Comparison Analysis on Spreading Distance of Spill Molten Salt with Molten Core Material using Analytical Model

Abstract

As a part of small reactor developments for the GEN-IV (Generation IV) reactors, a MSR (Molten Salt Reactor) is selected for reactor technology and safety aspects worldwide. In a severe safety of the MSR, the most important thing is a loss of the molten fuel salt with the coolant in the primary system. For this reason, the spreading and cooling process of the spill molten fuel salt is very important for MSR safety. The corium spreading and cooling in PWR (Pressurized Water Reactor) was widely studied for severe accident mitigation. The developed methodology for corium spreading may be used for spreading of the molten salt in MSR. This is focused on preliminary comparison analysis on spreading distance and time of the spill molten salt in MSR with corium in PWR using a simple analytical model with or without crust formation. In general, the spreading of the molten salt is not big difference with the corium spreading without crust formation, because there is no big difference in material property of viscosity. The spreading is restricted by inertia due to a low viscosity and a high released rate of the spill molten salt or the corium, that is, gravity-inertia spreading regime. The spreading distance and time of the molten salt with crust formation in MSR are longer than those of the corium spreading in PWR, because of radiation heat loss to the environment.