Validation of core debris/concrete interactions and source term models

Severe nuclear reactor accidents---accidents involving the melting of the reactor core---dominate the residual risk associated with the use of nuclear power. The uninterrupted progression of a severe reactor accident is expected to lead to the expulsion of core debris into the reactor containment. Many safety-significant phenomena may be hypothesized to occur when core debris is expelled from the reactor coolant system. The exact nature of these events depends on whether or not the coolant system is pressurized at the time of melt expulsion and whether or not expulsion is into water. Regardless of what transient events are associated with the initial expulsion of core debris from the reactor coolant system, a protracted period of core debris interactions with the structural concrete of the reactor is expected in most analyses of severe reactor accidents. The physical consequences of core debris interactions with concrete have been routinely considered in severe reactor accidents for a long time. The first comprehensive account of core debris/concrete interactions appeared in connection with the reactor safety study. This paper reports that experiments to examine high temperature melt interactions with concrete did not validate the model used in the reactor safety study