Simultaneous Evaluation of Fission Cross Sections of Uranium and Plutonium Isotopes for JENDL-3.3

Abstract

A simultaneous evaluation of the fission cross sections of 233U, 235U, 238U, 239Pu, 240Pu and 241Pu 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 233U and the cross sections above 15MeV, and give smaller X2 value than the JENDL-3.2 cross sections. The averaged fission cross sections of 233U, 238U, and 239Pu relative to that of 235U were calculated for a neutron spectrum produced by 9Be (d,xn) reaction. It was confirmed that the calculated cross-section ratios are in good agreement with the experimental data.