-C Lépy et al., this conference

Speaker: Prof. Octavian Sima (University of Bucharest & IFIN-HH Bucharest, Romania)

78 ICRM WG Meeting: Gamma-ray Spectrometry (GS)

Speakers: Marie-Christine Lépy (CEA-LNE-LNHB), Octavian Sima (University of Bucharest & IFIN-HH Bucharest)

1:15 PM Lunch Break

Research in Industry (Presentations by Commercial Companies)

79 HPGe detectors for challenging applications: Latest advancements and outlook

Speaker: Dr Gabriela Ilie (Mirion Technologies, Inc.)

80 Digital multi-input DAQ for low background measurements

Speaker: Mr Matteo Corbo (CAEN Spa, Italy)

Measurement standards and reference materials: 1 Oral and 5 Poster contributions

Measurement standards and reference materials for radionuclide metrology

Conveners: Lisa Karam (NIST), Nuria Navarro Ortega (CIEMAT)

81 Towards a Radon-in-water primary standard at LNHB

Measurement of 222Rn activity in water is important in many fields such as dosimetry, radiation protection, geology and volcanology. Various methods were developed to measure radon-in-water, namely: emanometry, gamma–ray spectrometry (GS), liquid scintillation counting (LSC) and track-etch techniques. Despite the importance of these measurement techniques, their long history and wide scale application, no primary standard for radon-in-water concentration currently exists. This impedes the establishment of a traceability chain for the radon-in-water measurements to a primary 222Rn standard as the calibrations are often performed usingother nuclides (e.g. 226Ra standards), which can introduce problems in certain cases.

The objective of this work is to fill this gap by developing a laboratory system for 222Rn-in-water standardization. We designed and constructed a dedicated instrumentation, which allows 100% transfer of 222Rn from the primary 222Rn standard (defined solid angle method, DSA), mixing of the transferred radon with water and preparation of radon-in-water samples with traceable radon activity concentration. The system allows preparing GS and LSC radon-in-water samples thus enabling the establishment of a traceability chain to the DSA standard.

The concept of the system is based on the cryogenic transfer of 222Rn from the DSA standard to water under controlled conditions, homogenization of 222Rn in water and 222Rn-loss-free simultaneous preparation of up to six 100 ml samples for GS and up to ten 10 ml samples for LSC. During the first repeatability tests, we obtained a relative standard deviation of 0.25% on the activity concentration of the 10 LSC samples prepared. We also achieved qualitative transfer of the water to LSC cocktail with 0.25% relative standard deviation of the mass of water transferred to the LSC samples, which was evaluated by repetitive sampling tests with radon-free water. A good agreement between the calculated activity concentration (based on the DSA activity and volume measurements) and the GS and LSC sample measurements is obtained within the estimated uncertainties. The results of the proof-of-concept experiments show that we can produce 222Rn-in-water with standard uncertainty of the activity concentration better than 1% and traceable GS and LSC sources with similar standard relative uncertainty.

We will discuss the concept and design of the system, its performance in pilot tests and the obtained results. We will also address the new possibilities of this system for radon metrology, especially the possibility to compare three different 222Rn measurement techniques: DSA, LSC and GS.

Speaker: Krasimir Mitev (Sofia University St. Kliment Ohridski, Bulgaria)

82 Intercomparison Exercises for Organically Bound Tritium to Develop Reference Materials of Environmental Matrices

Authors (affiliation): Simona Zaharov (SNN-Cernavoda NPP, Romania; UPB, Romania),
L. Samson, A. Nedelcu, V. Tudorache (SNN-Cernavoda NPP, Romania)

Tritium can be found in several forms, such as gaseous (HT, HTO), liquid (HTO or organic molecules in solution) or organically bound tritium (OBT), which can become incorporated into living organisms (vegetables, animals, humans). The complexity and the probability of increasing concentrations were the promotors for the research and development of laboratory methods that enable to accurately determine the various species of tritium in the environment for public and regulatory assurance. After the improvements of analytical data, it will be possible to evaluate the behavior of tritium in the environment, focusing on potential accumulation of OBT in organisms.
The measurement of tritium in its various forms is an important key step for health and environmental risk assessment. However, even in cases where tritium monitoring of atmospheric and liquid releases is currently carried out, very few countries are measuring OBT. In Romania, OBT has become of increased interest for the Cernavoda Nuclear Power Plant (NPP), to include its analysis in a monitoring program, which is important to estimate more accurately the doses for the public.
For this purpose, the Environmental Control Laboratory of the Cernavoda NPP collaborates with other laboratories to organize intercomparison exercises at the international level for OBT analysis in different matrices of environmental samples. If the number of participating laboratories is statistically reached, the evaluation of the OBT intercomparison results can provide a few essential indicators: the homogeneity of the matrix; the repeatability and traceability of the methods; the consensus values of the exercise for tritium concentration in the combustion water and for OBT concentration in the dry matter. The stability of the matrix depends on the storage conditions and this parameter can be determined after running the OBT analysis periodically on the matrix of interest, which can be then recommended to be used as a reference material.

Speaker: Mrs Simona Zaharov (SNN-Cernavoda Nuclear Power Plant, Romania)

83 Development of Reference Material for Quality Control of Uranium Analysis in Marine Sediments

Environmental radioactivity monitoring activities are being strengthened owing to concerns about radiation pollution. Therefore, various research laboratories, institutes, and universities are conducting environmental radiation investigations around nuclear power plants (NPPs). However, the reliability of the results continues to trigger controversy in society.
This study was conducted to develop a reference material (RM) for the quality control of 238U and 234U analyses in marine sediments. The RM was prepared according to ISO Guides 31, 34, and 35. The homogeneity test of the marine sediment RM was implemented by analyzing two batch samples from ten bottles using multiple acid digestion and alkali fusion. The homogeneity was evaluated as appropriate. The reference values of 238U and 234U in marine sediment RM were 43.4 ± 0.8 Bq kg-1 and 41.8 ± 1.0 Bq kg-1, respectively. The developed marine sediment RM is expected to be useful for the development of new analytical methods for similar samples, calibration of measurement systems, and quality control.

Speaker: Ms Yoonhee Jung (KRISS, South Korea)

84 Influence of humidity on activated carbon fabrics scheduled for use in high sensitivity radon detectors

Activated carbon is widely used for short-term (few days) radon sampling with consequent measurement of the adsorbed activity by liquid scintillation counting or gamma-spectrometry. This is a bulk material that can hardly be coupled with external detectors acquiring signal during exposure (e. g. solid state nuclear track detectors, semiconductor or scintillation detectors). The use of activated carbon fabrics is promising in this direction [1]. They are thin and easy to handle material that can be easily coupled with various detectors, aiming at measuring low radon levels in the environment. Their use for long term measurements is hampered by the strong influence of temperature and humidity on radon adsorption. Recent innovation combined the reciprocal temperature dependences of radon diffusive permeation through polymer foils and that of adsorption ability of activated carbon fabrics in order to compensate the influence of the temperature [2] and to retard the influence of humidity. Still, the last cannot be fully eliminated, therefore it is necessary to study it. In this report we present results of experimental study of the influence of humidity on two kinds of activated carbon fabrics that are promising for use in high sensitivity radon detectors [2]. The materials were ACC-5092-10 and ACC-5092-20, both produced by Kynol Europa GmbH, Germany. In the first set of experiments the adsorption of water was studied by exposing a number of fully dehydrated specimens at 100% RH for different time and weighting them before and after exposure. It was found that the ACC-5092-10 reaches saturation at water content of about 24% (w/w) while ACC-5092-20 at about 55%. The equilibrium of ACC-5092-10 is reached within less than 24 h exposure, while for ACC-5092-20 more than one day is needed. After saturation is reached the water content is not increased any more, even the exposure continues one month or more. In the second set of experiments specimens of fabrics with different water content – from zero up to saturation level were coupled with solid state nuclear track detectors Kodak-Pathe LR-115/II and exposed to controlled radon concentration. The dependence of the adsorption ability on water content was studied by analyzing the net track density of detectors that were coupled with different specimens. With ACC-5092-20 a break point was observed at water content 18-20%, where the signal drops by more than one order of magnitude. This is well-known phenomena, when the occlusion of the pores by water happens. However, with ACC-5092-10 only monotonic decrease up to saturation level was observed without any indication for break point. Although the signal from dehydrated to saturated specimens decreases by factor of about 3, correction of the results for humidity is possible. We conclude that ACC-5092-10 fabrics can be used even for long-term exposures at different humidity levels.

[1] Sohrabi M. JINST 13, P11012 (2018)
[2] Pressyanov D. Sci. Rep. 12, 8479 (2022)

Speaker: Prof. Dobromir Pressyanov (Faculty of Physics, Sofia University "St. Kliment Ohridski", Bulgaria)

85 Development of soil reference material for gamma radioactivity measurement in environmental samples

A new soil reference material (RM) to improve the quality assurance and quality control of the gamma radioactivity measurement in environmental samples was developed by the Korea Research Institute of Standards and Science (KRISS). Depending on the user's request, the type and specific radioactivity of radionuclides to be included in the soil RM can be selected. In this study, the homogenized raw materials were put in the drum container and the standard solution containing the 137Cs and 60Co radionuclides was slowly sprayed into the drum container. Ten samples were randomly selected for among-bottle homogeneity and two samples were taken from each bottle for within-bottle homogeneity. The homogeneity test for the soil RM fulfilled the requirement of the ISO Guide 35. The self-absorption correction factor and the coincidence summing correction factor were calculated by the Monte Carlo N-Particle (MCNP) code and the efficiency transfer (EFFTRAN) code, respectively. In conclusion, the reference values of 137Cs and 60Co in the soil RM were determined to be 118.7 and 124.4 Bq/kg, respectively. And the expanded uncertainties of the radionuclides were around 8.0%.

