Fukushima in Cold Shutdown

Monday, December 19, 2011 @ 04:12 PM gHale


The most critical phase of the Fukushima Dai-ichi disaster is now over as the nuclear plant is in cold shutdown.

In a nationally televised address Friday, Japan’s Prime Minister Yoshihiko Noda said the plant is in a cold shutdown nine months after an earthquake and tsunami hit the country and left almost 20,000 people dead and missing.

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Cold shutdown occurs when the temperature of water used to cool nuclear fuel rods remains below boiling point and radiation emitted by the reactors is no higher than the government-set limit for the public of one millisieverts a year.

In April, the plant’s operator, Tokyo Electric Power (Tepco), said it wanted to stabilize the reactors by the end of the year, but it managed to bring water temperatures to below boiling point for the first time in September. Officials say the temperatures inside reactors numbered one to three, which all suffered meltdown, now range from 38C to 68C.

Noda apologized for the anxiety the nuclear accident – the world’s worst since Chernobyl 25 years ago – had caused before paying tribute to the thousands of workers, soldiers and firefighters who risked their health battling to bring the plant under control.

He said radiation levels at the plant’s boundary could stay at lower levels, even in the case of an “unforeseen incident.”

But he was unable to offer a date for the return of any of the 80,000 residents evacuated from a 12-mile radius of the plant in the immediate aftermath of the accident, when three of six reactors suffered core meltdown.

“Our ultimate aim remains to get people back to their homes and resume the lives they had before the accident as quickly as possible,” he said.

The government, he added, would do its best to decommission the plant now that it stabilized it. “The government is due to set a clear road map and will do the utmost to decommission the plant,” he said.

Decommissioning will be a time-consuming and expensive process.

The government said workers will not be able to start removing the molten fuel from the three worst-hit reactors for another 10 years. They plan to remove spent fuel from four storage pools within the next two years, reports said.

Tepco must also find a way to treat and dispose of an estimated 90,000 metric tons of contaminated seawater used to cool the reactors. The operation to cool nuclear fuel rods and prevent further radiation leaks into the sea and atmosphere has suffered several setbacks. Earlier this month, Tepco said about 45 metric tons of highly radioactive water had leaked through a crack in the wall of a treatment facility.

On Thursday, government officials said it could take as long as 40 years to decommission the plant and decontaminate an area of about 930 square miles (2400 sq km).



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