Quasi-differential neutron induced neutron emissions from ²³⁵U, and ²³⁹Pu

Uncertainty in nuclear reaction cross sections, angular distributions, and other nuclear data directly impact how well simulations of nuclear systems represent physical observations. To determine how well the nuclear data in ENDF/B-VIII.0, JEFF-3.3, and JENDL-4.0 evaluations describe the physical behaviour of ²³⁵U, and ²³⁹Pu when subjected to a neutron flux, the neutron emission spectrum was measured for carbon, 93.0% ²³⁵U, and 93.9% ²³⁹Pu samples, and compared against detailed MCNP6 simulations. The measurements were performed at the Los Alamos Neutron Science Center using a quasi-differential method previously developed at Rensselaer Polytechnic Institute. The measurement spanned 0.82–20 MeV and 30–150 degrees. The measurements show there are a significant number of discrepancies between library predictions of the neutron yield and physical observation. A few of the main discrepancies found are described in this paper. Based on these results a new evaluation utilizing these results for carbon, ²³⁵U, and ²³⁹Pu is recommended.