Pioneering applications in AMS for the development of environmental radiology: Studies towards the implementation of ⁹⁰Sr and ¹³⁵Cs AMS

Abstract

We have developed new analytical methods for ⁹⁰Sr (28.79 yr) and ¹³⁵Cs (2.3x10⁶ yr) by accelerator mass spectrometry (AMS) for the further development of the research on the environmental fate of artificial radionuclides ⁹⁰Sr and ¹³⁷Cs (30.1 yr). The AMS method enables the analysis of trace amounts of ⁹⁰Sr and ¹³⁵Cs with a simple chemical separation procedure. Having a longer half-life ¹³⁵Cs applies as a proxy for ¹³⁷Cs. For ⁹⁰Sr, SrF₂ targets were prepared from radioactive environmental reference materials with known ⁹⁰Sr concentrations (IAEA) by a chemical separation procedure that takes about two days to complete. ⁹⁰Sr measured by AMS at VERA, University of Vienna. As a result, a limit of detection of ＜0.1 mBq was obtained, which is comparable to the β ray measurement. The detection of ⁹⁰Sr in environmental samples was also successful, indicating that the ⁹⁰Sr AMS can apply to environmental samples. On the other hand, there are still some technical challenges in the ¹³⁵Cs AMS. Therefore, the experimental measurements are in progress.