JAPAN | Radioactive water cleaning operation is behind schedule

Posted on July 28, 2011

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JAPAN | ASAHI SHIMBUN | 28 july 2011

Components of the radioactive water purifying unit SARRY are landed on July 26 at the Fukushima No. 1 nuclear power plant. (Tokyo Electric Power Co.)

A plan to remove all leaked radioactive water from the crippled Fukushima No. 1 nuclear power plant by the end of this year is in doubt because of continuing problems with its water cleaning system.

The highly radioactive water purification plant, which entered full operation on June 17, has been beset by suspensions and is operating at well below designed capacity, the nuclear plant’s operator, Tokyo Electric Power Co., said on July 27.

TEPCO said the plant operated at 58 percent of capacity during the seven-day period through July 26. That was little improvement over the 53 percent of capacity achieved the preceding week. It has treated about 30,000 tons since it entered full operation, equivalent to about 63 percent of designed capacity over the whole period.

TEPCO initially projected that the plant would be working at 80 percent of capacity in July. The figure was later revised downward to 70 percent, but that relaxed target has not been met.

The company had planned to set a target of 90 percent from August onward, but will now maintain the target at 70 percent for the time being. There is no immediate prospect of reaching 90 percent.

The amount of radioactive water on the site has actually increased since the start of the operation. Typhoon rainfall was partly to blame, but another factor was the pumping of reservoir water into the plant’s stricken nuclear reactors because of the failures of the plan to recycle contaminated water to cool the reactors using the purification system.

According to the latest figures, there are 120,650 tons of radioactive water at the plant, 3,000 tons more than at the start of the purification operation. The central waste treatment plant, which stores some of that radioactive water, is approaching full capacity.

The water purification plant, which started working on June 17, is now one component of a complex cyclic water injection and cooling system made up of about 4 kilometers of snaking pipes. Because of TEPCO’s focus on quickly achieving a “stable cool-down,” the first step of its roadmap to bringing the crippled reactors under control, the system entered operation on June 27 with only minimal testing.

Water leaks and design errors have plagued the system ever since. On July 24, a desalination unit, which removes seawater salt from purified radioactive water, halted automatically due to a wrong water level setting traced back to installation.

The radioactive water that passes through the pipes of the purifying plant has fallen to about 70 percent of capacity. This may be due to an accumulation of sludge on the inner surfaces of the pipes, and TEPCO is considering installing a separate piping system.

TEPCO also plans to install a new purifying unit in August. The SARRY (Simplified Active Water Retrieve and Recovery System) unit, developed by Toshiba Corp. and other companies, will be added to the existing setup and is similar in design to the purifying unit manufactured by Kurion Inc. of the United States that is currently being used. TEPCO is also installing a new desalination unit.

A key challenge will be addressing the situation at the plant’s No. 3 reactor, where TEPCO is currently pumping in more than twice the volume of water being injected into the No. 1 and No. 2 reactors. The company is considering using a different water injection method at the No. 3 reactor.

(This article was written by Naoya Kon and Takashi Sugimoto.)

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