Development of Numerical Simulation Method for Relocation Behavior of Molten Materials in Nuclear Reactors: Analysis of Relocation Behavior for Molten Materials With a Simulated Decay Heat Model

In order to precisely investigate molten core relocation behavior in the Fukushima Daiichi nuclear power plants, we have developed the detailed and phenomenological numerical simulation code named JUPITER for predicting the molten core behavior including solidification and relocation based on the three-dimensional multiphase thermal-hydraulic simulation models. In this paper, in order to distinguish a fuel component from core internals component in the JUPITER code, we added the multicomponent analysis method to the code and carried out to check effectiveness of the multicomponent analysis model based on the numerical simulation of melting behavior of the simulated fuel assemblies and core internals. From the present numerical results, it was confirmed that a newly developed multicomponent analysis method appropriately can predict the relocation behavior of molten materials in complicated structures, that is relocation and solidification behavior for fuel components including the heat source, i.e., simulated decay heat, and the core internals without heat sources from simplified fuel assemblies through the core support plate and simplified control rod guide tubes to the lower head in the reactor pressure vessel (RPV).