Research on natural convection of two-layer corium pools

As a promising mitigation strategy, In-vessel-retention (IVR) has been an important research focus in realms of nuclear safety analysis. For IVR analysis, it's of importance to study the natural convection behaviors of the corium pool formed in the lower plenum of the reactor vessel. Because of the different densities between corium compositions, typically the corium pool is believed to evolve to two-layer configurations, with a heavier oxide layer at bottom and a metal layer on top. To know better the convection behaviors of the layered corium pools, research was performed both experimentally and numerically. The test section for the experiment is a two-dimensional semi-ellipsoidal slice, which measures a span of 1.2m, a total pool depth of 0.75m and a thickness of 0.2m. Two immiscible fluid, i.e. fluorinert fluid FC-40 and water, were chosen to simulate the oxide layer and the metal layer respectively. Based on the experimental settings, numerical simulations were performed, and the results were compared with the experimental data. Further, discussions were made on the focusing effect, the relationship between the temperature and the velocity field, and also the coupling modes in the two-layer system. These results offer more details to the knowledge of layered corium pools and can be helpful for IVR analysis.