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Why Lady Godiva Should be Replaced as the Default Validation Experiment for U-235 Nuclear Data

For the past seven decades the Lady Godiva benchmark (HEU-MET-FAST-001) has been the primary experiment used for 235 U nuclear data validation. The papers associated with large nuclear data library releases such as ENDF/B-VII.1 and ENDF/B-VIII.0 refer to it frequently. The reasons why HEU-MET-FAST-001 has been used as the primary validation experiment for 235 U nuclear data validation will be discussed in the following section. However, as discussed among the benchmark community, the standards associated with International Criticality Safety Benchmark Evaluation Project (ICSBEP) evaluations have changed throughout time; this is subject of the OECD/NEA WPEC (Working Party on Nuclear Criticality Safety) Subgroup 8. HEU-MET-FAST-001 is an older benchmark (issued during the inaugural year of ICSBEP in 1996 with only minor revisions occurring since then) and (along with many of the other benchmarks from this era) does not meet the standards for a modern benchmark. This work explores why HEU-MET-FAST-001 is useful for 235 U nuclear data validation and discusses other alternative validation experiments.

07 ISOTOPE AND RADIATION SOURCES↗

Hierarchical Division and Clustering of Group Structures

When using multigroup neutron transport models, it is important to choose a suitable group structure due to the impact on runtime and accuracy. Group structures at LANL have been largely pared down to a handful of commonly used group structures, such as the LANL-30 and LANL-70 group structures. By identifying the key boundaries for a given problem, more insight can be gained into why the commonly used group structures are accurate and when they are inaccurate. This work focuses on using hierarchical division and agglomeration methods to identify the most critical boundaries in these group structures, using the ICSBEP HEU-MET-FAST-001-001 benchmark as a case study.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