Japanese authorities are preparing to release treated radioactive wastewater into the Pacific Ocean, nearly 12 years after the Fukushima nuclear disaster.
This will relieve pressure on more than 1,000 storage tanks, creating much-needed space for other vital remediation work. But the plan has sparked controversy.
At first glance, releasing radioactive water into the ocean seems like a terrible idea.
green peace fears the radioactivity released could change human DNA, China And South Korea expressed concern, while Pacific Island States worried about further nuclear contamination of the Blue Pacific.
An academic publication claimed that the total cost of global social protection could exceed US$200 billion.
But the Japanese governmentthe International Atomic Energy Agency (IAEA), And independent scientists said the planned release was reasonable and safe.
Based on our collective professional experience in the field of nuclear science and nuclear energy, we have come to the same conclusion. Our assessment is based on the type of radioactivity to be released, the amount of radioactivity already present in the ocean and the high level of independent monitoring by the IAEA.
How much water is there and what is in it?
Fukushima’s storage tanks contain 1.3 million tons of waterthat is the equivalent of approximately 500 Olympic swimming pools.
Contaminated water is produced daily by the continuous cooling of the reactor. Contaminated groundwater also accumulates in the basements of damaged reactor buildings.
The water is cleaned by a technology called ALPS, or Advanced Liquid Processing System. This removes the vast majority of problematic elements.
ALPS treatment can be repeated until concentrations are below regulatory limits. Independent monitoring by the IAEA will ensure that all requirements are met prior to release.
The main radioactive contaminant remaining after treatment is tritium, a radioactive form of hydrogen (H) that is difficult to remove from water (H₂O). There is no technology to remove traces of tritium from this volume of water.
Tritium has a half-life of 12.3 years old, which means that 100 years pass before the radioactivity is negligible. It is not realistic to store water for so long because the volumes are too large. Prolonged storage also increases the risk of accidental uncontrolled release.
Like all radioactive elements, international standards exist for safe levels of tritium. For liquids, these are measured in Bq per litre, where one Bq (becquerel) is defined as one radioactive decay per second.
At the point of discharge, the Japanese authorities have chosen a conservative concentration limit of 1,500 Bq per literseven times smaller than World Health Organizationthe recommended limit of 10,000 Bq per liter for drinking water.
Why is it acceptable to release tritium into the ocean?
One surprising thing about radiation is its frequency. Almost everything is radioactive to some degree, including air, water, plants, basements, and granite countertops. Even a long-haul flight provides everyone on board with a few radiation-equivalent chest X-rays.
In the case of tritium, natural processes in the atmosphere generate 50-70 peta-becquerels (PBq) of tritium each year. This number is difficult to grasp, so it is useful to think of it as grams of pure tritium. Using the conversion factor of 1 PBq = 2.79 g, we see that 150-200g (5.3-7.1 oz) of tritium is created naturally every year.
Looking at the Pacific Ocean, about 8.4 kg (3,000 PBq) of tritium is already in the water. By comparison, the total amount of tritium in Fukushima’s wastewater is much smaller, at around 3 g (1 PBq).
Japanese authorities do not plan to release the water all at once. Instead, only 0.06 g (22 TBq) of tritium should be released every year. Compared to the radioactivity already present in the Pacific, the expected annual release is a veritable drop in the ocean.
Current levels of tritium radioactivity in the Pacific are not of concern, and therefore the small amount added by Fukushima water will cause no harm.
Moreover, tritium makes only a tiny contribution to the total radioactivity of the oceans. The radioactivity of the oceans is mainly due to potassium, an element essential for life and present in all cells. In the Pacific Ocean there are 7.4 million PBq potassium radioactivity, more than 1,000 times greater than the amount due to tritium.
How do other countries deal with tritium releases?
All nuclear power plants produce tritium, which is regularly released into the ocean and other waterways. The amount generated depends on the type of reactor.
Boiling water reactors, as in Fukushima, produce relatively small quantities. When Fukushima was operating, the tritium release limit was set at 22 TBq per year. This figure is well below a level which could cause damage, but which is reasonably achievable for this type of plant.
In contrast, Britain’s Heysham nuclear power station has a limit of 1,300 TBq per year because this type of gas-cooled reactor produces a lot of tritium. Heysham has been releasing tritium for 40 years without harming people or the environment.
Annual release of tritium to nearby nuclear power plants far exceeds what is proposed for Fukushima. The Fuqing plant in China released 52 TBq in 2020, while the Kori plant in South Korea released 50 TBq in 2018.
Each of these plants discharges more than double the quantity discharged by Fukushima.
Are there other reasons for not releasing the water?
Objections to the planned release received extensive media coverage. TIME The magazine recently detailed how Pacific island nations have grappled for decades with the legacy of Cold War nuclear testing.
The Guardian published an opinion piece from Pacific activists, who argued if the waste was safe, then “dump it in Tokyo, test it in Paris, and store it in Washington, but keep our Pacific nuclear-free “.
But the Pacific has always contained radioactivity, especially potassium. The extra radioactivity to be added from the Fukushima water will make the smallest difference.
Striking a different tone, the Pacific Islands Forum mandated a panel of experts provide independent technical advice and guidance and help address sewage concerns.
The panel criticized the quantity and quality of data provided by the Japanese authorities and indicated that Japan should differ impending discharge.
While we support the idea that the science could be improved, our assessment is that the group unfairly criticizes ocean release.
The main thing missing from the report is a sense of perspective. The public seminar of the panel of experts, available on YouTube, presents only part of the context we provide above. The existing tritium in the ocean is not discussed and the predominance of potassium is passed over in silence.
The most reasonable comments relate to the performance of ALPS. This is largely in the context of strontium-90 and cesium-137, both of which are isotopes of legitimate concern.
However, the panel suggests that the authorities do not know what is in the tanks and that the ALPS is not working properly. There is actually a lot of public information on both topics. Maybe it could be repackaged in a clearer way for others to understand. But the inferences made by the panel give the wrong impression.
The most important thing the panel overlooks is that contaminated water can be repeatedly passed through ALPS until it can be safely released. For some tanks a single pass is sufficient, while for others additional cycles are required.
The big picture
The earthquake was the primary environmental disaster, and the planet will suffer the consequences for decades. In our opinion, the discharge of sewage from Fukushima does not add anything to the disaster.
It’s easy to see why people are concerned about the possibility of radioactive liquid waste being released into the ocean. But the water is not dangerous. The most harmful elements have been eliminated, and what remains is modest compared to the natural radioactivity.
We hope that science will prevail and that Japan will be allowed to continue the recovery process. 
Nigel’s Marksassociate professor of physics, Curtin University; Brendan Kennedychemistry teacher, University of SydneyAnd Tony IrvinHonorary Associate Professor, Nuclear Reactors and the Nuclear Fuel Cycle, Australian National University
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