The controlled discharge of wastewater, which contains tritium – a radioactive cousin of hydrogen - is taking place following the disaster that struck the Daiichi plant in 2011 when a tsunami hit the area.

While the UK is unlikely to see a nuclear power disaster like the one in 2011 in Japan, due to not facing the same risk of tsunamis inundating our nuclear plants, it has still raised questions about the safety and regulation of nuclear power in the UK and internationally.

Jonathan Cobb, senior communications manager at the World Nuclear Association, said: “The initial earthquake [in 2011 in Japan] meant that the [Daiichi] site lost offsite power because powerlines supplying the connection to the grid were lost.”

He said that the onsite backup generators kicked in to keep water pumping to keep the nuclear reactor cool.

Unfortunately, when the tsunami hit 45 minutes later, it “came over the sea defences and flooded the site,” which put the backup generators out of action.

Cobb said that the generators were flooded because they had been placed in a basement, as that was the safest place for them to mitigate risks during seismic activity. He said that other sites have tall exhaust pipes that can act as snorkels in the event of flooding, but the tsunami was higher than expected and overwhelmed the Daiichi plant.

He went on to say that the volume of tritium in the more than one million tons of water “would fit into something smaller than a cup” and that because the water is being diluted and released gradually over the course of 30 years, the tritium contamination will be “below their authorised discharge levels for back when they were operating normally.”

Moving on to the national regulatory context in the UK, Rob Allott, legacy and waste manager in the radioactive substances and installations regulation team at the Environment Agency, said: “There are international organisations that lay out standards and provide recommendations that provide information on good practise.

“The international Atomic Energy Agency (IAEA) and the International Commission on Radiological Protection (ICRP) are the two key organisations that provide our source of standards and guidance. Those standards used to get implemented in the UK via EU law but a lot of that has been transposed into UK law.”

Allott echoed Cobb’s sentiment around the hazardousness of tritium, saying “tritium is of low concern in terms of radioactive substances. It doesn't produce much dose to people and other organisms and it has a relatively short half-life around 10 years,” meaning it doesn’t stay radioactive for other substances such as uranium and can be disposed of into the environment earlier.

Andy Pynn, senior advisor (nuclear specialist) in the E&B radioactive substances regulation, new and operational sites team at the Environment Agency, said: “We differ from many other countries in terms of nuclear regulation because we have two separate national nuclear regulators.

“We have the Office for Nuclear Regulation which is the safety and security regulator, which means everything to do with the prevention of accidents, nuclear safety, criticality, and secure storage of spent fuel.

“The Environment Agency regulates the planned disposal of radioactive waste, which includes solid, liquid and gaseous wastes from nuclear power plants, via Environment Agency permits.”

Experts in nuclear safety agree that a significant reason for the international attention on the Fukushima release is due to public perception of contaminated water affecting fishing grounds, which many of Japan’s neighbours rely on for their economic well-being.

Given the dangers associated with nuclear power, companies and governments are keen to minimise risks wherever possible.

The National Risk Register released by the UK Government in 2023 paid particular attention to the likelihood and severity of cyber attacks against nuclear power plants. In its section on a cyber attack, it listed loss of supply to the UK National Grid as a potential outcome and did not mention the release of radioactive substances.

It did mention ‘radiological contamination off-site’ as a potential outcome of a conventional attack, i.e. using explosives and other weapons.

Dr Ian Fairlie, vice-president and scientific advisor at CND - the Campaign for Nuclear Disarmament, said: “Most people are unaware that the Fukushima disaster in 2011 is still occurring 12 years later, in that over 200 tons of water are being sprayed daily on the wrecked remains of Fukushima's 3 destroyed reactors to keep their nuclear fuels from melting further.

“Debate is ongoing regarding the safety or otherwise of the proposed dumping of tritium-contaminated water into the Pacific Ocean, despite worldwide protests. Tritium – the radioactive isotope of hydrogen – is a hazardous radionuclide even at low concentrations, as shown in many radiobiological studies.”

While we are unlikely to face tsunamis in the UK, a plethora of other threats remain such as coastal flooding which is increasingly likely due to the climate emergency.

We also have the potential development of small modular (nuclear) reactors (SMR) in the UK which could mean that communities away from coastlines could have nuclear power on their doorsteps.

Risks around nuclear are sometimes poorly communicated and understood, and accidents like the one that hit Fukushima challenge the social license afforded to the nuclear power sector. It is essential that expert insights are brought to the public's attention so that people can make more informed judgements about the realities of using nuclear power.

Please note: An updated version of this article with quotes from Dr Ian Fairlie was published shortly after the original, both on 24 August 2023.