Simultaneous evaluation of fission cross sections of uranium and plutonium isotopes for JENDL-3.3

A simultaneous evaluation of the fission cross sections of U-233, U-235, U-238, Pu-239, Pu-240 and Pu-241 was carried out for the evaluated nuclear data library JENDL-3.3. A least-squares method was applied to selected absolute and relative measurements on the fission cross sections. Covariance matrices of the experimental data were constructed from the uncertainty information reported in the references. The fission cross sections obtained were compared with the JENDL-3.2 and ENDF/B-VI evaluations. It was found from the comparison that the present results are not so different from those in JENDL-3.2, except for the fission cross sections of U-233 and the cross sections above 15 MeV, and give smaller chi(2) value than the JENDL-3.2 cross sections. The averaged fission cross sections of U-233, U-238, and Pu-239 relative to that of U-235 were calculated for a neutron spectrum produced by Be-9(d,xn) reaction. It was confirmed that the calculated cross-section ratios are in good agreement with the experimental data.