The freezing of soil around the Fukushima No. 1 nuclear power plant to block the flow of groundwater is proceeding “largely smoothly,” the plant operator said April 4.
Tokyo Electric Power Co. started making a frozen underground wall in late March around the No. 1 to No. 4 reactors at the plant, which suffered a triple meltdown triggered by the March 2011 earthquake and tsunami.
The final part of the construction process to freeze the soil was unveiled to the media for the first time April 4 during a visit to the site by Yosuke Takagi, state minister of the economy.
To build the frozen soil wall to prevent groundwater flowing into the four reactor buildings and becoming contaminated with radioactive substances, the utility inserted 1,568 pipes to a depth of 30 meters and 1 meter apart.
The company is now circulating liquid with a temperature of minus 30 degrees through the pipes to first freeze the soil on the side of the sea so as not to drastically change the groundwater level at the plant.
As of April 4, the soil temperature had dropped to minus 4 to 6 degrees at some locations, according to TEPCO.
“While we need to keep making efforts to control the temperature deliberately, we can say that the project is proceeding largely smoothly so far,” the company spokesman said.
The utility also unveiled new drainage outlets for the K drainage channel to discharge water into the plant’s harbor and block it from being released into the outer ocean.
The construction of the new outlets was completed March 28. Radiation-contaminated rainwater coming through the K drainage channel had previously often flown into the outer ocean when it rained.