Between July 1 and 3, 2025, nuclear power plants in France and Switzerland were forced to either shut down or scale back operations due to record river water temperatures triggered by an ongoing European heatwave.
In Switzerland, Axpo shut down one reactor and reduced output at another at the Beznau Nuclear Power Plant after the Aare River exceeded 25°C (77°F) — the regulatory threshold set by the Swiss Federal Nuclear Safety Inspectorate (ENSI). These regulations are in place to protect both reactor integrity and river ecosystems.
In France, Électricité de France (EDF) halted operations at the Golfech Nuclear Power Plant on July 1, when the Garonne River reached its maximum allowed intake temperature of 28°C (82°F). EDF also flagged potential output restrictions at other facilities such as Blayais and Bugey, though no specific shutdowns had occurred at those sites by July 3.
Environmental and Regulatory Pressures
Nuclear power plants rely heavily on river or seawater to cool reactor components. Normally, water is withdrawn, used to transfer heat from the reactors, and returned at a slightly higher but strictly regulated temperature.
During a heatwave, however, this process becomes inefficient — the incoming water is already too warm to absorb reactor heat effectively, and discharging even hotter water risks damaging aquatic ecosystems by reducing oxygen levels and stressing biodiversity.
Both France’s ASN and Switzerland’s ENSI maintain stringent environmental standards, requiring immediate operational changes when temperature limits are exceeded.
Despite these constraints, no widespread power outages were reported in either country due to existing contingency reserves and energy planning.
Europe’s Heatwave Intensifies
This disruption to nuclear operations comes amid one of the most intense early-summer heatwaves in recent European history. Key developments include:
- 🇵🇹 Portugal hit 46.6°C (116°F) on June 29.
- 🇪🇸 Spain saw widespread 40°C+ (104°F+) temperatures in Madrid and Seville.
- 🇫🇷 France reported its hottest June on record, with new highs in the Alps.
- The Mediterranean Sea is undergoing a record-breaking marine heatwave, with some coastal sea surface temperatures above 30°C (86°F) and 5°C (9°F) above average.
The heatwave, which began in late May, is forecast to persist into early July, with temperatures staying dangerously high across southern and central Europe through July 10.
Human Toll and National Responses
As of early July, the heatwave has caused at least eight confirmed deaths, including heatstroke fatalities during wildfires in Spain and France. Italy has reported multiple heat-related deaths and a 20% spike in hospitalizations in some regions.
Governments are taking action:
🇩🇪 Germany and the 🇬🇧 United Kingdom saw record-breaking temperatures, heat injuries, and wildfires.
🇫🇷 France issued nationwide health alerts, closed schools, and shut down public sites like the top of the Eiffel Tower.
🇬🇷 Greece evacuated 1 500 people in Crete due to wildfire threats.
