JAPAN | Hopes for water purification, cooling system to bring Fukushima nuke plant under control

Posted on July 9, 2011

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JAPAN | MAINICHI | 9 July 2011

The No. 1 reactor building at the Fukushima No. 1 Nuclear Power Plant is seen from the air in this April 10 file photo provided by TEPCO.

One week has passed since a system to purify water contaminated with radioactive substances began operations at the tsunami-hit Fukushima No. 1 Nuclear Power Plant.

Stable operation of the system, which plays the role of cooling down the reactors and reducing the amount of radioactive water, is a prerequisite for bringing the crisis to an end.

However, as the system was hastily installed over only a two-month period, experts have expressed fears that it may develop trouble such as water leaks and that it may be vulnerable to aftershocks and typhoons.

“The total length of the piping in the system is four kilometers. No one can tell what kind of potential risks it has,” said a Toshiba Corp. expert, who is responsible for operating part of the system.

In the water purification system, radioactive materials are removed from contaminated water after going through four devices — an oil separation device produced by Toshiba, a cesium absorption unit made by U.S.-based Kurion Inc., a decontamination device manufactured by France-based Areva SA, and a Toshiba-made desalting machine.

The purified water is then injected into the reactors to cool them down.

By the end of June, approximately 120,000 cubic meters of radioactive water had accumulated on the premises of the plant.

The plant’s operator, Tokyo Electric Power Co. (TEPCO), managed to put the water purification system into operation on June 27 — shortly before the water was feared to leak into the sea. Since July 2, the system has been able to treat enough water to cool down the reactors. The system had treated over 16,800 cubic meters of radioactive water by July 8.

Immediately after the tsunami generated by the March 11 Great East Japan Earthquake hit the plant, fresh water from outside sources, such as a nearby dam, had been used to cool down the reactors.

However, cooling water contaminated with radioactive substances began to leak outside the reactor buildings from containment vessels and other devices that sustained damage in the disaster. At the same time, if the amount of cooling water had been reduced, it would have caused the temperature and pressure inside the reactors to rise sharply. This problem had been regarded as a stumbling block to bringing the crisis to an end.

Since a roadmap to bring the plant under control, worked out by TEPCO, sets a goal of ensuring that the amount of radiation at the plant is on a steady decline by mid-July, TEPCO is now aiming to put the water recycling system into full operation.

The system can now treat slightly more than 1,000 cubic meters of contaminated water a day even though its target is 1,200 cubic meters. Furthermore, the system needs to be occasionally shut down to replace the radioactive cesium absorption filter. Therefore, the system’s current operating rate is only 76 percent. If the rate remains as it is, TEPCO is expected to finish treating all radioactive water in early November. If the rate rises to 80 to 90 percent, the process will likely be completed in late October.

However, the prediction is based on the assumption that rain water and underground water will not infiltrate into the plant as a result of typhoons or other disasters and cause the level of contaminated water to rise.

“Bringing the crisis to an end largely depends on the weather,” a TEPCO official says.

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