Japan’s government says it will release more than 1 million tons of contaminated water from the stricken Fukushima nuclear power plant into the sea, describing it as the best option despite vociferous protest from China, South Korea and Taiwan as well as the island nation’s fishing industry.

The first release of water will take place in about two years, giving Tokyo Electric Power Co, or Tepco, the plant’s operator, time to filter the water for harmful radioactive isotopes, build infrastructure and acquire regulatory approval.

The release of the water – which has been predicted – has long been delayed by public opinion and safety concerns. But the space to store the water is expected to run out next year, and Prime Minister Yoshihide Suga said during the cabinet meeting on Tuesday that disposing of the wastewater from the plant was “a problem that cannot be avoided,” various media reported.

The government also argues that the water release is necessary to press ahead with the complex decommissioning of the plant, which is expected to take decades after it was destroyed by a tsunami and earthquake in 2011. Inundated by sea water, three of the plant’s six reactors melted down and released massive amounts of radiation, constituting the worst nuclear accident since Chernobyl in 1986. Tens of thousands of people fled the area around the plant or were evacuated, in many cases never to return.

During a Tuesday press conference, the government stressed the water’s apparent safety, calling it “treated” rather than “radioactive,” even though radionuclides can only be reduced to disposable levels, not to zero.

Tepco says it can filter the contaminated water to remove isotopes, leaving only tritium, a radioactive isotope of hydrogen hard to separate from water. Tepco then plans to dilute the water until tritium levels fall below regulatory limits before pumping it into the ocean.

Tritium is considered to be relatively harmless because it does not emit enough energy to penetrate human skin. Other nuclear power plants around the world routinely pump water with low levels of the isotope into the ocean.

Residents, fisheries officials and environmental groups issued statements denouncing the decision as ignoring environmental safety and health, and further hurting Fukushima’s image and economy.

Japan Fisheries Cooperatives chairman Hiroshi Kishi told the Associated Press that the decision – which came less than a week after he met with Suga – “trampled on” all Japanese fisheries operators.

Local fisheries have just returned to full operation after a decade in which their catch was only for testing purposes, and they are struggling because of dwindling demand.Protestors gathered outside the Prime Minister’s Office to demand the plan be scrapped.

Cleanup is far from finished at the plant. In the ten years since the disaster, Tepco has had to pump water through the stricken reactors continuously to keep them cool. The water is then sent through a filtration system that is able to remove all of the radioactive material except for tritium.

There are now about 1.25 million tons of wastewater stored in more than 1,000 tanks at the plant site. The water continues to accumulate at a rate of about 170 tons a day, and gradually releasing all of it is expected to take up to 40 years.

Those tanks, which occupy a large space at the plant, and government officials say they interfere with the safe and steady progress of the decommissioning. The tanks also could be damaged and leak in case of another powerful earthquake or tsunami.

In 2019, the Japanese Ministry of Economy, Trade and Industry proposed disposing of the wastewater either by gradually releasing it into the ocean or by allowing it to evaporate. The International Atomic Energy Agency has said both methods are “technically feasible.”

The United States noted that Japan has worked closely with the International Atomic Energy Agency in its handling of the site.

“In this unique and challenging situation, Japan has weighed the options and effects, has been transparent about its decision, and appears to have adopted an approach in accordance with globally accepted nuclear safety standards,” the US Department of State said in a statement on its website.

China, South Korea and Taiwan disagree.

“This action is extremely irresponsible, and will seriously damage international public health and safety, and the vital interests of people in neighbouring countries,” Reuters quoted China’s foreign ministry as saying in a statement.

South Korea’s government summoned Japan’s ambassador to Seoul to protest at the move. Meanwhile, Taiwan’s Atomic Energy Council called Japan’s decision regrettable, and the country’s foreign minister asked Tokyo for more details about the planned release.

The International Atomic Energy Agency welcomed Japan’s announcement and said it would offer technical support. It called the plan to release the water into the sea in line with international practice.

“Today’s decision by the government of Japan is a milestone that will help pave the way for continued progress in the decommissioning of the Fukushima Daiichi nuclear power plant,” the agency said in a statement.