WPEC Subgroup Proposal
نویسندگان
چکیده
The cross sections of 235U were examined by WPEC Subgroup 18 focusing on the thermal and epithermal energy region. As a result, the ORNL group evaluated resolved resonance parameters of 235U up to 2.25 keV, which are currently used for all major libraries. Using the resolved resonance parameters, prediction accuracy of neutronic characteristics is satisfactory for thermal reactors. However, recent benchmark analyses have revealed a problem regarding the capture cross sections of 235U for fast-neuron critical experiments BFS and FCA using U fuels. The existing libraries JENDL-3.3, ENDF/B-VII.0 and JEFF-3.1 cannot describe the sodium voided reactivity and criticalities for these assemblies. The problem is attributable to large capture cross sections of 235U in the energy region form 100 eV to 2.25 keV where the same resolved resonance parameters are used for major libraries. Moreover, in the energy region from 30 keV to 1 MeV, there exists a big difference of 235U capture cross sections between JENDL-3.3 and ENDF/B-VII.0. The purpose of the subgroup is to address the problem of the U-235 capture cross section from the viewpoints of differential and integral data analyses and then obtain recommended cross sections in the energy region from 100 eV to 1 MeV.
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