France, which relies on nuclear power for approximately 70 percent of its electricity, is currently experiencing significant production disruptions. According to calculations based on data published by the energy group EDF since 2015, 20.4 percent of the nation's nuclear generating capacity is currently unavailable. Between 9:45 am and 10:00 am, the nuclear fleet recorded a new peak in outages attributed to environmental constraints or external environmental causes. In total, 13 of the 57 reactors in the EDF fleet were affected, with eight reactors completely shut down and five operating at reduced power.
Much of the lost nuclear generating capacity was due to full or partial shutdowns at five of the six reactors at the Gravelines nuclear power plant, the largest in Western Europe. The disruption occurred after a swarm of jellyfish clogged the pumps used to cool the units. Experts note that overfishing, plastic pollution, and warming seas resulting from climate change have created conditions that allow jellyfish to thrive and reproduce.
Outside of the Gravelines plant, the remaining shutdowns and production reductions are linked to extreme heat and droughts. It is a fairly regular event during a heatwave for open-loop power plants—those that pump water from rivers or the sea—to shut down or reduce power. These rules are not based on nuclear safety, but rather on environmental regulations intended to protect nearby flora, fauna, and waterways. Any used water discharged back into the environment is usually around 0.2C warmer than the source. However, if the river is already very warm due to a heatwave, the additional heat can raise temperatures to levels dangerous to local wildlife. The exact temperature thresholds are specific to each plant.
Drought is another primary cause for the current outages. If a local river is low, it becomes difficult or impossible to extract the water required for cooling. France is currently suffering a record drought, with 70 percent of the country under water restrictions. While France is usually a net exporter of electricity, EDF data shows that between 2000 and 2024, nuclear production losses due to environmental causes like high temperatures and low river flows represented an average of 0.3 percent of annual production. Amid these challenges, France has seen a strong increase in solar energy production due to major investments, and the country has been over-producing solar energy on most days since June.
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