NUCLEAR DATA EVALUATION OF ACTINIDES RELEVANT TO THORIUM FUEL CYCLE
Atomic Energy Research Institute, Kinki University
Kowakae, Higashi-osaka 577, Japan
Department of Nuclear Engineering, Kyushu University
Hakozaki, Higashi-ku, Fukuoka 812, Japan
Neutron nuclear data evaluation has been completed for Th-232, Pa-231 and Pa-233. Evaluation was made relying on the experimental data for the fission and capture cross sections and resonance parameters of Th-232. Theoretical models were employed if there were no or sparse data available. The neutron inelastic scattering leading to the excitation of strongly coupled states were calculated combining the coupled-channel and Hauser-Feshbach methods by means of the generalized transmission coefficients. The radiative capture cross sections for Pa-231 and Pa-233 were calculated with the statistical model. The (n,2n) and (n,3n) reaction cross sections were obtained using the Segev-Fahima model which allowed the preequilibrium effects in a simplified manner. The average prompt and delayed neutron multiplicities for Pa-isotopes were calculated using semi-empirical relations.
KEYWORDS: evaluation, Th-232, Pa-231, Pa-233, various cross sections