European nuclear power plants are reducing electricity output as extreme heat and low water levels limit their cooling capacity [1, 2].
This trend threatens the stability of the regional energy grid during peak summer demand. Because nuclear reactors rely on river water to cool their systems, rising temperatures can force operators to curtail power or shut down reactors entirely to prevent overheating.
Across Europe, including France and Hungary, plants have struggled with dwindling water resources [1, 3, 4]. In France, two reactors at the Chooz nuclear plant have been shut down since Aug. 1 [3]. The facility relies on the Meuse River, which has seen temperatures and levels fluctuate during recent heat waves.
Hungary has faced similar challenges at the Paks nuclear plant [1, 4]. Successive heat waves have drained the Danube River, reducing the volume of water available for essential cooling processes [4].
Reports on the total impact of these outages vary. Some data suggests that losses over the past year have been minimal, though critical heat-wave days can still affect energy grids and market prices [1]. Other reports indicate that high temperatures and low water levels have forced several countries to shut down reactors, leading to spikes in energy prices [2].
These disruptions are not isolated incidents. The region experienced critical heat-wave days in 2024 and 2025 that tested the resilience of the power infrastructure [1]. As river temperatures continue to rise, the ability of these plants to maintain full capacity during the hottest months remains uncertain.
“Nuclear reactors rely on river water to cool their systems.”
The vulnerability of nuclear infrastructure to rising temperatures highlights a systemic risk in Europe's energy transition. While nuclear power is often viewed as a stable baseline for carbon-free energy, its dependence on aquatic ecosystems means that climate-driven droughts can create a feedback loop where extreme weather directly undermines the power supply needed to manage that weather.
