Effect of Initial Particle Temperature on Formation of Ex-Vessel Debris Bed

Because severe accidents are caused by nuclear reactor failure, the formation of a debris bed is important to predict the coolability and safety of an entire containment system. However, owing to the difficulty of heating experiments, experimental data on the effects of thermal parameters on the formation of a debris bed are lacking. Therefore, in this study, experimental tests were conducted using the debris bed formation and coolability experiment facility. The cooling characteristics and debris bed formation process of heated particles falling into a saturated water pool were experimentally investigated. The results revealed that the cooling time for multiple heated particles was longer than that for a single heated particle. In addition, it was observed that high-temperature particles were significantly affected by convection flow. These results can be used as fundamental data for modelling debris bed coolability.