• Establishing a coupling method with the employment of RELAP5/MOD3.4 and the ANSYS FLUENT. • Simulating the in-box LOCA using the coupling method to obtain the precise distributions of pressure and velocity. • Comparing the results from systematic analysis code and coupling method, validate the necessity of this method in the simulation of a complex component. As the key component of the fusion reactor, the nuclear safety of the tritium breeding blankets has attracted considerable attention. Since the conventional analysis methodology using the systematic analysis code cannot reflect the specific distributions of temperature and pressure inside the component, the coupling method has been proposed as a solution to this problem. In this article, the in-box loss of coolant accident (in-box LOCA), which represents one of the crucial design basis accidents proposed by Southwestern Institute of Physics (SWIP), is simulated using the coupling method with the employment of RELAP5/MODE3.4 code and ANSYS FLUENT. Simultaneously, the porous media approach is employed for the simulation of pebble bed regions in ANSYS FLUENT. The results indicate that the coupling simulation exerts a substantial influence on the helium spray rate during the accident, leading to a reduction in pressure distribution within the pebble bed regions. Furthermore, the temperature of the first wall (FW) material obtained from the coupling simulation is higher due to the reduced cooling capacity during the initial few seconds. The findings suggest that the pebble bed regions would have a considerable impact. It is recommended that this method should be employed for the purpose of obtaining precise and reliable results.
Hu et al. (2026) studied this question.