Numerical simulation of fragmentation of melt drop triggered by external pressure pulse in vapor explosions

► A multi-phase thermal hydraulic code with volume of fluid method is developed. ► The molten metal drop fragmentation process is simulated to investigate the responsible mechanisms. ► The growth and breakup of filaments around the drop are numerically analyzed. ► High pressure spots which induce filament growth are observed in simulation results. ► Water jet penetration assumed in Kim's model (Nucl. Sci. Eng., 98, 16-28, 1988) is not observed in the simulation results.