23 Novembre 2016
FUKUSHIMA -- The Economy, Trade and Industry Ministry on Nov. 21 showed the media for the first time the visual inspections conducted on the condition of the subterranean ice wall around the nuclear reactors at the stricken Fukushima No. 1 Nuclear Power Plant to block groundwater from flowing into the plant buildings.
The ice wall project calls for freezing the soil around the No. 1 to No. 4 reactor buildings that stretches some 1.5 kilometers to a depth of about 30 meters to create a solid barrier by hammering in equidistant cooling pipes and circulating coolant chilled to minus 30 degrees Celsius.
The industry ministry on Nov. 21 dug a part of the ice wall to approximately 1.2 meters in depth on the mountain side of the No. 4 reactor building. The soil temperature around the cooling pipes 40 centimeters deep was about minus 10.3 degrees, while an area of 1.5 meters in radius around the cooling pipes was frozen at a depth of 1.2 meters.
While plant operator Tokyo Electric Power Co. claims that the ice wall could reduce the amount of groundwater flowing into the reactor buildings from some 400 metric tons a day to 100 tons or less, the Nuclear Regulation Authority cast doubt on the project during an August meeting, with a member saying that the plan was a failure.
Ice wall at Fukushima plant examined
Government officials have examined an underground ice wall built around Japan's crippled Fukushima Daiichi nuclear plant to confirm whether the soil has frozen.
Work is ongoing to build a 1.5 kilometer barrier of frozen soil encircling reactor buildings. The goal is to prevent underground water from seeping into the plant premises, resulting in more tainted water.
Coolants are being circulated from pipes buried around the reactor site.
Work to build an ice wall began in March, and is almost completed.
State minister for industry, Yosuke Takagi and others on Monday looked at an exposed section of the ice wall.
They said the ice wall had hardened enough to withstand being hit with a hammer.
Officials say prior to construction of the ice wall, workers collected some 350 tons of underground water on a daily basis. The amount has shrunk to about 200 tons.
Japan's nuclear regulator is also planning to assess the effectiveness of the ice wall installment.