Sorry for the shorthand version, but I wanted to quickly summarize what has happened since I last posted.
Operators were attempting to vent pressure inside the reactor vessel at Fukushima Daaichi Unit 1 when hydrogen gas ignited inside the reactor building, blowing out the walls of the building. Best guess for the source of the hydrogen was water coming in contact with extremely hot fuel rods, breaking the water into hydrogen and oxygen.
What is not known at this hour is if the relief valves on the reactor are still open, resulting in a direct pathway for radioactive gases now that the walls of the reactor building are gone.
A press report earlier today said that three people were exposed to radiation following the explosion. They were in a school yard near the plant, waiting to be evacuated by helicopter.
Press reports now say that mobile hospital facilities and potassium iodide tablets are being airlifted to the area around Fukushima, and plant operators are now pumping sea water into the facility in an attempt to keep the reactor cool.
Potassium iodide is used to prevent thyroid cancer in people exposed to radiation. The iodide prevents the uptake of radioactive iodine by the thyroid.
Sorry about the lack of sources. I’ll try to remedy that once some of the dust settles.