The Development and Verification of the Thermal Scattering Cross Section Calculation Module ThermalXS in AXSP

Abstract: This work first developed a neutron thermal scattering cross-section calculation module, ThermalXS, using an adaptive incident energy grid in the independently developed nuclear data processing program AXSP, based on the neutron thermal scattering theory. The module calculated different types of neutron thermal scattering cross-sections using the thermal scattering law files of nuclei such as U, H, Zr, and compared them with the calculation results of the THERMR module in the NJOY2016 program, verifying the correctness of the ThermalXS module for thermal neutron calculations. On this basis, the changes in the graphite thermal scattering cross-sections in the ENDF/B-VII.1, ENDF/B-VIII.0, and ENDF/B-VIII.1 nuclear data libraries were analyzed and compared with experimental values. It was found that the latest ENDF/B-VIII.1 introduced a non-cubic formula and a one-phonon correction for the graphite thermal scattering cross-section, which compared to the incoherent approximation, showed better agreement with experimental values. The calculated reactor graphite thermal scattering cross-sections in ENDF/B-VIII.1 were found to increase with increasing porosity but were still much smaller than the experimental data for porous graphite, indicating that the functionality of the thermal scattering data generation module needs further improvement.