Speaker: Dr Minju Lee (KRISS, South Korea)

86 Development of metal radioactive liquid reference material for the measurement of gamma and beta emitted radionuclide

Authors (affiliation): 1. Sang-Han Lee (KRISS, Rep of Korea), 2. Y. Jung (KRISS, Rep of Korea), 3. M.J. Lee (KRISS, Rep of Korea), 4. C. H. Lee (NDRI, Rep of Korea).

A metal wastes such as pipes, pumps and valves generated in large quantities in the operation of nuclear power plant and during the decommissioning process. In order to dispose of these metal wastes, it is announced that the concentration should be identified for 3H, 14C, 55Fe, 58Co, 60Co, 59Ni, 63Ni, 90Sr, 94Nb, 99Tc, 129I, 134Cs, 137Cs, 144Ce and total alpha.
The most ideal method for quality assurance to analyze the metal sample is to prepare the reference materials having same matrix composition and analyze each time using the same test procedure. However, in reality, developing a reference material using radioactively contaminated metal sample is a very difficult process in terms of sample acquisition and pretreatment. KRISS has recently developed a new liquid metal reference material that is a solution simulating an acid-dissolving 20 g of SUS-304/kg of acid and by adding radionuclides.
In addition to the metal solutions RM, research activity on the development of RM in various media developed by KRISS will be introduced.

Speaker: Dr Sang-Han Lee (KRISS, South Korea)

Source preparation techniques: 1 Oral and 2 Poster contributions

Radioactive source preparation techniques

Conveners: Lisa Karam (NIST), Nuria Navarro Ortega (CIEMAT)

87 Gravimetric deposition of microliter drops with radiometric confirmation

Authors (affiliation): 1. Denis E. Bergeron (NIST, USA), 2. Richard Essex (NIST, USA), 3. Svetlana Nour (NIST, USA), 4. Gordon A. Shaw (NIST, USA), 5. R. Michael Verkouteren (NIST, USA), 6. Ryan P. Fitzgerald (NIST, USA).

The aspirating pycnometer method for gravimetric preparation of radioactive sources routinely achieves relative mass uncertainties ≈ 0.05 % when several 10 mg to 25 mg drops of aqueous material are dispensed. To support new research into decay energy spectrometry with cryocalorimeters, our team is working to prepare sources with just 1 mg to 5 mg (< 5 μL) of aqueous material. Here, we demonstrate a manual gravimetric dispensing technique using a micropipettor modified for use with removeable microcapillaries. A well-characterized Am-241 standard reference material (SRM) was used to prepare sources for liquid scintillation counting, providing a precise radiometric check of the gravimetric dispensing.
Microliter sources prepared by direct deposition into vials containing liquid scintillation cocktail gave the same massic activity as sources similarly prepared with larger masses using the traditional aspirating pycnometer method to within the counting uncertainties (< 0.15 %). Using the same method, microliter sources were prepared on gold foils and then transferred to vials containing liquid scintillation cocktail; the massic activity of these sources was also consistent within uncertainties, but some evidence for activity losses (typically < 0.1 % of the total activity) was observed by measuring gel "placemats" upon which the target foils had been placed.
We present a detailed measurement equation for the weighing technique, including the corrections for evaporation while the microcapillary is on the ultramicrobalance and during dispensing and addressing attendant uncertainties. We continue to pursue alternative methods for drop deposition (including an inkjet-based approach) and for uncertainty characterization (including isotope dilution mass spectrometry).

Speaker: Dr Denis E. Bergeron (NIST, USA)

88 Preparation of 137Cs Sources From Nuclear Fuel Element Plate U3Si2/Al Post Irradiation for Calibrating Nuclear Instruments

Authors (affiliation): 1. Gatot Wurdiyanto (PRTSMMN – BRIN, Indonesia), 2. Aslina Br. Ginting (PRTDBBNLR – BRIN, Indonesia), 3. Hermawan Candra (PRTSMMN – BRIN, Indonesia), 4. Boybul (PRTDBBNLR – BRIN, Indonesia), 5. Arif Nugroho (PRTDBBNLR – BRIN, Indonesia), 6. Yanlinastuti (PRTDBBNLR – BRIN, Indonesia), 7. Erlina Noerpitasari (PRTDBBNLR – BRIN, Indonesia).

Since 2002, the Multi-Purpose Reactor G.A. Siwabessy (RSG-GAS) in Serpong, Indonesia has used U3Si2/Al nuclear fuel with a density of 2.96 gU/cm3. This reactor is operated using an U3Si2/Al fuel with an enrichment of 19.75 % and produce several fission products and heavy elements such as 137Cs, 134Cs, 90Sr, 235U, 238U, 234U, 236U, 239Pu, 148Th, and 143Ce. The spent fuel elements containing these radioactive elements have a very high level of radioactivity and have a very long half-life, so they cannot be disposed of in a radioactive waste storage area. However, the element of nuclear fuel still has a high enough economic value if it can be managed properly, especially 137Cs. In this paper, the source of the 137Cs is prepared from separating U3Si2/Al nuclear fuel elements so that it can be used to calibrate nuclear measuring instruments.
The separation methods of 137Cs in used fuel U3Si2/Al post irradiated was carried out using the cation exchange method using Lampung zeolite. The solvents used were 6 N HCl and HNO3 as a carrier. The preparation of the 137Cs source solution was carried out gravimetrically using a calibrated semi-micro balance. There were 15 point sources of 137Cs that prepared. The activity and impurity measurements were carried out using a gamma spectrometer, which was calibrated with a standard sources of 152Eu, 60Co and 137Cs that have traceability to the SI.
The results of the measurement of the 137Cs solution were very good with a homogeneous level below 1.5 %, and there was no significant impurity detected above 0.05% of the 137Cs. The measured specific activity values of 137Cs are 84.310 Bq/g with an expanded uncertainty of 3.8%, at k=2. From these results, the 137Cs source solution derived from the separation of spent nuclear fuel can be used as a secondary standard source to calibrate nuclear measuring instruments.

Speaker: Mr Gatot Wurdiyanto (BRIN, Indonesia)

P64-SP-Gatot-Wurdiyanto-Indonesia-BRIN.docx

89 Source preparation for activity measurement of Po-210 by transition-edge sensor

Authors (affiliation): 1 Yasushi Sato (NMIJ, AIST, Japan), 2 Takahiro Kikuchi (DTRI, AIST, Japan), 3 Ryan Smith (The University of Tokyo, Japan), 4 Akira Sato (DTRI, AIST, Japan), 5 Fuminori Hirayama (DTRI, AIST, Japan), 6 Hisashi Nakagawa (NMIJ, AIST, Japan), 7 Tomoya Irimatugawa (NMIJ, AIST, Japan), 8 Rio Furukawa (NMIJ, AIST, Japan), 9 Chihiro Shimodan (NMIJ, AIST, Japan), 10 Hideki Harano (NMIJ, AIST, Japan), 11 Hirotake Yamamori (DTRI, AIST, Japan), 12 Hiroyuki Takahashi (The University of Tokyo, Japan).

When lead is used as a radiation shield, the shielding itself can generate background radiation as a consequence of the presence of the radioactive Pb-210 isotope. To reduce this background radiation, it is important to selectively source the raw material based on measuring its activity. Liquid scintillation counting can provide accurate activity data but requires dissolution of the lead in a mixture of acetic acid and hydrogen peroxide. The present work devised a means of measuring the radioactivity of lead specimens without dissolution using a transition-edge sensor (TES), a cryogenic detector that responds to radiation based on increases in temperature. A TES in contact with a lead specimen was able to detect alpha particles emitted from Po-210, one of the progenies of Pb-210. The present TES, fabricated by DTRI, AIST (Device Technology Research Institute, National Institute of Advanced Industrial Science and Technology), is operated at approximately 100 mK and can be combined with a radiation absorber having a heat capacity from several to approximately 100 pJ/K. This device is also physically strengthened by incorporating a SiO2/SixNy/SiO2 tri-layer membrane for a heavy absorber.1)
Lead radiation absorbers that concurrently act as radiation sources having masses from 2 to 20 mg were fabricated by first flattening lead beads (Fujifilm Wako Pure Chemical Corporation, part number 125-05762) using a vice. Each lead specimen was subsequently cut out using an ultrasonic device (Nihon Seimitsu Kikai Kosaku Co., Ltd.) and shaped with a micro knife (Micro Support Co., Ltd.) under a microscope equipped with an LCD monitor. Each lead radiation source was then affixed to a 250 × 250 mm TES attached to a 1 × 1 mm tri-layer membrane using a micro manipulator (Micro Support Co., Ltd.). Stycast 2850 GT with a 9M catalyst (Henkel Corporation.) was used as the adhesive agent. A few lead samples having varying masses were attached to TES devices that could be operated simultaneously with a microwave-based readout. In future work, the optimum mass for the lead radiation source to allow activity measurements will be determined based on the estimated energy resolution and count rates.

