Benchmark experiment on slab 238U with D-T neutrons for validation of evaluated nuclear data

A benchmark experiment on 238U slab samples was conducted using a deuterium–tritium neutron source at the China Institute of Atomic Energy. The leakage neutron spectra within energy levels of 0.8–16 MeV at 60° and 120° were measured using the time-of-flight method. The samples were prepared as rectangular slabs with a 30 cm square base and thicknesses of 3, 6, and 9 cm. The leakage neutron spectra were also calculated using the MCNP-4C program based on the latest evaluated files of 238U evaluated neutron data from CENDL-3.2, ENDF/B-VIII.0, JENDL-5.0, and JEFF-3.3. Based on the comparison, the deficiencies and improvements in 238U evaluated nuclear data were analyzed. The results showed the following. (1) The calculated results for CENDL-3.2 significantly overestimated the measurements in the energy interval of elastic scattering at 60° and 120°. (2) The calculated results of CENDL-3.2 overestimated the measurements in the energy interval of inelastic scattering at 120°. (3) The calculated results for CENDL-3.2 significantly overestimated the measurements in the 3–8.5 MeV energy interval at 60° and 120°. (4) The calculated results with JENDL-5.0 were generally consistent with the measurement results.