A third blast has occurred at the Fukushima I site — this time in the #2 reactor. #1 and #3 already experienced explosions. They appear to all be hydrogen explosions from the buildup of hydrogen gas from the reaction of hot zirconium with water. (Zr + 2 H2O = ZrO2 + 4H as far as I can tell, though I’m not a freakin’ chemist.)
Earlier this morning (California Time), it was reported by official Japanese sources that the fuel rods at the #2 reactor had been out of the water — that is to say, uncooled — for almost two and a half hours, which is bad. (Though it does not mean the fuel itself was necessarily exposed to the air, or that the containment vessel had been breached).
Until this morning, California Time, there had been no mention whatsoever of problems at the #2 reactor — #1 and #3 were the only ones reported to be in trouble. Now #3 is apparently melting down, too (though by all confirmed accounts, the containment vessels are, for now, intact).
The disaster is now being rated as worse than Three Mile Island (TMI), which means it’s the second-worst civilian nuclear disaster in history, after Chernobyl.
The BBC Says:
The blast occurred at reactor 2 at the Fukushima Daiichi plant, which engineers had been trying to stabilise after two other reactors exploded.
One minister has said it is “highly likely” that the rods might melt. Radiation levels near the plant have risen.
The radiation levels, incidentally, were previously widely reported to have been falling, and U.S. news sources reported that as if it were an indication that the crisis was lessening.
Here’s The Japan Times, with a scary-ass headline:
Crisis continues at Fukushima nuclear plant as fuel rods exposed again
A crisis continued Tuesday at the troubled No. 2 reactor at the quake-hit Fukushima No. 1 nuclear power plant, as fuel rods became fully exposed again after workers recovered water levels to cover half of them in a bid to prevent overheating.
The plant operator, Tokyo Electric Power Co., said steam vents of the pressure container of the reactor that houses the rods were closed probably due to the battery problem, raising fears that its core will melt at a faster pace.
The firm said it will first lower the pressure of the reactor by releasing radioactive steam and open the vents with new batteries to resume the operation to inject seawater to cool down the reactor.
Earlier, cooling functions of the reactor failed, causing water levels to sharply fall and fully exposing the fuel rods for about 140 minutes. TEPCO said they could not pour water into the reactor soon as it took time for workers to release steam from the reactor to lower its pressure, the government’s nuclear safety agency said.
Earlier a cloud of radioactive dust billowed from the Fukushima Daiichi power plant after it suffered its second explosion in three days. [From the #2 reactor].
Government officials admitted that it was “highly likely” the fuel rods in three separate reactors had started to melt despite repeated efforts to cool them with sea water. Safety officials said they could not rule out a full meltdown as workers struggled to keep temperatures under control in the cores of the reactors.
The Fukushima crisis now rates as a more serious accident than the partial meltdown at Three Mile Island in the US in 1979, and is second only to the 1986 Chernobyl disaster, according to the French nuclear safety authority. After insisting for three days that the situation was under control, Japan urgently appealed to US and UN nuclear experts for technical help on preventing white-hot fuel rods melting.
At Three Mile Island, 30-50% of a single core melted, but the containment vessel was not breached. There is no indication so far that any of the three containment vessels at Fukushima I have been breached by either the explosions or the decay heat.