Prevention of early containment failure due to high pressure melt ejection and direct containment heating for advanced light water reactors: Advanced Reactor Severe Accident Program

The current knowledge base on high pressure melt ejection (HPME) and its consequence, direct containment heating (DCH), has been examined by the Department of Energy (DOE) Advanced Reactor Severe Accident Program (ARSAP) for advanced light water reactors (ALWRs). A two-pronged approach for the design of evolutionary advanced pressurized water reactors (APWRs) has been developed for minimizing the potential for early containment failure due to an HPME event that involves DCH. Criteria are provided for APWR reactor cavity and lower containment configurations to limit the amount of debris and energy that could enter the upper containment atmosphere; this provides a passive method for mitigating DCH. Also, the means for rapid, deliberate reactor coolant system (RCS) depressurization are provided in APWRs; depressurization can be used prior to reactor vessel meltthrough to minimize high pressure driving forces, thereby preventing DCH. This report summarizes the technical bases, both experimental and analytical, supporting a conclusion that these design approaches preclude early containment failure due to HPME for risk-relevant sequences in APWRs. 50 refs., 11 figs., 5 tabs.