Acoustic Fish Deterrent systems have been used at coastal power plants for nearly thirty years. 

Operated by Electrabel,the Doel Nuclear Power Station, situated on the River Scheldt near Antwerp, Belgium, comprises four pressurised water reactors (PWRs) with varying capacities. The Acoustic Fish Deterrent (AFD) system is installed exclusively on the intakes of reactors 3 and 4, which were constructed after reactors 1 and 2. The issue became apparent when the intake of reactors 3 and 4 started operating, revealing a significant number of seagulls feeding on dead fish that were being discharged into a skip from the bandscreens. To address this, a fish return system was installed to return the screened fish to the river. Additionally, the AFD system was implemented to minimise the number of fish being drawn into the intake.

The Environmental and Operational Challenges

Doel Nuclear Power Station’s reactors, commissioned between 1975 and 1985, rely on water from the River Scheldt for cooling purposes. The intakes for Doel 1 & 2 are connected to the shore via a concrete jetty, while those for Doel 3 & 4 are located 250 metres offshore, linked by an underground tunnel. These intakes, crucial for cooling, were drawing in substantial numbers of fish along with the much needed water, notably herring (Clupea harengus) and sprat (Sprattus sprattus). 

In addition to reducing the stocks of fish in the area, the volume of fish being drawn into the water intake system could lead to overwhelming impingement.  This is when fish become trapped on the physical bandscreens, potentially resulting in blockages of the cooling water supply, leading to the emergency shutdown of the reactors, as has happened at other nuclear cooling water intakes elsewhere in Europe.

Partnering for Solutions: Acoustic Fish Deterrent Systems

To address these challenges, Electrabel worked with Fish Guidance Systems Ltd in 1996 to design and implement an Acoustic Fish Deterrent (AFD) system. The AFD system works by projecting a sound using equipment positioned at the front of the intake to deflect fish and keep them in the river’s main flow. This system was tailored for the clupeid species, known for their responsiveness to an acoustic signal.

By 1997, after extensive acoustic modelling, the AFD system was installed. The setup included multiple Sound Projectors and amplifiers strategically positioned to create an effective deterrent field near the intake openings. This innovative approach significantly reduced the number of fish being drawn into the cooling system.

Measurable Success and Continuous Improvement

The AFD system at Doel has undergone rigorous evaluation by researchers from Belgium’s Leuven University. Independent trials demonstrated a remarkable reduction in fish entrainment:

  • Herring (Clupea harengus): 98% reduction in entering
  • Sprat (Sprattus sprattus): 97% reduction in entering
  • Bass (Dicentrarchus labrax): 89% reduction in entering
  • Gobies (Gobidae): 75% reduction in entering

Overall, the AFD system achieved an 80% reduction in the entrainment of all fish species. This success highlights the significant environmental benefits and operational efficiencies gained through the use of acoustic deterrents.

Long-Term Maintenance and Operational Reliability

Initially provided on a lease-purchase basis, the AFD system’s maintenance was included in the lease cost. Post-2007, Fish Guidance Systems Ltd has continually maintained the system under a service contract, ensuring its optimal performance through regular inspections and maintenance.


The implementation of Acoustic Fish Deterrents at the Doel Nuclear Power Station showcases the significant benefits such systems offer to nuclear power plants globally. By protecting local fish populations and reducing operational disruptions, AFD systems contribute to more sustainable and efficient plant operations. For more detailed trial results or information on other fish deflection systems, contact Fish Guidance Systems Ltd.