Overview
- Three 900 MW reactors at the Gravelines plant were taken offline and a fourth was reduced to 50% after a jellyfish swarm clogged seawater intake pumps on Monday, leaving one of six units operating.
- EDF deployed fishing vessels for targeted trawling and used vacuum trucks and on-site crews to clear the pumps, and the operator said the event posed no threat to reactor safety, staff, or the environment and that restarts should follow intake cleanup.
- The company said the swarm grew from around 100 kilograms to several dozen tons before overwhelming preventive measures that were put in place after a similar August 11 event last year.
- AFP calculations show the Gravelines disruption, together with heat- and drought-related limits at other sites, left 13 of EDF’s 57 reactors affected and about 20.4% of national nuclear capacity unavailable.
- Experts warn the episode underlines a systemic risk: coastal reactors depend on large volumes of cool water, so rising sea temperatures, invasive species and changes in marine ecosystems can create recurring operational threats and tighten electricity supply during heatwaves.