Molten drop oxidation of zirconium mixed with stainless steel in water

Ex-vessel molten fuel-coolant interaction is important for evaluating the integrity of the reactor containment vessel during a nuclear power plant accident. When molten metal discharged from the reactor vessel interacts with water in the containment vessel, the oxidation of the melt in water affects the occurrence and magnitude of a steam explosion. This study presents a small-scale experiment in which molten droplets of stainless steel mixed with zirconium for compositions ranging from 0 to 30 wt% zirconium are dropped into a water pool to clarify the oxidation characteristics of the molten droplets in water. The solidified particles with a relatively spherical shape for different metal compositions and initial pool water temperatures are obtained, and the oxygen content of the solidified particles, the thickness of the oxide layer, and the elemental distribution of the solidified particle cross-sections are evaluated. The oxide layer thickness on the surface of solidified particles and the oxygen weight percentage of solidified particles increased with the increase of zirconium content or the increase of initial pool water temperature.