An Acceleration Scheme for the Multigroup Sn Equations with Fission and Thermal Upscatter

Abstract

We have developed a three-step acceleration scheme for the outer-iterations of the multigroup Sn equations with fission and thermal neutron upscatter. Although it has only been tested in 1-D slab and 3-D rectangular geometries with linear-discontinuous and bilinear-discontinuous spatial differencing. respectively, previous experience suggests that it should be applicable in any geometry with any spatial differencing scheme for which an unconditionally efficient diffusion-synthetic acceleration scheme exists. The method is derived. theoretically analyzed, and computationally tested. Our results indicate that the scheme is unconditionally effective in terms of error reduction per iteration and highly efficient in terms of computational cost.