Evaluated nuclear data for thorium fuelled reactors and their integral test by neutron spectrum and decay heat

The requested nuclear data for designing thorium fuelled reactors fall into two categories, i.e. one is for the nuclides of nuclear fuels and the other is for those of structural materials and coolants. Among the nuclear data for nuclear fuels, those for 232Th and 233U are thought to be most important. However nuclear data for other actinides around these two nuclides are also important. One of the authors took a part in producing the Japanese Evaluated Nuclear Data Library, JENDL, concentrating on 232Th and other thorium isotopes. In this paper, the main data for 232Th in JENDL-2 are introduced and are compared with other evaluated nuclear data such as ENDF/B-IV or B-V. Secondly, these evaluated nuclear data for 232Th have been integrally tested by neutron spectra in thorium samples. The energy spectra of the neutrons extracted from a spherical pile of thoria and those scattered from a metallic thorium slab were measured by the time-of-flight method with an electron linear accelerator, and then the results have been compared with those which were theoretically calculated by a transport code DTF-IV using JENDL-2 and ENDF/B-IV. General agreement between the measured and calculated spectra is seen from 1 keV to 10 MeV, however the calculated spectrum with JENDL-2 is slightly lower than the measured from 800 keV to 2.5 MeV. Finally, samples of 233U and 232Th were irradiated by fast neutrons in a fast source reactor and then beta-rays (233U only) and gamma-rays from each sample were measured with specially designed detectors. The results have been compared with the calculated values with evaluated fission product nuclear data such as the JNDC file, Tasaka's file and ENDF/B-IV. The present results agree well with the summation calculations using the JNDC FP nuclear data library. (author)