Fukushima: TEPCO Admits Most Severe Radioactive Leak Since March 2011 Meltdowns

– Fukushima operator reveals leak of 300 tonnes of highly contaminated water (Guardian, Aug 20, 2013):

Spillage is most severe since March 2011 as Tepco says it does not know how the water leaked out or where it has leaked to

Frantic efforts to contain radioactive leaks at the wrecked Fukushima Daiichi nuclear power plant have been dealt another blow after its operator said about 300 tonnes of highly contaminated water had seeped out of a storage tank at the site.

The leak is the worst such incident since the March 2011 meltdown and is separate from the contaminated water leaks, also of about 300 tonnes a day, reported recently.

Tokyo Electric Power Co (Tepco) said it did not know how the water leaked out or where it had leaked to, but it believed that the spillage had not flowed into the Pacific ocean.

Tepco’s spokesman, Masayuki Ono, said the water had seeped into the ground after breaching a concrete and sandbag barrier around the tank. Workers were pumping out the puddle and removing the remaining water from the tank, he added. Despite efforts to contain the spillage, the leak is already the most severe since the crisis began.

News of the leak, which was discovered on Monday morning, comes after Tepco admitted that up to 300 tonnes of highly contaminated water from the site was seeping into the sea every day. Government officials said they could not rule out the possibility that the site had been leaking radioactive matter since the plant suffered a triple meltdown on 11 March 2011.

An official from Japan’s nuclear regulation authority said: “We have instructed Tepco to find the source of contaminated water – from which tank the water is leaking – and to seal the leakage point.

“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.”

The authority classified the latest leak as a level one incident on the International Atomic Energy Authority’s scale of nuclear and radiological accidents. The level is the second lowest on the scale.

The 2011 meltdowns in three of Fukushima Daiichi’s six reactors – caused when the plant was struck by a powerful tsunami that had been triggered by a 9.0 magnitude earthquake off Japan’s north-east coast – were given the highest severity rating of seven, the same level given to the Chernobyl disaster 25 years earlier.

It is the first time Japan’s nuclear regulator has deemed an incident serious enough to warrant an international classification since the country’s triple disaster almost two and a half years ago.

Tepco, which faces renewed criticism over its handling of the water leaks, has admitted that water in a puddle that had formed near the steel storage tank was emitting a radiation dose of 100 millisieverts an hour – five times the annual exposure limit for nuclear plant workers in Japan.

Hundreds of tanks have been built at the site to store contaminated water that is being fed into reactor buildings to cool melted fuel rods, as well as underground water running into reactor and turbine basements.Tepco suspects that the water may have leaked through a drain valve connected to a gutter around the tank, which is located about 500 metres from the shore.

Japan’s prime minister, Shinzo Abe, recently suggested he had lost faith in Tepco’s ability to handle the water crisis without government help. The firm’s failure to prevent leaks could frustrate his attempts to relaunch further reactors in Japan. The leaks are also causing concern abroad. On Tuesday, South Korea said it had asked Japanese officials to explain the leaks of contaminated water into the Pacific.