Gamma-Ray Spectrometric Determination of Isotopic Ratios of Plutonium

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.