Fukushima's ice wall keeps radiation from spreading around the world

Editor's note: This story originally ran on March 4, 2018, and we're reposting it for the 10th anniversary of the Fukushima Daiichi nuclear disaster to give readers a sense of the technology being employed to fix this enormous problem, which continues today. To learn more about the ongoing cleanup efforts, read Japan's latest report, issued to the International Atomic Energy Agency earlier this month.

As we drive north from Tokyo, the city fades to a picturesque landscape of rolling hills and tiny villages. 

Japan's Fukushima Prefecture, ravaged by a massive earthquake and a series of tsunamis that leveled buildings and dragged boats, cars and the lives of thousands inland, is beginning to recover eight years later. 

At the decommissioned Fukushima Daiichi Nuclear Power Plant, an army of robots has been enlisted to aid in the cleanup effort -- going into radioactive hotspots too dangerous for humans. The company that owns the facility, Tokyo Electric Power Co., or Tepco, has been investing in community projects for the surrounding area. 

But the visible recovery is undermined by the invisible; a still highly radioactive land and groundwater that continues to mix with the radioactive water of the destroyed reactors at Fukushima Daiichi.

One solution attempting to mitigate the ongoing water contamination is its ice wall, a super-cooler refrigerant being piped 100 feet underground, freezing the ground solid and stopping the flow of fresh water towards the sea.

The outer wreckage of the Unit 2 reactor, one of the most highly radioactive places at Fukushima Daiichi, so dangerous that no human can enter. With the Primary Containment Vessel damaged, the water needed to continually cool the reactors has been leaking from inside, mixing with the fresh groundwater flowing towards the sea.

A maze-like industrial landscape spreads out in front of us. Wearing multiple layers of cotton and latex gloves, three pairs of socks and rubber boots, we walk across a rusty ground towards the most recently conceived defense: a system of super-cooled pipes that freeze the soil going down 100 feet, stopping the outside fresh groundwater from mixing with the radioactive water within.

Though the defensive frozen wall goes down 30 meters, encircling reactor Units 1-4 in a 1500 meters ring, just the top portion of the pipe network freezing 70,000 cubic meters of soil is visible above ground.  

The coolant-filled pipes form the frozen-soil barrier that keeps the fresh groundwater running towards the sea from mixing with the contaminated water from the damaged leaking reactors. The idea is to keep the clean water on the outside of the wall, while the contaminated water stays inside.  

The $300 million structure uses a coolant to bring down the temperature of each pipe to minus 30 degrees Celsius, or minus 22 degrees Fahrenheit. The cold emanating from each one hardens the soil around it, creating a barrier which is intended to stop the flow of fresh groundwater toward the reactors.

A hole dug on the outside of the ice wall perimeter illustrates the high groundwater table below. A similar hole on the inside of the perimeter which shows no water present illustrates the absence of groundwater and thus the effectiveness of the ice wall's intent.

A technician monitors the ice wall operations from a building at the Fukushima Daiichi facility. Tepco says the wall is working, but a Reuters report in March of 2018 found the wall only somewhat effective.

"We know this is not the end of our effort," says a company spokesman. "We will be continuously working hard to reduce the amount of generation of contaminated water." Like much of the work being done at Fukushima Daiichi, this is all new territory, engineered on the fly, and every little bit of progress helps.

In a warehouse literally humming with activity, workers navigate the maze of valves and pipes inside the water purification facility at Fukushima Daiichi which is handling decontamination of radioactive water from the reactors.

Tepco's on-site purification process at the Advanced Liquid Processing System is able to remove 62 radioactive elements from the contaminated water used in the cooling Fukushima Daiichi's reactors. Remaining in the water is tritium, a lesser radioactive element that is more complicated to remove from water in purification processes. 

In the past eight years since the accident, this has meant TEPCO has collected more than 1.1 million tons of leaking, contaminated water.

Where does it all go? There are currently 900 huge silos on site, and counting. TEPCO estimates it has enough space in the 37.7-million-square-foot facility to house an additional 270,000 tons of water, which means it will run out space to store any more water sometime in 2020.

The ice wall is part of the solution to this problem. 

Less ground water mixing with contaminated water means then less contaminated water to store in the finite amount of space available.

From an ultra-clean environment in the water treatment analysis center, glass beakers containing sea water and groundwater and water from the Advanced Liquid Processing System facilities.