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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, the utility 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 accident — a project that would normally take about two years, he said.

“Accomplishing that was a miracle,” he said, adding that a cheer went up from his men when the first unit started working.

Using that equipment, TEPCO was able to circulate reprocessed water back into the reactor cores. But even though the reactors now are being cooled exclusively with recycled water, the volume of contaminated water is still increasing, mostly because ground water is seeping through cracks into the reactor and turbine basements.

Next month, Okamura’s 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, he said.

TEPCO claims the treated water from this new system is clean enough to be potentially released into the ocean, although it hasn’t said whether it would do that. Doing so 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. The utility has plans to install storage tanks for up to 700,000 tons — or about three more years’ worth — of contaminated water. If that maxes out, it could build additional space for roughly two more years’ worth of storage, said Mayumi Yoshida, a company spokeswoman.

But those forecasts hinge on plans to detect and plug holes in the damaged reactors to minimize leaks over the next two years. The utility also plans to take steps to keep ground water from seeping into the reactor basements.

Both are tasks that TEPCO is still not sure how to accomplish: Those areas remain so highly radioactive that it is unclear how humans or even robots could work there.

There’s also a risk the storage tanks and the jury-rigged pipe system connecting them could be damaged if the area is struck by another earthquake 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 reactor — a process that will easily take more than a decade.

He said TEPCO’s roadmap for dealing with the problem is “wishful thinking.”

“The longer it takes, the more contaminated water they get,” he said.

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Associated Press Writer Malcolm Foster contributed to this report.