Core-melt behavior in a LWR-containment

Three further experiments in the BETA facility have been carried out to investigate special aspects of molten corium interacting with concrete. The invesigation of Zr oxidation during concrete attack has been completed. The measurements show the dominance of Zr oxidation by the chemical reduction of SiO2 to elemental Si and the subsequent Si oxidation by the gases from the concrete. Serpentine concrete as used in Russian power plants releases a large amount of vapour and hydrogen when attacked by the hot melt. This is due to the high portion of crystal water in the serpentine mineral. Additionally, 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. The WECHSL code was improved in the description of the early melt/concrete interaction, predominantly in the high temperature phase of concrete erosion with high Zirconium content of the melt. (orig.DG)