Tokyo Electric Power Co. said Thursday it has detected high levels of radiation along the seams of two temporary storage tanks containing contaminated water at its crippled Fukushima No. 1 nuclear power station.
The seams on the bottom of the 1,000-ton tanks were dry, and no water was found near them, Tepco said.
Radiation levels of up to 100 millisieverts per hour were measured at each of the two tanks in question, according to the utility.
The cause of the high-level radiation along the seams of the two tanks remains unclear and the possibility of leaks cannot be ruled out, Tepco said.
The two tanks are the same type as the one that has leaked an estimated 300 tons of contaminated water at the plant, which suffered three reactor core meltdowns after the March 2011 mega-quake and tsunami. The leaking tank was discovered Sunday.
There are some 350 such tanks at the plant and about 300 are being used to temporarily store highly radioactive water. On Thursday, Tepco checked all 300 tanks. They are made of steel plates bolted together, with sealed seams. Tepco is also using more durable welded steel tanks.