Tokyo Electric Power Co. plans to restart a system to recirculate processed water to cool reactors at the crippled Fukushima No. 1 nuclear plant on June 29 at the earliest.
Tokyo Electric Power Co. plans to restart a system to recirculate processed water to cool reactors at the crippled Fukushima No. 1 nuclear plant on June 29 at the earliest.
The system was halted on the evening of June 27 after only 90 minutes of operation.
In the latest setback, TEPCO discovered that about a ton of water had leaked because of an improperly secured pipe joint.
The utility intends to restart the system after checking to ensure pipe fittings of the same type--used at 100 points in the system--are properly secured.
TEPCO said it did not recheck the pipes before it activated the system because it had done so on June 12.
The water recirculation system was installed to reduce the amount of radioactive water building up in the complex.
Sixteen tons of water per hour, brought in from a dam outside the plant, is being pumped in to cool the No. 1 through No. 3 reactors.
The water becomes radioactive after exposure to the nuclear fuel rods and accumulates in the basement of reactor and turbine buildings.
With the recirculation system in place, TEPCO hopes to cool the reactors with 3 tons of water from outside sources and 13 tons of treated water per hour, drastically reducing the need for outside water, and to clean up the already contaminated water in the plant.
The utility needs to deal with about 110,000 tons of radioactive water in the plant--the equivalent of 200 25-meter swimming pools.
The entire plan hinges on the effectiveness of the water purification unit. But numerous glitches have slowed progress. The unit, unprecedented on a global scale, is complicated and combines various technologies.
Equipment made by Kurion Inc. of the United States is designed to absorb radioactive material using minerals. Equipment made by French nuclear engineering company Areva SA lowers the concentration of radioactivity using chemical agents. An oil separator and desalination equipment are also part of the unit.
With the water purification unit, TEPCO hopes to push down radiation levels in contaminated water to one/10,000th to 1/1,000,000th of original levels.
Unless radiation levels are cut to below 1/10,000th, desalination equipment cannot treat radioactive salt water. Salt water was earlier used to cool the reactor cores.
The complexity of the unit, with its many pipes, valves and pumps, makes it susceptible to failure.
Engineers working on the unit say they did not expect the effort to be trouble free.
"We anticipated multiple difficulties," Junichi Matsumoto, a senior official at TEPCO's nuclear power section, said, speaking about earlier problems.
Even if the recirculation system works, processing the contaminated water will leave radioactive residue. According to a TEPCO estimate, it will run 200,000 tons of highly radioactive water through the unit by December.
The use of Areva's equipment alone is expected to leave about 2,000 cubic meters of contaminated waste, enough to fill four to five 25-meter swimming pools.
The waste will be stored in a tank in the basement of the intensive disposal and treatment facility plus another tank and other facilities to be installed in the compound.
How to ultimately get rid of the waste remains to be seen, with no applicable laws in place.
(This article was compiled from reports by Akihiko Honda, Takashi Sugimoto, Naoya Kon and Eisuke Sasaki.)