Thermal Hydraulic Performance Analysis for Passive Containment Cooling System of AP1000 in the Event of LOCA

The design of a nuclear reactor containment building is of key importance in order to enhance the safety of a nuclear power plant. Owing to nuclear accidents such as TMI, Chernobyl and Fukushima, more and more attention is paid to the passive concept in nuclear power development. In order to improve the safety of new generation nuclear power plant, passive systems are widely used, passive containment cooling system in AP1000 is one of the typical example of such kinds of systems. It’s function is to transfer the heat produced in the containment to the atmosphere and keep the pressure in the vessel below the threshold under such accidents as Loss of coolant (LOCA), main steam line break (MSLB), etc. The system operates based on natural circulations inside the steel vessel and in the air baffle outside the containment, and the cooling water is sprayed to the steel surface to enhance the heat transfer process. A proper model simulating the system behavior is needed for system design and safety analysis, and a multivolume lumped parameter approach is employed in order to analyze the containment integrity and to study the long term response of postulated Loss of coolant (LOCA) accidents and Main steam line break (MSLB) accidents. However, the temperature and pressure distributions cannot be described detailed by such model, which is important to study the T-H characteristics in the containment. In this paper LOCA has been simulated on MATLAB using a given pipe break size and the response of containment is analyzed. Furthermore, the results are compared with the results in the Westinghouse Design Control Document 2002. Then the thermal hydraulic performance is studied, the factors such as the air temperature, containment pressure and mass flow rate of the coolant and their effects on the containment are analyzed. This research is done to get further insight on the safety analysis of reactor containment regarding maximum temperature and stress calculation inside the containment.