Application of gamma-ray spectrometry for the assay of uranium in crude UF₄—An input material used for producing nuclear grade U-metal at the natural uranium conversion plants

Abstract

A γ-spectrometric method has been developed for the assay of uranium in crude UF₄, which is used as a secondary source of input material for producing nuclear grade U-metal at natural uranium conversion plants. The method makes use of a NaI (Tl) detector coupled with a multichannel analyzer. The 1 MeV γ-ray of²³⁸U is used for calibration. A method for the fabrication of uniform γ-assay calibration standards is also suggested, based on the results of this investigation. The calibration standards were prepared by soaking the matrix in uranium solution and then drying the whole material. The amount of²³⁸U in the crude UF₄ sample was directly estimated by comparing the areas under the 1 MeV γ-ray peak of known calibration standards with the corresponding areas of the samples to be measured. 100 g each of the standard and the sample were counted. 5 crude UF₄ samples were analyzed by this method. The uranium contents in these samples were found to be in the range of 12.2–28.7 g. To compare the γ-ray spectrometry results with a completely independent method, chemical analysis by potentiometry of all the samples was also done. The γ-spectrometric results were found to agree within ±18% with the chemical analysis results.