Overview
- EDF reported on Aug. 11 that mass jellyfish entered seawater intake pumps at its Gravelines plant, forcing the operator to stop three reactors, cut one to half power, and leave one offline for maintenance.
- Romania’s state nuclear company said on Aug. 11 that the only unit now running at Cernavodă may need to be shut as early as Aug. 13 because record-low Danube flows are creating a cooling‑water shortfall.
- Operators say facility integrity, staff safety, and the environment have not been harmed in either incident and standard safety procedures were used to reduce power or shut reactors.
- The Gravelines event repeats a similar jellyfish-related stoppage in August 2025 and shows how biological fouling can physically block intake screens and pumps that draw seawater for cooling.
- Beyond immediate outages, the cluster of events highlights a climate-linked vulnerability for river‑ and sea‑cooled power plants that could strain electricity supply during heatwaves and require new operational or infrastructure responses.