The explosion was likely a containment failure of the previously reported (radioactive) steam that had been building up in the containment building. More info:

The explosion was likely a containment failure of the previously reported (radioactive) steam that had been building up in the containment building. More info: http://www.world-nuclear-news.org/RS_Battle_to_stabilise_earthquake_reactors_1203111.html http://www.world-nuclear-news.org/RS_Battle_to_stabilise_ear...