Review of 10 years of molten corium concrete interaction R and D. Potential applications for containment integrity

In the frame of severe accident studies for Light Water Reactors, Corium Concrete Interaction (CCI) is one of the phenomena that might lead to a containment failure through a direct leak to the ground water or as a consequence of a progressive overpressurization. At the end of the 90s, the remaining uncertainties on the melt-through delay and the impossibility to conclude on the corium melt stabilization by water addition on top of a corium melt conducted the scientific community to maintain their R and D efforts. During the last 10 years, experimental programs in United States or in different European countries have provided additional results on corium concrete interaction mechanisms for standard top cooling conditions but also with an advanced cooling concept designed for a new reactor generation. Associated interpretation activities performed in the frame of international workgroups and the status of models improvement are briefly described. Regarding the containment integrity, if we can perform now more realistic simulations, there is still the need to increase the knowledge on the different cooling mechanisms in order to identify in a proactive way the more promising mitigation options and evaluate the designers' or utilities' proposals for both new generation and existing plants. In that perspective the remaining issues for the different mitigation options are summarized and the perspectives for new programs underlined. (orig.)