PNNL

Abstract

Field measurements of radionuclide activities in soil samples via gamma spectroscopy measurements are conducted for many applications. One example application space is on-site inspection for the Comprehensive Nuclear-Test-Ban Treaty. To extract isotopic activities from observed peak counting rates, it is necessary to understand the absolute efficiency of the detector system for the sample. In principle, this efficiency is a function of many parameters, such as sample geometry, soil elemental composition, and soil density. The demands of field measurements within the context of on-site inspections, however, places a premium on an easy-to-implement approach at the possible expense of accuracy given the need to process many samples in a short period of time. This paper presents a semi-empirical approach, using a calibrated standard and a correction that depends only on the relative differences in density of the sample and the standard. Field measurements were conducted to demonstrate the validity of the approach.