Simulations for cooling effect of PCCS in hot leg SB-LOCA of 1000Â MW PWR

The simulation results obtained from the 4 models show similar transient process, the difference between the steady-state analysis of three models is less than 3%. Meanwhile, the large mass flow rate of water loss inside the containment induce a high flow rate of steam which could be uniformly mixed with air in a short time, the impact of steam injection to different directions on the simulation results is not obvious. For the self-condensing efficiency of 3 groups of PCCS system, the non-centrosymmetric injection position resulting that the condensing efficiency is slightly higher for the two heat exchanger groups nearby. During the first 2400 s of simulation time, more than 75.69% of the steam is condensed, the occurrence of condensation at the wall mainly driven by natural convection, the effect of thermodynamic siphon could improve the flow rate of gas mixture inside the tubes when the velocity of mixture is not large enough. The steam could smoothly enter the tube and reach the internal cooling surface then to be condensed. Besides, PCCS ensure that the containment internal pressure is maintained below 2 bar and the temperature is maintained below 380 K during 3600 s.