ANKARA: As Japan moves ahead in its controversial plans to release treated nuclear waste into the sea, authorities have detected "higher-than-usual levels" of radioactive material in rainwater around a storage tank, local media reported on Friday.

The Tokyo Electric Power Company (TEPCO) said the leak was found "in a hose used to transfer treated water," Anadolu Agency cited Japanese broadcaster NHK.

It, however, added: "The water that leaked remained inside the barrier."

Amid criticism from neighbours especially China, Japan is set to release the treated nuclear water from the crippled Fukushima Daiichi nuclear power plant into the sea in the next few weeks.

"Someone caused the cracks with a cutter blade while removing the packaging around the hose after it was delivered," said the TEPCO.

The authorities found cracks on the hose measuring around four centimeters.

TEPCO said it "detected 33,000 becquerels of tritium per litre in rainwater collected from the dike surrounding a tank storing treated water" in June.

"As the hose was also used to transfer treated water from another tank, TEPCO analysed water in the dike around the tank and detected up to 67,000 becquerels of tritium per litre.

That exceeds 60,000 becquerels, the standard set by the Japanese government for releasing tritium into the environment," the NHK report said.

Japan has made plans to treat the nuclear waste to "reduce tritium levels to about one-seventh of the World Health Organisation's guidelines for drinking water quality before releasing it into the sea."

-- BERNAMA