Effect and treatment of angular dependency of multi-group total cross section and anisotropic scattering in fine-mesh transport calculation

The whole core heterogeneous high-fidelity transport calculation is widely researched recently, where the spatial meshes reach sub-pin level to provide accurate results. In this context, two issues, namely angular dependency of total cross section and anisotropic scattering, which greatly affect the precision of multi-group transport calculation are assessed in this paper. Two pin cell problems respectively fueled with UO2 and MOX are calculated. The numerical results show that neglecting angular dependency of total cross section leads to over-estimation of flux in resonance groups in fuel pellet and under-estimation of eigenvalue. Using angular-flux-weighted total cross sections can effectively reduce the error of flux in resonance groups. For UO2 fuel pin cell, angular dependency of total cross section is more important than anisotropic scattering. While for MOX fuel pin cell, anisotropic scattering is more important. And then SPH method and a newly developed method called auxiliary term method are introduced and tested on UO2 and MOX pin cell and 3 × 3 super cell with control rod. The numerical results show that both of these two methods are capable of capturing the effect of the angular dependency of total cross section. The accuracies of the methods are comparable.