# France nuclear power faces record unavailability > Live situation record from CLSTR: https://clstr.news/situations/france-heatwave-impacts-power-grid > Updated: 2026-08-11T09:48:20.000Z. Sources: 62. Developments: 6. The July heatwave intensified, prompting a production alarm at the 930 MW gas-fired Martigues plant when Mediterranean seawater exceeded 32 °C. Simultaneously, high river temperatures kept about 4.9 GW of nuclear capacity offline and low water levels removed another 2.5 GW, representing roughly 14 % of France’s electricity potential. By early August, the heat persisted for a 20th consecutive day in the Saône-et-Loire region. On 3 August, EDF pre-emptively shut down unit 1 at Cattenom and unit 1 at Chooz, joining an earlier outage of unit 2 at Chooz. EDF also announced short-term reductions at Bugey 3, Tricastin 4 and Saint-Alban 1 & 2. In southwest France, the Golfech nuclear plant faced severe disruption as temperatures reached 42 °C. The River Garonne exceeded the 28 °C regulatory limit, forcing the suspension of reactor 2 for the third time that summer, while reactor 1 remained offline for scheduled maintenance. Following a brief period where temperatures dipped below the threshold, Golfech's Unit 2 restarted on 7 August, only to be forced into another shutdown on the evening of 8 August to comply with environmental regulations regarding cooling water discharge. By 9 August, EDF reported that the nuclear fleet had reached a record level of unavailability, with approximately 15.6% of the country's installed nuclear capacity unavailable during the afternoon. By 11 August, new complications emerged at the Gravelines nuclear plant, where a massive jellyfish swarm forced the shutdown of reactors 2, 3, and 4, while reactor 1 was reduced to 50% capacity. EDF stated the situation poses “no impact on the safety of the facilities, the safety of personnel, or the environment” and has deployed fishing trawlers to recover jellyfish; fishermen reportedly recovered 26 tons to protect intake systems. ## Claims - The jellyfish swarm poses no risk to facility safety, personnel, or the environment. (corroborated by 20 sources) - Reactors 2, 3, and 4 at the Gravelines plant were shut down due to jellyfish clogging seawater pumps. (corroborated by 20 sources) - Reactor 1 output was reduced to 50% as a precaution. (corroborated by 20 sources) - Reactor 5 was already offline for scheduled maintenance. (corroborated by 20 sources) - Only reactor 6 remained operating at full capacity. (corroborated by 20 sources) - Climate change, overfishing, and plastic pollution are contributing to the increase in jellyfish populations. (corroborated by 9 sources) - The Gravelines plant is the largest nuclear power plant in Western Europe. (corroborated by 8 sources) - EDF has installed fixed cameras at intake canals and filter screens to detect blockages early. (corroborated by 4 sources) - French nuclear power production fell by 15.6% on Sunday, August 9, 2026. (corroborated by 4 sources) - Electricity prices in France rose by 21.8% to 142.5 euros per megawatt-hour on Tuesday morning. (corroborated by 2 sources) - Nuclear capacity in France is expected to decrease by 7.3 gigawatts, or 12% of total capacity, by Wednesday noon. (corroborated by 2 sources) ## Timeline ### 2026-08-11: Gravelines nuclear plant shuts down three reactors due to jellyfish swarm A jellyfish swarm forced the shutdown of three reactors at France's Gravelines nuclear plant. EDF reported no safety risks, noting the shutdown was a precaution to prevent pump clogging. 39 sources. https://clstr.news/cluster/gravelines-nuclear-plant-shuts-down-three-reactors-due-to-jellyfish ### 2026-08-11: France nuclear power faces record unavailability due to heat and jellyfish France's nuclear power production has hit record lows due to heatwaves, drought, and jellyfish clogging cooling pumps at the Gravelines plant, causing electricity prices to surge by over 21%. 15 sources. https://clstr.news/cluster/edf-nuclear-fleet-hits-record-unavailability-due-to-heat ### 2026-08-09: Golfech nuclear plant restarts and halts due to heat EDF has halted Unit 2 of the Golfech nuclear plant again due to rising Garonne River temperatures, marking the fourth heat-related shutdown at the site this summer. 8 sources. https://clstr.news/cluster/golfech-nuclear-plant-restarts-and-halts-due-to-heat ### 2026-08-02: France heat wave prompts nuclear plant output cuts France endures a record heat wave, with 20 days of extreme temperatures and thunderstorms in Saône‑et‑Loire, while nuclear plants cut output due to water shortages. 2 sources. https://clstr.news/cluster/france-heat-wave-prompts-nuclear-plant-output-cuts ### 2026-07-29: Golfech nuclear plant shut down in France amid record 42°C heatwave France’s Golfech nuclear plant was shut down for the third time this summer as a 42 °C heatwave pushed River Garonne temperatures above safety limits, halting reactor 2 and leaving the site offline. 2 sources. https://clstr.news/cluster/golfech-nuclear-plant-shut-down-in-france-amid-record-42c-heatwave ### 2026-07-17: France’s power grid strained as heatwave forces gas and nuclear plant reductions Heatwaves in southern France have nearly shut down the 930 MW Martigues gas plant and taken 14 % of the nation’s power capacity offline, affecting nuclear, gas and renewable generation. 2 sources. https://clstr.news/cluster/frances-power-grid-strained-as-heatwave-forces-gas-and-nuclear-plant-reductions --- Cite as: France nuclear power faces record unavailability. CLSTR, https://clstr.news/situations/france-heatwave-impacts-power-grid