Analytically Study On The Characteristics Of Passive Containment Cooling System

The integrity of containments is of extreme importance for ensuring the safety of nuclear power plants, especially in accident conditions. Since passive technologies have advantages of simplifying system operation, reducing human error, and power-independent etc., more and more research and development (R&D) institutes have shown their preference to use passive technologies in the design of containment cooling systems. In this paper,a numerical analysis has been conducted to study thermal-hydraulic characteristics of different configurations, such as open loop configuration (OLC), close loop single phase configuration (CLSPC) and close loop two phase configuration (CLTPC), for passive containment cooling systems (PCCSs).Using a home-made system analysis code of PCCS,the natural circulation flow rates and thermal powers of the OLC, CLSPC and CLTPC were compared, and structural parameters,operation parameters and initial conditions were further discussed to the system performance.The numerical calculation results show that the OLC, CLSPC and CLTPC of PCCS can start up normally and quickly, and achieve the minimum thermal power when the water temperature in the water tank increases to the saturate temperature. The height difference between the water tank and internal heat exchangers influences the flow rate and thermal power of the configurations in a limited degree, and the initial water temperature in the water tank has no influence the normal startup,thermal power in the stage of two phase flow of the systems, except of the flow and heat transfer in the stage of single phase flow. The comparisons of the three system configurations show that the OLC features simpler system configuration and higher thermal power than the other two configurations, and needs especial safeguard measures to deal with possible radioactivity leakage once the heat tubes of the internal heat exchangers are broken. The CLSPC and CLTPC of PCCS feature a better safety and worse capacity of heat removal than OLC. The latter requires the CLSPC and CLTPC a more heat transfer area for the same thermal power as the OLC, which increase the cost and difficulty of the PCCSs.