Accident Analyses of Loss of Flow Accident for China HCCB HCS

-The design of China helium-cooled ceramic breeder helium cooling system (HCCB HCS) and the test blanket module (TBM) is currently in the preliminary design (PD) phase. Based on the conceptual design (CD), the TBM and HCS have been refined to ensure component manufacturability, and the safety analysis has been correspondingly updated. In this article, the loss of flow accident (LOFA) is simulated. The simulation is performed using the RELAP5 MOD3.4. Furthermore, a specific thermal radiation model is incorporated for parametric analysis. Six different cases are chosen to investigate the effect of the shutdown time of fusion power on the first wall temperature, the effect of natural circulation in the primary loop, and the feasibility of the removal of decay heat by thermal radiation after LOFA. The study provides a scientific basis for the design of the safety instrument control system of China HCS, in particular, the safety characteristics in the case of an LOFA. The results demonstrate that plasma power must be stopped immediately after this accident occurs, but the stopping method can be relatively moderate. Both fast and normal fusion power stops are satisfactory, and the temperature of the first wall structure material remains within the design temperature range. The natural circulation is effective in removing decay heat from the primary loop during this accident, and the thermal radiation is helpful for decay heat removal after the accident, particularly on the first wall structure.