Speaker
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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.
