Improvement of a high-energy fission model for spallation reactions

Iwamoto, Hiroki   ; Meigo, Shinichiro   

In the research and development of spallation neutron source facilities including accelerator-driven systems, it is necessary to accurately predict the yields of fission fragments produced from the spallation reactions, which include various volatile materials such as xenon, iodine, and krypton important to their analysis of the gas treatment system for the target. To ameliorate the accuracy of the yield prediction, we have improved the high-energy fission model of Generalized Evaporation Model (GEM) implemented in the Particle and Heavy Ion Transport code System, PHITS. In this study, the description of the fission probability was modified to account for the fission cross sections for both subactinide and actinide nuclei. The fission probability was deduced from Prokofiev's phenomenological systematics of the proton-induced fission cross sections and the Lige intranuclear cascade model version 4.6, INCL4.6. Comparing with experimental data shows that the modified model can predict the proton-, neutron-, and deuteron-induced fission cross sections for a wide range of target nuclei from the threshold energies to the GeV range with markedly improved accuracy. We also provide comparisons with other spallation models embedded in MCNP6.