When extreme heat threatens Europe's nuclear power
Warm rivers and low water levels are forcing nuclear power plants to reduce output across Europe. Over a year, the losses are minimal, but on critical days the loss of power has consequences for grids and prices.
The Danube's water levels have recently revealed the crucial dependence of European nuclear power plants on their local conditions. Hungary's Paks power station, responsible for nearly 40% of the nation's electricity, has only one of its four turbine units operational due to record-low water levels in the Danube, which nearly caused a complete shutdown.
However, France remains the most significant player in the European electricity market, with no other country relying as heavily on nuclear power. If France's output drops, the country may turn into an electricity importer.
While France's annual nuclear power production losses due to high water temperatures and low river levels are minimal, individual weeks of extreme heat can result in significant restrictions. A 2023 report by France's official audit office estimated that between 2000 and 2022, annual losses across all nuclear reactors due to these factors amounted to less than 1% of yearly nuclear power production.
Nevertheless, short-term fluctuations can be substantial. During the scorching summer of 2003, French nuclear power plants had to reduce their output by over six gigawatts, and the recent heat waves in June and July 2026 limited the maximum available capacity temporarily by eight to nine gigawatts.
France's electricity network operators and traders must consider these production limitations even without low water levels, as some reactors may not operate at full capacity due to reduced summer demand, high solar power generation, or grid bottlenecks. The heat waves exacerbate electricity demand due to air conditioning, and the declining reserves from abroad exacerbate the situation.
Nuclear power plants, which release waste heat into rivers or the sea, face challenges due to low water levels, resulting in higher water temperatures and reduced oxygen levels. This forces operators to throttle back reactors in the summer, not to safeguard reactor safety but to protect local aquatic life.
In some cases, French authorities allow exemptions from water temperature limits, enabling power plants to produce additional electricity in the short term. However, even nuclear plants equipped with cooling towers, which draw less water from rivers and discharge less heat, are not entirely heat-resistant. For instance, France's Golfech plant, situated on the Garonne River, frequently experiences low water levels despite its cooling towers.
Similarly, the Chooz plant on the Meuse River had to reduce reactor output in 2020 due to elevated river temperatures, despite its cooling towers, to avoid compromising Belgium's drinking water supply.
While climate change is not the sole cause of France's declining nuclear power production, French authorities project that climate-related reactor downtime could increase three- to fourfold by 2050. Even with additional cooling towers, deeper water intake structures, and improved maintenance planning, the consequences of climate change on nuclear power plants in France could be significant.
France plans to construct four of the six proposed EPR2 reactors on the coast, in Penly and Gravelines, where cooling towers will limit the thermal load on the river. The remaining two reactors will be built near Bugey along the Rhone River.
Written by urgent.news from DW English (Top Stories)'s reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
