Development of discrete ordinates code supporting unstructured tetrahedral mesh and applied in neutronics analysis for the Korea Helium Cooled Ceramic Reflector Test Blanket Module

•We developed discrete ordinates transport solver which uses discontinuous finite element method (DFEM) as a spatial discretization to deal with an unstructured tetrahedral mesh.•For pre- and post-processing, Gmsh is used to generate unstructured tetrahedral mesh by importing CAD file (*.step) and visualize the calculation results.•We applied this code to a TBM neutronics analysis, the neutron flux distribution in the Korea HCCR TBM is compared with that of MCNPX, and visualized in a three-dimensional system domain.•Calculated total flux averaged over multilayer zone shows good agreement with that of MCNPX. The discrete ordinates code under development by KAERI uses an unstructured tetrahedral mesh, and thus it can be applied to solve the radiation transport in a complicated geometry. In addition, the geometry modeling process has become much easier because computational tetrahedral meshes are generated based on the CAD file by Gmsh. As our first phase of applying the code to a TBM neutronics analysis, the neutron flux distribution in the Korea HCCR TBM is compared with that of MCNPX, and visualized in a three-dimensional system domain. Visualization of the fluxes and associated reaction rates in the whole system with a single run is one of the merits of a deterministic method and is very useful for checking hot spots.