An ambitious plan by Tokyo Electric Power Co. to halt the seepage of contaminated water at the stricken Fukushima No. 1 nuclear power plant has hit a major glitch: "ice walls" have failed to form in underground trenches.
An ambitious plan by Tokyo Electric Power Co. to halt the seepage of contaminated water at the stricken Fukushima No. 1 nuclear power plant has hit a major glitch: "ice walls" have failed to form in underground trenches.
TEPCO workers are busy installing underground pipes to circulate coolant to create frozen soil walls encircling the No. 1 through No. 4 reactor buildings on the side away from the sea. Reporters were given a peek at the construction work on July 8.
TEPCO intends next March to start circulating coolants through the pipes to create frozen walls to block underground water from flowing into the reactor buildings.
But on the seaward side of the reactor buildings, the utility must first remove around 11,000 tons of contaminated water from underground trenches connected to the No. 2 and No. 3 reactor turbine buildings.
The trenches, built to house electrical cables and water pipes, are supposed to be kept dry. But contaminated water began seeping into them after the onset of the March 2011 nuclear crisis.
If the contaminated water is not removed from the trenches, it could eventually leak out. The Nuclear Regulation Authority instructed TEPCO to promptly remove the water, calling it the “most serious source of concern.”
To stop the flow of contaminated water into the trenches from reactor turbine buildings, workers have installed cement, clay and coolant pipes to create ice walls around the four connecting points between the reactor turbine buildings and trenches.
After installing the pipes, TEPCO started to freeze them on April 28 to create ice walls in the trenches. It was expected to take about a month to create ice walls, but they had not formed as of July 8.
After the flow of water is halted, the plan calls for the removal of the contaminated water in the trenches.
But TEPCO officials said the ice walls failed to form because of the constant flow of a maximum 2 milliliters of water per minute around the connecting points.
Toyoshi Fuketa, an NRA commissioner, has instructed TEPCO to come up with steps to resolve the matter by the end of July, arguing that the frozen walls should be able to withstand certain levels of water flow under normal circumstances.
The continued presence of water threatens to prevent the creation of outer frozen soil walls encircling the No. 1 through No. 4 reactors, which are a central part of TEPCO's plans to reduce the amount of contaminated water at the plant.
On June 2, the utility began installing more than 1,500 pipes around the four reactor and turbine buildings to circulate coolant of minus 30 degrees to create ice walls stretching 1,500 meters and running 30 meters deep.
On July 8, workers using heavy machinery were drilling holes to install pipes on the south side of the No. 4 reactor building.
Outfitted in radiation-proof vests, three to four workers manned each drilling machine, making sure not to hit underground obstacles. TEPCO officials said the work can only be carried out between 5 p.m. and 11 p.m. to avoid heatstroke.
The workers are able to install three pipes per day on average. They had installed 90 pipes as of July 7.
(This article was written by Akira Hatano and Shunsuke Kimura.)