Treatments of Thermal Neutron Scattering Data and Their Effect on Neutronics Calculations

In the conventional method to generate thermal scattering cross section of moderator materials, only one of the coherent elastic scattering and incoherent elastic scattering is considered in neutronics calculations. For the inelastic scattering, fixed incident energy grid is used in the nuclear data processing codes. The multipoint linearization method is used to refine the incident energy grid for inelastic scattering. We select ZrH_x (zirconium hydride) as an example to analyze the effects of the above described treatments on the reactivity of several critical benchmarks. The numerical results show that the incident energy grid has an obvious effect on the effective multiplication factor (k_eff) of the analyzed reactors; simultaneously considering the coherent and incoherent elastic scattering also affects k_eff by tens of pcm.