Update 11:00pm: In a terrifying dispatch The New York Times reports that an explosion on Tuesday morning at the No. 2 reactor of the Fukushima Daiichi Nuclear Power Station means that Japan faces "the likelihood of a catastrophic nuclear accident." The explosion, which occurred shortly after 6 a.m., has reportedly damaged the reactor's containment structure and lead to orders for emergency workers struggling to control the overheating nuclear facility to flee. The Times reports:
If all workers do in fact leave the plant, the nuclear fuel in all three reactors is likely to melt down, which would lead to wholesale releases of radioactive material — by far the largest accident of its kind since the Chernobyl disaster 25 years ago.
Original post: The latest news reports arriving from Japan's Fukushima Daiichi Nuclear Power Station indicate that authorities are struggling to treat the three damaged reactors at the six-reactor facility, and that the fuel rods in one or more reactors may be beginning to melt, "increasing the risk of a wider release of radioactive material," according to New York Times-cited Japanese officials. There is, in fact, concern that rods in the second reactor of the plant have already begun to melt, after attempts to pump seawater in for cooling proved insufficient, the water level dropping enough to expose the rods.
As the world watched late last week, the magnitude 8.9 earthquake malfunctioned the cooling systems in several units of the nuclear reactors and multiple explosions have rocked the facility as radiation levels in the plant rose. 185,000 people have been evacuated and 230,000 units of ingestible stable iodine have been distributed to evacuation centers as a precautionary measure, notes the Washington Post.
The most damaged appears to be the Unit 2 reactor. Tokyo Electric Power Co. had been trying to use seawater to cool the nuclear fuel rods, but now Tepco is warning that "it had lost the ability to cool Fukushima Daiichi's reactor 2," reports the BBC. The current failure of officials to keep water levels up to cool the fuel rods has heightened the possibility of a meltdown (as to what a full or partial meltdown actually entails, read here). The Times puts it this way: "Government and company officials said fuel melting has almost certainly occurred in that reactor, which can increase releases of radioactive material through the water and steam that escapes from the container vessel." Japan's Chief Cabinet Secretary Yukio Edano, quoted by the BBC, returns an opinion still more dire, discussing melting in all three reactors: "Although we cannot directly check it, it's highly likely happening."
Despite the explosions at Units 1 and 3, officials at Tokyo Electric Power Co. have previously today said that "conditions are stable" at those reactors and only "small amounts" of radiation from them have been released into the environment, reports the Los Angeles Times.