The effect of modern thermal neutron scattering sublibraries on criticality safety evaluations of wet storage pools

Abstract

Within the framework of a recent criticality safety evaluation (CSE) performed for the licensing of a new commercial wet storage pool using MCNPX-2.5.0 along with the ENDF/B-VII.0 and JEFF-3.1 continuous energy cross-section libraries, the maximum permissible initial fuel-enrichment limit for water reflected configurations was found to be dependant upon the applied neutron cross section library. More detailed investigations showed that the difference is mainly caused by different sublibraries for thermal neutron scattering based on parameterizations of the S ( α , β ) scattering matrix. This paper addresses the main findings of these investigations and emphasizes which configurations are particularly sensitive to the parameterization of S ( α , β ) applied in the CSE analysis. The results are presented in an attempt, on the one hand, to assess more precisely the sensitivity upon thermal scattering modeling data in CSE of wet storage pools, and on the other hand, to assess whether the data employed in the most recent neutron data libraries can be considered as an improvement for this type of analyses.