Experimental study on water injection and stratified steam explosion at the top of metal molten pool

Abstract

Metal layer induced heat flux focusing effect of In-Vessel melt Retention (IVR) strategy has become important weakness for high power core (APR1400, CAP1400). Injecting water on top of the metal layer can take heat away from the top and relief from heat flux focusing effect, but there can be stratified steam explosion and hydrogen risk. In this study, SUS321 steel melt pool (∼1600℃) top flooding experiments have been conducted, under diverse injecting modes, for exploring coolability and steam explosion risk. The tests results showed that the water jet, whose injecting velocity was 10 m/s, could be able to pierce the steel free surface and trigger steam explosion, and concurrently, the larger injecting flux was, the more violent steam explosion became. But steel melt pool was cooled quietly under water droplets injecting mode. The light refractory oxide layer, floating at the steel melt pool surface, could build a barrier to separate the injecting water.