Validation of ENDF/B-VIII.0 Cross-Section Library for METAL-FAST Graphite Systems

With the update from ENDF/B-VII.1 to ENDF/B-VIII.0, the performance of this new library requires validation to determine whether recent updates have been effective at improving experiment calculation agreement.To that end, this paper seeks to examine a collection of experimental benchmarks pertaining to fast systems with graphite reflectors.The choice of fast graphite systems could allow the examination of changes made to non-thermal scattering data for carbon.Experiments were chosen from the ICSBEP handbook consistent with that aim and modeled using SCALE continuous energy Monte Carlo simulations.To gauge relative performance, experiments were modeled in both ENDF/B-VII.1 and ENDF/B-VIII.0 to calculate keff to a precision of 10 pcm and compare to experimental benchmark criticality.Of the eighteen selected experiments with graphite reflectors, all are fast metal systems, eliminating the need to examine the multiple new graphite thermal scattering laws.The implementation of ENDF/B-VIII.0 in place of ENDF/B-VII.1 in simulations saw a slight decrease in Root Mean Square Deviation (RMSD) and Absolute Mean Deviation (AMD) - this decrease was within the calculated uncertainty bounds and therefore is statistically insignificant relative to experimental uncertainties- but a significant decrease in the Mean Deviation (MD) of about 100 pcm was calculated, as well as a 20.1% increase in the number of benchmarks falling within experimental uncertainty (1σ)Ǥ The update indicates a marginal improvement in the agreement between experimental benchmark data and simulation model data for graphite used as reflector material in fast systems and reaffirms the value in the continued update of cross-section library data.