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expert comment on release of waste water from Fukushima into the sea, expected later this year

Starting later time this year, Japan is preparing to release over a million tonnes of treated waste water from the Fukushima nuclear plant into the Pacific.


Prof Jim Smith, Professor of Environmental Science, University of Portsmouth, said:

“The controlled discharge of wastewater with small amounts of radioactive tritium happens regularly at nuclear sites all over the world. The wastewater at Fukushima has been treated to reduce other more dangerous radioactive elements to almost undetectably low levels. But tritium in the form of “tritiated water” is extremely difficult and costly to separate from ordinary non-radioactive water. So nuclear sites all over the world – including the UK, US, China and South Korea, discharge diluted wastewater to seas, rivers and lakes. This has been going on for decades without significant impacts. For example, the La Hague reprocessing facility releases about 10,000 Terabecquerels of tritium per year into the English Channel. Radiation doses from this are very low and there is no evidence of significant ecosystem impacts. The planned release from Fukushima of 22 Terabecqurels per year to the Pacific Ocean is about 450 times lower than the La Hague releases and 50 times lower than releases from the UK’s Sellafield facility.

“Claims have been made about significant risks to the Pacific Ocean ecosystem from the planned Fukushima release. But these are not founded in scientific evidence. Tritiated water can damage DNA if ingested but it is very weakly radiotoxic and does not biomagnify in the food chain so risks are extremely low. The concentration of tritium in the wastewater will be 1500 Bequerels per litre, about 7 times lower than the World Health Organisation’s recommended limit for tritium in drinking water.

“I and colleagues have studied ecosystems in lakes at Chernobyl including the Cooling Reservoir which are thousands of times more contaminated than the sea surrounding Fukushima will be from this release. At Chernobyl, we have found a thriving aquatic ecosystem and only very subtle potential impacts of radiation on aquatic organisms despite the high radiation levels.

“Suggestions have been made that using the wastewater to make concrete is a better option than discharge to the ocean. This is an interesting idea, but very speculative at present. No risk assessments have been made for this and this option needs to account for potential evaporation of tritium from the concrete. Previous experience has shown that evaporation of tritium leads to significantly higher doses than discharge to water.

“Those making claims of major risks to the Pacific Ocean should consider the negative impact of their – I think scientifically baseless – claims on the communities in Japan who have been affected by the Fukushima accident.

“I strongly believe that the plans of the Japanese government are robust and represent current best practice. Other options – which are, I think,  speculative – are worth exploring, but the Fukushima wastewater release should go ahead as planned.”


Comments sent out by our colleagues at SMC Australia:

Associate Professor Tony Hooker, Director of the Centre for Radiation Research, Education and Innovation, The University of Adelaide, Australia

“The proposed release of wastewater from the Fukushima Daiichi Nuclear Power Plant is controversial. I believe that the Tokyo Electric Power Company and the Japanese Government have developed a robust plan using their current radiation protection legalisation and practices to at least start disposing of water in the short term.

“This approach has been verified by the IAEA in their subsequent reports. These include reports assessing the Japanese regulatory system, safety review missions, and corroboration of the independent sampling, data and analysis as well as inter-laboratory comparisons.

“However, whilst this disposal plan meets the scientific and regulatory requirements for the disposal of radiation into the sea, and no environmental or human health impacts are likely to be observed, there is a growing question regarding the use of the sea as a dumping ground when our oceans are already stressed and struggling.

“Dilution is no longer the solution to pollution, so whilst the Japanese may dispose of their wastewater in the interim, it would be a good opportunity to look at other disposal methodologies in the future. The Pacific Island Forum Scientific Panel has proposed to use the wastewater to make concrete, therefore locking up the residual radioactive tritium.”


Associate Professor Nigel Marks, Professor in Physics & Astronomy, Curtin University, Perth, Australia, said:

“Japan is about to start releasing treated wastewater from the Fukushima nuclear power plant into the Pacific Ocean. At first, this sounds like a terrible idea, but in fact, it is sensible and safe. Similar releases have occurred around the world for decades, and nothing bad has ever happened.

“The radioactivity in the Fukushima water is almost entirely tritium, a form of hydrogen. For scale, the Pacific Ocean contains 8,400 grams of pure tritium, while Japan will release 0.06 grams of tritium every year. The minuscule amount of extra radiation won’t make the tiniest jot of difference. A lifetime’s worth of seafood caught a few kilometres from the ocean outlet has the tritium radiation equivalent of one bite of a banana.

“In South Korea and Pacific Rim nations, a disinformation campaign has whipped the public into a frenzy about the release. In truth, almost everything is radioactive, including the Pacific Ocean, where tritium accounts for a modest 0.04% of total radioactivity. Increasing this tiny amount by a tiny amount is hardly end-of-the-world stuff. It is time for informed scientists to stand up and be counted, and face down the doomsayers.”


Tony Irwin, Honorary Associate Professor, Australian National University and Technical Director of SMR Nuclear Technology Pty Ltd and Chair of Engineers Australia Sydney Division Nuclear Engineering Panel, Canberra, Australia, said:

“The Fukushima water discharge is not an event without precedent. Nuclear power plants worldwide have routinely discharged water containing tritium for over 60 years without harm to people or the environment, most at higher levels than the 22 TBq per year that is planned at Fukushima.

“For comparison, in South Korea the Kori plant discharged 91 TBq in 2019, more than four times the planned Fukushima discharge. Provided the levels of all dangerous radioisotopes are below regulatory levels, the planned discharge at Fukushima is very conservative. So the key question is do TEPCO accurately measure what is in the tanks to be discharged?

“The IAEA have carried out a series of missions. Their latest report, issued May 2023, reviews the determination of radionuclides in ALPS-treated water. Samples were taken from the first batch of ALPS-treated water expected to be discharged into the sea and independently analysed by TEPCO, by the IAEA at its labs in Monaco, Seibersdorf and Vienna, and in third-party labs in France, South Korea, Switzerland and the USA. The results show a very high level of agreement between all the labs. Importantly, neither the IAEA, nor the participating third-party laboratories, detected any additional radionuclides (i.e. radionuclides beyond what is included in the source term) at significant levels.

“The planned discharge is ultra-conservative.”



Declared interests

Prof Jim Smith: “I did a small (< £5k) project for Japan Atomic Energy Agency over 5 years ago and had a NERC grant 2012-2017 which was part funded by the Nuclear Decommissioning Authority. I don’t currently do consultancy work or have any nuclear industry links.”

Nigel Marks: “None. Previously worked for Australian Nuclear Science & Technology Organisation (ANSTO). Funding from Australian Research Council, ANSTO & Los Alamos National Laboratory on radioactive waste storage materials.”

Tony Irwin: “Tony is technical director of SMR Nuclear Technology, an independent company that advises on the siting, development and operation of safe nuclear power generation technologies.”

For all other experts, no reply to our request for DOIs was received.

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