Monday, March 14, 2011

NYTimes : Japan Faces Potential Nuclear Disaster as Radiation Levels Rise,Japan Three Reactors Raise Fear of Nuclear Disaster

Japan’s nuclear crisis verged toward catastrophe on Tuesday after an explosion damaged the vessel containing the nuclear core at one reactor and a fire at another spewed large amounts of radioactive material into the air, according to the statements of Japanese government and industry officials.

In a brief address to the nation at 11 a.m. Tokyo time, Prime Minister Naoto Kan pleaded for calm, but warned that radiation had already spread from the crippled reactors and there was “a very high risk” of further leakage. Fortunately, the prevailing winds were sweeping most of the plume of radioactivity out into the Pacific Ocean, rather than over populated areas.

Readings reported on Tuesday showed a spike of radioactivity around the plant that made the leakage categorically worse than in had been, with radiation levels measured at one point as high as 400 millisieverts an hour.

Even 7 minutes of exposure at that level will reach the maximum annual dose that a worker at an American nuclear plant is allowed. And exposure for 75 minutes would likely lead to acute radiation sickness.

The cascade of problems at Daiichi was initially difficult to interpret — with confusion compounded by incomplete and inconsistent information provided by government officials and executives of the plant’s operator, Tokyo Electric Power.

But industry executives in close contact with officials in Japan said that the chain of events at Daiichi suggested that the authorities had come close to losing control of the situation, and that it would be difficult to maintain emergency seawater cooling operations at stricken reactors if a fire at a fourth reactor nearby was releasing large amounts of radioactive material — at least without threatening the health of emergency workers onsite.

The problem at the fourth reactor had not been reported before late Tuesday morning. According to officials, a fire broke out at that reactor, which had been offline at the time of the earthquake but was storing spent nuclear fuel.

“Tokyo Electric has not been able to cool” the spent fuel pools at its two troubled nuclear plants, Daiichi and Daini, because power has been knocked out, said Johei Shiomi, a spokesman for the company.

“There may be some heating up,” he said.He also said water had spilled out from the pools, which lie close to the main reactors.Spent fuel can be as dangerous as active fuel if left uncovered for too long, experts say, though time-to-boil depends on how much fuel is present, and how old it is.

Still, Mr. Shiomi said that the company felt that there “was relatively little danger that temperatures would rise,” Mr. Shiomi said. “If you compare this to everything that’s been going on, it’s not serious,” he said. He made those comments before fire broke out at the No. 4 reactor.

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