Assessment of 232Th nuclear data through critical experiments using the Kyoto University critical assembly

An assessment of 232Th nuclear data was conducted through the analysis of critical experiments using the Kyoto University Critical Assembly (KUCA) of the thermal neutron system. The impact of the difference among evaluated nuclear data files was also examined for 232Th and 233U through the neutronics calculation. It was found that C/E values for cores containing 232Th became larger with hardening neutron spectrum, whereas these values for cores without 232Th were rather constant regardless of neutron spectrum. This fact indicates that there remains a certain problem in the evaluation of 232Th capture cross sections, which would be desirable to be solved for the purpose of developing the Th-U fuel cycle. It was also found that the difference in 233U fission and capture cross sections compiled in different nuclear data files could lead to a significant difference in reactivity. This result indicates that the assessment of 233U nuclear data through the systematic critical experiments would be inevitable to develop the Th-U fuel cycle. (author)