Updated The magnitude 8.9 or 8.8 earthquake that struck northeast Japan Friday has forced the evacuation of thousands within a three-kilometer radius of a nuclear power plant, after a failure in its cooling system lead to the threat of a fuel-rod meltdown that's yet to be fully mitigated.
According to Japan's Juji Press, the government declared a "nuclear emergency" after emergency diesel backup systems ceased functioning at the Tokyo Electric Power company's Fukushima No. 1 plant in Fukushima Prefecture. The same report indicated the government's concerns at the time that the plant "may not be able to have sufficient reactor cooling functions."
According to an AFP report, the International Atomic Energy Agency's Incident and Emergency Centre has said that they were informed by the Japanese Ministry of Economy, Trade and Industry (METI) that: "The four Japanese nuclear power plants closest to the quake have been safely shut down."
METI did not specifically mention which four plants those were, but a later Juji Press report said that in the Fukushima No. 1 plant's No.2 reactor, which had been shut down, water levels had dropped, "posing a threat of a radiation leak," and that the local government had urged residents within a two-kilometer radius to evacuate immediately.
A third Juji Press report extended that evacuation radius to three kilometers, and noted that Yukio Edano, Japan's Chief Cabinet Secretary – a position that includes press-secretary duties – had urged the 5,862 affected residents to remain calm.
The government also instructed the 45,345 residents within a 10-kilometer radius of the plant to remain in their homes, despite the fact that no radiation leak had yet been detected.
According to The New York Times, near midnight Friday Japan time, Japanese Trade Ministry officials told Jiji Press that the cooling system was to be reactivated and "should resume normal operations." The Reg however, was unable to find a second source for that report, nor is there any mention of it on the Jiji Press website.
According to Reuters, a spokesman for the World Nuclear Association – a nuclear industry trade group – told them that "we understand this situation is under control," after a battery-powered backup system was brought online and began pumping cooling water back into the affected reactor.
A source familiar with battery-power backup cooling systems, however, told the NYT that such systems typically have enough juice for only about four hours of operation. Should a consistent source of power not be restored by that point, the cooling water would boil away, and a fuel-rod meltdown would likely occur.
In perhaps the oddest detail in this still-developing story, the NYT also reported that: "United States Air Force planes based in Japan delivered emergency coolant to the plant, Secretary of State Hillary Rodham Clinton said." ®
Although the situation at the Fukushima nuclear plant was still unsettled as of Saturday morning in Japan, some additional details have emerged:
- Japan's Kyodo News reports that the country's nuclear safety agency is "set to issue an unprecedented order" to open a relief valve at the plant. Juji Press says that the release will involve not only reactor No.2, but reactors Nos. 1 and 3, as well. Venting the dangerous pressure build-up will also release radioactive steam into the environment – according to Yukio Edano, however, winds are blowing out to sea.
- Canadian television reports that "radiation has jumped to 1,000 times the normal level" inside the Fukushima plant.
- METI has now said that its earlier estimate that pressures inside the plant had reached 1.5 times normal levels were incorrect; the correct figure should have been 2.1 times overpressure.
- US officials have denied reports that they have provided coolant for the stricken plant.