Recent results from the Sandia steam-explosion program

The Sandia steam explosion program involves experiments at small and intermediate scale, and modelling and analysis, including estimates for the failure probability of the reactor pressure vessel and the containment building. Recent intermediate scale results show that molten corium A + R is as explosive as the molten simulant iron-alumina, with an average kinetic energy conversion ratio of approximately 2%. In addition, several iron-alumina tests produced rapidly sequential double steam explosions in which it appeared that the first explosion enhanced the coarse mixing process. Results at small scale indicate that the maximum pressure-volume product (the net work output) from the steam explosion of a single melt droplet increased four to five times for a ten-fold increase in ambient pressure. With the initial assumption that contact between molten core and coolant will produce a steam explosion, and futher assuming that such contact occurs in-vessel in the lower plenum, a Monte Carlo technique was used to calculate failure probabilities for a typical PWR