Development of transport solver based on Hybrid Finite Element Method in Griffin

Abstract

A new lower-order transport solver option based on the Hybrid Finite Element Methods (HFEM) was implemented in Griffin, the MOOSE-based reactor physics code, to support core design calculations for advanced reactor applications. The HFEM formulation with spherical harmonics expansion (PN), also known as the variational nodal method, effectively solves spatially homogenized problems with strong transport effects. The residual evaluations of the HFEM weak form were derived and implemented in Griffin, with PN and diffusion options available in the new HFEM-based transport solver. The red-black iteration and the Coarse Mesh Finite Difference (CMFD) acceleration schemes are incorporated within the Richardson iteration framework to effectively solve the HFEM formulation. Performance tests conducted using the simplified ABTR benchmark problems demonstrated that the HFEM-based transport solver is a preferable option for solving problems with spatial homogenization and significant streaming effects, providing superior accuracy with appropriate p-refinement.