Analyses of uranium and actinium gamma spectra: An application to measurements of environmental contamination

Abstract

A system for the reduction of the complex gamma spectra of nuclides in the uranium, actinium, and thorium series, tailored to calculation of line intensities, analyses of errors, and identification of nuclides is described. This system provides an efficient technique for characterizing contamination in the environs of uranium mines and mills. Identification of the nuclides and calculation of their concentrations requires accurate knowledge of gamma energies and absolute quantum intensities. For some spectral lines, there are no reported measurements of absolute quantum intensities and in some cases where reports are available the measured intensities are not in agreement. In order to improve this data base, the spectra of gamma rays (of nuclides in the uranium and actinium series) with energies between 40 and 1400 keV were measured using high-resolution germanium detectors. A brief description of the spectroscopy system, computational algorithms for deconvolution, and methods of calibration for energy and efficiency, are described. The measured energies and absolute quantum intensities are compared with those reported in the literature.