Japan has raised the alert level at the stricken Fukushima Dai-ichi nuclear plant from four to five on the seven-point international scale of atomic incidents March 18. The crisis, previously rated as a local problem, is now regarded as having "wider consequences." Officials said damage to the containment cores at reactors 2 and 3 prompted the raising of the severity grade. The level five rating does not yet apply to the cooling ponds that have lost water, despite the dangerous heating of the spent fuel stored there. Elevated radiation levels have been detected up to 30 kilometers away from Fukushima.

Japanese officials have ordered an evacuation within a radius of 20 kilometers (12 miles) of the plant, and told people who live 20 to 30 kilometers away to stay indoors and seal their homes. The US has told its citizens and military personnel in Japan to stay at least 50 miles away from the stricken plant

The 1979 incident at Three Mile Island in Pennsylvania also rated at five on the Nuclear and Radiological Events Scale (INES), whereas the 1986 Chernobyl disaster was rated at seven, a "major accident"—the only seven-rated incident in nuclear history. A level 6 incident was declared following an explosion in a waste tank at Kyshtym, Russia, in 1957. The Windscale incident in the UK that year was declared a level 5 incident. (BBC News, BBC News, March 18; NYT, March 17)

Tokyo Electric Power Co. (TEPCO) managing director Akio Komiri broke down in tears at a press conference announcing the move to level six, and the finding that radiation being emitted from Fukushima is now high enough kill humans. He acknowledged that response capacities have been overwhelmed, and that officials should have admitted earlier how serious the radiation leaks were. (Daily Mail, March 18)

Japan's Ministry of Defense has been sending specially equipped CH-47 Chinook helicopters to drop seawater over the Number 3 reactor building's cooling ponds, where spent fuel rods may have been exposed to air due to evaporation. The helicopter floors are fitted with lead plates to protect the crews, who also wore protective clothing. At the same time TEPCO repair crews were working to bringing power to the site from grid lines despite dangerous radiation conditions. (IEEE Spectrum, March 18; IEEE Spectrum, March 17)

See our last post on the Fukushima crisis.

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