LAUSR

Abstract In the current design, the blanket plays an important role of transporting heat and breeding Tritium. It is very necessary to analyze the accident of the blanket. In this study, the RELAP5 model of the Water Cooled Ceramic Breeder blanket (WCCB) was established. The numerical simulation of the in-vessel loss of coolant accident (LOCA) on the first wall (FW) were conducted. The instability phenomenon was detected and analyzed for the first time. In 1-channel-break LOCA, the instability phenomenon occurs because of the subcooled boiling. The pressure amplitude of the break downstream is almost 2MPa. The mass flow rate amplitude is around 0.5kg/s. This large oscillation amplitude may damage the FW and cause more serious consequences. In 15-channel-break case, as the pressure is reduced to very lower level, the saturation temperature decreases, and the nucleate boiling instead of the subcooled boiling occurs. The instability phenomenon doesn’t occur. The results show that the current design of WCCB cannot remain safe in the large break LOCA. In order to avoid further damage, relevant safety facilities need to be studied.