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Sunday, Oct. 28, 2012
New treatment system could see discharges into Pacific as storage space rapidly runs out
No. 1 radioactive water tanks maxed
By MARI YAMAGUCHI
Workers at the Fukushima No. 1 plant are struggling to find space to store tens of thousands of tons of highly contaminated water used to cool its crippled reactors, the manager of the water treatment team said.
About 200,000 tons of radioactive water — enough to fill more than 50 Olympic swimming pools — are being stored in hundreds of gigantic tanks built around the complex. Tokyo Electric Power Co. has already felled trees to make room for more tanks and predicts the volume of water will more than triple in three years.
"It's a pressing issue because our land is limited and we would eventually run out of storage space," the water-treatment manager, Yuichi Okamura, told AP.
Tepco is close to starting a new treatment system that could make the water safe enough to discharge into the ocean. But its tanks are filling up in the meantime, mostly because cracks in reactor buildings are allowing groundwater in.
Experts worry the highly radioactive water could have a lasting impact on the environment, and fear that because of the reactor leaks and water flowing from one part of the facility to another, this is already happening.
Nuclear engineer and college lecturer Masashi Goto said the contaminated water buildup poses a long-term health and environmental threat. He worries the radioactive water in the reactor buildings' basements may already be seeping into the groundwater system, where it could travel far beyond the plant and possibly into public water supplies and the Pacific.
"You never know where it's leaking out and once it's out you can never put it back in place," he said. "It's just outrageous and shows how big a disaster the accident is."
The concerns are less severe than the nightmare scenario Tepco faced in the weeks after the March 11, 2011, earthquake and tsunami knocked out power and cooling systems at the power station, causing hydrogen explosions and three reactor core meltdowns in the world's worst nuclear disaster since Chernobyl.
The plant released radiation into the atmosphere, soil and ocean, and displaced more than 100,000 local residents who are uncertain when — or even if — they will be able to return home.
Dumping massive amounts of water into the stricken reactors was the only way to avoid an even bigger catastrophe.
Okamura remembers frantically trying to find a way to get water to the spent-fuel pools located near the top of the 50-meter-high reactor buildings. Without water, the spent nuclear fuel likely would have overheated and melted, dispersing radioactive smoke over a vast area and potentially affecting millions of people.
"The water would keep evaporating and the pools would have dried up if we had left them alone," Okamura said. "That would have been the end of it."
Attempts to dump water from helicopters were ineffective, and spraying water from fire trucks into the pools didn't work either. Okamura then helped bring in a huge, German-made pump normally used for concrete with a remote-controlled arm long enough to spray water into the fuel pools.
The plan worked — just in time, Okamura said.
Those measures and others helped bring the plant under tenuous control, but it will take decades to clean up the radioactive material emitted by the three wrecked reactors. And those desperate steps created another huge headache for Tepco: What to do with all the radioactive water that leaked out of the reactors and gathered in the basements of the buildings housing them and nearby facilities.
Some of the water ran into the Pacific, raising concerns about contamination of marine life and seafood. Waters within a 20-km zone are still off-limits, and high levels of contamination have been found in seabed sediment and fish tested in the area.
Okamura was tasked with setting up a treatment system that would make the water clean enough for reuse as a coolant, and was also aimed at reducing health risks for workers and environmental damage.
At first, Tepco shunted the tainted water into existing storage tanks near the reactors. Meanwhile, Okamura's 55-member team scrambled to get a treatment unit up and running within three months of the disaster — a project that would normally take about two years, he said.
"Accomplishing that was a miracle," Okamura said, noting a cheer went up from his men when the first unit started up.
Using that equipment, Tepco was able to circulate reprocessed water back into the reactor cores. But even though the reactors are now being cooled exclusively with recycled water, the volume of contaminated water is still increasing, mostly because groundwater is seeping through cracks into the reactor building basements.
Next month, Okamura said his group plans to flip the switch on new purifying equipment using Toshiba Corp. technology that is supposedly able to decontaminate the water by removing strontium and other nuclides potentially below detectable levels.
Tepco claims the treated water from this new system is clean enough to be released into the ocean, although it hasn't said whether it would actually do so. At any rate, that would require the permission of authorities and local consent and would also likely trigger harsh criticism at home and abroad.
To deal with the excess tainted water, the utility has channeled it to more than 300 huge storage tanks placed around the plant. Tepco has plans to install storage tanks for up to 700,000 tons — about three more years' worth of contaminated water. If those facilities were to be maxed out, it could build additional space for roughly two more years' worth of radioactive water, said Mayumi Yoshida, a Tepco spokeswoman.
But these forecasts hinge on plans to detect and plug holes in the damaged reactors to minimize leaks over the next two years. Tepco also plans to take steps to keep groundwater from seeping into the reactor basements.
Both are tasks Tepco is still unsure how to accomplish, as those areas remain so highly radioactive it is unclear how humans or even robots can operate in them.
There's also a risk the storage tanks and jury-rigged pipe system connecting them could be damaged if the area is struck by another powerful quake or tsunami.
Goto, the nuclear engineer, believes it will take far longer than Tepco's goal of two years to repair all the holes in the reactors. The plant also would have to deal with contaminated water until all the melted fuel and other debris is removed from the reactors — a process that will easily take more than a decade.
He described Tepco's road map for dealing with the problem as "wishful thinking," adding that "the longer it takes, the more contaminated water they get."