Tokyo Electric Power Co. (9501) reported another breach of the defenses it has built at the Fukushima nuclear plant in its more than two-year struggle to stop leaks of radioactive water into the soil and sea.

Just weeks after the utility backtracked from earlier statements and acknowledged radiated water was flowing into the Pacific Ocean at a rate of 300 tons a day, it has found another leak from a storage tank.

Prime Minster Shinzo Abe weighed in on the disaster response this month, signaling that Tokyo Electric alone isn’t up to the task. The government has yet to say what other measures it’s considering to contain the worst nuclear disaster since Chernobyl, including bringing in foreign expertise.

“Two years down the line from the accident, I would expect there would have been better plans,” said Tom O’Sullivan, an analyst with Tokyo-based energy consultant Mathyos. “It’s a huge logistical challenge and perhaps the Japanese government should have gotten involved at an earlier stage.”

Shinichi Tanaka, the chairman of Japan’s Nuclear Regulation Authority, has said the water leaks are getting out of control and creating a state of emergency, according to Shinji Kinjo, who leads a disaster task force for the regulator.

Largest Leak

In the latest incident, the company said about 300 tons of contaminated water probably leaked into the soil from a tank due to an open valve in a containment barrier surrounding the storage vessel.

That’s equivalent to the amount of water used by about 200 U.S. families each day, according to calculations based on Environmental Protection Agency data. The leak is the largest from a storage tank to date, Masayuki Ono, an official at Tepco’s plant siting department, said at a press conference.

The leak was discovered after crews found a drop in the water level of the 1,000-ton capacity tank, Mayumi Yoshida, a spokeswoman for the company known as Tepco, said today in a phone interview. She wasn’t able to say why the valve, used to drain rainwater from the containment barrier, had remained open.

Radiation levels as high as 100 millisieverts per hour were detected near the tank, Ono said. Under government guidelines, plant workers are permitted exposure to 100 millisieverts over the course of five years.

Water Storage

The leaked water was found to have levels of beta radiation of 80 million becquerels per liter, including particles such as strontium, Ono said. That’s 8 million times the limit for drinking water under health ministry guidelines. Strontium has been linked to bone cancers.

Tepco stores about 400 tons of water a day at the plant after pumping it out from under the plant’s reactors, which melted down as a result of the March 2011 earthquake and tsunami. The water that is pumped is a combination of what is injected into the plant’s reactors to cool the fuel and groundwater that flows into the reactor basements from nearby hills.

There are more than 1,000 tanks on the plant grounds, with capacity for 390,000 tons of water, according to Kaoru Suzuki, a Tepco spokeswoman. About 330,000 tons of that capacity, or around 85 percent, had been used as of Aug. 13.

Radioactive

While the water is treated to remove some of the cesium radioactive particles before it is stored, higher levels of beta radiation remain, Yoshida said.

Infants exposed to radiation near the damaged nuclear power plant have a higher risk of developing cancer, though the threat outside the immediate area is low, the World Health Organization said in February in the first global assessment of risks from the 2011 disaster.

Seawater samples near the plant were found to have levels of tritium, another of the radioactive particles being monitored, at 4,700 becquerels per liter yesterday, the highest since sampling began, Kyodo news reported, citing the company.

Human exposure to radiation at moderate to high levels can lead to cancers, such as leukemia, according to the United Nations Scientific Committee on the Effects of Atomic Radiation.

The body, known as UNSCEAR, is in charge of the most comprehensive study of the Fukushima disaster and is expected to deliver its report to the UN in October this year.

To contact the reporters on this story: Jacob Adelman in Tokyo at jadelman1@bloomberg.net; Yuji Okada in Tokyo at yokada6@bloomberg.net

To contact the editor responsible for this story: Jason Rogers at jrogers73@bloomberg.net

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