| After some serious accidents happened in the nuclear reactor, such as loss ofcoolant accident (LOCA) and the main steam line break accident (MSLB), thepressure and the temperature in the containment will rise because of theaccumulation of the hot medium (water, stream and hydrogen, etc). If the heat cannot be transferred in time, the pressure and the temperature may exceed the designedlimitation and may cause the failure of the containment. In order to prevent thecontainment failure, it is necessary to design a reliable containment cooling systemto control the consequences of accidents. The passive containment cooling systemstudied in this report generates the natural circulation driving force by the differencein density between the hot and cold fluids in the system circuit. The heat transfermechanisms of the system are condensation, convection and boiling. Depending onthe configuration structure the system can be classified into closed and open systems,because of the different operating pressure, the closed systems can be divided intosingle-phase and two-phase system.A computer code (PCCS-C) written by C program was used to analyse thethermal hydraulic behavior of the three systems under different containmentconditions and different system structure parameters. Depend on the numericalcalculation results we change the system configuration. The results of the code showthat all of the three system were self-adaptive with the containment conditions.Changing the system elevation difference in a certain range had no significant effecton the natural circulation capacity and heat removal capacity.According to the design and structural parameters, we also use theRelap5/MOD3.4code to simulate the operation of the different systems.Calculation results by PCCS-C and Relap5were compared. The results indicate thatthe numerical simulation of Relap5code are coincided with the PCCS-C code of the one-phase closed system, and they have the same trend of the two-phase closedsystem and the open system. |
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