From: Kiyoshi Takenaka and Shinichi Saoshiro, Reuters, TOKYO
Published December 16, 2011 06:49 AM

Fukushima Daiichi nuclear plant finally in cold shutdown

Japan declared its tsunami-stricken Fukushima nuclear power plant to be in cold shutdown on Friday in a major step toward resolving the world's worst nuclear crisis in 25 years.

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The Fukushima Daiichi plant, 240 km (150 miles) northeast of Tokyo, was wrecked on March 11 by a huge earthquake and a towering tsunami which knocked out its cooling systems, triggering meltdowns, radiation leaks and mass evacuations.

In making the much-anticipated announcement, Prime Minister Yoshihiko Noda drew a line under the crisis phase of the emergency at the plant and highlighted the next challenges: post-disaster clean-up and the safe dismantling of the plant, something experts say could take up to 40 years.

"The reactors have reached a state of cold shutdown," Noda told a government nuclear emergency response meeting.

"A stable condition has been achieved. It is judged that the accident at the plant itself has ceased," he added, noting radiation levels at the boundary of the plant could now be kept at low levels, even in the event of "unforeseeable incidents."

"The government is due to set a clear road map and will do the utmost to decommission the plant," Noda later told a news conference.

A cold shutdown is when water used to cool nuclear fuel rods remains below boiling point, preventing the fuel from reheating. One of the chief aims of the plant's operator, Tokyo Electric Power (Tepco), had been to bring the reactors to cold shutdown by the year-end.

After months of efforts, the water temperature in all three of the affected reactors fell below boiling point by September, but Tepco has been cautious about declaring a cold shutdown, saying it had to see if temperatures and the amount of radiation emitted from the plant remained stable.

The declaration of a cold shutdown could have repercussions well beyond the plant. It is a government pre-condition for allowing about 80,000 residents evacuated from within a 20 km (12 mile) radius of the plant to go home.

But Kazuhiko Kudo, professor of nuclear engineering at Kyushu University, said authorities still needed to determine exactly the status of melted fuel inside the reactors and stabilize a makeshift cooling system, which handles the tens of thousands of tons of contaminated water accumulated on-site.

"What is more important is the next steps the government and Tepco decide to take," Kudo said.

Photo shows leakage from evaporative condensation apparatus inside the desalination facility at the tsunami-crippled Fukushima Daiichi nuclear power plant in Fukushima prefecture, in this handout picture taken December 4, 2011.

Credit: Reuters/Tokyo Electric Power Co./Handout

Article continues: http://www.reuters.com/article/2011/12/16/us-japan-nuclear-idUSTRE7BF06020111216

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