Japan will soon begin releasing treated radioactive water into the ocean following approval from the United Nations’ nuclear watchdog for a controversial plan that comes 12 years after the Fukushima nuclear meltdown.

The plan to release treated wastewater has been in the works for years, with the environment minister declaring in 2019 there were “no other options” as space runs out to contain the contaminated material.

Rafael Grossi, chief of the International Atomic Energy Agency (IAEA), arrived in Japan on Tuesday to visit Fukushima and present the UN body’s safety review to Prime Minister Fumio Kishida.

But the UN’s approval has done little to reassure rattled residents in neighboring countries, and local fishermen who still feel the impact of the 2011 disaster.

Some have cast doubt on the IAEA’s findings, with China recently arguing that the group’s assessment “is not proof of the legality and legitimacy” of Fukushima’s wastewater release.


There doesn't seem like a historical precedent or clear procedure set up for determining whether releasing treated wastewater from nuclear plants into the ocean is justifiable in the international community? Am I wrong? Is there a law that set something up in case something like this came up?

  • 3
    Legality... aargh!!! Who's going to enforce some "law" saying Japan can't release the Fukushima waste water?
    – RonJohn
    Jul 7, 2023 at 20:20

3 Answers 3


Discharge is Commonly Accepted in Other Contexts

The water that Japan will discharge is treated to remove radionuclides. The remaining radioactivity comes mainly from tritium, which is commonly released by many actors into the ocean.

For context, tritium is an isotope of hydrogen. In this case, it means that the water itself is radioactive - it is the H in the H2O that decays - not that the water contains Uranium or other radioactive particles.

Tritium has a shortish half-life (12 years) releases low energy beta particles, and decays to a stable isotope of Helium. Because it beta decays, you could safely hold a cup of highly concentrated tritium-water in your hand.

Because it decays quickly, has a low energy decay, dilutes easily in water, and does not decay into a heavy metal or poisonous substance, tritium is considered pretty "safe" as far as radioactive material goes.


It is nearly impossible to filter tritium out of water; it is chemically identical to regular Hydrogen, and the slight difference is in atomic weight is the only discriminating factor. Thus you need to use many powerful centrifuges to physically separate the heavy water, which is not feasible in any case where tritium is regularly produced.

Every operating nuclear reactor regularly produces tritium.

There is currently about 800 TBq of tritium in storage at the Fukushima plant, which will be discharged over the next 30 years.

The British currently dump about 800 TBq annually into the Irish sea from the Heysham power plant and Sellafield reprocessing center.

The Canadian Bruce Nuclear Generating Station dumps about 800 TBq annually into the Great Lakes.

These discharges are common, legal, and not controversial for the reasons discussed above.

Additional Approvals or Justifications are not Necessary

Japan's actions appear consistent with international norms. This discharge is just more visible because the it is in the news, and thus it triggers atom-phobia.

  • 6
    Yes, the missing context to these discussions is that seawater, like many parts of the environment, is already radioactive. After the initial Fukushima incident there were people on the Pacific coast of the United States taking geiger counters to the beach (months before currents could have brought water from near Japan) and freaking out that the sand was mildly radioactive -- which it has always been. Jul 7, 2023 at 15:56
  • I wonder how the amount of tritium released by the Fukushima plant compares to other natural radioactivity sources like potassium and carbon
    – Nayuki
    Jul 7, 2023 at 22:17
  • 1
    @Nayuki, carbon: the world's carbon-14 emits roughly 10,000 times as much radiation as the Fukushima wastewater. Potassium: the world's annual banana crop emits roughly 1/50th as much radiation as the Fukushima wastewater.
    – Mark
    Jul 8, 2023 at 2:20
  • 1
    @ jeffronicus and @Nayuki - I think the natural vs man-made radioactivity comparison is valuable, but I think it's more important that this radioactivity is chemically indistinguishable from water. There's no mechanism for it to concentrate in one section of the sea floor which could later be disturbed or in apex predators that could later be eaten by humans - which some other forms of pollution do. It's going to spread out through the entire global water cycle, which rapidly dilutes it to undetectable levels, even if it had started with a comparatively high amount of radiation.
    – codeMonkey
    Jul 10, 2023 at 13:00

There is no specific law that set up a procedure for determining whether nuclear fuel release into the ocean is justifiable in the international community. However, the United Nations Convention on the Law of the Sea (UNCLOS) does provide some general principles that could be applied to this issue.

Article 192 of UNCLOS states that states have the obligation to protect and preserve the marine environment. This obligation includes the duty to prevent, reduce and control pollution of the marine environment from any source.

Article 211 of UNCLOS provides that states are required to take measures to prevent pollution of the marine environment from radioactive materials. These measures must be consistent with generally accepted international standards and practices.

In the case of Japan's plan to release treated radioactive water into the ocean, the IAEA has concluded that the plan is consistent with international standards and practices. However, some countries, including China, have expressed concerns about the plan and have called for further review.

Ultimately, the decision of whether or not to release treated radioactive water into the ocean is a political one. There is no clear legal precedent or procedure that can be used to determine whether such a release is justifiable. However, the principles set out in UNCLOS provide some general guidance that states can use in making this decision.

  • 1
    UNCLOS apparently involves a wide range of dispute settlement mechanisms, some which could be used to judge the legality of Japan's actions (and hence permit or ban it), but I'm not an expert in a very complex area.
    – Stuart F
    Jul 7, 2023 at 10:02

Standards and precedents are in flux. Consider the operations of Sellafield, half a century ago. In recent decades, countries including Japan have adopted stricter environmental regulations than before.

In your question you ask about the release of nuclear fuel. Releasing fuel would violate various nuclear safeguard agreements. Releasing nuclear waste (i.e. materials which are no longer suitable for powering a reactor) is a different issue. It comes down to the issue if the nuclear waste has a sufficient concentration to become a concern.

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