Abstract
Abstract Advanced Passive Pressurized Water Reactor (AP1000) is one kind of advanced generation III, also called generation III+, nuclear power plant which is designed by an American company, Westinghouse Electric. Based on generation III pressurized light water reactor, the design of AP1000 changes the safety system into passive type. The advantages of passive safety system are no longer needs power to motivate the emergency core cool down devices, and reduces the chance of human mistakes during operating. Although AP1000 is designed by the passive concept, still have to consider the chance and situation of severe accident that causes vessel fails while the decay heat is not able to be removed. To understand and predict the corium thermal-hydraulic behavior in the space between vessel and containment is the main task of this study. In order to predict the thermal-hydraulic behavior of corium in ex-vessel situation of AP000 nuclear power plant, CFD (Computational Fluid Dynamics) is used to simulate the event in this study. The radiation heat transfer and heat transfer on containment are ignored to simplify the problems. In the simulation of this study, Volume of Fraction Multiphase Model, Solidification Model, k-ε Turbulence Model, Energy Equation and other conservation equations are used to calculate the thermal-hydraulic behavior of corium. The velocity of corium flowing out of vessel will decrease by time after vessel fails. Corium will spread uniformly at the bottom of the space between vessel and containment in semi-solidification form. These information are quite important for improving the decay heat removing method and Severe Accident Management Guide (SAMG). Key words: AP1000, ex-vessel, corium, CFD