Three triggered steam explosion experiments were performed in the TROI facility with a two-dimensional interaction vessel of 0.6-m diameter. The melt compositions were pure zirconia (ZrO2), 70:30 (UO2:ZrO2 = 70:30 wt%) eutectic corium, and 50:50 noneutectic corium. All tests were performed in a 1.0-m-deep water pool under atmospheric pressure. The water temperature was maintained at room temperature. The melt mass released to the water pool was [approximately]10 kg for each test. The tests with pure zirconia and 70:30 corium resulted in triggered steam explosions, while the test with 50:50 corium did not. However, a weak trace of a steam spike was detected with 50:50 corium with a fairly long delay time ([approximately]0.1 s) after an external triggering. The explosion efficiency was estimated from the dynamic load and dynamic pressure. The explosion efficiency was calculated to be 0.1% for zirconia and 0.04% for 70:30 corium. The explosivity of corium material was found to be rather low, compared to the simulant material (alumina, [approximately]3%).