Simultaneous determination of ²²⁶Ra and ²³⁸U in soil and environmental materials by gamma-spectrometry in the absence of radium progeny equilibrium

Abstract

The determination of ²²⁶Ra and ²³⁸U in environmental samples by gamma-spectrometry is most often carried out by hermetic sealing of the sample in a suitable container, waiting until secular equilibrium that has been established in the ²³⁸U decay chain below ²²⁶Ra and counting of the high intensity emissions of ²¹⁴Pb and ²¹⁴Bi. The 186 keV multiplet can then be corrected to provide a measure of ²³⁵U and hence, ²³⁸U. The work presented in this paper involves a critical examination of the analysis of ²³⁸U and ²²⁶Ra in environmental materials without secular equilibrium established between ²¹⁴Pb, ²¹⁴Bi and their progenitor. Results indicate that the correction of the 186 keV doublet via ²³⁴Th determination is possible, even for low-level samples but careful consideration of both experimental conditions and the composition of the sample matrix is required.