Quantification of Integral Benchmark Sensitivities to 1D and 2D Thermal Scattering Cross Sections

The sensitivity of two critical benchmarks to the individual components of the thermal scattering law cross sections was quantified in this work. The components in question were the incident energy dependent cross section (1D) and the exit energy and angle dependent cross section (2D). These individual components were characterized by creating ensembles of perturbed thermal scattering law files. These files were then mixed and matched to create a new set of files in which either the 1D or 2D cross sections were fixed to the unperturbed case and the other cross sections were perturbed. This process was performed using two moderator materials of key interest to the nuclear criticality safety community: light water and polyethylene. These two materials and their corresponding ensemble of perturbations were then used to calculate k_eff values of integral benchmarks chosen to have a significant sensitivity to the thermal scattering of light water and polyethylene, respectively. The results were then analyzed to show the effect the perturbation scheme has on the spread of eigenvalue results as well as how the design of the benchmarks affects the differences in the spread of results.