1) T. Kikuchi, G. Fujii, R. Hayakawa, R. Smith, F. Hirayama, Y. Sato, S. Kohjiro, M. Ukibe, M. Ohno, A. Sato, H. Yamamori, Gamma-ray transition edge sensor with a thick SiO2/SixNy/SiO2 membrane, Applied Physics Letters (2021) 119, 222602

Speaker: Dr Yasushi Sato (National Metrology Institute of Japan, Japan)

3:55 PM Coffee Break

Source preparation techniques: 1 Oral contribution

Radioactive source preparation techniques

Conveners: Lisa Karam (NIST), Nuria Navarro Ortega (CIEMAT)

90 Novel production method for traceable surface sources by aluminium functionalisation

During decommissioning, the initial cartography of all surfaces is crucial for identifying potential future waste based on its radiation level. Contamination detectors should be calibrated in terms of emission flux or Bq.cm-2 using suitable surface sources. Current standard sources, complying with ISO 8769 (Reference Sources-Calibration of Surface Contamination Monitors), lack representativeness since they are only made of aluminium and have a limited surface area. This research seeks to produce flexible, traceable surface sources for alpha and beta emitters with low radiation self-absorption. While the existing sources are produced by adsorption on the aluminium surface, we aim to have strong chemical bonds due to the grafting on the surface. A novel functionalisation strategy involving spacer chemicals was developed to provide these sources. We have studied two substrate types: polymeric sources that can be molded into complex shapes and flexible aluminium foils that can be compared to existing ISO 8769 sources. This contribution will focus on aluminium substrate functionalisation . It involved choosing bi-functional compounds that can bind to a radionuclide on one end and be grafted onto aluminium with the free functional group of the compound on the other end. Because the radioactivity is chemically bound to their surfaces, these sources are meant to be non-contaminating and easy to use on-site. Our calibration sources can also be used to assess the detector's performance in front of a curved radioactive surface. Three bi-functional compounds were identified and the three main surface functionalisation steps were optimized. The first step is cleaning, to remove all the residues from the substrates. Then etching proceeded to release hydroxide functions. Next, the etched samples are immersed in the bi-functional compound solution. The influence of the reaction time, temperature, and drying conditions was studied. After the functionalisation, the inactive samples were characterised. The Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy has demonstrated that the ligand molecules are successfully grafted to the aluminium surface. The Scanning Electron Microscopy (SEM) images revealed a change in surface morphology following each functionalisation step. In addition, X-ray Photoelectron Spectroscopy (XPS) was utilised for complementary analysis. Finally, radionuclide binding experiments were conducted with Eu-152 as trivalent Eu is an excellent chemical analog for trivalent actinides such as Am-241. Liquid scintillation counting and autoradiography were used to quantify the radionuclides bound to the grafted surface and check the uniformity of the sources.

Speaker: Ms Dilan Tuzun (Université Paris-Saclay, CEA, List, LNHB, Saclay, France)

91 END OF CONFERENCE DAY 3

Speaker: Aurelian Luca (IFIN-HH)

7:00 PM CONFERENCE DINNER at RESTAURANT PESCARUS

Buses departure from Hotel Radisson Blu at 18:30

Thursday, March 30

Liquid scintillation counting techniques: 4 Oral and 1 Poster contributions

Liquid scintillation counting measurements

Conveners: Karsten Kossert (Physikalisch-Technische Bundesanstalt), Philippe Cassette (Sofia University st. kliment ohridski)

92 Uncertainties in TDCR measurement revisited: contribution of optical effects

In the Triple to Double Coincidence Ratio (TDCR) method in Liquid Scintillation Counting, the detection efficiency is calculated from the value of a free parameter describing the intrinsic light yield of the counting system. This model is generally based on a Poisson distribution of the number of photoelectrons detected: if an energy E is transferred to the liquid scintillator, an average of m photoelectrons is detected. The detection efficiency for one photodetector, , is obtained from the complement of the non-detection efficiency, which is the probability to get zero photoelectron when a mean value of m is expected. In the classical free parameter model, m is a constant. Nevertheless, some variability of m could be expected from the following effects:
• With clear LS glass vials, the light emission somewhat depends on its place of emission: the scintillation light has to travel towards the photodetectors, with refractive index steps and, because of internal reflexions, part of the light emitted close to the vial walls could be trapped inside the LS source.
• The photocathode response of the PMTs is not homogeneous, which is due to the variation of its quantum efficiency and photoelectron collection probability.
Then, m becomes a random variable and the distribution of the photoelectrons becomes a compound Poisson distribution, with a random variable as mean value, and characterised by a probability density function depending on the photoelectrons detection process. A preliminary evaluation of the importance of this phenomena can be done by considering the mean value of m, and its associated variance u2(m). The detection efficiency, can still be derived from the non-detection probability by considering the mean value of m, but now, its variance introduces an uncertainty term, where the standard deviation of the detection efficiency is u(m) multiplied by exp(-m). When the number of photoelectrons is large, the exponential term is small and the standard deviation of  is negligible. This is not the case when measuring low-energy radionuclides like 3H or 55Fe, and when the detection efficiency of the counter is reduced (e.g., for finding out the optimal value of the kB parameter).
This paper explores the implications of the variance of the free parameter, which were, to our knowledge, never considered previously in the uncertainty budget of TDCR measurements. Three kinds of PMTs are considered: BURLE 8850 and Hamamatsu 7600 and H11934 square tubes. The non-uniformity of these later PMTs, used in miniature TDCR counters, have been experimentally quantified. A Monte Carlo approach is used to evaluate the uncertainty due to photocathode non-homogeneity in the measurement of 3H, 14C, 63Ni and 90Sr by the TDCR method under various counting conditions. Eventually, an evidence of this source of uncertainty is also presented, from the analysis of the experimental standard deviation of the counting rate observed during tritium measurement with reduced detection efficiencies. We demonstrate that the variance of the detection efficiency induces a distortion of the Poisson distribution of the observed disintegration events.

Speaker: Philippe Cassette (Sofia University st. kliment ohridski)

93 Activity standardization of 60Co and 106Ru/106Rh by means of the TDCR method and the importance of beta spectrum

This paper presents the results obtained with two primary techniques (4pibeta-gamma and TDCR methods) in the case of the activity standardization of two ߯ emitters (60Co and 106Ru/106Rh). In particular, the impact of the calculated ß-spectra implemented for the activity calculation with the TDCR statistical model is addressed.
Cobalt-60 (T½ ~ 5.2711 (8) a) disintegrates by ߯ emission to excited levels of 60Ni followed by two coincident ß-transitions (1173 keV and 1332 keV). Ruthenium-106 disintegrates through ߯ emission with max. beta energies of 39.4 keV (T½(106Ru) ~ 371.5 (21) d). The daughter radionuclide 106Rh also disintegrates by ߯ emission with maximum ß-energies ranging from 144 keV to 3.5 MeV (T½(106Rh) ~ 30.1 (3) s) to the ground state (~78.8%) and to 36 excited levels of 106Pd. The main ­gamma-photon emissions are: ~ 512 keV (~ 20.5%), ~ 622 keV (~ 9.9%) and ~ 1050 keV (~ 1.5%).
For both radionuclides, the TDCR method was applied using a stochastic approach based on the Geant4 simulation code for the calculation of energy deposition in the liquid scintillation vial. As already investigated in [1], the assessment of activity is sensitive to the calculated ß-spectra introduced in the statistical modelling and more accurate results are obtained when atomic screening and exchange effects [2] are considered in the spectrum computation.
The TDCR results were compared to those obtained with the 4pibeta-gamma coincidence method. The measurements of 60Co were carried out by means of a 4pibeta(PC)-gamma coincidence system using a proportional counter (CH4 at atmospheric pressure) in the beta-channel. In the case of 106Ru/106Rh, the measurements were performed using a 4pibeta(LS)gamma coincidence detection system equipped with a 3-PMTs TDCR set-up in the beta-channel and by setting a detection threshold to avoid counting from 106Ru decay emission. The TDCR method was carried out by measuring both 106Ru and 106Rh decay emission using the same 3-PMTs apparatus applied in the LS beta-channel.
For both radionuclides, a better agreement is obtained when atomic screening and exchange effects are considered in the computation of ß-spectra used in the TDCR modelling. Without those corrections, the deviation between both primary methods is about 0.2% for 60Co and about 0.4% for 106Ru/106Rh. These results confirm those describes in [1] in the case of 60Co.
1. Kossert K. et al., Activity determination of 60Co and the importance of its beta spectrum, ARI 134, 212 (2018).
2. Mougeot X., Bisch C., Consistent calculation of the screening and exchange effects in allowed ß- transitions. Physical Review A 90, 012501 (2014).

Speaker: Christophe BOBIN (LNE-LNHB)

94 Measurement of the activity and determination of the half-life of 225Ac at POLATOM.

Authors and affiliations: R. Broda 1, T. Ziemek 1, J. Marganiec-Gałązka 1, M. Czudek 1, K. Kossert 2, A. Listkowska 1, E. Lech 1, Z. Tymiński 1
1 NCBJ Radioisotope Centre POLATOM, A. Sołtana 7, 05-400 Otwock, Poland
2 Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116, Braunschweig, Germany

The applications of an alpha emitter 225Ac in targeted cancer therapy are being investigated at the NCBJ RC POLATOM. Thus, a method for absolute measurements of 225Ac activity in equilibrium with its progeny was developed. Measurements were performed using the triple-to-double coincidence ratio (TDCR) method in two different TDCR counters. The parameter TDCR of each measured source was determined. The counting efficiency of α particles with energy above 5 MeV in a liquid scintillator was assumed to be 100%. The theoretical counting efficiency of the beta branches was calculated using the free parameter model (Broda et al., Metrologia 44, 2007, S36-S52). The shape of the beta spectra was taken from calculations with the BetaShape program (Mougeot, Phys. Rev. C91, 2015, 055504). The total efficiencies of 225Ac in equilibrium with its progeny in T and D coincidence channels were calculated by the MetroActivityLSC program for various values of the free parameter and presented as functions of the TDCR parameter. The counting efficiency for individual sources was determined by interpolation from the above functions. The final massic activity of 225Ac solution was determined as the arithmetic mean of activity of all measured sources. In calculation of counting efficiency by Kossert et al. (ARI 156, 2020, 109020) with the MICELLE2 program, gamma transitions that occur directly after beta decays of 213Bi, 209Tl and 209Pb were taken into account. The massic activity determined in this case differed by 0.06%. The measurement result and an 225Ac solution were sent to the international reference system SIR in BIPM for a comparison. The decay half-life of 225Ac was also determined with high precision. One 225Ac source in an Ultima Gold scintillator was measured in one TDCR counter for a total of 9.9 hours over 43 days. The arithmetic mean of the measurements in channel T and D of 9.9139(63) days was taken as the final result, which was consistent with the values of 9.920(3) days and 9.9179(30) days reported by Pommé et al. (ARI 70, 2012, 2608-2614) and Kossert et al. (ARI 156, 2020, 109020), respectively. For validation, the 225Ac half-life was also determined in a scintillation counter with NaI(Tl) crystal. One source was measured for a total of 16.2 hours over 85 days and the result of 9.942(26) days was obtained.

