First Tokyo Electric Power Company said there were no melt downs, as they struggled to cool the Fukushima Daiichi reactors with salty sea water.  Then TEPCo admitted there were melt downs in reactors 1 and 3, but said they were contained by the water at the bottom of the containment vessels.  Now an independent study says not so.

Tanabe Fumiya, an expert in nuclear safety, studied data from Reactor 3.  Reactor 3 uses MOX fuel.  Most of Reactor 3’s mixed uranium-plutonium oxide fuel might have made it through the containment vessel.  Fumiya says on 21 March 2011 TEPCo was unable to inject water to cool the reactor.  Over the next four days the fuel reheated and melted through.  This explains why plutonium is being found outside the reactors.