Submoment Expansion of Neutron-Scattering Sources

The submoment method was originally introduced to compute spherical harmonic moments of the neutron elastic-scattering source for discrete ordinates calculations with pointwise nuclear data. This work extends the submoment method to include discrete-level inelastic, as well as elastic, S-wave reactions. New applications of the submoment expansion to compute spherical harmonic moments of the slowing-down density and the elastic removal rate are also presented. Numerical stability and computational considerations are discussed.