April 5, 2016 – The nearly mile-long structure consists of underground pipes designed to form a frozen barrier around the crippled reactors.
The $312 million system was completed last month, more than a year behind schedule.
The operator of Japan’s destroyed Fukushima nuclear plant switched on a giant refrigeration system on Thursday to create an unprecedented underground ice wall around its damaged reactors.
Radioactive water has been flowing from the reactors, and other methods have failed to fully control it. The decontamination and decommissioning of the plant, damaged by a massive earthquake and tsunami in 2011, hinge of the success of the wall.
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The wall consists of a series of underground refrigeration pipes meant to form a frozen soil barrier around the four reactors.
In a video detailing the ice wall’s design, TEPCO said the technology has been successfully used to prevent water intrusion during the construction of tunnels, but this is the first time it has been used to block water from entering a nuclear facility.
“We will create an impermeable barrier,” the company said, “by freezing the soil itself all the way down to the bedrock that exists below the plant. When groundwater flowing downhill reaches this frozen barrier it will flow around the reactor buildings, reaching the sea just as it always has, but without contacting the contaminated water within the reactor buildings.”
TEPCO says the ice wall will be activated in stages over the next several months and is one of several measures the company is taking to reduce the amount of water being contaminated on the site.
The pipes are 30 meters (100 feet) deep, the equivalent of a 10-story building. Engineers say coolant in the pipes will freeze the surrounding soil to minus 30 degrees Celsius (minus 22 Fahrenheit), creating the wall over several months.
The cores of three of the damaged reactors melted during the accident and must be cooled constantly with water to keep them from overheating again.
The cooling water becomes radioactive and leaks out through damaged areas into the building basements, where it mixes with groundwater, increasing the volume of contaminated water.
Nearly 800,000 tons of radioactive water have been pumped out, treated and stored in 1,000 tanks that now occupy virtually every corner of the Fukushima plant, interfering with its decontamination and decommissioning and adding to the risk of further leaks of water into the nearby ocean.
While hopes are high that the ice wall will prove successful in stopping additional radioactive water from seeping into the Pacific Ocean, Shunichi Tanaka, chairman of the Nuclear Regulation Authority, urged caution.
“It would be best to think that natural phenomena don’t work the way you would expect,” he told reporters Wednesday, according to the AP report.
The activation of the ice wall comes just weeks after a TEPCO official reported that robots designed to access the dangerous interior of the plant and seek out the melted fuel rods were “dying” from the high levels of radiation.