Adjustment of Multigroup Neutron Cross Sections by a Correlation Method

The benchmark experiments, performed in a plutonium-fueled critical assembly (ZPR-6 Assembly 7) in support of the fast reactor demonstration plant program, were used, in conjunction with a statistical method of correlation, as a source of suggestions for possible modifications to multigroup neutron cross-section sets based on ENDF/B files. Version 1 of these files was a starting point in the correlation procedure. The general trends of the results (lower ²³⁸U capture cross section and ²³⁵U fission cross section, higher ²³⁹Pu capture to fission ratio, with respect to ENDF/B Version 1 data) are discussed, and the suggested multigroup cross-section adjustments are compared with recent evaluations. Calculations of keff, and of the ratios of ²³⁸U and ²³⁵U fission rate and of ²³⁸U capture rate to 239Pu. fission rate, using the proposed adjusted set, give results in good agreement with the experiments.