An Evaluation of ENDF/B-IV and Hansen-Roach Uranium-233 Cross Sections for Use in Criticality Calculations

Eleven ²³³U solution critical assemblies spanning an H/²³³U ratio range of 40 to 2000 and an unreflected metal ²³³U assembly have been calculated with ENDF/B-IV and Hansen-Roach cross sections. Results from these calculations are compared with the experimental results and with each other. We observed an increasing disagreement between calculations with ENDF/B and Hansen-Roach data with decreasing H/²³³U ratio, indicative of large differences in their intermediate energy cross sections. The Hansen-Roach cross sections appeared to give reasonably good agreement with experiments over the whole range, whereas the ENDF/B calculations yielded high values for k_eff on assemblies of low moderation. We conclude that serious problems exist in the ENDF/B-IV representation of the ²³³U cross sections in the intermediate energy range and that further evaluation of this nuclide is warranted. In addition, we recommend that an experimental program be undertaken to obtain ²³³U criticality data at low H/²³³U ratios for verification of generalized criticality safety guidelines.