Abstract:
The multigroup cross sections and scattering matrices are fundamental data for deterministic reactor physics calculation and reactor design. In the generation of group constants, many domestic and international codes adopt the asymptotic model for scattering in the epithermal energy region, which approximates the target nucleus as stationary and assumes a uniform distribution of the outgoing energy. However, this asymptotic scattering model may lead to discrepancies in the infinite medium multiplication factor exceeding 400 pcm. To improve the accuracy of scattering treatment in the resonance energy region, a resonance elastic scattering kernel calculation module, HNScatXS, has been developed in the advanced cross-section processing code AXSP. Firstly, the Doppler-broadened transfer kernels are accurately calculated using the anisotropic resonance elastic scattering kernel formula for arbitrary Legendre orders. The correctness of the method is verified by comparing the scattering kernels of different nuclides, temperatures, and incident energies. Subsequently, a scaling factor method is proposed for updating the IAEA69-group library in WIMS-D format, and it is validated using several benchmark problems. Numerical results show that the HNScatXS module can accurately account for the effects of neutron scattering on the energy spectrum. The proposed scaling factor method enables precise scattering kernel calculations with minimal modifications. When up-scattering effects are considered, noticeable changes are observed in both the fuel temperature coefficient and the eigenvalue when using accurate scattering kernels.