Mass Distribution of the Fission Products of Plutonium Isotopes as Calculated by Using a Semi-empirical Model

Abstract

The fission product yields (FPYs) of plutonium isotopes induced by thermal, 500-keV and 2-MeV neutrons are calculated by using a semi-empirical model recently developed and applied to uranium isotopes. In this model, the FPYs are assumed to be proportional to the level density of a compound nucleus at the fission barrier. The fission barrier height that determines the level density is modeled as a sum of a macroscopic term and four microscopic terms. The model has ten parameters, four of which are taken to be the same as those fixed for the uranium isotopes. The remaining six parameters are adjusted to reproduce the FPYs of plutonium isotopes. The resulting parameters for the plutonium isotopes are discussed in comparison with those for the uranium isotopes. The calculated FPYs are compared with experimental and evaluated data, as well as the calculation results from other fission models such as GEF and TALYS. Our semi-empirical model is shown to reproduce the overall features of the FPYs of plutonium isotopes.