Steam explosions of molten iron oxide drops: easier initiation at small pressurizations

Abstract

If a light water nuclear reactor core were to overheat, hot molten materials might contact liquid water and cause a steam explosion damaging to the containment structure¹. To predict such an occurrence and the ensuing damage, we in the Sandia National Laboratories have been performing large² and small^3,4 scale experiments coupled with analytical modelling^5,6. As part of this effort, we have been releasing single drops of a core melt simulant, molten iron oxide, into liquid water. Small steam explosions are triggered shortly afterwards by applying a pressure pulse to the water. The threshold peak pulse level above which an explosion always occurs was studied at ambient pressures between 0.083 and 1.12 MPa. Unexpectedly, the threshold decreased to a minimum in the range 0.2–0.8 MPa and then increased again. The observation that gentle pre-pressurization meant easier triggering should improve the predictive capability of our models and suggest conditions for reducing the hazards of these explosions.