Indirect determination of the Th230(n,f) and Th231(n,f) cross sections for thorium-based nuclear energy systems

The surrogate ratio method (SRM) was employed in the first experimental determination of the Th231(n,f) cross section, relative to the U235(n,f) cross section, over an equivalent neutron energy range of 360 keV to 10 MeV. The Th230(n,f) cross section was also deduced using the SRM, relative to the U234(n,f) cross section, over an equivalent neutron energy range of 220 keV to 25 MeV. The desired compound nuclei were populated using (He3,He3') and (He3,α) reactions on targets of Th232 and U236 and relative fission decay probabilities were measured. The surrogate Th230,231(n,f) cross sections were compared to cross section evaluations and directly-measured experimental data, where available. © 2009 The American Physical Society.