The sensitive analysis of radionuclide migration for the scenarios on deterioration or loss of safety functions expected in HLW disposal system due to the human error (initial defective scenarios) is performed in this study. Release rates for Cs-135 and Se-79 are estimated from Monte Carlo-based analysis. Maximum release rates of Se-79 and Cs-135 from natural barrier in initial defective scenarios for vitrified waste and overpack are approximately equivalent to that in normal scenario on all safety function working. Maximum release rate of Se-79 in initial defective scenario of buffer under the condition of colloidal migration is about 30 times as high as that in normal scenario. Maximum release rate of Cs-135 in initial defective scenario of plugs is about two orders of magnitude higher than that in normal scenario. These results especially indicate the need to understand the feasibility on two types of initial defective scenario, leading to the loss of restraint for colloidal migration in buffer and the loss of restraint with plugs from short-circuit migration.