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Ice wall may contain nuclear contamination

Japan considers freezing ground at Fukushima

A tsunami hit near a radioactive solid waste storage facility (above) and other structures at the Fukushima Daiichi nuclear station in 2011, crippling the power station.

Tokyo Electric Power Co.

A tsunami hit near a radioactive solid waste storage facility (above) and other structures at the Fukushima Daiichi nuclear station in 2011, crippling the power station.

TOKYO — Turning soil into virtual permafrost with refrigerated coolant piped through the earth was first used in the 1860s to shore up coal mines. Now it’s the newest idea for containing the Fukushima nuclear disaster.

At least 300 tons of water laced with radioactive particles of cesium, strontium linked to bone cancer, and tritium flow each day into the Pacific Ocean from the crippled atomic station in Japan. The plan to contain the health threat is to build an underground containment wall made of ice.

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After repeated failures to hold back water contaminated by the 2011 disaster, plant operator Tokyo Electric Power Co. is running out of options to deal with what has been called an ‘‘urgent problem’’ by Prime Minister Shinzo Abe.

Dealing with the water leaks is an ‘‘emergency,’’ the Nuclear Regulation Authority said. Japanese taxpayers already face a $112 billion estimated cleanup cost.

Underground ice walls have been used to block radiation before, in an experiment at the former site of the Oak Ridge National Laboratory in Tennessee, which produced plutonium for atomic weapons, according to a report by Arctic Foundations Inc., an earth-freezing contractor based in Alaska.

‘‘It’s just sometimes it’s the only scenario that will really work,’’ said Joseph Sopko of Moretrench, a New Jersey contractor specializing in frozen-earth projects.

The plan at Fukushima has drawbacks: It won’t be completed until 2015, and there’s no cost estimate yet. The wall of ice would run about a mile underground, the world’s longest continuous stretch of artificially frozen earth, according to Japan’s nuclear accident response office.

Kajima Corp., the construction company that was the principal builder of the Daiichi nuclear plant, has been given until March 31 to complete a feasibility study of the project.

Highly contaminated water started to accumulate in basements of Fukushima buildings when crews began injecting tons of water into the reactors after the earthquake and tsunami on March 11, 2011, knocked out power to cooling systems.

Groundwater then started leaking into the basements, adding to the volume of contaminated water. In turn, radiated water seeped into groundwater. At least 300 tons of contaminated groundwater are thought to be flowing into the ocean from the plant each day, according to the Ministry of Economy, Trade and Industry.

Kajima’s proposal calls for engineers to sink vertical pipes into the ground around the structures. Coolant would be cycled from on-site refrigerator units into the pipes, where they would form a frozen wall to keep contaminated water in and keep out freshwater flowing from nearby mountains. The government anticipates keeping the ground frozen for six years starting in July 2015.

‘‘We expect the walls will stem the flow of groundwater from the mountain side and also keep water inside the buildings from leaking,’’ said Tatsuya Shinkawa, director of the nuclear accident response office in the Agency for Natural-Resources and Energy.

Government officials have not released a cost estimate for the project.

‘‘The proposal to freeze the earth is nothing but a cash cow for the contractor,’’ said Richard McPherson, a California-based energy and defense consultant who has researched the nuclear accidents.

Kajima declined to comment on details of the project, indicating that it has yet to start the feasibility study.

The technique of freezing the earth was devised in the late 19th century by German scientist F.H. Poetsch.

It’s now commonly used for temporary reinforcement in tunnel building and other projects, such as the construction of the Second Avenue subway in New York and the Port of Miami tunnel, according to Sopko, who worked on the projects. Ground was also frozen during construction of the Interstate 90 connector tunnel for Boston’s Big Dig project.

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