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Friday, Aug. 5, 2011
Tepco makes little headway in decontaminating water
Tokyo Electric Power Co. continues to struggle with cleaning up the more than 120,000 tons of radioactive water flooding the Fukushima No. 1 power plant, as the utility has hardly been able to reduce the overall amount of the water in the past several weeks.
Although Tepco said Wednesday it finally raised the efficiency of the plant's new water treatment system to 74 percent from around 50 percent the previous week and is looking to launch new measures, like a backup treatment system, it still remains unclear if the utility can continue to improve the situation.
Tepco's weekly water report said Wednesday that more than 28,000 tons had been processed since June 28, when the volume reached 121,770 tons.
As of Tuesday, however, the crippled plant still contained 120,770 tons of contaminated water — 96,920 tons in reactor turbine buildings 1 through 4 and 23,850 tons in storage.
Even when the efficiency rate went up between July 27 to Aug. 2, "the water from last week's rain kept flowing into the turbine buildings, so the amount did not really decline (last week)," Tepco spokesman Junichi Matsumoto said.
The irradiated water is believed to be leaking from reactors 1 to 3 and accumulating in their basements and external trenches.
To stop the water from rising and to prevent it from contaminating the environment, Tepco has been cleaning the water and sending it back to the reactors since July 2 in a setup called a circulation cooling system.
Yet because of the constant cleaning work and other troubles with the Japanese-French-U.S. system, particularly leaks, its effectiveness has been rather low.
One reason why its efficiency improved to 74 percent is because there weren't any major problems last week, Matsumoto said.
To reduce the contaminated water, it is crucial to increase the efficiency and stability of the new system, which can process 8,400 tons of water a week at full bore and Tepco is now trying two measures to improve the situation.
Matsumoto said the utility's goal is to have the cleaning system running at 90 percent efficiency next week by creating a new bypass hose that will help the water flow more smoothly.
He said the water is being hindered by sludge accumulating in a carbon steel pipe that is connecting storage tanks holding the decontaminated water.
To solve the problem, Tepco installed a polyvinyl chloride bypass hose Thursday. But Matsumoto said he wasn't making any promises.
"We don't know if the sludge will stick easily to a polyvinyl chloride hose or not," he said.
Another backup in the pipeline is a new water treatment system jointly developed by Toshiba Corp., IHI Corp. and the U.S.-based Shaw Group that is expected to come online next week.
The sarry (simplified active water retrieval and recovery) system uses zeolite to absorb cesium isotopes and reduce radiation levels to 1 millionth, Tepco said.