Technical support for the EPRI [Electric Power Research Institute] debris coolability requirement for advanced light water reactors

The Electric Power Research Institute (EPRI) advanced light water reactor (ALWR) design requirement for cavity sizing to promote long-term core debris coolability specifies that the reactor containment be arranged to afford a floor area for potential core debris spreading of at least 0.02 square meters per thermal megawatt of reactor power. This requirement has substantial experimental and analytical support as a sufficient basis to ensure long-term debris coolability. A logical framework and presentation of such support is provided in this document. The evidence as presented demonstrates that, following vessel failure, core debris in the cavity would consist of a mixture of fragments and a relatively continuous, but porous and cracked, phase that would be distributed relatively uniformly over the area that would be available per the requirement. Considering pertinent operative heat transfer phenomena, it is also demonstrated that the heat removal rate from core debris in this configuration would be sufficient to ensure debris coolability in the reactor cavity, even when the cavity is flooded after vessel failure. 29 refs., 6 figs., 8 tabs