Determination of the plutonium mass in containers with plutonium dioxide according to the γ radiation from spontaneous-fission products

A nondestructive method of determining the mass of large plutonium samples which is based on measuring their characteristic γ radiation is presented. The mass and the isotopic composition of the plutonium were determined according to a single measured γ spectrum in two energy ranges: the middle range, where the isotopic composition of plutonium is determined from the lines of the plutonium isotopes, and high-energy, where the radiation of the products of the spontaneous fission of plutonium gives information about the mass of the sample. The dependence of the counting rate in the peaks of the fission products on the effective mass of 240 Pu was calibrated according to measurements performed with standard samples of the enterprise. As a result of the measurements, corrections were made for the self-absorption of γ radiation and induced fission, which were calculated by the Monte Carlo method. The error in determining the plutonium dioxide mass is 3-10% for containers with different cool-down times and isotopic composition of plutonium.