Evaluation of neutron cross section of 27 fission product nuclides important for fast reactor.

概要

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Results of evaluation of neutron cross sections are presented for 27 fission product nuclides selected as being most important for fast reactor calculation. The cross sections considered are total, elastic scattering, inelastic scattering and capture cross sections in the energy range from thermal to 15 MeV. Thermal and resonance cross sections were calculated from resonance parameters. The calculated thermal capture cross section was adjusted by the measured value by adding a background cross section of 1/υ form. A modified multi-level Breit-Wigner formula was developed to avoid the well-known occur-rence of negative values in elastic scattering cross section. Smooth cross sections above resonance region were calculated with the spherical optical model and the statistical theory, taking account of neutron width fluctuation and level interference. The calcula-tion was adjusted by capture data when available. The joining between the resonance and smooth cross sections was performed with the aid of statistical examination using Monte Carlo method. Present results are discussed in comparison with other evaluated data sets. Numerical results are stored on magnetic tape in the ENDF/B format.
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