Analysis of containment venting strategy under severe accident conditions

Under severe accidents without containment heat removal, the containment integrity can be challenged due to over-pressurization by the steam and non-condensable gas generation. Containment filtered venting has been considered as an effective measure to avoid or delay the containment failure by over-pressurization. In order to minimize the environmental effects and maximize the effectiveness of filtered venting, it is critical to initiate venting in timely manners with sufficient discharge flow rate. It is also important to optimize the vent line size to prevent additional risk of leakage and to minimize the space and the cost requirement. In this study, the various venting strategies are investigated with respect to possible release flow characteristics. First of all, the accident scenarios representing the core meltdown accident with containment pressurization are selected by reviewing relevant literature. With those scenarios, thermal hydraulic behaviors in the containment and the discharge flow depending on the different venting strategies (i.e. vent line size and vent initiation pressure) are analyzed. MAAP5 model for the OPR1000 Korean nuclear power plant has been used for simulation.