Energy dependent calculations of fission product, prompt, and delayed neutron yields for neutron induced fission on 235U, 238U, and 239Pu

We perform energy-dependent calculations of independent and cumulative fission product yields for U-235, U-238, and Pu-239 in the first chance fission region. Starting with the primary fission fragment distributions taken from available experimental data and analytical functions based on assumptions for the excitation energy and spin-parity distributions, the Hauser-Feshbach statistical decay treatment for fission fragment de-excitation is applied to more than 1,000 fission fragments for the incident neutron energies up to 5 MeV. The calculated independent yields are then used as an input of beta-decay calculations to produce the cumulative yield, and summation calculations are performed. Model parameters in these procedures are adjusted by applying the Bayesian technique at the thermal energy for U-235 and Pu-239 and in the fast energy range for U-238. The calculated fission observable quantities, such as the energy-dependent cumulative yields, and prompt and delayed neutron yields, are compared with available experimental data. We also study the possible impact of the second chance fission opening on the energy dependence of the delayed neutron yield by on the opening of second chance fission on the energy dependence calculation.

Automated summary

Energy-dependent calculations of fission product yields for different fissile materials were conducted and compared with experimental data. The study also investigated the possible impact of second chance fission on the energy dependence of delayed neutron yield.