[REVISION HISTORY]

France nuclear power faces record unavailability

Updated 9 times since CLSTR started tracking revisions of this situation.

What changed

2026-08-11 21:34 UTC → 2026-08-12 13:43 UTC · added ~~removed~~

France ~~heatwave and jellyfish swarm strain~~ nuclear power ~~grid~~ faces record unavailability

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.

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