Jellyfish swarm shuts down reactors at France’s Gravelines nuclear plant

Three reactors at France’s Gravelines nuclear power plant were taken offline late Monday after a massive jellyfish swarm clogged the facility’s cooling system, prompting preventative measures introduced after a similar incident shut down the entire plant last year, operator EDF has said.

It noted that Gravelines, one of France’s largest nuclear power plants, is located in the north of the country and uses water from a canal connected to the North Sea for cooling, Caliber.Az reports, citing Reuters.

Its six reactors each have a capacity of 900 megawatts, giving the plant a combined capacity of 5.4 gigawatts.

Reactors 2, 3 and 4 were shut down after the jellyfish swarm reached the plant, while Reactor 1 was reduced to 50% of its capacity as a precaution. Reactor 5 was already offline for scheduled maintenance, while Reactor 6 continued operating at full capacity, the company added.

Following last year’s complete shutdown, EDF introduced additional monitoring and trawling measures to reduce the risk posed by future jellyfish swarms.

Fixed cameras have been installed at the water intake canals and on filter drum screens to detect blockages as early as possible, an EDF engineer explained.

The company has also teamed up with a French fishing organisation and a sea rescue group to monitor jellyfish swarms. When a swarm is detected, fishermen can be alerted and deployed to carry out targeted trawling operations aimed at reducing its density before it reaches the plant.

Fishing boats were sent out on Saturday after an initial warning, helping limit the swarm’s impact. Jellyfish that have already reached the facility are being cleared using vacuum trucks, the engineer said.

With no new jellyfish entering the plant, cleanup operations are nearing completion, which is expected to allow the affected reactors to restart quickly.

EDF also said the incident poses no threat to the safety of the plant, its personnel or the environment.

Scientists warn that jellyfish swarms could become more frequent because of factors including global warming, the spread of invasive species, declining predator populations and overfishing.

EDF is also dealing with reduced output from other French nuclear reactors because of high temperatures. A fifth heatwave is expected to intensify during the week, putting further pressure on the country’s nuclear generation.

One reactor in northern France has been offline for much of the summer because of low river levels, while another has undergone limited restarts and remained largely out of service throughout most of July.

By Bakhtiyar Abbasov