Analysis Of Molten Core-Concrete Interactions And Its Influence

In a postulated core melt accident of PWR, if the molten core is not retained in-vessel despite taking severe accident mitigation actions, the core debris will relocate in the reactor cavity region. There, it will interact with the concrete basemat, producing lots of hydrogen, and may lead to containment failure through erosion. The combustion or detonation of hydrogen may cause early failure of the containment by thermal and pressure load imposed on RCB(reactor containment building). Once the containment failed, the radionuclides will release to the atmosphere and cause great threats to the public. Therefore the study of molten core-concrete interactions (MCCI) is an important task in severe accident analysis.By using a systematic code, the concrete ablation rate and hydrogen generation rate are focused in typical severe accidents of 600MW PWR. The accidents induced by station blackout (SBO), large and small LOCA are analyzed. Under different consequences, the total mass of debris falls into the cavity is different, which leads to different concrete ablation rate.Based on the analysis of concrete ablation rate under severe accidents, some influence of MCCI is discussed. It shows that the models of thermal resistance between the concrete and the debris, the configuration of debris layer, and the chemical reaction heat include or exclude the oxides as reactants take a great effect on concrete ablation rate. Some parameters relate to the lower head failure model also have some impacts on concrete ablation rate. As a mitigation action, the effect of wet cavity is discussed. It seems that the sooner and more water poured into the cavity, the better.The analysis of concrete ablation rate and hydrogen generation rate during molten core-concrete interactions may give some technical supports to the severe accidents management of a PWR.