Multigroup neutron reflection and leakage conditions for axial core models with anisotropic scattering

In this article, multigroup discrete ordinates interface conditions for neutron reflection and leakage were derived for axial models of nuclear reactors with anisotropic scattering. These conditions are completely free from spatial truncation error. The key to the derivation is a suitable reformulation of exact discretized equations - the multigroup spectral nodal equations - defined in the nonactive boundary regions at top and bottom. The resulting interface conditions can be used to replace the nonactive boundary regions of a nuclear reactor core in axial reactor computations. In order to illustrate the improvements that can be experienced by most one-dimensional multigroup discrete ordinates codes with our multigroup interface conditions, we perform a numerical experiment with a representative multigroup code and an axial core model with anisotropic scattering.