PARTICLE METHOD FOR COMPLEX THERMAL-HYDRAULIC PHENOMENA IN SEVERE ACCIDENTS

摘要

Grids are not necessary for numerical simulation in moving particle semi-implicit (MPS) method The particles move as fully Lagrangian description. Governing equations are transformed to particle dynamics using particle interaction models representing differential operators. Phase changes between gas, liquid and solid are also modeled as particle dynamics. Neither the numerical diffusion nor the grid tangling appears when large deformation of interfaces takes place. Jet injection into a pool is calculated by the MPS method to investigate the basic behavior in fuel-coolant interaction. The jet penetration speed agrees well with that of an experiment. Fragmentation process of a melt droplet in vapor explosions is analyzed. Three-dimensional process is clarified. The MPS method is also applied to molten core-concrete interaction in SWISS-2 experiment. Stable crust is formed on the melt pool in this small-scale geometry. Rapid decrease of heat flux to the water pool agrees with the experiment.