Jellyfish clog cooling intake at France’s Gravelines plant, forcing reactor shutdowns

Electricite de France (EDF) said a jellyfish influx at the Gravelines nuclear power plant near Dunkirk forced units 2, 3 and 4 offline and cut unit 1 to half power, removing 3.2 GW of capacity from the grid in a single day. Gravelines, the largest commercial nuclear plant in Western Europe, has six reactors with net capacity of 910 MW each. Only unit 6 remained at full output, while unit 5 was already in a scheduled outage. EDF said the jellyfish clogged filter drums at the seawater intake pumping station used for cooling. The company stated that the event did not affect plant safety, worker safety, or the environment. According to NucNet, EDF had already installed monitoring cameras, deployed three fishing boats on 24-hour patrols, used preventive trawling, added thermal imaging, and worked with fishing and rescue organizations to track jellyfish populations. AFP, citing EDF data, reported that climate-related unavailable nuclear capacity in France reached 15.6% on Aug. 9, 2026, the highest on record. Nuclear output was down about 3% in June and about 6% in July. Estimates cited in the report say climate factors could reduce annual nuclear generation by 1.4% by 2035, versus an average of 0.3% since 2000.