Abstract: Using the measured leakage rate of the CARR building, MELCOR code was used to calculate the pressure of the building under the severe accident conditions. The results indicate that the maximum pressure difference in the progress of the accident is less than 5 kPa which is much lower than the structure design limiting value of 10 kPa; the calculated maximum leakage rates are lower than vol.2.5%/d in 8 hours and vol.2.8%/d in 1 day after the initiation of the accident. The dose of the radioactive fission product released to the environment is lower than the safety criteria under the leakage rate.