Fukushima

UPDATE, 7:30 pm, Friday, Units 1, 2 and 3 at the Fukushima Daiichi site have lost offsite power. Pressure is building up inside Unit 1 (a General Electric Mark I reactor, see below). The normal procedure to release the pressure is to vent the containment (a procedure that releases radiation into the air), but the utility has been unable to do so because of the lack of power. Plant workers may need to enter the containment to do so manually.

UPDATE, 6: 45 pm, Friday Numerous sources are reporting radiation levels at Fukushima to be 1,000 times higher than normal inside Unit-2 (though some sources have also reported high radiation levels inside Unit 1) and at least eight times higher than normal at the plant gates outside. The evacuation zone has been expanded to 10 kilometers (about 6 miles) from the Fukushima reactor site.

UPDATE, 3:30 pm, Friday, A Japanese Cabinet Office report released at 12:30 am Saturday, March 12, 2011 (Japanese time) predicts that fuel damage will occur at the Fukushima Daiichi Unit-2 reactor late Saturday night (Japan time, early Saturday morning US time) if cooling is not restored before then.

Activists believe this is indicative of an attempt to downplay potential radioactive releases, especially as Tepco says it plans to vent the containment to relieve pressure, which will cause release of radioactivity into the air. There are six nuclear reactors at the Fukushima Daiichi nuclear power site, located near the town of Okama in the Fukushima Prefecture. Another site in the same Prefecture, Fukushima Daini, contains four nuclear reactors. The sites are on the eastern Japanese coast about 200 miles north of Tokyo. All of these reactors are owned and operated by Tokyo Electric Power Co. (Tepco). The earthquake of appears to be causing the greatest problems for the Fukushima Daiichi reactors, although several reactors at both sites were affected by the earthquake. Specifically, Fukushima I-2 has lost backup power and necessary cooling capability. As of 11:30 am Eastern time March 11, cooling capability has not been restored.

This factsheet will be updated as new information becomes available. Michael Mariotte,

For perspective, a radiation level of about 0.19 MicroSieverts/hour is roughly equivalent to the maximum allowable radiation exposure level (1 MilliSievert/year or 100 Millirems/year (note 0.19 actually comes out to 166 mrem/year) for the United States. Until , that was also the allowable exposure level in Japan.

presentation from Tokyo Electric Power on how high-level radioactive waste is stored at Fukushima (including pool inventory and dry cask info).

At least one reactor at the complex, Fukushima I-3, began using MOX (mixed plutonium-uranium) fuel in

On , the same Fukushima I-2 reactor experienced a loss-of-power accident. According to Citizens’ Nuclear Information Center, “On June 17, Tokyo Electric Power Company’s Fukushima I-2 (BWR, 784MW) scrammed due to a problem with the generator. Power was lost for a time, because the switchover to the offsite power supply was unsuccessful. As a result, the feedwater pump stopped and the water level in the reactor core fell about 2 meters. The emergency diesel generator started up just in time, so the Emergency Core Cooling System was not activated. The water level was restored by an alternative pump in the core isolation cooling system.”