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One of the companies involved in a new nuclear reactor at Taishan in Guangdong, China, has written to the US government warning of an “imminent radiological threat” at the plant. The memo from French firm Framatome to the US Department of Energy, , said Chinese authorities were raising acceptable radiation limits around the power station, to avoid shutting the reactor down. How serious is the issue, and should you be worried?

Do we know what’s causing the problem?

Framatome parent firm EDF, which has a 30 per cent stake in the company that owns the plant, that the problem appears to be an issue with one or more of the fuel rods. It appears there is a potential hole in the casing of the fuel rods, which contain the uranium used to create a fission reaction. In , EDF said there had been an “increase in the concentration of certain noble gases in the primary circuit” in reactor number one at the power station. The primary circuit is the part of the plant that transfers heat from the reactor to water, generating steam and producing electricity. The noble gases include krypton and xenon.

Has there been a radiation leak?

Yes. New Ů��С��Ƶ understands there has been a radiation leak at the plant. However, it is solely within the primary circuit, which is within multiple layers of containment. The radiation leak doesn’t extend beyond the circuit and no radioactive material has been detected outside the plant. “If the inert gases are in the primary coolant then it is unlikely that any radioactivity will be released outside of the reactor,” says of the University of Sheffield, UK.

How long has this been going on for?

EDF first received reports of increases in contamination in the primary circuit in October 2020. The government of Hong Kong, which is 130 kilometres from the plant, there was an “operational event” at the plant on 5 April, which involved the release of a “very small amount of gas”. The gas wasn’t named.

Are people at risk?

It appears not. Carrie Lam, the leader of the government of Hong Kong, said today that monitoring of radiation levels around the city shows “everything is normal”. EDF maintains the level of radioactivity observed at the plant is below levels required by Chinese authorities. Framatome described the problems at the plant as “a performance issue”. “According to the data available, the plant is operating within the safety parameters,” .

What do others say?

“This situation in principle does not pose any immediate danger,” says , a nuclear analyst in Paris and editor of the World Nuclear Industry Status Report. “Should we be concerned? It’s not clear that there’s cause for alarm at this stage, but clearly the situation needs to be monitored,” says Corkhill.

What are the ramifications of this?

The Taishan plant is an unusually high profile one, due to its reactor design, known as EPR. The plant has two of these reactors, jointly designed by Siemens of Germany and EDF of France, and Taishan’s reactor number one was the first EPR in the world to become operational when it was . EDF hopes to build nuclear plants elsewhere in the world using the EPR design, which is the basis of a pair of reactors it is building at Hinkley Point in Somerset, UK.

What will the UK do?

Paul Dorfman at University College London says the UK nuclear regulator, the Office for Nuclear Regulation, needs to receive significant detail on the incident given Hinkey Point and EDF’s aspirations to build an EPR-based plant at Sizewell in Suffolk, UK.  However, it appears the issue isn’t the reactor design, but a phenomenon known as fuel failure – the possibility of a hole in a fuel rod – which has been widely observed in the UK and France.

What happens next?

Eventually the fuel rod will need to be replaced. For now, the plant will continue operating as the contamination in the primary circuit isn’t considered significant enough to turn the reactor off. Cleaning up the contamination could be financially costly for the Chinese and French state companies that own the plant, says Schneider.