Analysis On The Accident Of AP1000 Steam Generator Tube Rupture And Sensitivity Research

In this paper, to verify the design features of the AP1000, RELAP5 was applied to model refering to the process of SGTR accident from the westinghouse. Firstly, the trigger signal of the security system and the auxiliary system was set to calculate the figures of the steady condition and the transient one-tube-rupture conditon. Then the results were compared with those of Westinghouse's reports to make sure the validation of the present model. After that,based on the model of single tube rupture accident, the muti-tubes rupture accident was simulated. Then the effects of the off-site power and release valve were investigated to verify the safety of the passive design. Finally, the effects of tube rupture model and the node number were studied to do the sensitivity research.The results show that, the calculation results of RELAP5 model is quite consistent with those of Westinghouse. The values of the pressure, temperature and flow rate in steady condition agree well. The transient parameters' tendency matches and the values are slightly different. Because of the passive safety system, the AP1000 could make sure that the steam generator wouldn't overflow in the procedure of SGTR accident. However,the phenomenon of flow instability is happened in the muti-tube rupture accident because of two-phase flow ocuuring in the core. It should be noticed. The different tube reputure models change the process and the loss mass of coolant. The changed number of the nodes have an obvious effect on the critical flow rate. The reactor response to the accident is not significant impact by all the conditions and the steam generator doesn't outflow, which further confirms the security of the third generation nuclear power plant. The calculation results can be used for referencing in preparing the safety analysis report.