A 2-D/3-D cartesian geometry non-conforming spherical harmonic neutron transport solver

A new 2-D/3-D transport core solver for the time-independent Boltzmann transport equation is presented. This solver, named Fiesta, is based on the second-order even-parity form of the transport equation. The angular discretization is performed through the expansion of the angular neutron flux into spherical harmonics (PN method). The novelty of this solver is the use of non-conforming finite elements for the spatial discretization. Such elements lead to a discontinuous scalar flux approximation. This interface continuity requirement relaxation property is shared with mixed-dual formulations discretized using Raviart–Thomas finite elements. Encouraging numerical results are presented.