Criticality Benchmark Results Using Various MCNP Data Libraries
- LANL
A suite of 86 criticality benchmarks has been recently implemented in MCNP{trademark} as part of the nuclear data validation effort. These benchmarks have been run using two sets of MCNP continuous-energy neutron data: ENDF/B-VI based data through Release 2 (ENDF60) and the ENDF/B-V based data. New evaluations were completed for ENDF/B-VI for a number of the important nuclides such as the isotopes of H, Be, C, N, O, Fe, Ni, {sup 235,238}U, {sup 237}Np, and {sup 239,240}Pu. When examining the results of these calculations for the five manor categories of {sup 233}U, intermediate-enriched {sup 235}U (IEU), highly enriched {sup 235}U (HEU), {sup 239}Pu, and mixed metal assembles, we find the following: (1) The new evaluations for {sup 9}Be, {sup 12}C, and {sup 14}N show no net effect on k{sub eff}; (2) There is a consistent decrease in k{sub eff} for all of the solution assemblies for ENDF/B-VI due to {sup 1}H and {sup 16}O, moving k{sub eff} further from the benchmark value for uranium solutions and closer to the benchmark value for plutonium solutions; (3) k{sub eff} decreased for the ENDF/B-VI Fe isotopic data, moving the calculated k{sub eff} further from the benchmark value; (4) k{sub eff} decreased for the ENDF/B-VI Ni isotopic data, moving the calculated k{sub eff} closer to the benchmark value; (5) The W data remained unchanged and tended to calculate slightly higher than the benchmark values; (6) For metal uranium systems, the ENDF/B-VI data for {sup 235}U tends to decrease k{sub eff} while the {sup 238}U data tends to increase k{sub eff}. The net result depends on the energy spectrum and material specifications for the particular assembly; (7) For more intermediate-energy systems, the changes in the {sup 235,238}U evaluations tend to increase k{sub eff}. For the mixed graphite and normal uranium-reflected assembly, a large increase in k{sub eff} due to changes in the {sup 238}U evaluation moved the calculated k{sub eff} much closer to the benchmark value. (8) There is little change in k{sub eff} for the uranium solutions due to the new {sup 235,238}U evaluations; and (9) There is little change in k{sub eff} for the {sup 239}Pu metal assemblies, but a decrease in k{sub eff} for the solution assemblies, moving them closer to the benchmark value.
- Research Organization:
- Los Alamos National Lab., NM (US)
- Sponsoring Organization:
- USDOE Office of Defense Programs (DP) (US)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 9446
- Report Number(s):
- LA-13627
- Country of Publication:
- United States
- Language:
- English
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