"Nuclear fuel at the stricken Fukushima Daiichi power plant began melting just five hours after Japan’s March 11 earthquake, a Japanese nuclear engineer told a panel of U.S. scientists Thursday.
About 11 hours later, all of the uranium fuel in the facility’s unit 1 reactor had slumped to the bottom of its inner containment vessel, boring a hole through a thick steel lining, the University of Tokyo’s Naoto Sekimura told a committee of the National Academy of Sciences.
Sekimura’s assessment further damages the credibility of the plant’s operator, the Tokyo Electric Power Co. (Tepco). This week, the company admitted for the first time that nuclear fuel in three of the plant’s reactors had melted — a conclusion that independent scientists had reached long ago."
Brian Vastag and Steve Mufson report for the Washington Post May 26, 2011.