Analysis of AP1000 severe accident induced by SBO using MAAP5

摘要

The total loss of AC power is an essential initiating event of PWR which can lead to a severe accident like Fukushima in Japan. For such improbable accidents, three cases of severe accidents of AP1000 induced by the station blackout (SBO) were simulated based on MAAP5 code. This particular analysis was conducted at 100 core power with different approaches. For the case with auto depressurization system (ADS), the primary system pressure appeared to uphold a low level for a longer duration and the external reactor vessel cooling (ERVC) system had sufficient capacity to eliminate the heat from the molten pool with a ratio of ex-vessel heat flux to critical heat flux (CHF) at about 0.49. For the case without ADS, the reactor pressure vessel (RPV) rupture will occur due to the creep effect inducing a sudden shock to the containment, and the peak pressure in the containment is still under the level at which the inelastic deformation may take place. The hydrogen production of the case without ADS in the core is 83 more than that of having ADS, while the hydrogen mole fraction in the upper containment is lower before the RPV failure. Overall, our findings are meaningful and significant for comprehending the detailed process of AP1000 severe accident induced by SBO, which is the basic standard for the development of the severe accident management guidelines (SAMG).