Speaker: Dr Ryszard Broda (National Centre for Nuclear Research Radioisotope Centre POLATOM, Poland)

95 Primary standardization of Ac-225 at NRC

A solution of Ac-225 was standardized by NRC using the triple-to-double coincidence ratio (TDCR) method. The counting efficiencies were calculated assuming a counting efficiency of 100% for alpha decays and those calculated using the MICELLE2 monte carlo code for beta decays and was approximately 500% for the NRC TDCR system. The relative uncertainty for the activity concentration was determined to be 0.25% and this agreed with measurements performed using gamma spectroscopy and a predicted calibration factor for the Vinten Ion Chamber as calculated using an EGSnrc model, implementing radioactive decay. Finally, the half life of Ac-225 was determined from long term measurements using ion chambers and liquid scintillation counting. The NRC measured half life for Ac-225 was found to be 9.909(6) days and is consistent within an expanded uncertainty coverage of k=2 with the most recent [1,2] measurements of this decay parameter.

References:
[1] Pomme et. al., Appl.Radiat.Isot. 70, (2012) 2608-2614.
[2] Kossert et. Al, Appl.Radiat.Isot. 156 (2020) 109020.

Speaker: Raphael Galea (National Research Council of Canada)

96 Liquid scintillation counting of internal conversion electrons for the quantification of 109Cd activity using a 3 photomultipliers tubes system and a specific energy distribution unfolding method

109Cd is an electron-capture radionuclide used to calibrate gamma spectrometer in the low energy domain thanks to its 88 keV gamma-rays. Therefore, it is critical to produce standard solutions of 109Cd with a high accuracy. However, the specific decay scheme of 109Cd is a challenge for metrology. It indeed disintegrates by electron capture into 109mAg whose metastable state makes it impossible to implement 4πβ-γ coincidence or anti-coincidence techniques. One possibility is to count internal conversion electrons (CE) from the isomeric transition of 109mAg. Competing with the 88 keV gamma rays transition, these electrons are generated with an emission probability equal to 0.9634(5) [1]. The energies of the conversion electrons are of 62.5 keV for the K shell, and between 84.2 keV and 88 keV for the L, M, N shells, while Auger electrons and x-rays are all with energies below 25.5 keV. Moreover, the 88 keV gamma rays interact mainly by Compton scattering in the scintillating liquid , depositing a maximum energy of 22.5 keV. Assuming a 100% detection efficiency of these conversion electrons in a liquid scintillation (LS) counter, it is possible to separate conversion electrons (> 62.5 keV) from the other components (<25.5 keV) by analysing the energy distribution. This approach has originally been developed by the PTB in 2006 [2].
In the framework of the CCRI(II)-K2.Cd-109.2021 international key comparison , the BIPM has implemented this approach using the 3-photomultiplier tubes system of the ESIR, an international comparator of primary standards under development [3]. Much of the uncertainty comes from the overlap between the peak of the conversion electrons peak and lower energy peak due to the other decay products. The energy resolution of the LS system is therefore the most critical parameter to get an accurate measurement. The present study demonstrates the advantage of summing the 3 PMTs signal to enhance the energy resolution and then reduce the peak overlap. In addition, the energy distribution has been processed by a specific unfolding method to properly separate the spectral components. Thanks to the optimization introduced in this study, an activity estimation has been performed with a relative standard uncertainty of 0.5 %.
[1] Bé M-M et al. 2016 Table of Radionuclides. vol. 8
[2] Kossert K et al. 2006 Applied Radiation and Isotopes 64 1031–5
[3] Coulon R et al. 2022 Journal of Radioanalytical and Nuclear Chemistry

Speaker: Dr Romain Coulon (BIPM)

10:25 AM Coffee Break

Liquid scintillation counting techniques: ICRM WG Meeting

Liquid scintillation counting measurements

Conveners: Karsten Kossert (Physikalisch-Technische Bundesanstalt), Philippe Cassette (Sofia University st. kliment ohridski)

97 A Personal Evaluation of Atomic and Nuclear Decay Data Over the Years; invited talk presented by Dr. Alan L. Nichols (Department of Physics, University of Surrey, Guildford, United Kingdom; Manipal Academy of Higher Education, Manipal, Karnataka, India)

Speaker: Dr Alan L. Nichols (Department of Physics, University of Surrey, Guildford, United Kingdom; Manipal Academy of Higher Education, Manipal, Karnataka, India)

Nuclear decay data: 2 Oral and 2 Poster contributions

Nuclear decay data and their use in radionuclide metrology

Conveners: Mark Kellett (CEA\LNE-LNHB), Alan L. Nichols (Department of Physics, University of Surrey, Guildford, United Kingdom; Manipal Academy of Higher Education, Manipal, Karnataka, India)

98 Absolute emission intensities of the gamma -ray for 224Ra and 212Pb progeny and half-life of 212Pb decay

In 2020, the National Institute of Standards and Technology (NIST) reported on a primary activity standardization of 224Ra in equilibrium with its progeny. Subsequently, measurements of the absolute emission intensity for its main gamma ray were reported in the contexts of a bilateral comparison with the National Physical Laboratory (NPL). More recently, NIST has standardized 212Pb in equilibrium with its progeny and included an improved approach to the propagation of decay data uncertainties. Here, the high-purity germanium (HPGe) gamma-ray spectrometry data collected during those standardizations are used to assess the absolute photon emission intensities for the main gamma rays of 224Ra, 212Pb, and their progeny. In addition, the half-life for 212Pb, was measured using several HPGe detectors, ionization chambers, and a well-type NaI(Tl) detector.
The measured decay data were compared with the evaluated values for 212Pb reported by K. Auranen and E.A. McCutchan Nuclear Data Sheets 168, 117 (2020) as part of the Evaluated Nuclear Data Structure File (ENSDF, available at https://www.nndc.bnl.gov/) and by A.L. Nichols as part of the Decay Data Evaluation Project (DDEP) evaluated in 2001 and reevaluated in 2004 and 2010 (available in the Laboratoire National Henri Becquerel (LNHB) website http://www.lnhb.fr/nuclear-data/nuclear-data-table/).
Agreement between the absolute gamma-ray emission intensities determined by NIST and NPL was found. Most measured photon emission intensities are within 2 % of the evaluated values, except for gamma rays with low emission intensities, for which the observed differences were larger. There is an improvement in the precision quoted for many of the observed gamma rays. The measured half-life values were compared with the values used in the DDEP evaluation and the recommended value in the ENSDF evaluation. The measured values agree with the tabulated ones within the measurement uncertainties.

Speaker: Dr Leticia Pibida (NIST (USA))

99 New DDEP recommendations for the radioactive decay scheme of 137Cs

Caesium-137 is a non-naturally occurring fission product, in particular one of the many radionuclides produced in uranium-based nuclear reactors. It decays through β- transitions, populating both the ground state and the first two excited states of 137Ba. With a half-life of approximately 30 years, and a well-known and intense 662 keV gamma-ray emission, this radionuclide is relatively easy to detect in the environment as an unambiguous trace of human activity. In addition, due to its simple decay scheme and limited number of emitted radiations, the 137Cs is widely used in laboratories as a gamma calibration standard.

The decay of the 137Cs has been intensively investigated since the early days of Nuclear Physics, with more than one hundred studies reported over the years. However, despite such abundant literature, some ambiguities remain on the decay parameters for this important radionuclide. In particular, the previous DDEP evaluation [1] has pointed out inconsistencies between the numerous half-life measurements, leading to an evaluated value (T1/2 = 30.05 ± 0.08 a) having a much larger uncertainty than the most precise measurement (T1/2 = 30.174 ± 0.011 a) [2]. A comparable evaluated value (T1/2 = 30.08 ± 0.09 a) is also recommended by in the latest ENSDF evaluation [3] confirming the complexity of the half-life evaluation of 137Cs.

In the scope of the DDEP project, a complete re-evaluation of the 137Cs decay scheme has been performed, taking advantage of the measurements [4,5,6] published after the above-mentioned evaluations. A new evaluated half-life, T1/2 = 30.018 ± 0.022 a, is recommended and a revision of beta decay branching ratios is proposed, leading to a reevaluation of the 662 keV gamma transition probability. The consistency of the deduced decay scheme will be discussed as well as the needs for new measurements.

