Comments on the ENDF/B-VI evaluation for {sup 235}U in the neutron energy region from 1 to 20 eV

Abstract

A discrepancy of 6% has been reported between the measured capture resonance integral of {sup 235}U and that calculated from the resonance parameters in ENDF/B-VI. This discrepancy may be due to the use of a value for the average radiation width which is too small. The possibility that small resonances whose widths are primarily capture were missed experimentally due to their proximity to resonances with large fission widths was also considered, but dismissed. Since accurate values of neutron widths, {Gamma}{sub n} and total widths,{Gamma}{sub T}, of resonances can be determined from transmission data and are not dependent on any normalization factors, an interim solution might be to assume an average radiation width {Gamma}{sub {gamma}} and calculate the fission width {Gamma}{sub f} for each resonance from the relation {Gamma}{sub T} -- {Gamma}{sub n} -- {Gamma}{sub {gamma}}. The ratio of the partial fission widths of the two fission channels for each resonance would be kept the same as in ENDF/B-VI data flies. The average value of the radiation width selected should also be consistent with differential and integral measurements.