Development of multi-chance fission module for fission event generator FIFRELIN

Ogawa, Tatsuhiko   ; Litaize, O.*; Mancusi, D.*; Chebboubi, A.*; Serot, O.*

The Monte-Carlo code FIFRELIN was originally developed for the simulation of first chance fissions of fissile nuclei and spontaneous fissions. In this study, a reaction module for multi-chance fission was developed. Multi-chance fission reaction are fission reactions preceded by neutron emission owing to the incident neutron energy higher than the fission barrier. For this development, an algorithm to calculate the excitation energy, spin and parity of the compound nucleus was implemented. In addition, a fission width and neutron emission width were calculated by Bohr-Wheeler formula and Hauser-Feshbach formula, respectively. If neutron emission reaction is sampled and the excitation energy reaches below the fission barrier, fission reaction is prohibited and the nucleus is deexcited by evaporation. The prompt fission probability of U(n,fission) calculated with these new algorithms, qualitatively agreed with experimental data. By improving the neutron transmission coefficient and level density formalism used in the Hauser-Feshbach calculation to calculate multi-chance fission calculation more accurately.