Meltdown at Fukushima Daiichi Unit 1 began within 50 minutes

In an article entitled "Fukushima reactor had meltdown 3.5 hours after cooling system collapsed," the Mainichi Daily News of Japan has reported that a U.S. researcher at Idaho National Lab had concluded by late March that a meltdown had begun in the Fukushima Daiichi nuclear power plant's reactor unit 1 less than an hour after emergency core cooling ceased in the aftermath of the March 11 earthquake and tsunami. The researcher, Chris Allison, concluded that by three hours and twenty minutes, most of the melted nuclear fuel had already fallen to the bottom of the reactor pressure vessel, and that an hour after that, the molten mass had risen in temperature to 1,642 degrees Celsius -- close to the melting point of the stainless steel lining, likely resulting in damage to the reactor pressure vessel. NHK public broadcasting in Japan has reported that Tokyo Electric Power Company now admits the Unit 3 reactor may have melted down within two and a half days, and Unit 2 within four days, of the initial loss of power to run cooling systems.