[en] MELCOR code has been improved to estimate ex_vessel explosion work. First, steam explosion sample calculations and sensitive studies on uncertain parameters at PWR cavity were conducted using TEXAS-V, which is a mechanistic steam explosion analysis code. TEXAS-V simulations were performed to evaluate steam explosion work based on the thermal-hydraulic conditions of fuel and coolant, which cover the actual situation during the accident. Those results were used to prepare the look-up table. That table and Largangian interpolation scheme were merged into MELCOR code. To simulate fuel-coolant interaction at the reactor cavity. MELCOR input data were prepared. It was found that the improved MELCOR could estimate the steam explosion work at the reactor cavity from the look-up table for a given initial condition calculated from MELCOR. As the steam explosion module is limited by the upper and lower boundary of the look-up table parameters, these boundaries will be expanded to cover various accident sequences