Nov. 25, 2021
Tokyo Electric Power Company (TEPCO) announced on November 25 that it may have thawed part of the frozen soil barrier wall built around the No. 1 to No. 4 reactors at the Fukushima Daiichi Nuclear Power Plant (Okuma and Futaba towns, Fukushima Prefecture) to prevent the inflow of groundwater. The company has announced that it will try to stop the flow of water by driving several steel pipes into the wall. The project will start as early as early December, and if the temperature in the ground continues to rise, additional steel plates will be driven in.
　According to TEPCO, a thermometer installed in the ground at the intersection of the southwest side of Unit 4 and the underground tunnel for drainage confirmed that the temperature exceeded zero degrees Celsius in late August. Since late September, the temperature has sometimes been above 10 degrees Celsius. A spokesperson explained at a press conference that the groundwater level outside the wall was high, and water pressure may have created a water path.
　The steel pipe is 35 centimeters in diameter and up to six meters long. Nine of them will be driven into the ground outside the frozen soil wall, which may have thawed, to create a wall three to four meters wide.
　The freezing wall, which has been in operation since 2017, was built to prevent groundwater from flowing into the reactor building, where melted nuclear fuel (debris) remains from the accident, and to reduce the amount of contaminated water generated. The wall is about 1.5 kilometers long. About 1,600 freezing pipes (30 meters long) were driven into the ground. The freezing pipes are about 1,600 tubes (30 meters long) driven into the ground and circulated with a cooling liquid of 30 degrees Celsius to freeze the surrounding soil. (Kenta Onozawa)
https://www.tokyo-np.co.jp/article/144800