CFD Simulation of High Temperature Corium Interaction with Coolant in Pre-flooded Cavity

Abstract

Many efforts have been concentrated on the study of the severe accident to guarantee the integrity of containment function when the reactor vessel is penetrated by high temperature corium. The present study focuses on modeling of ex-vessel fuel-coolant interactions such as jet breakup and debris bed formation by using a commercial CFD code, STAR-CCM+. The corium is assumed to have a very high temperature near 3000 K and injected directly into the pre-flooded cavity. As a preliminary study, the major objectives of the study are to evaluate the capability of the CFD code for the simulation of ex-vessel phenomena in extreme high-temperature and to establish the required CFD models. The heat transfer and phase change of coolant are described by the intrinsic boiling curve. The formation and movement of steam are modeled by adopting the volume-of-fluid (VOF) model and adaptive mesh control. The corium breakup mechanisms are incorporated by using detached eddy simulation (DES) turbulence model. The solidification process is considered by changing the viscosity of the corium with temperature change. The initial conditions and properties of corium are determined from the experimental condition of TROI test, which had been performed by the KAERI. The simulation results show that a large volume of steam is generated along the corium jet, which forms a steam pocket. It is observed that the jet breakup mechanisms are continuously exerted by the highly turbulent motion of the steam. This study is expected to contribute to expanding the insights on ex-vessel phenomena occurring in real plant situation.