The question of how many fish a nuclear power station kills might seem morbid, but for engineers building the Hinkley Point C station on the Somerset coast, it’s a pressing concern.
Likewise, conservationists and locals around the River Severn in Gloucestershire are so invested in the issue that they packed a village hall to discuss it.
The crux of the problem is rooted in the nature of nuclear plants: they produce immense heat. This heat drives turbines that generate electricity, requiring cooling systems that use massive amounts of seawater to keep the plant stable.
EDF, the company behind Hinkley Point C, estimates that its cooling system could draw in and kill about 44 tonnes of fish annually.
“This scheme will decimate fish stocks,” said Dave Seal, a wildlife campaigner.
“We already have lost 80% of our salmon, and half of the salmon that get into Hinkley’s cooling system will be destroyed.”
But Andrew Cockroft, from Hinkley Point C, insisted there will be a “very very small impact on fish populations”.
To maintain cool operations, EDF has constructed tunnels five miles long under the Bristol Channel to intake 132,000 litres of seawater per second. This water circulates around pipes carrying the superheated steam that powers the turbines, cooling it back into water that can be reused.
Although the seawater doesn’t contact the nuclear reactor and is safely released back into the sea, the influx will inevitably draw in fish from the Bristol Channel, home to salmon, eels, sprats, herring, and other protected species.
In an effort to mitigate the impact, engineers have fitted the intake pipes with concrete “heads” that include narrow vents and grills to keep larger creatures out. However, some fish will still make it through, leading to EDF’s annual estimate of 44 tonnes of fish mortality.
While this amount is equivalent to about a day’s catch at the Newlyn fishing port in Cornwall, the environmental impact has raised concerns from both the public and the Environment Agency.
“In proportion, it’s a very very small number of fish,” said Andrew Cockroft, from Hinkley Point C.
To offset this effect, EDF is exploring a plan to create 340 hectares (840 acres) of saltmarsh habitat along the River Severn. This area could provide a breeding ground for fish and other marine species affected by the plant’s operations.
However, identifying suitable land for this habitat has been challenging, especially as the village of Arlingham—one of the proposed sites—has expressed opposition to the plan.
Mr Cockroft, who runs the public engagement programme for Hinkley Point, said saltmarshes are a “natural” compensation for the nuclear plant’s impact.
He said: “Saltmarsh reduces flooding. It provides shelter and breeding grounds for fish, it’s an amazing place for birds, and can be great for people too.”
Residents are concerned about the impact of flooding fertile farmland to create this saltmarsh.
“We have fertile farmland, we have rare wildlife,” said one woman. “Hares, bats, hedgehogs. Why would you choose Arlingham?”
Another man told EDF representatives: “Arlingham is a unique part of the country, and I see no reason for you ruining that just to solve your problem with dead fish”.
EDF’s initial plans included an ‘Acoustic Fish Deterrent’ system, a series of underwater loudspeakers designed to scare fish away from the intake pipes. However, EDF later reconsidered the deterrent, citing potential issues: some fish species are unable to hear the frequencies used, while dolphins and whales might suffer from hearing loss. Additionally, maintaining these speakers would be hazardous, requiring divers to work in low visibility and at significant depths.
Local campaigners, however, argue that the acoustic deterrent is a better alternative than flooding valuable land.
“You agreed the acoustic fish deterrent,” said Godfrey Bragg.
“And now you want to wriggle out of it and inconvenience all these people. It just gets you off the hook with your problem killing fish.”
Dave Seal, a wildlife activist, advocates for keeping fish away from the intake pipes rather than allowing them to be drawn in and killed.
“Imagine a windfarm was killing 184 million birds a year, that would be a wholly unacceptable situation. So why is it ok to kill all these fish?” he said.
Nevertheless, in 2023, the Environment Agency sided with EDF and removed the acoustic deterrent requirement from Hinkley’s construction license, leaving EDF to focus on finding a suitable location for the saltmarsh habitat.
Hinkley Point C represents one of Europe’s largest construction projects, where engineers have used advanced technology like “Big Carl,” the largest land-based crane, to build the reactor’s structure.
Yet creating a new saltmarsh habitat that can sustain salmon, eels, and other species in the Severn may be one of the most complex challenges EDF faces.
The company remains committed to working with local communities, but the debate over the fish population’s safety remains unresolved. The plant cannot proceed with operations until a solution is found that meets environmental standards without further dividing the surrounding communities.
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