Host: The Japan Society of Mechanical Engineers
Name : The 30th International Conference on Nuclear Engineering (ICONE30)
Date : May 21, 2023 - May 26, 2023
The helium cooled ceramic breeder blanket (HCCB) is one of the candidate conceptual designs for the China Fusion Engineering Test Reactor (CFETR) blanket. A typical accident sequence involved in the design phase of the fusion reactor is the In-vessel Loss of Coolant Accident (In-vessel LOCA), which is caused by the coolant pipe rupture of the first wall of the helium-cooled blanket. During the accident, the high-temperature and high-pressure helium gas will be discharged into the vacuum vessel from the first wall coolant pipes. Due to the very high-pressure ratio between the coolant and the vacuum vessel. A highly-under-expanded jet phenomenon is expected to occur.
During the accident, the pressure and temperature distribution in the vacuum vessel may be in a very uneven state due to the high y under-expanded jet and there exists a local risk. Therefore, a helium jet simulation model under In-vessel LOCA condition is developed using the CFD approach. The distribution of pressure and temperature in the vacuum vessel is obtained. The simulation results with suitable turbulent models are in good agreement with the relevant supersonic jet experiment data.
The results show that high-pressure helium gas is discharged into the vacuum vessel with sound velocity and subsequently expands to supersonic jet. Near the inlet region, the structure of Mach disk is developed. At the beginning of the accident, the pressure and temperature distribution in the vacuum vessel is not uniform. The pressure peak appears near the wall where the jet collided. The temperature peak occurs in the vessel opposite the break. The results can be used as a supplement to the system-level analysis and provide a reference for the design of the CFETR safety system.
