Keisho Shirakata, Toshihisa Yamamoto

Power Reactor and Nuclear Fuel Development Corporation
9-13, 1-chome, Akasaka, Minato-ku, Tokyo 107, JAPAN

Akira Yoshimura, Toshikazu Takeda

Department of Nuclear Engineering, Osaka University
Yamada-oka 2-1, Suita, Osaka 565, JAPAN

Critical assembly experiments on large fast breeder reactor were analyzed by a current neutronics analysis method for fast reactor core using a group constant set based on the JENDL-2 library. It was made clear that there were some radial dependence of C/E(Calculation/Experiment) values for integral physics parameters, in addition to discrepancies between calculation and experiment. A cross section sensitivity analysis was conducted on the assembly to investigate sources of the radial dependence and discrepancies. The result showed that absolute values of sensitivities to the 239Pu fission and 238U capture cross sections were overwhelmingly large for most of integral physics parameters, compared with other cross sections. Next, the group constant set was adjusted by using these sensitivity coefficients and the C/E values. As the result of adjustment, the 239Pu fission cross section was increased by 2% for the energy range below 10keV, and the 238U capture cross section was decreased by about 6% for the 1keV-1MeV range.

KEYWORDS: Fast Critical Experiment, Integral Physics Parameter, Neutronic Analysis, Sensitivity Coefficient, Cross Section Adjustment, JENDL-2 library, 238U Capture Cross Section