TEPCO: Meltdown of Fukushima #1 Occurred Sixteen Hours After Quake
"Around 7:30 p.m., the fuel was fully exposed above the water surface and overheated for more than 10 hours. At about 9 p.m., the temperature in the reactor core rose to 2,800 degrees Celsius, the melting point for fuel. At approximately 7:50 p.m., the upper part of the fuel started melting, and at around 6:50 a.m. on March 12, a meltdown occurred." [rdbrewer]