References
[1] R.G. Helmer, V.P. Chechev, LNE-LNHB CEA/Table of Radionuclides (2006)
[2] L.A. Dietz, C.F. Pachucki, Journal of Inorganic Nuclear Chemistry 35 (1973) 1769-1776
[3] E. Browne, J.K. Tuli, Nuclear Data Sheets 108 (2007) 2173-2318
[4] E. Bellotti, et al., Physics Letters B 710 (2012) 114-117
[5] M.P. Unterweger, R. Fitzgerald, Applied Radiation and Isotopes 87 (2014) 92-94
[6] F. Juget, et al., Applied Radiation and Isotopes 118 (2016) 215-220

Speaker: Sylvain Leblond (LNE-LNHB)

100 A New Evaluation of the Decay Data for Ho-166

The short-lived (T1/2 = 26.801(2) h) beta- - emitting radionuclide has been investigated for a wide range of therapeutic medical applications over the past several decades (c.f., Klaassen et al 2019). The safe and effective use of these types of radionuclides for therapy requires accurate dose assessments, which in turn require the most accurate nuclear decay data as input to the calculations. The most recent evaluations of the nuclear and atomic data or 166Ho were performed by the Decay Data Evaluation Project (DDEP) in 2004 (Bé et al. 2005) and by the Evaluated Nuclear Structure Data File (ENSDF) in 2008 (Baglin 2008). Since that time, however, several new measurements of the photon emission rates and decay half-life have been made, many of which were prompted by the EURAMET MetroMRT (Bobin et al. 2019) with the express goal of improving the decay data necessary for dosimetry calculations.
This paper presents the results of a new decay data evaluation of 166Ho that includes 5 new sets of measurements of photon emission rates and the half-life and updates the atomic and beta decay data based on these results and using the latest available calculational models. The result is a more robust recommended half-life value of 26.801(2) h and more precise emission probability values for the 17 gamma rays observed in the decay scheme. Comparisons with previously recommended values are provided, as are suggestions for future measurements.

References
Klaassen, N.J.M., Arntz, M.J., Gil Arranja, A., Roosen, J., and Nijsen, J.F.W., “The various therapeutic applications of the medical isotope holmium-166: a narrative review”, Eur. J. Nucl. Med. Molecul. Imaging Radiopharmacy and Chemistry, (2019). https://doi.org/10.1186/s41181-019-0066-3
Bé M.-M., Chisté V., Dulieu C., Browne E., Chechev V., Kuzmenko N., Helmer R., Nichols A., Schönfeld E., Dersch R., “Table of Radionuclides Volume 2 - A = 151 to 242”, BIPM Monographie 5 – Volume 2, https://www.bipm.org/documents/20126/53814638/Monographie+BIPM-5+-+Volume+2+%282004%29.pdf/047c963d-1f83-ab5b-7983-744d9f48848a?version=1.3&t=1617184334160&download=true (2005).
Baglin, C., Nuclear Data Sheets, 109, 1103 (2008).
Bobin, C., Bouchard, J., Chisté, V., Collins, S.M., Dryák, P., Fenwick, A., Keightley, J., Lépy, M.-C., Lourenço, V., Robinson, A.P., Sochorová, J., Šolc, J., and Thiam, C., “Activity measurements and determination of nuclear decay data of 166Ho in the MRTDosimetry project”, Appl. Radiat. Isot., 153 (2019). https://doi.org/10.1016/j.apradiso.2019.108826

Speaker: Dr Brian Zimmerman (NIST, USA)

101 On-site measurement of C-11 and F-18 half-life by TDCR counting

The triple to double coincidence ratio (TDCR) liquid scintillation measurement technique is commonly used in national metrology institutes (NMIs) to perform standardization of pure beta emitters. LNE-LNHB has developed two new portable TDCR devices. Such portable instrumentation gives end-users access to a reference measurement method that can be used for a large number of radionuclides. It addresses a wide range of industrial and medical applications for radionuclide metrology such as calibrating solutions with short-lived radionuclides, preventing radioactive source transportation, and performing on-site comparisons to promote radionuclide metrology harmonization.
The standardization of 11C and 18F measurement devices, such as a dose calibrator, is necessary in radiopharmaceutical production sites. Due to their short half-life, a primary on-site calibration is more interesting for the laboratory. However, impurities in the radiopharmaceutical solution must be checked in such a context. While this is easily done in the case of gamma emitters, it is much more complicated for pure beta emitters, for example. One solution is then to follow the radioactive decay of the solution in order to quantify possible impurities. In this work, we present new half-life measurements of 11C and 18F decays performed at the Orsay Hospital in the CEA/SHFJ laboratory (France). These measurements were carried out by liquid scintillation using two custom portable micro-TDCR and mini-TDCR devices. The measured data were analysed to evaluate the half-life of these two radionuclides as accurately as possible, and those for count rates above 400,000 s-1 until almost complete decay of the radionuclide. The measured half-lives were determined to be 20,333 (7) min for 11C and 1,8287 (2) h for 18F. The former result is more precise by a factor of three compared to DDEP recommendation of 20,361 (23) min. The latter falls in the most precise available measurements as the DDEP recommended value is 1,82890 (23) h. In this paper, the results and corresponding uncertainty budgets will be described precisely. Accidental coincidence correction and background influence will be discussed in detail. Indeed, these two parameters were identified as the major contribution for such on-site measurements. A review of the half-life data and the impact of its measures will also be discussed.
Finally, an evaluation of the sensitivity to impurities will be carried out in order to define the detection capabilities of such an on-site measurement technique.

Speaker: Benoit Sabot (LNE_LNHB (France))

12:50 PM Lunch Break

102 OPTIONAL: Visit to IFIN-HH (Ionizing Radiation Metrology Laboratory, ELI-NP), with Coffee Break included

Nuclear decay data: 3 Oral contributions and ICRM WG Meeting

Nuclear decay data and their use in radionuclide metrology

Conveners: Mark Kellett (CEA\LNE-LNHB), Alan L. Nichols (Department of Physics, University of Surrey, Guildford, United Kingdom; Manipal Academy of Higher Education, Manipal, Karnataka, India)

103 Liquid scintillation efficiencies, gamma-ray emission intensities, and half-life for Gd-153

Authors (affiliation): Denis E. Bergeron 1, Jeffrey T. Cessna 1, Ryan P. Fitzgerald 1, Lizbeth Laureano-Pérez 1, Leticia Pibida 1, Brian E. Zimmerman 1
(1 NIST, USA)

Gadolinium-153 decays 100 % by electron capture to several excited levels of Eu-153.Applications in nuclear medicine and in gamma-ray spectrometry calibrations require improved nuclear decay data for Gd-153.Several studies have now established that the exact electron capture branching is uncertain, with discrepant data evaluations estimating anywhere from 0 % to 4 % probability for electron capture directly to the Eu-153 ground state (i.e., the ϵ0,0 transition).

NIST recently measured a solution of 153GdCl3 in HCl by live-timed 4πβ(LS)-γ(NaI(Tl)) anticoincidence counting (LTAC) and submitted an ampoule to the International Reference System (SIR) as part of the BIPM comparison BIPM.RI(II)-K1.Gd-153[1]. As part of this measurement campaign, gravimetrically-related sources were measured by liquid scintillation counting, including triple-to-double coincidence ratio (TDCR) counting, providing a set of LTAC-based empirical LS efficiencies against which calculated efficiencies could be benchmarked. Calculated TDCR efficiencies are particularly sensitive to the adopted electron capture branching scheme and the experimental data are clearly more consistent with a scheme that excludes the ϵ0,0 transition.

Linked sources were measured with calibrated HPGe and Si(Li) detectors to determine absolute emission intensities for the main γ rays (Iγ). These results were generally consistent with the recent report from Shearman et al. [2] and support a decay scheme without the ϵ0,0 transition.For the 97.4 keV γ ray, we found Iγ = 0.3022(24), consistent with Shearman and approximately 3.4 % higher than the DDEP evaluated value. For the 69.7 keV γ ray, we found Iγ = 0.0255(4), significantly higher than previous reports. Finally, new half-life measurements were acquired over up to 3 half-lives with ionization chambers, a well-type NaI(Tl) detector, and a HPGe detector.

[1] C. Michotte et al., Metrologia, 58, 06027 (2021).
[2] R. Shearman et al., EPJ Web of Conferences,146, 10008 (2017).

Speaker: Denis E. Bergeron (NIST (USA))

104 Determination of the 68Ga half-life

Gallium-68 is a short lived (T1/2 = 67.83 (20) min), positron-emitting radionuclide that is commonly used in the diagnosis of prostate cancer via positron emission tomography (PET), along with other diagnostic techniques. Due to its medical relevance, the accuracy of its half-life is of great importance.

There have been at least 12 determinations of the 68Ga half-life, occurring from 1960 to 2016. However, these determinations continue to result in a discrepant dataset [1]. This discrepancy has resulted in a relative standard uncertainty of 0.29 % on the evaluated half-life. The National Physical Laboratory (NPL) previously determined a half-life value in 1971 using an ionisation chamber, whilst this value agreed with the current half-life it was excluded from the final analysis in Kuzmenko, 2019 [1]. To aid in the resolution of this discrepant dataset and lead to an improvement in the accuracy and precision of the evaluated half-life, the National Physical Laboratory has performed a new half-life campaign and compared results against the previous literature.

Samples containing 68Ga were measured on both of the NPL secondary standard ionisation chambers, along with a high-purity germanium gamma spectrometer, over a period of more than 15 half-lives.

The resulting half-life from the ionisation chamber datasets was determined to be 67.801 (43) min, which is in agreement with the previously derived NPL value from 1971 (67.80 (8) min), along with the current evaluated half-life of 67.83 (20) min.

