Results of Recent Investigations at Sandia National Laboratories on Core Debris Interactions with Concrete

Studies of core debris interaction with concrete have been extensive over the last decade. These studies have reached a climax in recent tests of the interactions of prototypical melts of UO₂, ZrO₂, zirconium, and stainless steel with concrete. Zirconium metal has been found to have profound effects on melt interactions with concrete. Zirconium metal reacts with condensed-phase products of concrete decomposition as well as with steam and carbon dioxide evolved from the concrete. Models of core debris interactions with concrete have been modified to include heat produced by the condensed-phase reactions of zirconium. The modified models predict well the high-temperature interactions of prototypical melts with concrete. Discrepancies between predictions and observations are being addressed by improving models of phase relationships in the melt-concrete system.