Paper N ° 3.5 Investigations of Direct Containment Heating (DCH) in European Reactors: Database of Integral Tests and Progress in Modeling

The DISCO test facility at Forschungszentrum Karlsruhe (FZK) has been used to per-form experiments to investigate direct containment heating (DCH) effects during a severe ac-cident in European nuclear power plants, comprising the EPR, the French 1300 MWe plant P’4, the VVER-1000 and the German Konvoi plant. A high-temperature iron-alumina melt is ejected by steam into scaled models of the respective reactor cavities and the containment vessel. Both heat transfer from dispersed melt and combustion of hydrogen lead to contain-ment pressurization. The main experimental findings are presented and critical parameters are identified. In the framework of SARNET part of this experimental data base is subject for a com-mon interpretation work performed by the participating organizations, including application and assessment of the DCH in MAAP, ASTEC/RUPUICUV, COCOSYS and CONTAIN. Even the more mechanistic approaches in the models require the use and adoption of empiri-cal parameters which are specific to the layout of the plant and which have significant impact on the calculations. Based on the calculations the models are compared and their potential for predictions is assessed. Supporting analyses are performed with the multi-fluid code MC3D for a deepened understanding of the key processes of melt fragmentation and dispersal. A