[1] Kuzmenko, N. K., 2019, Updated decay data evaluation for 68Ga, Appl. Radiat. Isot., 152, 188-192.

Speaker: Ms Natasha Ramirez (National Physical Laboratory, United Kingdom)

105 Measurement of the absolute gamma emission intensities from the decay of 166Ho

Authors: Marco Capogni 1,*, Aldo Fazio 1, Maria Vaccaro 2 and Pierino De Felice 1
Affiliation:
1 Istituto Nazionale di Metrologia delle Radiazioni Ionizzanti (INMRI)-ENEA
C.R. Casaccia - Via Anguillarese 301 I-00123 Roma, Italia;
2 University of Rome “La Sapienza”- Department of Physics – P.le Aldo Moro 2, I-00185, Rome, Italy

Holmium-166 is a radionuclide of interest in medical treatments both for diagnostics (imaging) and therapeutic applications thanks to its peculiar decay scheme characterized by beta and gamma emissions with the main gamma-ray of 80.5725(13) keV which makes it suitable for SPECT (Single Photon Emission Computed Tomography) diagnosis. In recent therapy, tiny particles called microspheres filled with 166Ho are delivered directly to the tumour site by a catheter. The main gamma-ray can be used to monitor by SPECT the delivery of the 166Ho radiopharmaceutical to the location of the cancer in the organs, in particular for treatment of liver diseases. This radionuclide has also paramagnetic properties that makes it possible to be used in magnetic resonance imaging (MRI).
The Italian National Institute of Ionizing Radiation Metrology (INMRI) belonging to ENEA, and located in the Casaccia Research Centre near Rome, developed before the covid-19 pandemic a primary standard of 166Ho by using the absolute technique of Triple-to-Double Coincidence Ratio (TDCR). The 166Ho absolute gamma emission intensities were obtained by high energy resolution gamma-ray spectrometry performed on the ENEA-INMRI HPGe detector calibrated by the new 166Ho standard and also by other ENEA-INMRI gamma-emitter standards. The new set of gamma emission intensities, Igamma, for 166Ho was then compared with the values published in the literature. The new set was also communicated to the DDEP (Decay Data Evaluation Project) Working Group to improve the quality of nuclear data for such kind of radionuclide.

Speaker: Marco Capogni (ENEA)

106 ICRM WG Meeting (ND)

Speakers: Alan L. Nichols (Department of Physics, University of Surrey, Guildford, United Kingdom; Manipal Academy of Higher Education, Manipal, Karnataka, India), Mark Kellett (CEA\LNE-LNHB)

107 END OF CONFERENCE DAY 4

Speaker: Aurelian Luca (IFIN-HH)

4:17 PM Coffee Break

108 Meeting of the Decay Data Evaluation Project (DDEP) - Not included in ICRM 2023 Agenda

Speaker: Xavier Mougeot (CEA-LNHB)

Friday, March 31

Low-level measurement techniques: 3 Oral and 6 Posters contributions

Low-level activity measurements

Conveners: Begoña Quintana Arnés (Universidad de Salamanca), Dirk Arnold (Physikalisch-Technische Bundesanstalt)

LLMT-WG-SESSION-agenda.pdf

109 ONLINE ANALYSIS OF GAMMA-RAY SPECTRUM BY SPECTRAL UNMIXING

Authors (affiliation): Paul Malfrait (IRSN, France), Jérôme Bobin (CEA, France), Anne de Vismes-Ott (IRSN, France).

In the context of environment surveillance, more precisely in the framework of the air monitoring, we aim at (i) reducing the time between the sampling and the detection of radionuclides in the samples and (ii) get a precise estimation of the activity in the sample we analyse (even at low-level). To achieve this, we focus on a full spectrum analysis algorithm on gamma-ray spectrum obtained on HPGe detectors.
The full spectrum analysis is proven to perform better than the usual peak-based analysis as viewed in Xu et al. (2020, 2022), lowering the detection limits and estimating the activity of the radionuclide which activity is at the mBq level. In Malfrait et al. (2022) we achieved to detect the activity of low-level radionuclide earlier thanks to temporal analysis of the gamma-ray spectra. In a nutshell, we split the one-week measurement in multiple short duration ones. This allows us to estimate the activity of the radionuclides earlier than before as the analysis is carried out during the measurement. The model uses the joint analysis of the different time segments and the decay model to estimate the activity in the sample.
Speeding up gamma-ray spectrum analysis mandates processing increasingly smaller and therefore more numerous time intervals at the cost of dramatically increasing the computation time. To that purpose, and building upon Malfrait et al. (2022), we first introduce an online temporal full spectrum analysis algorithm to process gamma-ray spectra. Such a procedure allows to update the radionuclides' activity each time a new measurement is available. We show that the proposed online algorithm allows for a faster processing of the sample. More precisely, the detection of Cs-137 at trace level (few µBq/m3, namely few millibecquerel per sample) can be reached one day after the sample has been collected, much faster than the 8-day delay in routine procedure and 4 days with the method proposed in Xu et al. 2020, 2022).

Speaker: Mr Paul Malfrait (IRSN, France)

110 Low-level activity determination of 14C from marine shells by the CIEMAT/NIST method

Authors: Begoña Quintana 1, María Zurrón 1, David Borrego-Alonso 1, Nuria Navarro 2, Eduardo García-Toraño 2
Affiliation: 1 Universidad de Salamanca, Spain, 2 CIEMAT, Spain.

14C dating of actual marine records as shells gives an essential insight in the CO2 Ocean intake, which has a crucial impact on the greenhouse effect and, therefore, in the global climate change. Shells are mainly composed by carbonates, which requires a chemical carbon extraction process that synthetizes benzene, highly immiscible, when low-level-background liquid scintillation counting (LSC) is used to determine 14C. However, 14C standard solutions are not easily available. At that point, a primary radiometric method as CIEMAT/NIST solve this drawback and, at the same time, gives us the advantage of avoiding the use of a secondary standard.
In this work, the CIEMAT/NIST method has been upgraded to deal with this type of samples, which requires to be measured Butyl-PBD as primary scintillator in benzene solution. The theoretical efficiency calculation made by the last version EFFY8 software has been performed for the specific sample vial composition, including now in EFFY8 the new solute as well as primary and secondary scintillators. The method has been successfully tuned in the [100, 0.01] Bq 14C activity range using an ultra-low-level background LSC device, model Quantulus 1220TM by Perkin Elmer. Validation has been performed in the CIEMAT metrology laboratory.

Speaker: Begoña Quintana Arnés (Universidad de Salamanca)

111 Improvements in the detection capability for monitoring low levels of radionuclides in atmospheric aerosols at IAEA's Marine Environment Laboratories in Monaco

Besides applications for radiation safety purposes in routine and accidental situations, monitoring of natural and anthropogenic radionuclides in atmospheric aerosols and deposition can provide valuable information on atmospheric processes, climate change and atmosphere-ocean fluxes. In addition to a time-series of measurements of radionuclide specific activities in atmospheric aerosols and in wet and dry deposition, uninterrupted since 1992, in 2016 IAEA’s Marine Environment Laboratories in Monaco upgraded their capability to detect and measure low levels of radionuclides in the atmosphere. This development was brought about by the generally decreasing levels of anthropogenic radionuclides, in particular the gamma-emitting 137Cs, in the environment at large and by the interest in detecting in a timely manner traces of radionuclides relevant for environmental monitoring. In addition, the use of radionuclides as proxies to assess fluxes of atmospheric contaminants to the sea surface requires their accurate and precise measurement in both seawater and atmospheric samples.
To achieve lower minimum detectable activities (MDA), it was planned to commission a high flow-rate sampler, to optimize the counting geometry and use as appropriate low-background high resolution detectors in the IAEA’s low-level gamma-ray spectrometry underground laboratory. A Senya JL-900 Snow-White high-volume air sampler, routinely collecting 700-800 m3 h-1, has been put in operation in 2016 on the roof of the Marine Environment Laboratories in Monaco, located on the seafront in an urban area. In routine mode samples are collected once a week, typically totaling over 120,000 m3. The sampling frequency can be increased based on the expert evaluation of alerts from the nearby continuous gamma dose-rate monitoring station. The flowrate through large surface glass microfiber filters is continuously recorded and complete meteorological data are collected from a local station. The filters are compacted to a standardized cylindrical geometry and measured on low-background n-type and p-type coaxial HPGe detectors of 50% respectively 100% relative efficiency and various broad energy range detectors. Calibration was carried out with a water solution volume sample in identical geometry with the filters and corrections were calculated with EFFTRAN and GESPECOR.
Optimized sampling-measurement parameters for different applications, and results obtained over 6 years for natural 7Be, 22Na, 210Pb, and anthropogenic 137Cs, and on occasionally measured radionuclides such as the 106Ru detected over Europe in 2017 and 131I, are presented for the first time here, demonstrating the performance of the developed system.

