Abstract

The Melt-Fuel-Coolant Interaction (MFCI) is one of the important phenomena during reactor severe accidents. In particular, the fragmentation process of the molten fuel in the metal coolant is a complicated multi-phase and multi-component heat transfer phenomenon accompanied by solid-liquid coupling and phase change, which is of great significance to the formation of debris bed on core catcher as well as the coolablity of debris bed after severe accident. It is of great significance to conduct research on MFCI of sodium-cooled fast reactor. A moving-particle-method based program is developed for the melt fragmentation analysis of sodium-cooled fast reactor in the present study. The program is based on the finite volume particle method and improved free surface pressure model, smoothing model, heat transfer and phase change model, interface surface tension model and solid-liquid coupling model are incorporated. Afterwards, the process of fragmentation is compared against the experimental data. The effects of initial temperature of melt, velocity of melt entering coolant, and jet diameter on the fragmentation are analyzed. The results show that the initial temperature of the melt has a great influence on the melt fragmentation, and a higher initial temperature makes the melt fragmentation more complete. Secondly, in the simulation of melt jet fragmentation, the process can be divided into six phases by analyzing the variation of the amount, the maximum mass, and the maximum size of fragments with time. Thirdly, by changing the initial velocity and diameter of the melt jet, it is concluded that the higher initial velocity and the larger melt jet diameter will produce a higher peak amount of fragments.

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