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 some locals, those in the fishing industry, as well as China and South Korea, have opposed the plan.
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.
Currently, the radioactive water is treated in a complex filtration process that removes most of the radioactive elements, but some remain, including tritium.
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.
Around 1.3 million tonnes of radioactive water – or enough to fill about 500 Olympic-sized swimming pools – are currently stored in these tanks, according to a Reuters report.
Is there opposition?
Environmental groups like Greenpeace have long expressed their opposition to releasing the water into the ocean.
The NGO said Japan’s plans to release the water showed the government “once again failed the people of Fukushima”.
The country’s fishing industry has also argued against it, worried that consumers will refuse to buy produce from the region.
The decision has also prompted criticism from Japan’s neighbours. Ahead of the decision, South Korea’s foreign minister on Monday expressing “serious regret”.
Chinese foreign ministry spokesman Zhao Lijian also urged Japan to “act in a responsible manner”.
“To safeguard international public interests and Chinese people’s health and safety, China has expressed grave concern to the Japanese side through the diplomatic channel,” Mr Zhao said.
The US however, appears to support Japan’s decision, saying that it appeared to have “adopted an approach in accordance with globally accepted nuclear safety standards”.
How safe is this water?
Japan argues that the release of the waste water is safe as it is processed to remove almost all radioactive elements and will be greatly diluted.
The plan has the backing of the International Atomic Energy Agency which says the release is similar to the disposing 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.
What happened in Fukushima?
On 11 March 2011, a 9.0 magnitude earthquake struck off the north-eastern coast of Japan, triggering a 15-metre tsunami.
While the back-up systems to prevent a meltdown at the Fukushima nuclear plant survived the initial quake, further damage was inflicted by the tsunami.
As the facility’s cooling systems failed in the days that followed, tonnes of radioactive material were released. The meltdown was the worst nuclear accident since Chernobyl in 1986.
Around 18,500 people died or disappeared in the quake and tsunami, and more than 160,000 were forced from their homes.