A series of TROI steam explosion experiments was performed using various prototypic melts. The melt was pure zirconia, eutectic corium ( 70: 30 weight percent of UO(2): ZrO(2)) or iron-added eutectic corium. In this series, an experiment with pure zirconia, two experiments with eutectic corium, and three experiments with iron-added corium were carried out. A steam explosion was found to be somewhat related to the melt composition and an external triggering. As with most of the previous tests, zirconia melt led to a steam explosion again. It is quite certain that a zirconia melt will more than likely result in an energetic steam explosion. Meanwhile, eutectic corium led to an energetic steam explosion by applying an external trigger, but it had a weak steam spike without an external trigger. The explosivity of eutectic corium cannot be ignored, as an external trigger led to an energetic steam explosion. Iron-added corium did not lead to an energetic steam explosion. The reason for this is likely to be a relatively low melt temperature ( superheat) when compared to zirconia melt or oxidic corium melt, resulting from the melting method used in the TROI experiments, an induction heating applied to a cold crucible. The iron-added corium at a low temperature was solidified easily so a steam explosion did not occur.