BETA-EXPERIMENTS ON MELT-CONCRETE INTERACTION - THE ROLE OF ZIRCONIUMAND THE POTENTIAL SUMP WATER CONTACT DURING CORE MELT-DOWN ACCIDENTS

In the BETA test facility of Kernforschungszentrum Karlsruhe, prototyp ical core melts can be simulated in concrete structures sufficient in size to allow a computer-code-assisted extrapolation to be made to the reactor geometry. Three experiments have been carried out to investig ate special aspects of molten corium interacting with concrete. The in vestigations and measurements show the dominance of Zr oxidation durin g concrete attack by the chemical reduction of SiO2 to elemental Si an d the subsequent Si oxidation by the gases from the concrete. Addition ally, the failure of a cylindrical concrete wall was studied, which is eroded on the inner side by a heated melt while being cooled outside by stagnant water. In the experiment wall failure occurs and the melt relocates into the water annulus. Application of the experimental resu lts to light-water reactor severe accidents is discussed.