Design and Evaluation of Mitigation Measures for Tsinghua High Flux Reactor Loss-of-Coolant Accidents

Abstract Tsinghua High Flux Reactor is a planned new high flux research reactor in China. This paper designs a set of mitigation measures for loss-of-coolant accidents and preliminarily proposes the emergency core cooling scheme for Tsinghua High Flux Reactor. To verify the effectiveness of the current scheme, the corresponding Relap5 model is established, based on which break accidents at four different locations are simulated. 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 five stages: non-shutdown stage, high-injection stage, low-injection stage, stable forced circulation stage and natural circulation stage. The non-shutdown stage is the most dangerous, and thus high core pressure and flow must be guaranteed. Sudo CHF correlations are used to predict critical heat flux. Results show that the minimum departure nucleate boiling ratios of all break accidents are larger than the safety limit of 1.5. Therefore, the current scheme can ensure core safety even if a double-ended rupture accident occurs.