Speaker
Description
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
