EXFOR-based simultaneous evaluation for fast neutron-induced fission cross section of thorium-232

The ²³²Th neutron-induced fission cross section was evaluated from 500 keV to 200 MeV. The experimental ²³²Th fission cross sections and their ratios to the ^235,238U fission cross sections in the EXFOR library were reviewed and analysed by using the least-squares method. The newly published ²³²Th/²³⁵U fission cross-section ratios from the time-of-flight measurements at the CERN n_TOF and CSNS Back-n facilities were compiled in EXFOR. Additional simultaneous evaluation was performed by including the experimental ^233,238U and ^239,240,241Pu fission cross sections and their ratios. The new evaluation provides the ²³²Th fission cross section systematically lower than the JENDL-5 cross section. The reduction is 4% in the plateau region between 2 and 6 MeV and more significant in the subthreshold fission region. The present evaluation reduces the ²³²Th fission cross section averaged over the ²⁵²Cf spontaneous fission neutron spectrum from the JENDL-5 evaluation by 4%, which is closer to the other general purpose libraries but underestimates Grundl et al.’s measurement by 11%.