Benchmark analysis of fission-rate distributions in a series of spherical depleted-uranium assemblies for hybrid-reactor design

The nuclear performance of a fission blanket in a hybrid reactor has been validated by analyzing fission-rate experiments with a series of spherical depleted-uranium assemblies. Calculations were made with the Monte-Carlo transport code MCNP5 and the ENDF/B-V.0 continuous-energy cross sections and compared to the measured results. The ratios of calculated to experimental values (C/E) for the fission rate and the fission-rate ratio of 238U to 235U are presented along with a discussion of the validation of the ENDF/B-V.0 library regarding its use in the design of the fission blanket. Overestimations are observed in the calculation of the 238U and 235U fission rates at all positions, except the ones near the outer surfaces of the assemblies, and the C/Es of the fission rate decreased as the thickness of the depleted-uranium (DU) layer increased, while most of the C/Es of the fission-rate ratio of 238U to 235U were close to unity, being within the range of 0.95-1.05.