An internal parallel coupling method based on NECP-X and CTF and analysis of the impact of thermal–hydraulic model to the high-fidelity calculations

An internal parallel coupling scheme was developed for the coupling between high-fidelity neutronics code NECP-X and sub-channel thermal–hydraulic code CTF. A new coupling iteration scheme is proposed based on NECP-X/CTF in which CTF will run after each NECP-X outer iteration. CTF was involved in NECP-X as a shared library object and driven by NECP-X, NECP-X and CTF have their coupling interface, respectively. Coupling data was transferred via memory rather than files. Based on the new developed high-fidelity neutronics/thermal–hydraulic coupling system NECP-X/CTF, the impact of the hydraulic cross-flow model, heat conduction model and gap conductance model was studied by calculating the VERA hot full power assembly and core cases. The results are compared with NECP-X/InternalTH model, a simplified closed channel thermal–hydraulic model. The numerical results show that the internal parallel coupling method is an effective approach for reactor core coupling simulation for the steady state calculation, the new coupling iteration method is more effective than traditional Picard iteration. The sensitivity analysis demonstrates that the cross-flow and gap conductance are very important parameters in coupling.