Energy dependence of chain fission product yields from neutron-induced fission of 235U, 238U, and 239Pu

Abstract

The lack of completeness and systematic studies of cumulative fission product yield (FPY) from the three major actinides of ²³⁵U, ²³⁸U, and ²³⁹Pu, over a broad energy range, was the primary motivation for the LLNL-LANL-TUNL collaboration. Given the focus on resolving FPY behavior around fission spectrum neutron energies, our 2016 data provides FPY measurements in fine energy steps in the range of 0.5–5.5 MeV and an additional anchor point at 14.8 MeV. Recently, our collaboration filled the gap between second chance fission and 14.8 MeV, providing a comprehensive study at eleven incident neutron energies from 0.5 to 14.8 MeV. However, during the course of the last measurements, it was found that the reported masses of the actinide deposits in the fission ionization chambers, which were used to measure the number of fissions, were not consistent with the complementary tests. Therefore, some corrections to the old data are needed. The purpose of this paper is to summarize all of the high-yield FPY data obtained for ²³⁵U, ²³⁸U, and ²³⁹Pu isotopes using quasi-monoenergetic neutron beams at 11 incident energies ranging from $E_n=0.5$ to 14.8 MeV.