The operator of the crippled Fukushima No. 1 nuclear complex is hoping a deep freeze will quell the issue of contaminated water at the beleaguered site.
Work began Tuesday to extend an underground ice wall to prevent contaminated water increasing at the site.
The coolant-filled wall is designed to prevent groundwater from seeping into the facilities and coming into contact with melted nuclear fuel or becoming mixed with highly contaminated water inside reactor buildings.
The government has spent about $320 million on the project. Work by Tokyo Electric Power Company Holdings Inc. (Tepco) 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 should 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 into the buildings per day, but the amount has fallen to 120 to 130 tons this year, Tepco officials said. 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.
“We want to carefully freeze (the wall) by monitoring water levels both inside and outside the reactor buildings,” a Tepco official said.
Some experts have cast doubt on the ice wall’s effectiveness. Cleaning up the world’s worst nuclear accident since Chernobyl in 1986 is expected to take decades.
On March 11, 2011, a magnitude 9.0 undersea earthquake off the Tohoku coast sparked a massive tsunami that swamped cooling systems and triggered three reactor meltdowns at the Fukushima plant.
Workers had to keep pouring water onto the reactors to prevent the temperature of the nuclear fuel from rising uncontrollably.