Soil Sample Efficiency Approach for OSIRIS

Abstract

The OSIRIS project is developing an approach to enable high-resolution gamma spectroscopy measurements for On-sight Inspections in support of the Comprehensive Test Ban Treaty (CTBT). This document discusses an approach for determining the detection efficiency the detector for a soil sample based on a radiation transport modeling study. The recommended efficiency calibration approach is inspired by the semi-empirical approach of Huy et al. (Huy and Binh 2014; Huy et al. 2013), which performs an efficiency measurement on a soil sample of known composition and known activity which is then corrected based on radiation transport modeling results. The primary difference between the approach of this paper and that of Huy et al., is a simplified correction for energy and density. While this approach is less than perfect, they provide reasonable uncertainties for on-site measurements. A more refined approach should be considered for laboratory measurements which may place greater demands on the uncertainties.