22 Août 2017
August 22, 2017
Fukushima ice wall's last section being frozen
Final procedures have begun to complete an ice wall to prevent groundwater from entering the contaminated Fukushima Daiichi nuclear power plant.
Tokyo Electric Power Company workers started the process to freeze the remaining 7-meter section of the ice wall on Tuesday.
They opened 11 valves to allow coolant at a temperature of minus 30 degrees Celsius to circulate in the underground pipes.
TEPCO began freezing the 1.5 kilometer long wall in March of last year. The last section on the mountain side of the facility had been left unfrozen as officials said the move could cause a sudden drop in groundwater levels around the reactor buildings.
But the Nuclear Regulation Authority said safety measures were in place and gave permission for the procedure earlier this month.
TEPCO says it could take longer than the 2 months projected based on past records for the section to freeze, because the groundwater is flowing at a rapid rate.
They say once the wall is completed, the volume of groundwater flowing into the reactor buildings will be reduced to less than 100 tons a day, from the current 140 tons.
The nuclear regulators say they will carefully monitor the effectiveness of the wall.
TEPCO begins extending ice wall to reduce tainted water in Fukushima
FUKUSHIMA, Japan (Kyodo) -- The operator of the crippled Fukushima Daiichi nuclear complex began work Tuesday to extend an underground ice wall to prevent contaminated water increasing within the facilities.
The coolant-filled wall is designed to prevent groundwater from seeping into the facilities and touching melted nuclear fuel or becoming mixed with highly contaminated water inside reactor buildings.
The government has spent some 35 billion yen ($320 million) on the project. Work by Tokyo Electric Power Company Holdings Inc. to freeze the wall began in March last year.
On Tuesday, the utility opened valves to circulate coolant for the remaining section of the 1.5-kilometer-long, 30-meter-deep wall around the four reactor buildings.
TEPCO is expected to complete the wall possibly this fall by cooling the remaining portion on the west side of the buildings, a section stretching for about 7 meters.
About 400 tons of water was initially flowing inside the buildings per day but the amount has fallen to 120 to 130 tons this year, according to TEPCO. The utility aims to slash the daily inflow of groundwater to less than 100 tons with the full operation of the ice wall.
Pipes have been inserted into the ground to circulate coolant and freeze the nearby soil. Since starting the freezing work in March last year, the operator has gradually expanded the ice wall as freezing the entire wall at once could change the groundwater level, possibly causing highly radioactive water in the basements of the buildings to leak outside.
"We want to carefully freeze (the wall) by monitoring water levels both inside and outside the reactor buildings," a TEPCO official told a press conference in the city of Fukushima.
See also : https://www.japantimes.co.jp/news/2017/08/22/national/tepco-begins-extending-ice-wall-reduce-tainted-water-fukushima-plant/