[國際新聞] TEPCO says 300 tons of contaminated water leaked from tank believes, designed, nuclear, storage, plant

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http://www.japantoday.com/category/national/view/tepco-says-300-tons-of-contaminated-water-leaked-from-tank

Aug. 20, 2013 - 01:55PM

TOKYO

The operator of Japan’s crippled Fukushima Daiichi nuclear plant said on Tuesday it believes about 300 tons of highly contaminated water has leaked from a storage tank designed to hold overflows from the site.

The leaked water contains 80 million becquerels of radiation per liter, a Tokyo Electric Power Co (TEPCO) spokesman said by phone.

The Nuclear Regulation Authority has classified the leak as a level 1 incident, the second lowest, on an international scale for radiological releases.

It is the first time Japan has issued a so-called INES rating since three reactors melted down at Fukushima in March 2011, shortly after the plant was wrecked by a an earthquake and tsunami, and the disaster was assigned the highest rating of 7.

Since then, TEPCO has been struggling to contain radioactive leaks. It has been criticized for its failure to prepare for the disaster and it has also been accused of covering up the extent of the problems at the plant.

A puddle that formed near the tank that leaked is emitting a radiation dose of 100 millisieverts an hour measured about 50 centimeters above the surface, Kyodo News reported, citing TEPCO.

That is equivalent to the limit for accumulated exposure over five years for Japanese nuclear workers.

A TEPCO spokesman said the information on the dose rate did not come from the company, saying only the leaked water contains 80 million becquerels of radiation per litre, without putting it into perspective.

A becquerel is a measure of the release of radioactive energy, while dose rate indicates how much radiation a person would receive standing near the source of radiation.

TEPCO uses a jerry-rigged system to wash water over the melted uranium fuel rods to keep them cool and stable. The water flows into basements that have been leaking since the disaster.

Highly contaminated excess water is pumped out and stored in steel tanks on elevated ground away from the reactors, which lie adjacent to the coast. TEPCO said it does not believe the water that leaked from the storage tank, which is about 500 meters from the shore, has escaped into the ocean.

But only this month the company, after months of denial, admitted contaminated water escaping from basements and trenches closer to the coast is reaching the ocean, prompting the government to step up its involvement in the plant’s cleanup.

“We have instructed TEPCO to find the source of contaminated water—from which tank the water is leaking—and to seal the leakage point,” an NRA official said. “We have also instructed them to retrieve contaminated soil to avoid a further expansion of toxic water, and to strengthen monitoring of the surrounding environment.”

Drain valves on the water tank may have been left open, allowing the water to flow out, TEPCO said.

(c) Copyright Thomson Reuters/AFP