Interpretation of Integral Test Results of FP Cross Sections in JENDL-3.2 by Analyzing the STEK Experiments

Abstract

The integral test of the fission product cross sections in JENDL-3.2 was made as an activity of the Subgroup 10 in the Working Party for Evaluation Cooperation in NEANSC by analyzing the sample reactivity worths measured at the STEK cores. Analyses were separately made by a JNDC team at JAERI and K.Dietze at JNC by using the 70-group cross sections. Neutron and adjoint fluxes used in the analysis by JNDC were converted from the 25-group ones which were adjusted to reproduce the reactivity worth for standard samples by Janssen et al. At ECN, while those used for analysis by K.Dietze were calculated with the reactor core design code system of JNC. The results of both analyses were very similar to each other for strongly absorbing nuclides and in good agreement with the experimental values except for nuclides heavier than A=130 for which the reactivity worth was underestimated by about 10%. However, there were some discrepancies for weakly absorbing nuclides: The analysis by K.Dietze gave a better agreement with the experimental values than those by JNDC. In order to interpret the discrepancies among both calculations and the experimental values, the neutron and adjoint fluxes used in the JNDC calculations were compared with those calculated by K.Dietze. Additionally, flux calculations were also made with diffusion and Monte Carlo codes. For weakly absorbing nuclides, a detailed comparison of sample reactivity worths as well as adjoint spectra was made.