Quantification of uranium-238 in environmental samples using gamma-ray spectrometry

EC-JRC Institute for Reference Materials and Measurements Retieseweg 111, B-2440 Geel, Belgium

^* E-mail: mikael.hult@ec.europa.eu

Abstract

A large number of environmental samples are routinely measured world-wide using gamma-ray spectrometry some of its assets being easy sample preparation and comprehensive data for many radionu-clides in one analysis. Although other techniques can be considered more suitable for analysing ²³⁸U in environmental samples, it is also routinely done by gamma-ray spectrometry. One mainly uses γ-ray emissions following the decay of the first daughter, ²³⁴Th, for determining the ²³⁸U activity. However, the low-energy gamma-rays at 63 keV and 92.5 keV are very difficult to quantify in a robust way due to high attenuation and interferences. This paper quantifies parameters affecting the possibility of making robust quantification of ²³⁸U via ²³⁴Th using gamma-ray spectrometry. It addresses the use of correct decay data, suitable detectors, optimised sample size, enhanced spectral amplification, correction for peak interferences and control of background.