Study on Heat Transfer Characteristics and Nuclear Thermal Coupling Effect of HFETR High Temperature and High Pressure Test Device

To meet the design and development requirements of new PWR fuel assemblies in the high-flux engineering test reactor (HFETR) test loop, this study aimed to address the interference of complex heat transfer phenomena caused by the presence of the downcomer and riser in the active zone coolant channels on the nuclear power measurement. A full-scale three-dimensional model of the high-temperature and high-pressure test device was constructed based on the code STAR-CCM+, and the coolant flow and heat transfer characteristics were systematically analyzed. It was found that the heat transfer power of the diversion pipe and the downcomer of the irradiation device accounted for approximately 5% of the measured thermal power of the test assembly. Meanwhile, an external interface between the two codes Monte Carlo (MC) and computational fluid dynamics (CFD) was developed using the Python language to achieve rapid data interaction and coupled calculation of nuclear and thermal data. Ultimately, the deviation between the calculated and measured thermal power values before and after the nuclear-thermal coupling was reduced by 1.5%. The research results verified the effectiveness of the CFD model and the nuclear-thermal coupling method under complex structures, providing a high-precision thermal-hydraulic analysis method for the irradiation test of new PWR fuel assemblies.