An underground wall of frozen soil surrounding the stricken Fukushima No. 1 Nuclear Power Plant that blocks groundwater from flowing into the plant has cut back on the amount of radiation-tainted water that is generated by an estimated 95 metric tons a day, plant operator Tokyo Electric Power Co. (TEPCO) announced March 1.
This marks the first time a provisional calculation has been made on the efficacy of the "ice wall" on its own.
The 1.5-kilometer wall comprises approximately 1,500 pipes that have been buried 30 meters underground surrounding the nuclear plant's No. 1 to 4 reactors, through which a liquid with a temperature of minus 30 degrees Celsius is circulated to create a wall of frozen soil.
TEPCO used computers to estimate the flow of groundwater, concluding that having the ice wall reduces the amount of contaminated water that is generated by 95 metric tons, or half of what would be produced if the wall did not exist.
At the same time, according to the utility, by the winter of 2017, when the construction of the ice wall was almost fully completed, the amount of contaminated water that was generated had dropped by approximately 380 metric tons per day compared to the winter of 2015, when the freezing process of the wall had not yet begun.
The effects of the ice wall at the Fukushima plant are believed to be limited compared to the process of pumping groundwater upstream and releasing it into the Pacific Ocean, and introducing a subdrain system in which water is drawn from wells around the reactor buildings. Not only did it cost 34.5 billion yen from public coffers to build the structure, maintaining the ice wall will cost 1 billion-plus yen per year. The Nuclear Regulation Authority had been doubtful about the cost efficiency of the project from the outset.
"It has become clear that the ice wall, on its own, has the effect of reducing contaminated water," a TEPCO representative said. A government panel of experts will deliberate the validity of the power company's estimate.
When the construction of an ice wall was given the green light in May 2013, the Japanese government was fighting to win the bid for the 2020 Summer Olympics, and presented the wall as a trump card in controlling the ever-increasing volumes of radiation-tainted water. It was a way for the Japanese government to show the rest of the world that it was leading efforts to suppress further generation of contaminated water, and gave the government an excuse to pump public funds into the cleanup of a disaster caused by a private company.