Crippled Fukushima nuclear plant: 300 tons of radioactive water spilled

Members of a Fukushima prefecture panel, which monitors the safe decommissioning of the nuclear plant, inspect the construction site of the shore barrier, which is meant to stop radioactive water from leaking into the sea. Kyodo via Reuters, file

TOKYO - The operator of Japan's crippled Fukushima nuclear plant said an ongoing leak had spilled some 300 tons of radioactive water into the ground - the latest in a series of embarrassing revelations involving the tsunami-struck power station. 

"We believe it is still leaking at this moment," Tokyo Electric Power Company General Manager Masayuji Ono told reporters at press conference in Tokyo Tuesday.

High levels of radiation were detected at several hot spots along the hillside section of the plant where the water was thought to have spilled onto the ground, the company said. These areas were emitting a radiation dose of 100 millisieverts an hour measured about 1.6 feet above the surface, it added.

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That is equivalent to the limit for accumulated exposure over five years for Japanese nuclear workers, Ono said. Japan's Nuclear Regulation Authority classified the leak as a level 1 incident, the second lowest, on an international scale for radiological releases.

Officials at Tokyo Electric Power Company, or TEPCO, said they had not discovered any high radiation levels in the nearby water trench and because of the tank's distance from the harbor, did not believe the contamination has reached the ocean. 

Workers at TEPCO had started to pump out the remaining water from the defective tank as well as collect the surrounding soil which is thought to have absorbed the radioactive material, TEPCO said.

"We'd like to apologize for the concern we've caused people due to this problem," Ono added.

On April 5, a cooling system at the plant failed for the second time in a month after an outage caused by construction work to keep out rats suspected of setting off the earlier blackout. The following day, the company announced that as much as 120 tons of radioactive water may have leaked from a storage tank.

On June 19, TEPCO said high levels of toxic Strontium-90 were been found in groundwater Fukushima.

Two weeks ago, the nation's nuclear regulator reprimanded the utility for its poor handling of containing contaminated underground water from seeping into the ocean. And on Aug. 7, the government estimated that the damaged plant was leaking about 300 tons of contaminated water into the ocean every day.

Meanwhile, TEPCO has dug a well and inserted over 26 pipes to pump out 100 tons of contaminated water a day, in addition to erecting an underground barrier.

A much larger plan has also been proposed, involving creating an underground wall to surround the crippled reactor, but the project is still in its planning stage and is expected to take several years to build.

Reuters and The Associated Press contributed to this report.