AP1000® Passive Cooling Containment Analysis With Computational Fluid Dynamics Codes

Abstract

The passive safety systems of the AP1000® nuclear reactor are based on natural phenomena to ensure containment integrity during an accident. One of the most important passive systems is the Passive Containment Cooling System (PCS), responsible for cooling the containment in operation and during an accident, guaranteeing the core residual heat evacuation. The main objective of this research is to simulate the performance of this passive cooling system under operating conditions and in a LBLOCA type accident. Simulations were performed with the codes STAR-CCM+ 10.04 and GOTHIC 8.1 reproducing the airflow established by natural circulation to ensure the reactor containment cooling. The results of these simulations show how the cooling caused by the natural circulation is enough to evacuate the reactor residual heat, both in operation and under LBLOCA conditions. The temperature and flow stabilization during the transient evidences a balance in the heat exchange between the air flow and the containment surface, maintaining a suitable heat transfer in the containment. In addition, the different simulations manifest how both the air flow and the flow pattern formed depend on the containment temperature, and the geometry of the components of the Passive Cooling System and the Shield Building. The Shield Building model is a part of the AP1000 full containment model with the GOTHIC code, and it has been connected thermally to the inner containment model to simulate dynamically the PCS actuation.