May 31, 2013

Japan plans frozen wall around reactor

But if the proposed wall is even technically feasible, it will take a huge amount of time and money to build.

The Yomiuri Shimbun

TOKYO - Technological and financial obstacles are mounting in front of a Japanese government plan to erect an underground wall of frozen soil around Tokyo Electric Power Co.'s crippled Fukushima No. 1 nuclear power plant.

click image to enlarge

The Japanese government wants to erect an underground wall of frozen soil around Tokyo Electric Power Co.’s crippled Fukushima No. 1 nuclear power plant.

The Associated Press

A government panel on the contaminated water issue decided Thursday to create the wall, about 1.4 kilometers long (.86 miles) and extending as deep as 30 meters underground, around nuclear reactor buildings, along with four other measures.

The wall, comprising series of pipes with coolant running through them, would prevent groundwater from seeping into contaminated areas -- believed to be the main reason for the increase in contaminated water.

However, it is uncertain whether the plan is technically feasible, and it will take an enormous amount of time and money to complete. The risk thus remains of a shortage of storage tanks for contaminated water.

"Considering how serious the contaminated water issue is, measures must be taken at multiple levels. We ask for the immediate preparation and operation of a frozen soil wall around the entire plant," said Economy, Trade and Industry Minister Toshimitsu Motegi when he met TEPCO President Naomi Hirose after government panel on the contaminated water issue met Thursday.

Motegi instructed Hirose to carry out countermeasures proposed by the committee.

Currently, there are 390,000 tons of contaminated water -- enough to fill about 1,500 25-meter pools -- at the nuclear plant. As groundwater continues to seep into the reactor buildings through gaps in the walls or other places, the total amount increases every day.

Although TEPCO continues to make efforts to pump groundwater up before it leaks into the buildings and becomes contaminated, the committee concluded that the measure is insufficient and requested a frozen wall.

Freezing soil to make an underground wall involves relatively new technology. It is used in civil engineering work to prevent landslides.

To make such a wall, a series of pipes are installed underground, and coolant materials at dozens of degrees below zero are circulated through them. This technology was used in the building of tunnels on the Tokyo Bay Aqualine highway.

TEPCO previously studied a plan to build an underground wall near the reactor buildings but abandoned it out of concern that the water could change course during construction, possibly leading to changes in water levels outside the building that would allow contaminated water inside to more easily flow out.

In contrast, a frozen soil wall could be completed in only one or two months, meaning a large change in the water level is less likely. As the wall would prevent water from flowing in or out, contaminated water could be pumped out of the building.

However, the wall TEPCO has been told to make would be the largest such wall in the world.

 

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