Scaling analysis of the spreading and deposition behaviors of molten-core-simulated metals

On March 11, 2011, huge earthquake and tsunami attacked Fukushima Daiichi Nuclear Power Plant. After the accident, research on plant decommissioning has become actively worldwide. Several research institutes have performed experiments to investigate methods of identifying the location and spreading/deposition behaviors of molten core debris in the bottom of Primary Containment Vessel (PCV) using Severe Accident (SA) analysis codes. Nevertheless, knowledge of spreading and deposition behaviors of corium is not sufficient, especially phenomena involving collision against the floor surface. In this study, experimental investigations on molten metal spreading and depositing behaviors on the steel plate were carried out. Zinc and copper were utilized for the molten metal samples and spreading behaviors were carefully observed using high speed video camera. Immediately after the collision between falling molten metal and steel surface, initial pause on spreading was observed. New scaling relation based on Dinh et al. (2000) was developed by focusing on the initial spreading pause of the molten metal droplet. Proposed correlation is capable to predicting the spread and deposition of falling molten metal at average error of 18.1%.