A Three-Dimensional Time-Dependent Unstructured Tetrahedral-Mesh SP_N Method

A three-dimensional time-dependent multigroup SP_N method for unstructured tetrahedral meshes is developed. The SP_N equations are expressed in a canonical form that allows them to be solved using standard diffusion solution techniques in conjunction with source iteration, diffusion-synthetic acceleration, and fission-source acceleration. A computational comparison of this SP_N method with an even-parity S_N method is given.