Validation of the SCALE broad structure 44-group ENDF/B-Y cross-section library for use in criticality safety analyses

This report documents the validation of the recently developed 44-group ENDF/B-V based cross-section library (44GROUPNDF5). This cross-section set has been developed for use in the SCALE code system in the analysis of fresh and spent fuel and radioactive waste systems. Collapsed from a 238-group fine-structure cross-section library (238GROUPNDF5), this broad-group library contains approximately 300 nuclides from the ENDF/B-V data files. Additionally, ENDF/B-VI oxygen data have been substituted for ENDF/B-V oxygen, because of discrepancies in ENDF/B-V data. The 44 GROUPNDF5 library was tested against its parent library using a set of 33 benchmark problems in order to demonstrate that the collapsed set was an acceptable representation of 238GROUPNDF5. Results show that the broad 44-group structure is an acceptable representation of its parent 238-group library for thermal as well as hard fast spectrum systems. Accurate broad-group analyses of intermediate spectrum systems will require either a more detailed group structure in this energy range or a more appropriate collapsing spectrum. Further, validation calculations indicate that the 44-group library is an accurate tool in the prediction of criticality for arrays of light-water-reactor-type fuel assemblies, as would be encountered in fresh or spent fuel transportation or storage environments. However, a bias caused by inadequate representation of plutonium cross sections was identified. Further, a possible bias exists with respect to uranium enrichment; however, experiments referenced in this report provide an inadequate sampling of uranium enrichments. Additional work will be required to quantify any bias that may be present