Sample Association by using Anomalous Concentration Episodes and Decay-Consistent Isotopic Ratios at IMS Radionuclide Stations

For enhancement of the International Data Centre (IDC) products such as the Standard Screened Radionuclide Event Bulletin (SSREB), there is a need to associate the detections of CTBT relevant isotopes in samples at International Monitoring System (IMS) radionuclide stations with the same release to characterize its source for the purpose of nuclear explosion monitoring. Episodes of anomalous concentrations at the stations are the best first guess for being related to the same event. For multiple isotope observations, the consistency of their isotopic ratios in subsequent samples with radioactive decay is another plausible hint at coming from the same source. Moreover, atmospheric transport modelling (ATM) will help to get further evidence and gain confidence in sample associations by identifying the air masses that link the release to multiple samples. We focused on the basic approach as well as the criteria for automatic sample association for the SSREB.