Passive system reliability estimation with the accident development

Passive containment cooling system (PCCS) is novelly used in AP1000, which is one of the typical passive safety systems widely used in new generation reactor design. The system operates based on natural circulations in and outside the steel vessel, the heat produced in the containment will be transferred to the atmosphere by such processes, which is easily affected by some uncertain factors, air temperature, power, etc. Especially for PCCS the water sprayed to the outside surface of the containment is one of the crucial factors to heat and mass transfer, and the film on the outside surface of the vessel is influenced by the accident development. In this paper, we analyze the film under different accident conditions, then discuss the system reliability along with the accident scenarios.