EXPERIMENTS ON STEAM EXPLOSION BY INTERACTION OF WATER WITH SILICATE MELTS

An experimental set-up for the generation of mixtures of silicate melt (remolten volcanic rocks) and water and the triggering of steam explosions was built at the Institut fur Kernenergetik (IKE) at Stuttgart. The temperature of melts investigated ranged from 1200 to 1600 degrees C. The chosen experimental configuration resulted in mixtures of 0.5-20 ml of water in 125 ml of melt, the water dispersed into droplets that were entrapped by domains of melt. More than 300 experimental runs were performed using a variety of remolten volcanic rocks. Explosive premixtures were triggered by shock waves of less than 8 J kinetic energy. Only part of the melt and part of the water of the mixture reacted thermally, thus causing an explosion. The most intensive explosions were produced by reaction of about 3 ml of water and 6 ml of melt and released kinetic energy of more than 600 J. Higher melt viscosity resulted in weaker explosions. Higher mixing energy enhanced probability and intensity of explosions. Melt temperatures were only of minor influence. If bubbles of non-condensible gases were abundant in a mixture of otherwise explosive water/melt ratio, explosions could not be triggered.