Ablation and melting relocation of hemisphere vessel due to natural convection

In order to investigate ablation failure mode of lower head with molten core during a severe accident of light water reactors, ablation and melting relocation experiments were conducted with a hemisphere vessel with a drain hole. Three different silicone oil were used to investigate an effect of fluid viscosity to simulate a molten core. The hemisphere vessel is molded with lead bismuth eutectic alloy. The vessel wall thinning and melt relocation occurred just below the silicone oil level by ablation due to natural convection. For the lower-viscosity silicone oil, it results in breaking all around the vessel wall. On the contrary for the higher-viscosity silicone oil, the drain hole were ablated as well which enhance drainage flow. The time series of ablated molten wall and silicone oil weights drained from the hole were quantified separately on the basis of measured volume and weight of drained fluids for the code validation.