ABSTRACT
Ex-Vessel melt-water interactions can take place within cavities outside of the reactor pressure vessel (RPV) in both cases, boiling water reactors (BWR) and pressurized water reactors (PWR). These events are summarized under the phenomenology of “Cavity Phenomena”. Starting from the region, where an interaction takes place, pressure pulses penetrate the compartment. There are several effects, mainly acceleration of water slugs, acceleration of solid debris and impact of shock waves on structures. The chapter deals predominantly with the impact of shock waves. In general, the pressure pulse, generated by the extended and escalated triggering shock wave is high, but of short duration. Therefore it is not so much a major threat to the containment or compartment structure than the effect of the expansion of the highly pressurized reaction volume, left behind by the shock wave.
