Application of a two-call adiabatic model for direct containment heating to the ABB C-E system 80+ ALWR

During certain severe reactor accidents, such as those initiated by a station blackout or small-break loss of coolant accident (LOCA) degradation of the reactor core can take place while the reactor coolant system remains pressurized. If unmitigated, core materials will melt and relocate to the lower regions of the reactor pressure vessel and ultimately melt through the reactor pressure vessel (RPV) lower head. Once the RPV is breached, core debris will be ejected from the RPV and entrained from the reactor cavity by the high velocity gases blowing down from the reactor vessel. During the entrainment process, metallic constituents of the ejected material, principally zirconium and steel, exothermically react with oxygen and steam to generate chemical energy and (in the case of reactions with steam) hydrogen. Concomitant with the high pressure melt ejection (HPME) process, there is the potential for hydrogen combustion and vaporization of available water. The sensible heat loss to the containment atmosphere and the associated processes are typically referred to as direct containment heating (DCH). If large quantities of energy from the corium and corium-steam reactions are transferred directly to the containment atmosphere, the containment may pressurize to a point where failure is possible. Since the containmentmore » threat is coincident with vessel breach, relatively high containment radiation releases would be expected from this type of containment failure.« less