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Built by the central government at a cost of 35 billion yen, or some $320 million, the ice wall is intended to seal off the reactor buildings within a vast, rectangular-shaped barrier of man-made permafrost. If it becomes successfully operational as soon as this autumn, the frozen soil will act as a dam to block new groundwater from entering the buildings. It will also help stop leaks of radioactive water into the nearby Pacific Ocean, which have decreased significantly since the calamity but may be continuing.
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The buildings managed to keep the water out until the accident on March 11, 2011. Either the natural disasters themselves, or the explosive meltdowns of three of the plant’s six reactors that followed, are believed to have cracked the buildings’ basements, allowing groundwater to pour in. Nearly 40,000 gallons of water a day keep flooding into the buildings.
Once inside, the water becomes highly radioactive, impeding efforts to eventually dismantle the plant. During the accident, the uranium fuel grew so hot that some of it is believed to have melted through the reactor’s steel floors and possibly into the basement underneath, though no one knows exactly where it lies. The continual flood of radioactive water has prevented engineers from searching for the fuel.
Since the accident, five robots sent into the reactor buildings have failed to return because of high radiation levels and obstruction from debris.
The water has also created a waste-management nightmare because Tepco must pump it out into holding tanks as quickly as it enters the buildings, to prevent it from overflowing into the Pacific. The company says that it has built more than 1,000 tanks that now hold more than 800,000 tons of radioactive water, enough to fill more than 320 Olympic-size swimming pools.
On a recent visit to the plant, workers were busily erecting more durable, welded tanks to replace the temporary ones thrown up in a hurry during the early years after the accident, some of which have leaked. Every available patch of space on the sprawling plant grounds now appears to be filled with 95-foot tanks.
“We have to escape from this cycle of ever more water building up inside the plant,” said Yuichi Okamura, a general manager of Tepco’s nuclear power division who guided a reporter through Fukushima Daiichi. About 7,000 workers are employed in the cleanup.
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Since the start, the project has attracted its share of skeptics. Some say buried obstacles at the plant, including tunnels that linked the reactor buildings to other structures, will leave holes in the ice wall, making it more like a sieve. Others question why such an exotic solution is necessary when a traditional steel or concrete wall might perform better.
Some call the ice wall a flashy but desperate gambit to tame the water problem, after the government and Tepco were initially slow to address it. Adding to the urgency is the 2020 Olympics, which Prime Minister Shinzo Abe of Japan helped win for Tokyo three years ago by assuring theInternational Olympic Committee that the water troubles at Fukushima Daiichi were under control.
“It’s a Hail Mary play,” said Azby Brown, a Japan-based researcher forSafecast, an independent radiation-monitoring group. “Tepco underestimated the groundwater problem in the beginning, and now Japan is trying to catch up with a massive technical fix that is very expensive.”
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Mr. Abe said the wall was intended to operate until 2021, giving Tepco five more years to find and plug the holes in the reactor buildings, though skeptics say this difficult task will require more time. Mr. Abe also pointed out that the ice wall was part of a broader strategy for containing the radioactive water. Before installing the ice wall, Kajima also built a conventional steel wall underground along the plant’s border with the Pacific last year.
Tepco says that wall has already stopped all measurable leaks of radioactive materials into the sea. However, some scientists say that radioactive water may still be seeping through layers of permeable rock that lie deep below the plant, emptying into the Pacific far offshore. They say the only way to eliminate all leaks would be to repair the buildings once and for all.
Even if the ice wall works, Tepco will face the herculean task of dealing with the huge amounts of contaminated water that have accumulated. The company has installed filtering systems that can remove all nuclear particles but one, a radioactive form of hydrogen known as tritium. The central government and Tepco have yet to figure out what to do with the tritium-laced water; proposals to dilute and dump it into the Pacific have met with resistance from local fishermen, and risk an international backlash.
Read more at Japan’s $320 Million Gamble at Fukushima: An Underground Ice Wall