Corresponding author e-mail address: i.osvath@iaea.org
Proposed session: Radionuclide metrology in life sciences or Low-level measurement techniques
Proposed presentation type: Poster or Oral

Speaker: Mrs Iolanda Osvath (International Atomic Energy Agency, Marine Environment Laboratories, 98000 Monaco)

112 Radon metrology for use in climate change observation and radiation protection at the environmental level

Authors: 1. Stefan Röttger (PTB, Germany), 2. Annette Röttger (PTB, Germany), 3. Tanita Ballé (PTB, Germany), 4. Claudia Grossi (UPC, Spain), 5. Ute Karstens (Lunds Universitet, Sweden), 6. Giorgia Cinelli (ENEA, Italy), 7. Chris Rennick (NPL, Great Britain)

Radon gas is the largest source of public exposure to naturally occurring radioactivity, and concentration maps based on atmospheric measurements aid developers to comply with EU Safety Standard Regulations. Radon can also be used as a tracer to evaluate dispersal models important for supporting successful greenhouse gas (GHG) mitigation strategies. One of the recently most applied technique for this propose is being the Radon Tracer Method (RTM). To increase the accuracy of both radiation protection measurements and those used for GHG modelling, traceability to SI units for radon exhalation rate from soil, its concentration in the atmosphere and validated models for its dispersal are needed. The EMPIR project 19ENV01 traceRadon(1) started to provide the necessary measurement infrastructure. This is particularly important for GHG emission estimates that support national reporting under the Paris Agreement on climate change.
Compared to the large spatiotemporal heterogeneity of GHG fluxes, radon is emitted almost homogeneously over ice-free land and has a negligible flux from oceans. Atmospheric measurements of radon activity concentrations can be used for the assessment and improvement of atmospheric transport models.
Similarly, for radiological data, all European countries have installed networks of automatic gamma dose rate and air concentration levels monitoring stations and report the information gathered to the European Radiological Data Exchange Platform (EURDEP). Currently, EURDEP exchanges real-time monitoring information from 39 countries collected from more than 5500 automatic surveillance systems. Therefore, improving contamination detection requires greater accuracy in determining environmental radon concentrations and their movement in the atmosphere.
An overlapping need exists between the climate research and radiation protection communities for improved traceable low-level outdoor radon measurements, combining the challenges of collating and modelling large datasets, with setting up new radiation protection services. The project traceRadon works on this aspect for the benefit of two large scientific communities. An overview will be presented, as well as results with respect to radionuclide metrology will be discussed.
(1): This project 19ENV01 traceRadon has received funding from the EMPIR programme co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation programme. 19ENV01 traceRadon denotes the EMPIR project reference.

Speaker: Dr Stefan Rottger (PTB, Germany)

113 Metrology for the harmonisation of measurements of environmental pollutants in Europe

Authors: Dirk Arnold 1, Ben Russell 2, Tea Zuliani 3, Valérie Lourenço 4, Betül Ari 5,Simon Jerome 6
1 PTB, Braunschweig, Germany, 2 NPL, Teddington, UK, 3 JSI, Ljubljana, Slovenia, 4 Université Paris-Saclay, CEA List, LNE-LNHB, Palaiseau, France, 5 TÜBİTAK, Ankara, Turkey, 6 NMBU, Ås, Norway

The European Green Deal’s ambition for zero pollution requires the development of highly sensitive techniques to detect ultra-low amounts of pollutants and to determine their isotope ratiosfor source attribution. Mass spectrometry is a key method for non-radioactive polluting elements determination and is of increasing importance for long-lived radionuclides. This project started in October 2022 and will run for three years and aims to bridge the gap between decay counting and atom counting methods and will establish new tools for tracing pollutants. Understanding of the advantages, limitations, measurement uncertainties and detection limits achievable by different mass spectrometer designswill be significantly improved using newly developed reference materials and SI-traceable measurement procedures and interlaboratory comparison exerciseswith an immediate impact for tracking pollution sources by commonly available mass spectrometers.
The scientific work of this project falls into four main areas:
• Establish and compare the selectivity and detection limits of different mass spectrometers by establishing the capabilities of different mass spectrometry designs using radionuclide standard solutions. The focus will be on relative instrument performance with respect to current measurement challenges around detection limits.
• Advancing stable and long-lived radiogenic isotope ratio measurements of environmental pollutants through the development of new and improved generic methods for stable and long-lived radioactive isotope ratio measurements by mass spectrometry with uncertainties that allow resolving natural mass dependent isotope fractionation.
• Development of two reference materials, one liquid and one solid, containing radioactive pollutants (237Np, 234,235,236,238U, 239,240Pu, 241Am and possibly 226Ra and 90Sr) addressing end users and stakeholders needs.
• Development of SI traceable certified reference material for inorganic environmental pollutants which will be designed according to the needs of the end users performing environmental analysis and monitoring. The production and certification of the material will be carried out in accordance with EN ISO 17034 standard (General requirements for the competence of reference material producers) requirements.
• The scientific outputs of the project will be disseminated via the scientific literature and by using the outcomes from the project through standards committees concerned with the determination of environmental pollutants.
The project (21GRD09 MetroPOEM) has received funding from the European Partnership on Metrology, co-financed by the European Union’s Horizon Europe Research and Innovation Programme and from by the Participating States.
Funder name: European Partnership on Metrology
Funder ID: 10.13039/100019599
Grant number: 21GRD09 Metro POEM

Speaker: Dirk Arnold (Physikalisch-Technische Bundesanstalt)

114 A comparison of different approaches for the analysis of 36Cl in graphite samples

Authors (affiliation): 1. Inés Llopat Babot (SCK CEN, Belgium), 2. Mirela Vasile (SCK CEN, Belgium), 3. Andrew Dobney (SCK CEN, Belgium), 4. Ben Russell (NPL, UK), 5. Svetlana Kolmogorova (NPL, UK), 6. Sven Boden (SCK CEN, Belgium), 7. Michel Bruggeman (SCK CEN, Belgium), 8. Martine Leermakers (VUB, Belgium), 9. Jixin Qiao (DTU, Denmark), 10. Valdir de Souza (SCK CEN, Belgium), 11. Alex Tarancón (UB, Spain), 12. Hector Bagán (UB, Spain), 13. Phil Warwick (University of Southampton, UK)

The safe disposal of wastes originating from decommissioning of nuclear installations generally entails restrictions on the radioactivity concentrations of the radionuclides that are addressed by the risk analyses for the disposal site. 36Cl is one of these radionuclides considered in the Belgian legislation for the final classification of the waste (e.g. category) and route for disposal (Fréchou and Degros 2005; Poncet 2017; FANC 2001). It is a neutron activation product of natural chlorine, which is commonly present as an impurity in construction materials (such as graphite or concrete). Its high soil-plant transfer factor, volatility and long half-life (T1/2 = 3,02 • 105 year) require the follow up of this radionuclide and the need for its characterization in decommissioning waste streams from nuclear facilities (Hou, Østergaard, and Nielsen 2007). In our previous work, we reported two approaches for the determination of 36Cl in solid samples from decommissioning activities by means of liquid scintillation counting (LSC) (Llopart Babot et al. 2022; Llopart Babot 2022).
Croudace et al. 2017 reported inductively coupled plasma mass spectrometry (ICP-MS) as a possible technique for the quantification of 36Cl (Croudace, Russell, and Warwick 2017). However, the isobaric interferences 36S and 36Ar can clearly limit the application of the technique. More recently, Warwick et al. 2019 described the use of tandem mass spectrometry (ICP-MS/MS) for 36Cl analysis. This spectrometric technique uses a collision cell in order to remove the isobaric interferences (i.e. 36S and 36Ar) (Warwick et al. 2019; Russell et al. 2021). Also the use of Accelerator Mass Spectrometry (AMS) for the quantification of 36Cl has been reported in the literature, however, AMS is not usually accessible to all the scientific community (i.e. expensive technique) (Hou 2013; Hou and Roos 2008; Ashton 2000; Tolmachyov et al. 2001).
This work compares two different measurement techniques for the analysis of 36Cl in graphite samples: LSC using LS cocktail and plastic scintillation resin (PS resin), and ICP-MS/MS. Controlled pyrolysis was used for sample combustion, release and trapping of 36Cl in all cases. Interaction with a Cl resin was used for the radiochemical separation followed respectively by the measurement of the pure chlorine fractions by LSC and by ICP-MS/MS. For the application of LSC when using PS resin, the trapping solution was loaded onto a PS resin and the cartridge was measured directly. The advantages and disadvantages of these techniques following from their comparison will be described and discussed in detail.

