COMPARISON OF MEASURED AND CALCULATED NEUTRON TRANSMISSION THROUGH STEEL FOR A CF-252 SOURCE

The ENDF/B-VI evaluated nuclear data file, recently released by the U. S. National Nuclear Data Center, contains several improvements over ea rlier ENDF/B-IV and ENDF/B-V evaluations which are known to overestima te the iron inelastic cross sections in the energy interval above 1.0 MeV. In order to benchmark the ENDF/B-VI iron data, in this paper a co mparison is made of calculated vs measured neutron leakage spectra obt ained for a Cf-252 fission source located at the center of an iron sph ere. In addition, various response parameters that are sensitive to hi gh-energy neutrons are examined. It is found that although the ENDF/B- VI cross sections substantially improve the computed neutron transmiss ion relative to ENDF/B-V results, the differential energy spectrum obt ained using ENDF/B-VI above 1.0 MeV is generally lower than that of th e measurements. However, the integrated flux above the 1 MeV threshold is within the experimental uncertainty. The results appear to indicat e that the ENDF/B-VI cross sections will not entirely resolve the spec trum discrepancies observed at high neutron energies.