JAPAN | Decontamination delayed / TEPCO fails to meet goal in removing radioactivity from water

Posted on July 29, 2011



Decontamination of highly radioactive water at the Fukushima No. 1 nuclear power plant has been proceeding at a snail’s pace because of various malfunctions and other problems.

Even though one month has passed since decontaminated water began to be used to cool the plant’s reactors, the average operating rate of the decontamination system is only 63 percent.

Tokyo Electric Power Co., operator of the plant in Fukushima Prefecture, had planned to reduce the contaminated water to a safe level by early August.

However, TEPCO said the decontamination operation rate for the week up to Tuesday was 58 percent. The rate was 54 percent the previous week.

About 29,000 tons of radioactive water have been decontaminated so far, an average operation rate of 63 percent.

The system, which was built in less than two months, has frequently broken down due to faulty valve operations and a malfunctioning alarm system. Last Friday, it stopped working for eight hours due to a power outage.

TEPCO’s target operation rate is 90 percent. The utility expected the operation rate this month would be 80 percent, but later lowered this to 70 percent. The current rate does not even meet this target.

By early August, TEPCO had intended to lower the level of radioactive water accumulated in the basement of the reactors to ensure it would not flow out of the plant, even though rainwater would be allowed to enter.

However, the decontamination operation target will not be reached until late September, two months behind schedule, according to the company.

To help facilitate decontamination operations, TEPCO is planning to introduce new machinery manufactured by Toshiba Corp. and other companies next month.

“As we’re operating a brand-new system, it’s not surprising there are some problems,” said Junichi Matsumoto, a TEPCO spokesman on nuclear issues. “But we’ve solved most of the problems that have occurred in the initial phase. When we start using the new equipment, the [system’s] rate of operation should increase.”

Decontamination work has been further delayed by the inflow of rainwater and groundwater.

Last week, torrential rain brought by a typhoon poured into the plant’s reactors. As a result, the quantity of radioactive water increased by 3,000 tons over the past week, registering about 120,700 tons as of Tuesday.

Of the decontaminated water, about 390 tons have been used to cool the reactors each day, but this water automatically becomes radioactive again.

Due to its poor cooling efficiency, the No. 3 reactor requires nine tons of water per hour, more than two times that used to cool Nos. 1 and 2 reactors. TEPCO is therefore considering a more efficient cooling method that uses less water.

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