A review of research on melt and coolant interaction under different injection modes

The interaction of high-temperature melt with coolant, also known as fuel–coolant interaction (FCI) or coolant-coolant interaction (CCI), should be considered one of the crucial factors causing devastation in nuclear reactor accidents. Based on different accident scenarios, the interaction modes between melt and coolant can be categorized into the melt-injection (MI) mode and the coolant-injection (CI) mode. In previous research, performing visualization experiments of the CI mode was challenging due to the opacity of metals. Considering that the CI mode is geometrically opposite to the MI mode, it is promising to obtain the fundamental interaction mechanisms of the CI mode from the research on the MI mode. Therefore, this review systematically summarizes the essential theories, prevailing experiments, and simulations of melt-coolant interaction according to the different interaction modes, focusing on the thermodynamic and hydrodynamic interaction processes, as well as current hotspots and challenges. Its core significance is to analyze melt-coolant interaction from the opposite processes of the CI mode and the MI mode, which could provide a new perspective for the research of the CI mode. Meanwhile, this review offers valuable insights for the subsequent research directions of melt-coolant interaction, such as optimizing empirical parameters in existing theoretical models and developing corresponding interfacial heat transfer model and the thermal expansion model of vapor explosions, which is crucial for predicting the potential risk of nuclear reactor accidents.