[en] Accident analysis was performed to calculate the behaviours of major thermal hydraulic parameters and to check the integrity of fuels during the loss of coolant accident in the KMRR which is designed to be operated under low pressure and low temperature conditions. For the analysis, RELAP5/MOD2 code for commercial power reactors in high pressure and high temperature conditions has been modified as RELAP5/KMRR to be applicable to the KMRR accident conditions. The major code modifications were made in the areas of the heat transfer correlation package, steam table and heat exchanger model to account for plate type heat exchanger characteristics. The simulation results show that the maximum centerline temperature of the fuel reaches 209^oC and subsequently drops although critical heat flux occurs in the hot channel. The calculation also shows that the pool natural circulation via flap valves and the emergency water supply system which are engineered safety features, have the capability of long term core decay heat removal and hence verifies their design adequacy. (author)