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Saturday, June 18, 2011

Tepco begins work to clean coolant water

Month needed to make reactor circulation safe


Staff writer

Tokyo Electric Power Co. confirmed Friday that the treatment facility to clean highly radioactive water accumulating at the crippled Fukushima No. 1 nuclear plant started full-scale operations at 8 p.m.

Tepco also revealed its updated road map to bring the Fukushima nuclear crisis under control, saying it aims to cool the stricken reactors with a circulating coolant system through processed contaminated water in a month as well as to improve the medical care and mitigate the radiation exposure of its workers.

The latest plan does not appear to deviate from the goals of cooling the reactors and still aims to effect a cold shutdown in which the temperature of the reactor-core coolants is brought below 100 degrees, by mid-January.

In the short term, the utility hopes to be able to cool down the reactors in a month by circulating the decontaminated water and avoid adding to the current massive amount of radioactive water in the turbine buildings.

Pipes for the circulating cooling systems have already been installed, so the system can start when the water treatment facility begins operations, according to Tepco.

The utility resumed the trial run of the system and commenced full-scale operations Friday, after dealing with water leakage a day before.

"This is a quite big step, although we have to closely watch as troubles may occur. But operating this water treatment system should bring about stable cooling," said Goshi Hosono, a special aide to Prime Minister Naoto Kan in charge of overseeing the accident.

Meanwhile, the updated road map also highlighted the need to improve medical care and mitigate the radiation exposure of workers at the site, as the utility found out recently that several exceeded the 250-millisievert limit.

Tepco plans to set up more whole-body radiation counters that can check internal exposure, more decontamination facilities and an automated record system of each worker's exposure.

Tepco also said it will increase medical offices and doctors with help from the government. They also raised concern about the heat stroke threat workers face this summer that will aggravate their efforts.

"There are more than 2,000 people working at the site, and securing their safety and limiting their radiation exposure are key goals of the road map," said Muto.

New elements include plans to build underground walls near the reactors and turbine buildings to prevent groundwater contamination.

The full-scale operation of the new water treatment system is seen as a key step to containing the crisis because it would not only help reduce the polluted water but would create clean water that can be injected into the reactors, whose cooling systems were knocked out by the March 11 earthquake and tsunami.

Tepco has pumped water into the reactors from outside as an emergency measure to keep the nuclear fuel inside cool, but one side effect has been that the contaminated water has filled up the reactor turbine buildings and nearby areas, and spilled into the sea.

With the system, composed of equipment developed by Kurion Inc. of the United States and France's Areva SA, some of the polluted water transferred to a facility on the plant's premises would be cleaned through several processes, including removing oil and reducing the amount of cesium and other radioactive substances.

Tepco announced its first plan on April 17, and the utility has been giving monthly updates on its progress and strategy.

Looking back the past few months, Tepco Vice President Sakae Muto said some things went well, including cooling spent-fuel pools, while others did not, such as pouring nitrogen into reactors 2 and 3 to prevent hydrogen explosions. Tepco has also not been able to pinpoint holes and cracks in the containment vessels of reactors 1 to 3.

INFORMATION FROM KYODO ADDED



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