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Sunday, May 29, 2011
As nuke workers wait, tainted water climbs
While Tokyo Electric Power Co. plans to set up a water treatment facility in mid-June to decontaminate the thousands of tons of radioactive water being generated at the Fukushima No. 1 power plant, the utility must also find a safe place to store it before it leaks into the ground or finds its way to the sea.
Compounding the problem are the reactors, which are believed to be ridden with cracks, holes or damaged pipes that are allowing the water being used to cool what's left of the reactor cores to escape.
With the rainy season approaching, speed is of the essence. But experts say plugging the leaks is extremely difficult because of the high radiation, which means Tepco could be stuck with the water for years.
"The tainted water needs to be processed as quickly as possible," said Kenji Takeshita, a professor at the Research Laboratory for Nuclear Reactors at the Tokyo Institute of Technology and an expert on nuclear waste disposal. "If the amount continues to increase, there will be nowhere to store it. And if it overflows, the water could leak into the sea, which will be a big problem."
The tainted water is becoming such a big problem in fact that it is interfering with the beleaguered utility's main task of securing the stricken reactors.
So far, the basements of the turbine buildings of all six reactors have been flooded by about 100,000 tons of radioactive water. That's enough to fill roughly 40 Olympic-size swimming pools.
Tepco started pumping out unit 2 in April and unit 3 last week after leaks in cracked utility pits were found draining into the sea after being filled via trenches linked to the turbine buildings. But these operations had halted by Friday because the temporary storage facility set up for the water is nearly at its full capacity of 14,000 tons.
Now Tepco must wait for the water treatment facility. In the meantime, it has cut the water flow to unit 3 to 14.5 tons per hour from 15.5. Unit 2 continues to get 7 tons per hour.
The water will only rise, but the act of keeping it in the turbine buildings presents the risk of a leak somewhere making it to the Pacific, experts said. As of Saturday morning, water levels had risen to 3.382 meters in unit 2 and 3.570 meters in unit 3, up about 16 mm since 5 p.m. Friday.
The extracted water put in the nuclear waste disposal area is already a problem: It is leaking into a corridor connecting the two buildings storing it.
"The water is not stored in tanks but in the building, so there is the possibility of it leaking from somewhere" to the outside and flowing into the sea, said Akio Koyama, professor at Kyoto University's Research Reactor Institute and an expert on managing radioactive waste.
Tepco said the water in the waste disposal area is not entering the sea and that daily radioactivity tests show that ground water has not been affected. This may change as the rainy season gets under way and starts filling the trenches around the plant, which could overflow.
Much of Tepco's hopes have been pinned on the water treatment facility being set up by Areva SA. The facility removes radioactive substances from water, canceling out the danger.
But it's not cheap. Tepco said the filtering costs ¥210,000 per ton, which means it might cost about ¥53.1 billion to treat 250,000 tons of radioactive water. The utility said its target for this year alone is 200,000 tons.
The utility plans to keep the filtered water in a closed system so it can be recirculated as the main coolant for the reactors. But as long as the breaches in the pressure and containment vessels do not get fixed, any water that touches the melted fuel will flood the facility unless it can be trapped or stored.
"The first thing is to make a circulating cooling system by processing the water, and then Tepco will have to wait until the fuel gets cooled," said the Tokyo Institute of Technology's Takeshita. "I think the only option is to process and circulate it" because of all the leaks.
Since this process will likely have to continue for some years, Tepco has to spend htat time looking for other methods to secure the reactors, he said.
But Koyama said time is not on Tepco's side.
"Because of the high radiation, I'd assume the workers won't be able to build the cooling system that strongly," he said, confirming that it might not be able to hold up if big aftershocks occur.