Particle effects on penetration and solidification of flowing mixed melts on metal structures

In severe-accident analyses of liquid-metal-cooled reactors, assessing the relocation and solidification of disrupted core materials is of importance. We investigate here the fundamental characteristics of these behaviors in flowing melt mixed with solid particles under various conditions. To simulate the melts, we use a low-melting-point metal (viz., Bi-Sn-In alloy) mixed with various concentrations of copper and bronze as solid particles; the flow channels used were inclined open ones with a V-shaped cross section made of either stainless steel or brass plate. Transient melt flow was recorded, and melt penetration lengths and frozen melt distributions along the channel were measured. Results indicate that penetration length decreases for molten-metal/solid particle mixtures (mixed melts) compared with a pure molten metal (a pure melt), as well as decreases with decreasing solid particle size and increasing particle volume fraction in the melt. For the pure melt, we found only one freezing mode of all melt adhesions along the channel, whereas there were two freezing modes of melt separation with high solid particle concentrations, as well as melt adhesion, along the channel for mixed melts. The results obtained will be utilized in an experimental database to validate and improve physical models used for reactor safety analysis codes.