Development and verification of the hexagonal core simulation capability of the NECP-X code

The whole-core high-fidelity calculation capability for hexagonal cores is developed in the NECP-X code for VVER and other hexagonal reactors, including the 2D/1D based transport and Global-Local resonance calculation methods. Furthermore, the spatial domain decomposition-based parallel strategy and the unstructured coarse-mesh finite difference (CMFD) acceleration method is developed to improve the efficiency, which can realize rectangular, hexagonal, and other polygon grid-based pin-by-pin acceleration. The C5G7 3D hexagonal benchmark problem is calculated to test the performance of the transport solver. The results agree well with the Monte Carlo solutions and demonstrate good acceleration performance. The code is then applied to the “X-2” VVER-1000 benchmark, and the results show that the bias of eigenvalue is less than 30pcm, and the maximum bias of assembly power is 0.61 %.