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Japanese nuclear plants' operator scrambles to avert meltdowns
Experts said the decision to pump seawater into the unit was a recognition that the elaborate system of valves, pumps and pipes, and the layers of steel and concrete, might not be enough to guarantee that the nuclear facility could avoid a disaster of Chernobyl proportions.
The water and boric acid would absorb neutrons, Tokyo Electric said. But experts said it would also make it unlikely that the plant would operate again.
"We're past worrying about ruining the reactor," said Victor Gilinsky, another former commissioner at the U.S. Nuclear Regulatory Commission. "It's gone."
Already, Tokyo Electric reported that radiation levels next to the unit 1 building had increased nearly a hundredfold.
The Nuclear Energy Institute said the incident at Fukushima Daiichi had been given a rating of 4 on its 7-point International Nuclear and Radiological Event Scale, lower than the 5 earned by the 1979 Three Mile Island incident in Pennsylvania and the 7 earned by the 1986 Chernobyl disaster.
But many experts said it was too early to reach conclusions while new information was emerging.
Meanwhile, Tokyo Electric was still trying to get control over reactors at the second complex, Fukushima Daini. A water condensate system used to supplement the cooling system at Fukushima Daini unit 1 stopped working when temperatures reached 100 degrees Celsius.
Tokyo Electric also announced that it would carry out controlled releases to ease pressure in the containments of all four units at Fukushima Daini.
Nuclear safety experts were seeking answers to other questions about Japan's nuclear facilities that have been obscured by the focus on the Fukushima reactors. The nuclear plants also have spent fuel pools that some experts say may have spilled during the earthquake and its aftershocks. Tokyo Electric has not commented yet on those pools, which in the case of the General Electric-designed reactors are on the roof, possibly making them vulnerable.
Similar pools are found at other nuclear power plants around the country.
The U.S. government and private companies said they had offered assistance to Japan but had not received any requests. The Energy Department said it was "in close contact" with its Japanese counterparts and would "provide whatever assistance they request to help them bring the reactors under control."
Harlan reported from Tokyo.