Investigations on the phenomenology of ex-vessel core melt behaviour (COMAS)

Within the COMAS (corium on material surfaces) project, representative experimental and analytical investigations on the ex-vessel spreading behaviour of prototypic corium were performed to provide a realistic technical basis for the development of core catchers for future nuclear reactor generations. In various large-scale experiments, melts in the Mg-range with real corium compositions and temperatures around 2000 °C were tested using different substratum materials (concrete, ceramics, cast iron). These tests were carried out at Siempelkamp's CARLA melting facility for radioactively contaminated metal scrap supported by laboratory experiments at Siemens, Erlangen. The COMAS results indicate that for a sufficiently high melt release rate a quick and homogeneous coverage of an ex-vessel spreading compartment as realized in the Franco-German EPR project can be expected. Regarding the analytical assessment, it can be concluded that some spreading codes have reached a sufficient level to provide guidelines for the evaluation of spreading concepts. Open questions are mainly related to segregation and immobilization of the melt.