A 218 neutron group master cross section library for criticality safety studies

Abstract

The AMPX system was used to generate a P$sub 3$ 218 neutron group master cross-section library from ENDF/B-IV data for the fuel, structural, and neutron- absorbing materials tabulated. The library is the data base for the generation of broad-group cross sections for shipping cask calculations and other criticality safety analyses using codes such as KENO and ANISN. Selection of the fine-group energy structure for the 3-eV to 20-MeV energy range included consideration of the resonance structure of prominent nuclei, the thresholds of important reactions, and the fission spectra. For 10$sup -5$ less than or equal to E/sub n/ less than 3 eV, 78 closely spaced thermal groups were chosen to examine the effects of low-energy resonances and thermal-neutron upscatter. Distribution of the 218 groups within the Hansen-Roach 16-group boundaries is shown. Adequacy of the group structure and validity of selected data sets from the library were tested by P$sub 3$S$sub 8$ XSDRNPM calculations of k-eff for two benchmark critical experiments; first, the 4.9 percent-enriched UO$sub 2$F$sub 2$- H$sub 2$O solution critical sphere experiment of Johnson and Cronin was analyzed, and, second, the 93.2 percent-enriched UO$sub 2$F$sub 2$-H$sub 2$O solution critical sphere experiment of Fox was analyzed. (auth