More Trouble At Fukushima No. 1

The Japanese cabinet secretary, Yukio Edano, has been speaking on state TV. He said a third reactor at the Fukushima No. I plant was in danger but attempts were under way for a controlled release of air.

Sea water is also being pumped in to attempt to cool the reactor core.

US nuclear experts warn that pumping sea water to cool a quake-hit Japanese nuclear reactor is an "act of desperation" that may foreshadow a Chernobyl-like disaster, AFP reports. "The situation has become desperate enough that they apparently don't have the capability to deliver fresh water or plain water to cool the reactor and stabilize it, and now, in an act of desperation, are having to resort to diverting and using sea water," said Robert Alvarez, who works on nuclear disarmament at the Institute for Policy Studies.

"I would describe this measure as a 'Hail Mary' pass," added Alvarez, using American football slang for a final effort to win the game as time expires.

What occurred at the plant was a "station blackout," which is the loss of offsite air-conditioning power combined with the failure of onsite power, in this case diesel generators.

"It is considered to be extremely unlikely but the station blackout has been one of the great concerns for decades," said Ken Bergeron, a physicist who has worked on nuclear reactor accident simulation.

"We're in uncharted territory," he said.

The reactor has been shut down but the concern is the heat in the core, which can melt if it's not cooled. If the core melts through the reactor vessel, Bergeron explained, it could flow onto the floor of the containment building. If that happens, the structure likely will fail, the experts said.

"The containment building at this plant is certainly stronger than that at Chernobyl but a lot less strong than at Three Mile Island, so time will tell," he said.

Peter Bradford, former head of the US Nuclear Regulatory Commission, said that if the cooling attempts fail, "at that point it's a Chernobyl-like situation where you start dumping in sand and cement."

The two worst nuclear accidents on record are the 1986 Chernobyl disaster in Ukraine and the partial core meltdown of the Three Mile Island reactor in the US state of Pennsylvania in 1979.

Another expert said the Japanese accident will rank as one of the three worst in history.

"If it continues, if they don't get control of this and... we go from a partial meltdown of the core to a full meltdown, this will be a complete disaster," Joseph Cirincione, the head of the Ploughshares Fund, said in an interview on CNN.

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