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Tuesday, Nov. 15, 2011

Contaminated water still headache for Tepco


Staff writer

Tokyo Electric Power Co. has fought an eight-month battle to decontaminate the massive amounts of radioactive water in the reactor basements of the Fukushima No. 1 plant, and the struggle is far from over.

News photo

Though it continues to process contaminated water currently flooding the basements of the reactor and turbine buildings for recycling to cool the reactors, the utility has yet to come up with a way to drain all the water from the buildings. With the trouble unlikely to be resolved anytime soon, the threat of further soil, groundwater and sea contamination near the power plant continues.

Tepco originally planned to process 200,000 tons of contaminated water and remove it all by the end of this year, but some 200 to 500 tons of groundwater flows into the buildings every day, rendering this option impossible.

The massive inflow of groundwater indicates the basement walls may be cracked, and thus there is a risk that the contamination can spread to the outside environment. Tepco does not know exactly where the groundwater is coming in from.

The amount of groundwater changes depending on the weather, and increases when it rains, Tepco spokesman Junichi Matsumoto said Friday.

Groundwater around the Fukushima plant flows from mountains in the west toward the Pacific.

Tepco takes groundwater samples every day and has so far said the contamination has not spread below the water table or, during the current cleanup operations, to the sea, at least to any significant extent.

Matsumoto stressed the importance of keeping the current water levels both inside and outside the reactor and turbine buildings constant.

The water level inside the reactor and turbine buildings is about 3 meters above mean sea level, and lower than the groundwater, which is 5 to 6 meters above sea level.

As long as these water levels are kept in balance, the contaminated water will not leak into the ground, he said.

"We will maintain the current balance for a while," said Matsumoto, adding that the utility is not sure how long it will have to do so.

This means the water from inside the buildings will not leak out and contaminate the groundwater. But because groundwater continues to flow into the buildings, Tepco's water removal efforts are endless and until the problem is resolved, the plant won't be brought under control.

The reactor basements contained 77,000 tons of radioactive water as of Nov. 8. Until most is cleared out, it won't be possible to spot cracks or holes in the containment vessels.

In addition, the amount of radioactive waste, particularly sludge, created through processing tainted water keeps increasing. The amount of sludge was 581 cu. meters as of Nov. 8. Reactors 1, 2 and 3, which suffered meltdowns, are currently being cooled by circulating the contaminated water, which is being processed before it is pumped in.

To keep the radioactive water from draining into the sea, Tepco started constructing an underground wall between the shore and the reactor buildings late last month.

The wall, about 800 meters long and 22 to 23 meters deep, will take two years to complete.

Experts say, however, that building the containment wall just on the east side will not be effective.

"The groundwater keeps flowing in the direction of the sea. Even if the wall blocks a certain amount of it, the water will accumulate behind it, eventually build up and flow around the wall into the ocean," said Yoshikazu Suzuki, who heads Chiba-based Kimitsu System Co., which specializes in soil and water decontamination.

It would be more effective to build a wall around the west, north and south sides to keep the groundwater from reaching the reactor and turbine buildings rather than building a wall by the sea, said Suzuki, who surmises the contaminated water is already flowing into the groundwater and sea. He said Tepco should then dig wells at the plant complex to pump the contaminated water out of the ground.

Tepco considered the full enclosure option but decided against it for now because it entails further risk and would upset the current water level balance, posing the danger of the contaminated water inside the buildings escaping into the ground.



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