Study on the Remelting Process of the Debris Bed in the Lower Head of Reactor Pressure Vessel Based on Lattice Boltzmann Method

Abstract The retention of core melt (corium) in the lower head of the reactor pressure vessel (RPV) has been considered as a severe accident management strategy to maintain the RPV integrity of a light water reactor. To study the debris bed remelting process in the lower head of the reactor pressure vessel, as well to explore the influence of external cooling on the debris bed remelting process, the Lattice Boltzmann Method (LBM) is employed to simulate the remelting process of the debris bed. The Lattice Boltzmann Method, as a powerful numerical method for simulating fluid flow and complex physical processes, has been widely used in the solution of solid-liquid phase change problems in recent years. Thermal Lattice Boltzmann Method (TLBM) based on total enthalpy is adopted to handle the latent heat in the phase change process, and the Immersed Boundary Method (IBM) is used to account for the velocity and boundary conditions of the solid-liquid phase interface. In addition, the calculation results from the present LBM model are also compared with the experimental data based on the COREM experimental system which is design and constructed to investigate the melting process of a debris bed packed with multi-component particles. The simulation results and experimental results have good consistency in the natural convection phenomenon during the melting process, which is been simulated successfully.