Jellyfish Swarm Forces Three Reactors Offline at Gravelines

Overview

• EDF stopped reactors 2, 3 and 4 and cut reactor 1 to 50% after several tonnes of jellyfish clogged seawater intake drum filters at Gravelines, while unit 5 was in scheduled maintenance and unit 6 ran at full power.
• The plant’s automatic and manual shutdowns followed a rapid proliferation detected over the weekend and on Tuesday, with EDF using boats, onboard cameras and partnerships with fishermen and the SNSM to push and catch jellyfish offshore.
• EDF said the incidents have had no impact on nuclear safety, staff security, or the environment and that affected units are being reconnected to the grid on a staggered schedule, with some already returned to full power.
• The Gravelines event helped push AFP’s calculation of EDF’s environmental unavailability to a record 20.4% of capacity, with 13 reactors affected by heat, drought and biofouling that restrict cooling water intake or discharge limits.
• Operators plan short-term surveillance and removal measures now while investing €8.7 billion by 2040 to adapt cooling systems and reduce future climate-driven losses to nuclear output, a risk analysts say could modestly cut annual production without action.