OpenMC interpretation and analysis of two series highly-enriched-uranium thermal-spectrum benchmarks for nuclear data validation.

• Two series HEU-THERM benchmarks are interpreted using OpenMC for nuclear data analysis; • Analysis of ENDF/B-VII.1, ENDF/B-VIII.0, JEFF-3.3, and JEFF-4 T1 is performed; • 9Be evaluation (especially for ENDF/B-VIII.0) should be reviewed; • Thermal Scattering Law (TSL) of BeO has a great influence on HMT-027 benchmarks (up to 2500 pcm); • TSL of metal Be is negligible for the HMT-026 experimental benchmarks. This study aims to provide additional validation of nuclear data performance through a comparative analysis of the evaluated nuclear libraries ENDF/B-VII.1, ENDF/B-VIII.0, JEFF-3.3, and JEFF-4 T1. The study utilizes the OpenMC Monte Carlo neutron transport code and integral benchmarks provided by the International Criticality Safety Benchmark Evaluation Project (ICSBEP) which have not been interpreted since their first modeling. The criticality benchmarks assemblies used in this study cover 2 series which are fueled with Highly Enriched Uranium (HEU) in Metal form (MET) and have Thermal neutron spectra (THERM), referred to as HMT-026 and HMT-027, respectively. The results show that for the HMT-026 benchmarks, ENDF/B-VII.1 and ENDF/B-VIII.0 have results close to experiments. The best global agreement with the HMT-027 experiments was found to be ENDF/B-VII.1. Through relevant critical and nuclear data sensitivity analysis, it is found that Be and BeO are respectively of crucial importance for HMT-026 and HMT-027 and the nuclear data of 9Be (especially for ENDF/B-VIII.0) should be reviewed. Additionally, it is worth noting that the Thermal Scattering Law (TSL) of BeO has a great influence on the k eff calculation for the HMT-027 benchmarks, while the influence of TSL of metal Be is negligible for the HMT-026 experimental benchmarks. [ABSTRACT FROM AUTHOR]