Workers at Japan’s stricken Fukushima nuclear power plant discovered the leakage of 300 cubic metres of highly contaminated water on Monday, the worst such incident since the plant’s March 2011 meltdown.
According to reports, at around 9:50 a.m. a Tepco worker on patrol discovered a pool of more than 100 litres of highly contaminated water thought to have escaped from a concrete barrier’s drain valve that surrounds the temporary storage tanks.
Tepco said the water level from storage tank No.5 dropped by 3 metres, meaning that about 300 tonnes of contaminated water had been lost.
According to the Japan Times, “From Monday to Tuesday, about 10 tonnes were lost, indicating this amount may have leaked every day over the past 30 days.”
The radiation level measured around 50 centimetres above the toxic water stood at about 100 millisieverts per hour.
Tepco claims none of the water has flowed directly into the Pacific. The water was apparently contained by the 30-centimetre-high waterproof barrier surrounding the tanks.
According to the International Commission on Radiological Protection, exposure to 100 millisieverts increases the incidence of death by cancer by 0.5 percent, the Japan Times reported.
Among 1,000 tanks built by Tepco to hold highly contaminated coolant water at Fukushima, 350 are temporary.
Similar leaks have occured since 2012, but not on this scale, a Tepco official said.
News of this latest leak comes after Tepco admitted that up to 300 tonnes of contaminated water from the site was seeping into the sea every day.
According to the Guardian, the causes of this leak have still to be determined.