Unike three mile island

The most severe test of a containment system occurred during an accident in the United States in 1979 at Three Mile Island Unit 2, near Harrisburg, Pa. In this installation, a stoppage of core cooling resulted in the destruction, including partial melting, of the entire core and the release of a large part of its radioactivity to the enclosure around the reactor. In spite of a hydrogen deflagration that also occurred during the accident, the containment structure prevented all but a very small amount of radioactivity from entering the environment and must be credited with having prevented a major radioactive release and its consequences.

http://m.eb.com/topic/421763/nuclear-reactor#45760.toc

The same cannot be said in Fukushima so tragic.