Simultaneous evaluation of fission and capture cross sections and their covariances for heavy nuclei

Abstract

Abstract The fission cross sections of 235U, 238U, 239Pu, 240Pu, and 241Pu, and the capture cross sections of 197Au and 238U have been simultaneously evaluated for JENDL-3 in the energy range from 50 keV to 20 MeV. A generalized least squares method has been applied to estimate their cross sections and associated covariances from experimental data of absolute and ratio measurements. The experimental covariances were estimated from the partial errors for each measurement. The partial errors were categorized to a few groups which have specific correlation factors. The correlation only in neutron energies was taken into account. The presently evaluated fission cross sections of 235U and 239Pu are a few percent lower than those of JENDL-2 below 1 MeV.