Qualification of the JEF2.2 Cross Sections in the Epithermal and Thermal Energy Ranges Using a Statistical Approach

The calculation of reactor design parameters with ever higher accuracy requires constant improvement in basic nuclear data and computational techniques. Several methods based on formal statistical techniques have been studied to adjust cross sections used in fast reactor design calculations; nevertheless, these techniques have never been used for epithermal and thermal energy ranges. In this study, the statistical adjustment technique is reviewed, the integral experiments that serve as the adjustment database are presented, and suggested adjustments are discussed. If the cross sections of the main heavy nuclides seem to be well known, this study shows a very strong modification of the ²³⁵U capture cross section in the resonance range (∼10%). This trend can be explained by an underestimation of the mean capture width used in the ²³⁵U evaluation. The statistical technique used in this study allows us to qualify the JEF2 cross sections with a high quality of confidence.