Gamma-Ray Spectrometric Determination of Isotopic Ratios of Plutonium

Abstract

Abstract Plutonium samples (3–30 μg) of various isotopic compositions were measured with a high-resolution Ge(Li) detector. The γ-rays counted are the 43.5 keV of 238Pu, the 38.7, 51.6 and 129.3 keV of 239Pu, the 45.2 keV of 240Pu, and the 148.6 keV of 241Pu. To estimate the relative photopeak efficiencies of the γ-rays, an empirical curve was derived from measurements of the three γ-rays of 239Pu adopted as internal standard. Data treatment is described in detail as well as the method of correction to account for the activities of 237U and 241Am inherently accumulating in the plutonium sample. The branching ratios of the γ-rays of plutonium were also evaluated by comparing the γ-ray spectrometric results with mass-spectrometric data.