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

Abstract

ABSTRACT 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%.