The Japanese safety agency has raised the country's nuclear severity rating as emergency crews continued frantic efforts to restore power and cool spent fuel pools at a quake-damaged plant.
Last Friday's 9.0 quake and the tsunami in Japan's northeast set off the nuclear problems by knocking out power to cooling systems at the nuclear complex. Since then, four of the plant's six reactor units have seen fires, explosions or partial meltdowns.
Japan's nuclear safety agency bumped the alert level at parts of the Fukushima Daiichi complex from Level 4 to 5 on a seven-level international scale on Friday. That puts it on par with the Three Mile Island accident in Pennsylvania in 1979.
The International Nuclear Event Scale defines a Level 4 accident as having local consequences and a Level 5 accident as having wider consequences.
"Japanese authorities have assessed that the core damage at the Fukushima Daiichi 2 and 3 reactor units caused by loss of all cooling function has been rated as 5 on the INES scale," the International Atomic Energy Agency said Friday.
The IAEA said authorities assessed the loss of cooling and water supply functions at the spent fuel pool at reactor 4 as a level 3, while the loss of cooling functions at Units 1, 2 and 4 were also rated as 3.
The rating change came as Japanese crews spent a second day spraying seawater on one of the plant's reactor units.
Japanese self-defence force members started spraying Unit 3 from the ground and the air on Thursday, and ground crews returned to the scene Friday to douse the fuel pools again, broadcaster NHK reported.
Special fire engines, including one lent by the U.S. military but operated by Japanese workers, were on the scene Friday, NHK said.
While crews worked to cool the reactors, the plant's operator, Tokyo Electric Power Co., is trying to restore power to at least part of the damaged plant.
"The company said today it made progress in restoring some power in a bid to restart the plant's electric cooling systems," CBC's Curt Petrovich said from Tokyo. "But given that there has been such extensive damage, it's not clear how much good that's going to do."
Jeremy Whitlock, a reactor physicist with Atomic Energy of Canada Ltd., said it appears that progress is being made, despite the increased alert level.
"Currently, we're not out of the woods," he said. "But it looks to be that it's in a stabilizing condition."
"What's happening in the plant is very dire, and very grave, and lots of good people are working around the clock in very harsh conditions, but it's always about what you are measuring offsite," Whitlock said.
He said like Three Mile Island, " we haven't had significant radiation releases offsite for the public, and that's always the final concern in this case."
In Geneva, the World Health Organization said Tokyo's radiation levels are increasing but are still not a health risk, and the group sees no reason to ban travel to Japan because of its nuclear crisis.
WHO spokesman Gregory Hartl said Friday the organization "is not advising travel restrictions to Japan" outside the 30-kilometre exclusion zone around the Fukushima Daiichi complex.
'Racing against the clock'
Meanwhile, Yukia Amano, head of the International Atomic Energy Agency, said he believes Japanese authorities are "racing against the clock,"and called for more support."This is not something that just Japan should deal with, and people of the entire world should co-operate with Japan and the people in the disaster areas," Amano said.
Municipal office employees observe a minute of silence in Tono, northern Japan, on Friday, to mark the one-week anniversary of the deadly earthquake that triggered a tsunami and nuclear crisis in Japan. Yuriko Nakao/Reuters Edano said Tokyo is asking the U.S. government for help and that the two are discussing the specifics.
"We are co-ordinating with the U.S. government as to what the U.S. can provide and what people really need," Edano said.
While Tokyo quickly welcomed international help for the natural disasters, the government initially balked at assistance with the nuclear crisis. That reluctance softened as the problems at Fukushima multiplied. Washington says its technical experts are now exchanging information with officials from Tokyo Electric Power Co. and with government agencies.
More than 6,900 are dead and more than 10,700 are missing after last week's earthquake and tsunami, Japan's national police agency said Friday.
Police said more than 452,000 people made homeless by the twin disasters were staying in schools and other shelters, as supplies of fuel, medicine and other necessities ran short. Both victims and aid workers appealed for more help, as the chances of finding more survivors dwindled.
About 343,000 Japanese households still do not have electricity, and about one million have no running water.
Tsunami survivors held a moment of silence in the afternoon at the one-week mark since the 9.0-magnitude quake.
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