Severe heatwaves across Europe have forced nuclear reactors in France and Hungary to reduce power output or shut down due to insufficient cooling water.

These disruptions highlight a critical vulnerability in European energy infrastructure, as nuclear plants rely on river water that can become too warm or too scarce during extreme weather events.

In France, state-owned EDF managed a reduction in nuclear power generation of 6.4 GW [1]. The impact varied across sites, with reports indicating that as many as eight reactors [1] or up to five nuclear plants [3] faced output cuts. Specifically, three reactors were temporarily shut down [4]. These measures were taken as temperatures reached 44 °C [5], the highest recorded during the heatwave.

The energy strain extended to consumers, with 70,000 households in France left without power on the hottest day [5]. Similar conditions affected Switzerland, where plants also faced operational challenges [6].

In Hungary, the Paks nuclear plant, which is the country's only nuclear facility, faced a similar crisis on the Danube River. High water temperatures and low levels threatened the plant's ability to cool its reactors. Consequently, the plant is scheduled to be shut down next week [7].

The situation in Hungary is particularly acute because the country relies on a single site for its nuclear energy production. Operators from MVM and the Hungarian government have had to coordinate closely with French counterparts as the regional heatwave persists.

While some reports mentioned Romania, verified data does not confirm nuclear output reductions or shutdowns in that country at this time.

“France reduced nuclear power generation by 6.4 GW.”

The simultaneous struggle of French and Hungarian nuclear plants reveals a systemic risk where climate-driven heatwaves directly threaten energy security. Because nuclear reactors require massive amounts of cool water to function safely, the reliance on river systems creates a single point of failure during droughts. This may force European governments to either invest in expensive closed-loop cooling technologies or diversify their energy mix to avoid total grid failure during future temperature spikes.