ABS T R A C T In this paper, the preliminary emergency core cooling scheme for Tsinghua high flux reactor is designed. The corresponding Relap5 model is established, based on which four double-ended rupture accidents are simulated. The four breaks are located at core inlet, core outlet, primary heat exchanger inlet and main pump inlet. The simulation results are presented. The core pressure, mass flow, coolant temperature, etc. in the transient process are studied and analyzed. According to the characteristics of the accidents, all break accidents are divided into four phases: non-shutdown phase, high-injection phase, low-injection phase and stable forced circulation phase. Sudo CHF correlations are used to predict critical heat flux. Results show that the minimum departure nucleate boiling ratios of four break accidents are larger than the safety limit of 1.5. The current emergency core cooling scheme can ensure core safety in the case of large breaks.