References
Ashton, Linda. 2000. "Determination of 36Cl and Other Long-Lived Radionuclides in Decommissioning Concrete Wastes." Loughborough University. Thesis. https://hdl.handle.net/2134/14125.
Croudace, I W., B C. Russell, and P W. Warwick. 2017. "Plasma Source Mass Spectrometry for Radioactive Waste Characterisation in Support of Nuclear Decommissioning: A Review." Journal of Analytical Atomic Spectrometry 32 (3): 494–526. https://doi.org/10.1039/c6ja00334f.
FANC. 2001. "20/07/01 ARBIS - Bijlage IB." 2001. https://www.jurion.fanc.fgov.be/jurdb-consult/faces/consultatieOverzicht.jsp.
Fréchou, C., and J. P. Degros. 2005. "Measurement of 36Cl in Nuclear Wastes and Effluents: Validation of a Radiochemical Protocol with an in-House Reference Sample." Journal of Radioanalytical and Nuclear Chemistry 263 (2): 333–39. https://doi.org/10.1007/s10967-005-0059-4.
Hou, Xiaolin. 2013. "Determination of Pure Beta Emitters Using LSC for Characterization of Waste from Nuclear Decommissioning." In Advances in Liquid Scintillation Spectrometry (LSC 2013). Barcelona.
Hou, Xiaolin, Lars Frøsig Østergaard, and Sven P. Nielsen. 2007. "Determination of 36Cl in Nuclear Waste from Reactor Decommissioning." Analytical Chemistry 79 (8): 3126–34. https://doi.org/10.1021/ac070100o.
Hou, Xiaolin, and Per Roos. 2008. "Critical Comparison of Radiometric and Mass Spectrometric Methods for the Determination of Radionuclides in Environmental, Biological and Nuclear Waste Samples." Analytica Chimica Acta 608 (2): 105–39. https://doi.org/10.1016/j.aca.2007.12.012.
Llopart Babot, Inés. 2022. "Investigation of a New Approach for 36Cl Determination Using Plastic Scintillators." In Radchem 2022. Mariánské Lázně, Czech Republic.
Llopart Babot, Inés, Mirela Vasile, Andrew Dobney, Sven Boden, Michel Bruggeman, Martine Leermakers, and Jixin Qiao. 2022. "On the Determination of 36 Cl and 129 I in Solid Materials from Nuclear Decommissioning Activities." Journal of Radioanalytical and Nuclear Chemistry, no. 0123456789. https://doi.org/10.1007/s10967-022-08327-9.
Poncet, Bernard R. 2017. "Long History of Cl-36 Assessment of Graphite Waste by EDF Engineering and the Latest Suggested Developments - 17043." In . United States.
Russell, B., S. L. Goddard, H. Mohamud, O. Pearson, Y. Zhang, H. Thompkins, and R. J.C. Brown. 2021. "Applications of Hydrogen as a Collision and Reaction Cell Gas for Enhanced Measurement Capability Applied to Low Level Stable and Radioactive Isotope Detection Using ICP-MS/MS." Journal of Analytical Atomic Spectrometry 36 (12): 2704–14. https://doi.org/10.1039/d1ja00283j.
Tolmachyov, S, S Ura, N Momoshima, M Yamamoto, and Y Maeda. 2001. "Determination of 36 Cl by Liquid Scintillation Counting from Soil Collected at the Semipalatinsk Nuclear Test Site" 249 (3): 541–45.
Warwick, P. E., B. C. Russell, I. W. Croudace, and Zacharauskas. 2019. "Evaluation of Inductively Coupled Plasma Tandem Mass Spectrometry for Radionuclide Assay in Nuclear Waste Characterisation." Journal of Analytical Atomic Spectrometry 34 (9): 1810–21. https://doi.org/10.1039/c8ja00411k.

Speaker: Dr Mirela Simona Vasile (SCK CEN, Belgium)

115 Estimation of Correction Factors for RadonEye Continuous Radon Monitors

Authors (affiliation): I. Dimitrova (SU, Bulgaria), K. Mitev (SU, Bulgaria), S. Georgiev (SU, Bulgaria), V. Todorov (SU, Bulgaria), Z. Daraktchieva (UKHSA, UK), C B Howarth (UKHSA, UK), J. M. Wasikiewicz (UKHSA, UK), Benoit Sabot (LNE-LNHB, France).

Recently, affordable and sensitive continuous radon monitors became available at the market. They could open the doors to new approaches for estimation and reduction of the indoor radon exposure. Metrological tests of these monitors are necessary to uncover their full potential and support their wider application.
Metrological tests of 20 RadonEye continuous monitors were performed at Sofia University (SU), Bulgaria and UK Health Security Agency (UKHSA), United Kingdom. Their backgrounds and correction factors to referent activity concentration were determined. The correction factors were estimated by exposure to activity concentration traceable to the primary radon standard at LNHB, France. Two approaches for exposure were compared – several longer sessions with different constant activity concentrations and a single session with continuously increasing activity concentration. It is shown that the two approaches give comparable results.
The correction factors of the 20 monitors in the range in which the RadonEye's response can be considered linear (below 3500 Bq/m3) varied from 0.70 to 1.06. Eight of the monitors were also exposed at LNHB, France to a traceable radon activity concentration of 4702(61) Bq/m3. The correction factors at this level were 15 to 20 % higher than these in the range below 3500 Bq/m3. This was attributed to the non-linearity of the RadonEye response, which has been reported previously. The upper limit of the monitors was tested at Sofia University. It is demonstrated that different monitors saturate at different levels that are significantly below the upper limit of 9435 Bq/m3 declared by the producer.
The background of the monitors was determined by exposure in a nitrogen atmosphere for about ten days. The estimated background values for 1-hour-long measurements were below 3.5 Bq/m3 for all monitors. This shows that the monitors are sensitive enough for indoor radon measurements.
The results demonstrate that these monitors should be calibrated at radon activity concentrations close to the typical values observed in buildings and below 3500 Bq/m3. The exposure can be carried out in a single exposure session at changing activity concentration. Data from the conducted exposures and from ongoing measurements in buildings is presented. It is shown that RadonEye monitors follow promptly (with an effective time of about 90 minutes) the changes in the radon activity concentration. This indicates that they can be used for exploration of new approaches for estimation of the radon exposure in homes and workplaces.

Speaker: Dr Ivelina Dimitrova (Sofia University, Bulgaria)

116 Upgrade of HPGe spectrometry system for low level activity determination with cosmic veto

Authors (affiliation): 1. Tomislav Ilievski (Ruđer Bošković Institute, Croatia), 2. Luka Bakrač (Ruđer Bošković Institute, Croatia), 3. dr.sc Nikola Marković (Sahlgrenska Academy at University of Gothenburg, Sweden), 4. dr.sc. Damir Bosnar (Faculty of Science, Universtiy of Zagreb, Croatia), 5. dr.sc. Ivana Tucaković (Ruđer Bošković Institute, Croatia).

As a part of RiChFALL project, analysis of radioactivity in children food in Croatia and raw materials for its production (mainly fruits and vegetables) is carried out by HPGe spectrometry. Since low level activities of naturally occurring and anthropogenic radionuclides in such samples are expected (except K-40), the aim of this work is to upgrade the existing setup. Existing setup consists of Canberra Broad Energy HPGe enclosed in the original lead shield with nitrogen flushing.
Detectors are normally placed in shields (usually made of lead) to reduce the background radiation from the environment. Radon is removed from the detector environment under pure nitrogen overpressure, pushing out of the shielded area the air that contains it. Large portion of the remaining background signals are produced by muons coming from cosmic radiation, by interacting with the detector and surrounding materials. To reduce the contribution, an active scintillator shield was introduced together with the existing lead shield. The scintillator is a plastic (polyvinyltoluene) plate (70x70x5 cm) from Saint-Gobain. It is used as a veto guard to reject events produced by muons. To achieve this, a new digital MCA (Caen DT5781 Quad Digital Multi Channel Analyzer) with time-stamping capabilities was used. Both scintillator and existing HPGe (Canberra BE5030P) were connected to separate channels of the MCA.
By using the time stamping feature of the MCA, time difference between muon detection and HPGe signal was known with sub-microsecond precision. By varying the anti-coincidance rejection window length and delay, it was found that most coincidence events are produced within 2 μs after muon detection, while coincidence was observable up to 15 μs. While scintillator position on top of the shield is obviously the most efficient one, different positions and distances from the shield were tested as well. By using the correct scintillator signal threshold, no increase in back-scattered photon signals were observed when placing the scintillator closer to the shield.
With optimized settings, when the scintillator plate is placed directly on top of lead shield, 30% to 50% of total counts have been removed from the background spectrum. Test results with shielding from the sides were also promising, so additional plates are planned to further enclose the lead shield and achieve the lowest background possible. Described cosmic veto system has proven to be quite modular and easily introduced into existing gamma spectrometry systems.

Speaker: Mr Tomislav Ilievski (Ruđer Bošković Institute, Croatia)

117 Algorithms development for low level radioxenon spectrum analysis

Authors (affiliation): Hugues Paradis (CEA, France), Anthony Der Mesrobian-Kabakian (CEA, France), Antoine Cagniant (CEA, France), Olivier Delaune (CEA, France), Charles Philippe Mano (CEA, France), Luc Patryl (CEA, France)

Underground or underwater nuclear tests can eventually lead to radioxenon releases in the atmosphere. In this scope, the verification regime of the Comprehensive nuclear Test Ban Treaty installed dedicated noble gas systems for the detection of low-level radioxenon activity in the air.
Recent development of these noble gas systems included new detector technologies. They exhibits very low background count rates. In this case, radioxenon signal as low as a few counts per 12h are expected. Therefore, for such low count measurements, classical Currie law estimation for measurement detection thresholds and detection limits are not precise enough. In this context, the CEA/DAM implemented several algorithms (matrix inversion, iterative process), and keeps the effort to improve the data analysis with innovative tools, such as spectral unmixing.
Due to the lack of statistics, it is not convenient to test and compare these algorithms on measured low-level radioxenon spectra, therefore a Monte Carlo simulated database of spectra was generated, for several detection configuration (high resolution beta/gamma spectra, low resolution gamma/ high resolution beta spectra, lowresolution beta/gamma spectra). To optimize the analysis of this database, the spectral unmixing algorithm was ported on GPU, leading to a drastic decrease in computation time and allowing for the processing of large simulated datasets in reasonable delay.
This work will be presented, and algorithms key performance indicators for each detector configuration will be compared.

Speaker: Mr Charles Philippe Mano (CEA, France)

118 BEST POSTER AWARD

Speaker: Brian Zimmerman (NIST)

10:25 AM Coffee Break

Low-level measurement techniques: ICRM WG Meeting

Low-level activity measurements

Conveners: Begoña Quintana Arnés (Universidad de Salamanca), Dirk Arnold (Physikalisch-Technische Bundesanstalt)

LLMT-WG-SESSION-agenda.pdf

119 CLOSING OF THE CONFERENCE ICRM 2023

12:30 PM Lunch Break

THE GENERAL MEETING OF THE ICRM: Part 1

4:00 PM Coffee Break

THE GENERAL MEETING OF THE ICRM: Meeting close

5:00 PM Break

120 ICRM Executive Board Meeting