Covariance comparisons between ENDF/B-VII.1 and ENDF/B-VIII.0 with application for the UAM-LWR exercises

In this study, the nuclear-data covariance data have been compared between ENDF/B-VII.1 and ENDF/B-VIII.0. Using NJOY2016.34, the multigroup cross-section covariance libraries based on ENDF/B-VII.1 and ENDF/B-VIII.0 have been generated respectively. From the direct comparisons of the covariance data between ENDF/B-VII.1 and ENDF/B-VIII.0, very notable differences can be observed in the uncertainties and correlations. Based on the multigroup cross-section covariance libraries generated from ENDF/B-VII.1 and ENDF/B-VIII.0, our home-developed UNICORN code has been applied for the uncertainty analysis. The exercises proposed by UAM-LWRs in Phase I have been chosen as the analysis exercises, including the UOX fuel pin-cells, UOX fuel assembly and MOX fuel assembly. The relative uncertainties of the eigenvalues, two-group constants and burnup-related parameters have been quantified and compared, quantifying the uncertainty differences of covariance data in ENDF/B-VII.1 and ENDF/B-VIII.0. Through analysis, the conclusions can be given that more reliable, not smaller nuclear-data covariance data can be provided in ENDF/B-VIII.0.