NHK World has the story here:
The operator of the damaged Fukushima Daiichi nuclear plant says steam was observed coming out of the floor of the No.1 reactor building, and extremely high radiation was detected in the vicinity.
Tokyo Electric Power Company inspected the inside of the No.1 reactor building on Friday with a remote-controlled robot.
TEPCO said it found that steam was rising from a crevice in the floor, and that extremely high radiation of 3,000 to 4,000 millisieverts per hour was measured around the area. The radiation is believed to be the highest detected in the air at the plant.
That's an astounding number, also expressed as 3 to 4 sieverts per hour. See this series of charts to appreciate the significance of the level, which is deadly:
It seems pretty clear that the earthquake damaged the floor of the reactor building, causing the crevice. And it also seems pretty clear that the water which has had to be supplied continually to the core to cool it has been leaking out, along with melted fuel materials, from holes caused in the pressure vessel by the meltdown and out onto the floor and into the crevice. Or something close to that.
A monumental mess.
