Tokyo Electric Power Co. on Aug. 22 began freezing the remaining section of the 1.5-kilometer underground “ice wall” to prevent radioactive water from accumulating at the embattled Fukushima No. 1 nuclear power plant.
The 7-meter section west of damaged reactor buildings is expected to take months to freeze--longer than the time needed for other parts--because of the fast-flowing groundwater there, TEPCO said.
The project, which cost 34.5 billion yen ($312 million), started in March 2016. The wall was created around the four reactor buildings to block groundwater from entering the buildings and becoming contaminated with highly radioactive substances.
Workers installed 1,568 pipes at a depth of 30 meters in the ground to circulate liquid at minus 30 degrees, thereby freezing the surrounding soil.
At one point, the nuclear complex was producing 400 tons of contaminated groundwater on a daily basis, and efforts to store and decontaminate the water could not keep pace.
The figure has been reduced to about 140 tons a day, TEPCO said.
The utility estimates the volume will fall below 100 tons when the final section is frozen.