Japan has said that it will pump more than a million tonnes of contaminated water from the Fukushima nuclear power plant into the Pacific, provoking angry protests from fishermen and other east Asian countries.
Beginning in two years’ time, the waste water will be released into the sea over a period of 30 years. It will be treated and diluted to remove most radioactive contaminants but will still contain traces of the radioactive isotope tritium.
“Disposal of the treated water is an unavoidable challenge for the decommissioning of the plant,” Yoshihide Suga, the Japanese prime minister, said at a cabinet meeting. “The government concluded that the ocean release is a realistic method.”
He added: “We will aim to ensure safety that is higher than existing standards. The government will make all-out efforts to deal with unfounded rumours.”
Local fishermen, whose produce has been shunned by many customers since a tsunami caused a meltdown at Fukushima No 1 in 2011, denounced the decision as “absolutely unacceptable”. The government of South Korea, whose waters adjoin those of Japan, summoned Tokyo’s ambassador to make a formal protest.
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Ten years after the catastrophe, the three destroyed reactors are still decades away from being safely dismantled. In the meantime, 170 tonnes of water is contaminated by them every day.
Some of this is poured directly on to the broken reactors to cool them. Much is natural ground water which flows through the earth towards the sea, picking up radiation on the way. To prevent the groundwater reaching the plant in the first place the authorities built an underground “ice wall” of frozen earth, but this has been only partly effective.
The Tokyo Electric Power Company (Tepco), which operated the plant, pumps out the irradiated water — 1.25 million tonnes so far — and stores it in more than 1,000 huge storage tanks. Tepco says that by 2022 it will have run out of space for new storage.
In theory, filtering can remove all the radioactive elements except for tritium, which is routinely released into the sea in diluted form from nuclear plants around the world. But trace elements of more dangerous radioactive substances, including strontium-90 and iodine-129, have also been detected in the water.
Some environmental and nuclear experts say that in the circumstances, pouring the water into the ocean is the best of a range of bad options, and that the diluting effect of the Pacific will render the radiation harmless to humans.
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The Japanese government says that tritium will be diluted to less than one 40th of the concentration permitted under Japanese safety standards and one seventh of the World Health Organisation’s permitted level for safe drinking water. It says that the discharge of the water will be carried out in co-operation with the International Atomic Energy Agency.
Some governments, including the United States, have cautiously supported the plan. “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 state department said in a statement.
Hiroshi Kishi, of the National Federation of Fisheries Cooperative Associations said: “It is very regrettable and unacceptable. It will hurt the feelings of fisherfolk around the nation.”
Koo Yun-cheol, a spokesman for the South Korean government, said: “We will strongly demand from Japan concrete measures for the safety of our people and prevention of damage to the maritime environment.”
