Europe’s Oldest Nuclear Plant Shuts Down as Heatwave Cripples French Reactors

A punishing June heatwave sweeping across Europe has forced the shutdown of Europe’s oldest operating nuclear power plant — Switzerland’s Beznau facility — and knocked out up to 4.1 gigawatts of French nuclear capacity, exposing the growing vulnerability of the continent’s aging nuclear infrastructure to climate change.

Switzerland’s Beznau Nuclear Power Plant (KKB), located on the Aare River in the canton of Aargau, was completely shut down on June 26 after river water temperatures reached 25°C, making it insufficient for cooling. Operator Axpo Holding AG had already reduced output to 50 percent two days earlier under an interim order from the Swiss Federal Office of Energy. The shutdown came as Basel recorded 38.8°C, breaking nearly 80-year June heat records for two consecutive days, according to Xinhua News.

Nuclear Infrastructure Under Strain

Beznau, which began commercial operation in December 1969, is Europe’s oldest operating nuclear plant. Its two reactors — Block 1 commissioned in 1969 and Block 2 in 1971 — together generate approximately 730 MW, accounting for a significant portion of Switzerland’s nuclear output. Nuclear power supplies roughly one-third of Switzerland’s electricity.

Axpo confirmed the shutdown in a press release, stating that the measure “serves to protect the Aare ecosystem and to ensure compliance with strict environmental legal requirements.” The company noted it is continuously monitoring water temperatures and will plan a restart once conditions allow, pending regulatory approval.

This marks the second consecutive year that Beznau has been forced to suspend operations due to heat — a similar shutdown occurred in July 2025, raising concerns that the pattern is becoming annual.

France’s Nuclear Fleet Hit Hard

Simultaneously, French state-owned utility EDF was forced to shut down or reduce output at three nuclear plants. The Golfech plant in Tarn-et-Garonne was the first affected, with Reactor #2 shut down on June 22 after the Garonne River approached the regulatory limit of 28°C. Reactor #1 was already offline for maintenance, leaving the entire plant disconnected from the grid.

EDF explained in a statement reported by La Dépêche du Midi that “the climatic conditions of these last days have caused a significant rise in the temperature of the Garonne which should reach 28°C.” Output was also reduced at the Bugey plant on the Rhône and Nogent-sur-Seine, removing up to 4.1 GW of capacity — roughly 3.5 percent of France’s nuclear capacity and about 7 percent of peak midday power demand.

French grid operator RTE confirmed that electricity supplies remain secure despite the disruptions, according to SWI swissinfo.ch.

A 20th-Century Technology in a 21st-Century Climate?

The shutdowns have reignited debate about nuclear power’s suitability in an era of accelerating climate change. France generates approximately 70 percent of its electricity from nuclear power — the highest share of any country globally — and most of its 56 reactors are inland, relying on rivers for cooling.

“Nuclear power is clearly a 20th-century technology that is ill-suited to the 21st,” Yves Marignac, an independent nuclear expert and spokesperson for the négaWatt think tank, told RFI. “The warning signs are becoming stronger every year.”

Marignac highlighted the fundamental challenge: France’s nuclear plants withdraw approximately 15.3 billion cubic meters of water annually from rivers for cooling — 31 percent of total French water use, second only to agriculture at 45 percent. With projections of up to 40 percent less freshwater availability by 2050, he warned that “maintaining both agriculture and the nuclear fleet in their current form becomes extremely difficult.”

EDF has committed €8.7 billion by 2040 to adapt its nuclear and hydroelectric plants to warmer conditions. However, critics argue that the basic design of pressurized water reactors — including France’s planned EPR2 reactors — remains fundamentally dependent on large volumes of cooling water.

Economic Toll Mounts

The heatwave’s impact extends well beyond the energy sector. According to a study by Allianz Trade cited by France in English, heatwaves are projected to cost the French economy €42 billion annually from 2026 to 2030, with cumulative losses reaching approximately $240 billion — roughly 7 percent of GDP.

Productivity drops by 3 percent for each degree above 30°C and by two-thirds at 37-38°C. Agriculture, tourism, construction, and transportation have been severely affected. Over 850 schools have been closed, disrupting education for six million children, and 55 drowning deaths have been recorded during the heatwave period.

France’s “green fund” for climate adaptation has been cut to €837 million by 2026, raising concerns that government investment is inadequate for the scale of the challenge.

What’s Next

The immediate question is when Beznau and the French reactors can restart — a decision that depends entirely on weather patterns and river temperatures. With over 90 percent of France under heat alerts and 39 million people under red alert as of June 23, no immediate relief is in sight.

Looking further ahead, the events of June 2026 pose strategic questions for both countries. Switzerland, where nearly 60 percent of citizens recently expressed support for new nuclear plants, must reconcile public enthusiasm with the operational reality of climate vulnerability. France faces the even greater challenge of adapting its nuclear-dominated energy system to a warming world while managing mounting fiscal pressures.

As Marignac put it: “We’re entering a period where climate change and biodiversity loss are producing changes that are no longer linear. That makes them much harder to anticipate.”