Continuous-Energy ENDF/B-VIII.0 Cross Section and SCALE 6.2.4 Performance for Nuclear Criticality Safety Applications: <sup>1</sup>H, C, <sup>58,60</sup>Ni, <sup>182,183,184,186</sup>W, <sup>235,238</sup>U, <sup>239</sup>Pu
Creators: name: Shaw, Alex
name: Rahnema, Farzad
name: Holcomb, Andrew
name: Bowen, Doug
Publisher: name: Taylor & Francis
Year: 2022
Subjects: subject: Biochemistry
subject: Medicine
subject: Cell Biology
subject: 59999 Environmental Sciences not elsewhere classified
subject: FOS: Earth and related environmental sciences
subject: 39999 Chemical Sciences not elsewhere classified
subject: FOS: Chemical sciences
subject: Immunology
subject: FOS: Clinical medicine

description: As part of the nuclear data evaluation and validation cycle, the ENDF/B-VIII.0 cross-section library released in 2018 requires testing to determine areas of improvement and deterioration. Previous work by the authors investigated the performance of <sup>16</sup>O, <sup>56</sup>Fe, and <sup>63,65</sup>Cu cross sections, with this study acting as an extension of the prior work. In addition to the isotopes and nuclear criticality safety benchmarks of interest to the prior work, benchmarks from the International Criticality Safety Benchmark Evaluation Project Handbook were selected for their k<sub>eff</sub> sensitivity to <sup>1</sup>H, C, <sup>58,60</sup>Ni, <sup>182,183,184,186</sup>W, <sup>235,238</sup>U, or <sup>239</sup>Pu cross sections and were modeled in the SCALE code system maintained by Oak Ridge National Laboratory. In total, 253 benchmark configurations were selected for their sensitivities and modeled using SCALE 6.2.4 Criticality Safety Analysis Sequences (CSAS) continuous-energy Monte Carlo k<sub>eff</sub> calculations. This collection includes and expands upon the 99 benchmarks in the prior work. The AMPX-processed ENDF/B-VIII.0 library was decomposed into individual ENDF/B-VIII.0 datum libraries for each isotope of interest. Doing so allowed for the individual substitution of an ENDF/B-VIII.0 cross section in the place of ENDF/B-VII.1, determining isotope-specific effects of ENDF/B-VIII.0 relative to ENDF/B-VII.1. Full library calculations with entirely ENDF/B-VII.1 data or entirely ENDF/B-VIII.0 data were also executed. As a measure of performance, the average relative deviation was determined as the ratio of the deviation between calculated and experimental k<sub>eff</sub> to the propagated calculational and experimental uncertainty. With calculated full library and isotope-specific ENDF/B-VIII.0 k<sub>eff</sub>’s, an optimized combination of data libraries was estimated and confirmed with SCALE calculations. This showed that reverting <sup>239</sup>Pu, <sup>58</sup>Ni, <sup>16</sup>O, and <sup>65</sup>Cu cross sections to ENDF/B-VII.1 resulted in improved performance relative to the full ENDF/B-VIII.0 library. Across all 253 benchmarks, the average relative deviation was 1.29σ for the full ENDF/B-VII.1 library, 1.17σ for the full ENDF/B-VIII.0 library, and 0.97σ for the optimized combination. The reversion of <sup>239</sup>Pu, <sup>58</sup>Ni, <sup>16</sup>O, and <sup>65</sup>Cu cross sections to ENDF/B-VII.1 in the 99 benchmarks of the prior work resulted in further improved experimental agreement compared to the previously reported improvement from <sup>16</sup>O and <sup>65</sup>Cu alone. Therefore, it is suggested that applications with significant sensitivities to <sup>239</sup>Pu, <sup>58</sup>Ni, <sup>16</sup>O, and <sup>65</sup>Cu consider their choice of nuclear data library.