Development and verification of the high-fidelity neutronics and thermal-hydraulic coupling code system NECP-X/SUBSC

The development and verification of a coupling code system named NECP-X/SUBSC which integrates a high-fidelity neutronics code NECP-X and a thermal-hydraulics (T/H) subchannel code SUBSC are presented. In order to accomplish high-fidelity, improved and realistic geometry modeling such as semi-explicit representation of grid spacer, resonance self-shielding treatment with pseudo-resonant-nuclide subgroup method, anisotropic scattering treatments and 2D/1D fusion method are implemented in the NECP-X code. A group of benchmark problems, including VERA core physics benchmark progression problems 2–3, are utilized to verify NECP-X. A sub-channel code SUBSC is developed for the pin-by-pin thermal-hydraulics calculation. The high-quality experimental data provided by the OECD/NRC PWR Subchannel and Bundle Tests (PSBT) benchmark is used to validate SUBSC. After assessing the two separate codes, an internal coupling method is used to integrate SUSBC with NECP-X. Finally, the coupling code system NECP-X/SUBSC is applied to the VERA core physics benchmark problem #6, 3D Hot Full Power (HFP) assembly. Axial normalized pin power shapes for the pin with the highest power and the pin at the assembly corner, subchannel exit coolant temperature and volume averaged fuel pin temperatures at the axial level of maximum temperature are compared to results from the Consortium for Advanced Simulation of Light Water Reactor (CASL)’s MPACT/CTF code.