France’s nuclear reactors are running hot and still keeping the lights on

The Cattenom Nuclear Power Plant in Cattenom, eastern France. (AP Photo/Jean-Francois Badias) France’s nuclear reactors are running hot and still keeping the lights on Published: August 20, 2026 12.55pm EDT Share article Print article Much of western Europe has endured long stretches of hot weather and heatwaves this summer. France recently experienced the hottest day in its recorded history and placed 54 of its 96 departments under the highest heat alert. In response, the state-owned utility, EDF, began cutting output at several nuclear plants along the country’s rivers. Some reactors ran at reduced power while others shut down temporarily. For some, the episode appeared to confirm that nuclear power, for all its low-carbon promise, cannot survive the climate crisis. While that reading may be tempting, it’s mistaken. What the heatwave revealed was not a failure of nuclear technology, but rather a narrow, well-understood constraint in how some riverside plants are allowed to operate during extreme heat. To dissipate the heat they produce, plants draw water from a body of water and return it a few degrees warmer. French law limits how much warmer that water may be, a rule meant to protect fish and other aquatic life. During a heatwave, the rivers are already warm, so it’s that legal ceiling, not any technical limit of the reactor itself, that obliges EDF to reduce output. Thus, the cuts here were a deliberate measure to protect river ecosystems — not a reactor failing to generate electricity. As Canada develops new nuclear power projects, some might worry that hotter weather could undermine nuclear reliability. However, France’s experience this summer suggests otherwise. Heat and nuclear plants The Bugey nuclear plant in Saint-Vulbas, near Lyon, France. (AP Photo/Laurent Cipriani) The recent reductions in nuclear power generation did not undermine France’s electricity supply. The reductions began on June 22 and continued through the week as the heat persisted, reaching about 4.1 gigawatts, or seven per cent of national demand, at their peak. Even then, a large majority of France’s reactors remained in operation. The grid operator, RTE, said France had “sufficient generation capacity to meet electricity demand,” even with several reactors offline. It is true that prices rose, exports to neighbouring countries fell and the grid relied more heavily on gas as well as oil-fired reserve generation. Yet these were temporary strains, and at no point…