Nuclear power facilities in northern France, operated by Alforrecas, have been decommissioned.
Jellyfish Cause Temporary Shutdowns at Europe's Largest Nuclear Power Plant
The Gravelines nuclear power plant in France, the largest in Western Europe with six water reactors, temporarily shut down four of its units in August 2025 due to a massive influx of jellyfish. This event underscores a growing global challenge for coastal nuclear power plants, particularly those relying on seawater cooling, as changing marine ecosystems influenced by climate change and human activity contribute to rising jellyfish populations.
Located on the shores of the North Sea, the Gravelines plant draws water for its cooling systems from a canal that is home to several native jellyfish species. The jellyfish entered the water pumping stations used to cool the reactors, leading to blockages in the filters of the lifting stations in non-nuclear parts of the plant. This disruption in the cooling operations triggered safety shutdowns.
Similar incidents have been reported worldwide. In 2021, the Torness nuclear power plant in Scotland and the Oskarshamn nuclear power plant in Sweden experienced emergency shutdowns due to jellyfish blockages. While specific incidents are not detailed in the available results, jellyfish-related shutdowns have been increasingly reported globally, including in the U.S. and Japan.
Jellyfish blooms can be so dense that they cover screens in minutes, and even dead jellyfish can turn to gel that passes through filters and damages deeper systems. Cleaning these blockages can take up to two days and poses hazards to workers due to jellyfish stings.
The growing frequency of these events is attributed to rising jellyfish populations, likely fueled by warmer oceans, overfishing, coastal development, and increased marine pollution, including plastics that serve as breeding grounds.
The teams at the Gravelines plant are currently conducting necessary diagnostics and interventions to restart the production units safely. The plant also plans to host two new generation reactors (EPR2), each with a capacity of 1,600 MW, by 2040.
This incident serves as a reminder of the challenges faced by coastal nuclear power plants in adapting to changing marine ecosystems. As the world continues to grapple with climate change and its effects, it is crucial for these facilities to develop strategies to mitigate the impact of such events and ensure the safety of their operations.
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- The growing challenge for coastal nuclear power plants worldwide, highlighted by the Gravelines incident, is due to rising jellyfish populations, which are influenced by climate change, human activity, warmer oceans, overfishing, coastal development, and increased marine pollution.
- As the number of jellyfish blockages in cooling systems increases globally, resulting in temporary shutdowns at facilities like the Torness and Oskarshamn plants, it is essential for the industry to develop strategies to mitigate their impact, especially in regions with seawater cooling systems.
- In the face of these challenges, the Gravelines plant is currently conducting necessary diagnostics and interventions to ensure safe operation, and they plan to install two new generation reactors (EPR2) by 2040.
- As the world continues to adapt to the effects of climate change, it is crucial for environmental science, finance, and the energy sector to collaborate and establish effective solutions, such as investing in renewable energy, to reduce reliance on coastal nuclear power plants and protect the environment.
