2D/3D GPU-accelerated deterministic neutronics solver based on planar method of characteristics and hybrid finite element method

The newly developed 2D/3D method operating over the unstructured mesh geometry is introduced. Implemented in the NuDEAL code, the method alternates the planar method of characterization (MOC) and the diffusion-based hybrid finite element (HFEM), with planar MOC solving the 2D decoupled fine mesh and HFEM providing 3D coarse mesh flux distributions based on the MOC solution. The consistency between the planar MOC and the diffusion HFEM is made with the devised consistency factors operating on volumetric and surface flux distributions. Furthermore, the consistent HFEM is fully accelerated using GPUs, which results in a 50-speedup in the red-black sweep compared to the runtime of the single CPU core. As a result, the accelerated HFEM takes less than 30 seconds to solve the multigroup benchmark problem, which is 20 times faster with a single gaming GPU than with a single CPU core.