The mercury in France has climbed to apocalyptic heights, with temperatures exceeding 45°C in some regions. This extreme heat has forced Électricité de France (EDF) to shut down four nuclear reactors, including the Golfech and Cruas plants, as river temperatures rise beyond safe thresholds. When river water becomes too warm, it cannot effectively cool the reactors without risking a critical failure.
The result is a loss of around 4 GW of capacity during a period of peak demand for air conditioning. France, historically reliant on nuclear for 70% of its electricity, now faces a stark reality: its fleet is vulnerable to a warming climate. This is not an abstract future scenario but a present operational failure.
The reason is simple physics. Nuclear plants use water for cooling, and when the water is too hot, the second law of thermodynamics dictates that heat transfer becomes less efficient. In extreme cases, the reactor must be throttled down or, as France is witnessing, entirely disconnected from the grid.
The irony is poignant: a technology designed to combat carbon emissions is being hobbled by the very heat those emissions cause. For the UK, this serves as a validation of a long-running strategy: energy diversification. Britain has spent decades building a mix of gas, wind, solar, and biomass.
It has not invested in new nuclear since Sizewell B in 1995. While critics have derided this approach as lacklustre, the present French predicament shows its unsung benefit: resilience. When one source falters, others can compensate.
The UK’s offshore wind capacity, for instance, now exceeds 14 GW. During a heatwave, wind patterns can actually strengthen along the coast, providing power when solar and nuclear are compromised. Gas plants, though controversial, can ramp up within minutes.
And interconnectors to Norway and France allow imports when domestic supply dips. This is not to say the UK is immune. Heatwaves affect thermal plants here too, and droughts can impede hydro.
But by not placing its eggs in one basket, Britain avoids a single point of failure. The economic calculus is also shifting. France’s nuclear fleet requires increasing maintenance and refits, with EDF’s debt ballooning to €43 billion.
Unplanned outages during heatwaves force France to buy electricity from neighbours, including Britain, at inflated prices. Meanwhile, UK renewable projects have seen costs plummet. Offshore wind is now cheaper than new gas and nuclear.
The lesson is that pursuing low-carbon energy through a single technology is risky when climate change introduces new variables. The biosphere does not negotiate; it responds to forcing with physics and chemistry. We must design systems that can bend, not break.
The French heatwave shutdowns are a canary in the coal mine, a canary that happens to be a nuclear reactor. For British policymakers, the path forward is clear: continue to diversify, prioritise technologies that are weather-flexible, and invest in storage to handle the vagaries of wind and solar. Do not be seduced by the false certainty of yesterday’s solutions.
