LAUSR

Abstract Some efforts have been made to exactly consider the effect of neutron up-scattering caused by thermal motion of target nuclei and resonance elastic scattering on the multi-group cross sections and scattering matrices. Firstly, the resonance elastic scattering kernel (RESK) formulations for anisotropic scattering up to any Legendre order has been adopted to represent the exact Doppler broadened energy transfer kernels. A semi-analytical integration method is applied to perform the RESK calculations. Combining with the RESK calculations, a linearization algorithm is proposed to generate the RESK interpolation tables. The RESK data can be interpolated precisely based on the interpolation tables to reduce the calculation burden. Secondly, a neutron slowing-down equation solver is developed based on the RESK instead of the conventional asymptotic scattering kernel, where the effect of neutron up-scattering on the neutron energy spectrum can be exactly considered. The accuracy of the multi-group cross sections and scattering matrices are significantly improved when the exact energy spectrum is applied for the group collapsing calculations. All the methods mentioned above have been implemented into a newly developed nuclear data processing code called NECP-Atlas. Numerical results show that the proposed methods are capable of producing accurate multi-group cross sections for downstream calculations; the fuel Doppler coefficients and eigenvalues of the real problems will be improved if the up-scattering effect is incorporated into the multi-group cross sections and matrices.