To deter fish or not deter fish? That is the question EDF is facing at its Hinkley Point C plant.

The Acoustic Fish Deterrent (AFD) delivery group has called for the company to install a device to prevent fish from investigating the nuclear power plant’s cooling system. EDF is unconvinced.

The AFD group said there was no valid reason why EDF should not install an acoustic fish deterrent at the plant. At least, according to its analysis.

French utility EDF, the lead partner on the Hinkley power plant, was required to install the deterrent as part of its Development Consent Order (DCO) to build the plant in 2012. The deterrent would emit a constant sub-surface noise to prevent fish from “impinging” on the plant’s cooling system, via an underwater intake in the Bristol Channel.

In 2019, EDF applied to remove the AFD requirement from the DCO. A public enquiry denied the application and a subsequent plan to develop a saltmarsh at Pawlett Hams near Bridgwater to offset fish stock losses.

Now, EDF is considering saltmarsh plans in other locations to avoid using the AFD solution.

Gone fishing

EDF has proposed two main reasons against installing an AFD system at Hinkley Point C. First, it has said it would have a limited effect on protected fish species in the area. Furthermore, it has said that installing and maintaining the system would pose unacceptable risks for divers.

“Hinkley Point C is the first power station in the Severn with fish protection built into its design – the remaining impact is very small,” said Andrew Cockcroft, head of stakeholder engagement at Hinkley Point C, in a statement to E-FWD.

“Nevertheless, Hinkley Point C is obliged to mitigate for the remaining small impact and creating a nature reserve is better than risking an untried, untested system that creates noise pollution for sixty years louder than a jumbo jet taking off and would risk the lives of divers for little benefit to fish.”

The AFD delivery group refutes the claims that the AFD system would have a limited effect and pose a risk to divers.

“We don’t believe now there is any reason why EDF cannot install the acoustic fish deterrent. The delivery group has looked at all of their concerns and addressed them with sound scientific research from independent scientists, engineers and experts,” said Lewis English of Underpin Consultants, a member of the AFD delivery group.

Fish vs man

An EDF spokesperson said the amount of fish estimated to be harmed without the AFD “has been agreed with the Environment Agency, Natural England and Natural Resources Wales at 44 tonnes a year in total”. This is equivalent to approximately 440,000 small fish of 0.1 kg each.

But the AFD delivery group point to a Welsh government report with evidence from an expert. It warned that without an AFD system, the plant would see over 182 million fish enter its cooling system. “And it is likely that many of these will not survive.”

On the question of risk, EDF has said the Bristol Channel’s poor underwater visibility and large tidal ranges pose challenges. This means safely installing and maintaining the AFD endangers divers, it has said.

Number crunching

EDF is wrong, the AFD delivery group report claims. It found that using Remotely Operated Vehicles (ROVs) and new technologies like Active Pressure Compensation Systems could reduce maintenance times from 72 days per year to just 19.

“These improvements mean divers will not be required to carry out the routine maintenance work on the AFD system, and won’t be required for any of the installation work,” says the AFD Delivery Group report. “In relation to installation, no more diving time would be required than for other Hinkley Point C installations.”

The AFD group also disputes EDF’s claim that the noise would be louder than a jumbo jet. It found the volume would be cushioned by the water depth. When heard from the beach, it would be much lower than the lapping waves on the estuary, it said.

Furthermore, tests of AFDs in real-world environments show marine mammals would not be affected by the deterrent. The frequency is too low for them to detect, it said.

Has the group thought about other fauna? EDF claims the AFD would have an unknown impact on porpoises, seals, whales and other species is still unknown. A Scottish government report found some evidence that acoustic deterrents have had an impact on seal behaviour near salmon farms.

Solving through saltmarsh

EDF is still planning to proceed with filtration systems and a fish recovery and return system. It is also investigating new locations for saltmarsh creation to offset the power station’s impact on fish numbers.

Arlingham, Rodley and Littleton-upon-Severn, in South Gloucestershire, are all potential locations.

“The development of a saltmarsh habitat will … help support fish populations and minimise the small environmental impact of operating the new power station,” said Cockcroft in a media release last month.

But the AFD report calls the saltmarsh plan “disruptive”. The proposal has faced opposition from local farmers.

Mark Everard, professor of Ecosystem Services at the University of West of England and a member of the AFD group, said the company should pursue both solutions.

“Ideally, saltmarsh restoration should be implemented additionally to the AFD to mitigate the still substantial likely entrainment of multiple life stages of fish and invertebrates, even with deflection from the intake,” he said.

“Cost reduction is cited by EDF as one element of its plan to remove the mandated AFD and would appear to be its principal consideration,” he added.

EDF has said if it cannot remove the AFD requirement from its plans, start up could be delayed further. Early this year, it said the first reactor could start generating between 2029 and 2031. Previously, it had aimed for 2028.

Political problems

EDF is expected to submit a material change application for Hinkley Point C, based on the saltmarsh plan, to the planning inspectorate by mid-2025.

The planning inspectorate will review the application. Then, the Secretary of State for Energy and Net Zero Ed Miliband will make a quasi-judicial decision on whether the AFD must be installed as part of Hinkley Point C’s final plan.

The concept of building a saltmarsh as compensation for fish deaths has received some criticism. MP Tessa Munt, of nearby Wells and Mendip Hills, speaking in the House of Commons earlier this month, said she did understand “how it is that we can suddenly be looking at creating saltmarsh and dismissing the number of fish that are going to be killed when that was a critical factor when Hinkley Point C was being discussed.

*Steam Generator making its final approach to Hinkley Point C. Source: EDF*

Statement of interest

Fish Guidance Systems, which developed the system, is also a member of the AFD delivery group. The 2021 public inquiry received evidence from some witnesses claiming that Fish Guidance Systems employees’ evidence could be biased because the firm stood to gain financially from the legal requirement for an AFD.

A final report from the planning inspectorate found that the employees “were not guaranteed to gain from adopting this stance at the inquiry, a stance that is consistent with their research and writing over many years.”

A spokesman said about the scientific independence of the AFD delivery group that the “non-payment of experts was a conscious choice made by the group to ensure its integrity”.

Speed bumps

There is a complex interplay of environmental and commercial needs at work in the debate over an AFD for Hinkley Point C. EDF can well argue that such a system would be limited in effectiveness and a danger to divers, while the AFD group stick to their guns on minimising the impact on fish populations.

Ultimately, both sides want the plant to move ahead. The same cannot be said for some groups opposed to nuclear entirely, using the AFD debate to hamper development.

The decision will lie with Ed Miliband, once again giving crucial power to the highest levels of government. In the past, he has been willing to step into see off environmental considerations over solar plans, while stepping back from such a defence of oil and gas.

Does the government intend to prioritise progress in nuclear above the impact on nature? The debate over Hinkley Point C is just getting going. Whatever the outcome, it seems likely that progress will be slow – as it has been for other nuclear plans in the UK.

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