EXPERIMENTAL INVESTIGATION OF THE INTERACTION KINETICS BETWEEN METALLIC MELT AND SPECIAL CONCRETE

The ablation kinetics of special concrete, which has been developed as one of the candidate protecting materials for the EU-APR1400 ex-vessel core catcher, was investigated experimentally. Metallic corium and stainless steel melts were generated using an induction heating technique in a cold crucible and used for the interaction tests with the special concrete. The melt delivery system was designed to prevent the melt impingement effect and chemical changes of the concrete specimen owing to preheating during the melt generation process. The metallic corium melts above the activation temperature interacted with the concrete specimens very intensively, which led to an abrupt increase of concrete ablation. However, in the interactions with the steel melts, the concrete specimens were ablated slowly even though the melt temperatures were higher than the metallic corium melts. A postanalysis of the chemical compositions and microstructures of the ingot with the ablated concrete was peiformed to understand the ablation phenomena. It was found that the U and Zr contained in the metallic corium melt reacted with the oxygen released by the dissociation of ferric oxides in the special concrete above the activation temperature. As a result of the exothermic reaction, both the ablation rate and the reaction layer coefficient were increased with a higher melt temperature and exhibited higher values than those in the interactions with the steel melt. Moreover, it was verified that the oxidation quotients of U and Zr are higher than those of Fe and Cr.