Corrosion has been found on the inside of tanks used to store treated radioactive water at the crippled Fukushima Daiichi nuclear power plant, its operator has revealed.

Tokyo Electric Power Company Holdings Inc. said there are no problems with the strength of the tanks, but added that some of the more than 1,000 containers at the plant were installed over 10 years ago and have aged over time.

A TEPCO official said the operator will continue to inspect the tanks.

Photo shows corrosion found inside a tank used to store treated radioactive water at the crippled Fukushima Daiichi nuclear power plant on March 26, 2024. (Photo courtesy of Tokyo Electric Power Company Holdings Inc.)(Kyodo)

The firm began releasing the treated water containing tritium from the plant into the Pacific Ocean in August 2023 despite backlash from local fisheries and China.

In March, corrosion and peeling paint were spotted in three empty tanks that have been in use since 2016 at the plant, which suffered meltdowns following the devastating earthquake and ensuing tsunami in March 2011.

As it is impossible to check the inside of tanks currently containing treated water, other than with the use of underwater robots, TEPCO conducts annual exterior inspections to detect any abnormalities.

Tanks that have been used for more than 10 years also have the thickness of their steel plates measured using ultrasonic waves to assess their strength, TEPCO said.

The Japanese government and TEPCO have said that the treated water released from the Fukushima plant is diluted to reduce the levels of tritium to less than one-40th of the country's national safety standards.

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