The operator of Japan's crippled Fukushima nuclear power plant has found that a coolant solution, used to create an ice wall halting the seepage of groundwater into reactor buildings, has leaked from two storage tanks, Reuters reported.

The leakage has had no impact on the wall or environment, said Tokyo Electric Power Co Holdings Inc (Tepco) (9501.T).

Still, it underscores the unpredictable challenges in the clean-up of the site, nearly 11 year after an earthquake and tsunami ravaged Japan's northeastern coast, causing the world's worst nuclear disaster since Chernobyl, Ukraine, in 1986.

Only last year, Japan's government approved the release of over 1 million tons of irradiated water from the site after treatment, starting around spring 2023. Tepco last month said it would build a tunnel reaching into the sea for the operation. read more

On Sunday, Tepco spokesperson Tsuyoshi Shiraishi said about four tons of a calcium chloride solution used to maintain the ice wall had leaked in what was the eighth such leakage.

"We're now confirming the reason," he said.

The last leak in December 2019 saw 16 tons spilled, likely due to metal fatigue resulting from vibrations caused by construction vehicles, Shiraishi said.

There was no immediate impact on the wall's function as it takes several months for the wall to thaw in the absence of coolant, he said.