Water storage tanks

Should Japan dump radioactive water from Fukushima into the ocean?

By Adam Vaughan

Water storage tanks at the Fukushima Daiichi nuclear power plant in Japan


Around 1.2 million tons of water contaminated by radioactive substances from the Fukushima nuclear disaster in 2011 will be dumped in the Pacific under a plan that the Japanese government is expected to approve within a few weeks.

The water is in around 1000 tanks at the former nuclear power plant, but the amount is growing every day as rainfalls and groundwater entering the site continue to be contaminated. The International Atomic Energy Agency assumes that existing capacities will be full by mid-2022. Last year, an average of 160 tons were added per day.

Because of this, the Japanese government is reportedly going to approve a strategy to discharge the water into the ocean, as advised by advisors. Release would begin around 2022 and would last for decades. The news sparked immediate complaints from Japanese fishing groups and masked warnings that China would ban Japanese imports of seafood. But are people rightly concerned about the environmental and health effects of the release of such a large amount of contaminated water?


Much of the existing water has already been filtered through a process that aims to remove more than 62 radioactive contaminants. The Japanese government and Tokyo Electric Power Company (TEPCO), the company that operates the site, have emphasized that the main remaining radionuclide is tritium. Francis Livens of the University of Manchester, UK, says this is very difficult to separate because it is a radioactive isotope of hydrogen and so is part of the water molecules themselves.

TEPCO looked at tritium removal technology, but a presentation from the company shows that most methods would not work at low concentrations in the tanks. Livens points out that most operational nuclear facilities release this isotope.

Tritium is light and could reach the west coast of the United States in two years, says Ken Buesseler of the Woods Hole Oceanographic Institution in Falmouth, Massachusetts. Fortunately, tritium is relatively harmless to marine life because the low-energy particles it emits do little harm to living cells, he says.

A more serious issue is other, potentially more dangerous, radionuclides in the water, including strontium-90 and iodine-129. TEPCO first published a list of contaminants in 2018. While the filtering has reduced its concentrations, around 70 percent of the water still has to go through a secondary filtering process. “There are big questions about whether it will work as planned,” says Shaun Burnie of Greenpeace.

According to Livens, filtering reduces the concentrations of non-tritium isotopes, but not to zero. Nevertheless, we shouldn't worry about the discharged values, says Pascal Bailly du Bois from the Cherbourg-Octeville radio-ecology laboratory in France. "The radiological impact on fisheries and marine life will be very little, much like if the Fukushima reactors were operated under normal conditions." Buesseler believes the effects on marine life – and on the people who eat it – are unknown until we have a "better balance" of the radionuclides in the tanks.

Simon Boxall of the University of Southampton, UK, says any potential risk would come from radionuclides building up in shellfish in coastal waters, but he thinks this is likely to be low. Further out in the Pacific Ocean, the risk is extremely small, but close monitoring and adherence to scientific recommendations will be key, he says.

There is no easy alternative. Another option to expand the capacity and store the water on land or underground would cause 97 percent of tritium decay within 60 years due to its short half-life. But this has to be weighed against the costs and the risk of tanks leaking in an earthquake-prone region, says Buesseler. "It's probably the sensible option (dumping into the ocean) because anything else is causing bigger problems," says Livens.

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