Japan has approved a plan to release more than one million tonnes of contaminated water from the destroyed Fukushima nuclear plant into the sea.

The water will be treated and diluted so radiation levels are below those set for drinking water.

But the local fishing industry has strongly opposed the move, as have China and South Korea.

Tokyo says work to release water used to cool nuclear fuel will begin in about two years.

The final approval comes after years of debate and is expected to take decades to complete.

Reactor buildings at the Fukushima power plant were damaged by hydrogen explosions caused by an earthquake and tsunami in 2011. The tsunami knocked out cooling systems to the reactors, three of which melted down.

More than a million tonnes of water have been used to cool the melted reactors.

Currently, the radioactive water is treated in a complex filtration process that removes most of the radioactive elements, but some remain, including tritium - deemed harmful to humans only in very large doses.

It is then kept in huge tanks, but the plant’s operator Tokyo Electric Power Co (TepCo) is running out of space, with these tanks expected to fill up by 2022.

About 1.3 million tonnes of radioactive water - or enough to fill 500 Olympic-sized swimming pools - are currently stored in these tanks, according to a Reuters report.

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The plan has the backing of the International Atomic Energy Agency, which says the release is similar to the disposal of waste water at other plants around the world.

“Releasing into the ocean is done elsewhere. It’s not something new. There is no scandal here,” IAEA Director General Rafael Mariano Grossi said in 2021.

Scientists argue that the elements remaining in the water are only harmful to humans in large doses. With dilution the treated water poses no scientifically detectable risk, they say.

While the tritium is radioactive, it has a half-life of around 12 years, meaning it will disappear from the environment over a period of decades rather than centuries.

Radiation from tritium can be ingested, however, which is why fishing industry groups are concerned about the risk of it getting into the food chain and being consumed through sea food.

The risk of this happening is not zero, but the scientific consensus is that it does not pose a threat to human health.

Scientists also point out that vastly more radiation has been released into the pacific by nuclear weapons tests carried out by the US, UK and France during the 1940s, 50s and 60s.