Bibliographic overview of German and French works about slug impact

The most severe mechanical consequence of an in-vessel steam explosion is the impact of a slug of molten core material against the head of the reactor pressure vessel. This matter has been mainly studied b y the german and french research centers FZK and CEA-Saclay for many years. FKZ aims at the quantification of the maximum mechanical energy that the upper head would be able to resist without failing. The investigation work is largely based on the german experiments BERDA which consist in simulating the impact of a slug on a reduced-scale replica models of the upper part of reactor pressure vessel. Besides this important experimental effort on refined mock-ups of the reactor, complementary experimental data have been acquired to help the interpretation of the BERDA tests. The transfer of the BERDA reduced-scale results to reactor dimensions is done by using scale factors based on similarity laws whose validity is checked thanks to the german test-facilities FLIPPER. As the BERDA tests are performed with a material different from corium because of the difficulties introduced by manipulating radioactive materials, the understanding of the slug material influence and the extrapolation to the corium is investigated with the french test-facilities SKIPPY. In order to deepen the understanding of the impact process and to extrapolate the experimental results to other combinations of parameters, corresponding theoretical work has been performed, mainly with the finite element code CASTEM-PLEXUS developed by CEA-Saclay. In this code, a specific model was implemented to represent a liquid splash against a solid structure. As this model suits well to the impacts investigated here, computations of the tests BERDA and SKIPPY were carried out by both german and french teams. The following chapters give a description of the experimental and numerical tools and summarize the main results obtained. (author)