• ‘While a lot of the nuclear public relations relates to nuclear as a sort of savior of climate change, unfortunately, the reverse is true,’ says expert Paul Dorfman

• Operations of nuclear plants are being strained by warming rivers, storm surges and rising sea levels

ISTANBUL

As the summer sun scorches Europe, the effects of a warming planet are becoming increasingly tangible – and while nuclear energy is often touted as part of the solution, it too is buckling under the heat.

“While a lot of the nuclear public relations relates to nuclear as a sort of savior of climate change, unfortunately, the reverse is true,” Paul Dorfman, chair of the Nuclear Consulting Group and a senior academic at the University of Sussex, told Anadolu. “Nuclear will be a significant and early climate casualty.”

This year, several European plants have reduced output or shut down altogether – not due to technical faults, but because the rivers that cool them are either too shallow or too hot.

France, where nuclear accounts for around 65% of electricity, has been particularly affected, with nearly all of its 18 nuclear sites reporting capacity reductions this summer.

Cooling crisis: Rivers too warm for reactors

Europe hosts around 166 operable nuclear reactors with a combined capacity of nearly 149 gigawatts (GW), approximately one-third of the global total.

France leads with 57 reactors, followed by the UK with nine. Other major operators include Spain, Sweden, Finland, Switzerland and Belgium, with smaller but strategic fleets in the Czech Republic, Hungary and Slovakia.

Most were designed decades ago without climate resilience in mind, and rely heavily on water – often drawn from nearby rivers – to cool the systems that produce electricity.

After absorbing heat from the reactor, this water is typically returned to the environment. But when river levels drop or water temperatures rise too high, the cooling process becomes less effective, and in some cases, dangerous.

“If that … superheated water is discharged back to the rivers, basically it kills the river ecology,” said Dorfman. “So, there are regulatory temperature thresholds – and France has breached those numbers.”

He explained that inland reactors are already suffering due to “low flow and heating” in rivers such as the Rhone and the Loire, two of the country’s most crucial cooling sources.

While France may be the worst hit, the same situation played out in several countries this summer.

In Switzerland, at the Beznau plant on the Aare River, one reactor was halted entirely and the other reduced to 50% capacity. Other inland reactors across Central Europe, including those in countries like the Czech Republic, Hungary and Slovakia, face similar vulnerabilities.

Europe especially vulnerable

The issue is compounded by projections that Europe’s extreme heat events will only intensify in the coming decades.

According to the European Environment Agency, Europe is the fastest-warming continent in the world, with temperatures rising at roughly twice the global average rate.

Recently, the UK Met Office said that scorching temperatures are becoming the new normal, along with more frequent extreme events like drought, flash flooding and storms.

“We know what will happen in the next 10 to 20 years. We know that inland rivers will suffer. This is absolutely going to happen,” Dorfman said.

He added that even coastal plants are not safe from climate volatility.

“Coastal reactors will be increasingly subject to climate-driven storm surge flooding,” Dorfman warned. “We know that sea level rise, glacier melt, and storm surges will increasingly threaten nuclear sites. This is not speculative. It’s already happening.”

The majority of nuclear power plants were constructed long before climate change was evident. Now, he said, “they’re at greater risk.”

Demand soars, output drops

Europe’s energy dilemma is further complicated by surging electricity demand during heat waves, driven largely by air conditioning. Just as power is needed most, nuclear output often declines.

According to a new report by energy think tank Ember, the June-July 2025 heat wave caused electricity demand to surge by 14% in Spain, 9% in France and 6% in Germany. Peak demand was even higher.

The current energy model is showing its limits during temperature extremes, said Pawel Czyzak, Ember’s interim Europe Program director.

“Any thermal power plant draws water from a lake, river or the sea to cool its systems, like a car engine. But if the river is already hot, then it can’t cool efficiently,” he told Anadolu. “If you have a week of 35C (95F)-plus, rivers warm up, and you have issues with the cooling systems.”

The result, Czyzak explained, is that nuclear output is often scaled back.

“Normally that’s okay in summer, but during a heat wave, demand grows – and that causes a lot of stress for the power system.”

He explained that France is particularly vulnerable since it relies on nuclear for the bulk of its energy. “If nuclear goes down … then you don’t really have anything else to switch on,” he said.

Turning to renewables

But there are signs of a shift. According to Ember, solar power accounted for 22% of the EU’s electricity generation in July, narrowly surpassing output from the bloc’s nuclear power plants.

Combined generation from natural gas and coal fell short of both solar and nuclear. Meanwhile, electricity produced from wind and hydropower sources exceeded that of all fossil fuels combined.

“We know that 94.2% of all new worldwide electricity capacity last year was renewables,” Dorfman said.

“Nuclear takes 13 to 17 years to build, and that’s much too late for our climate needs,” he added.

He argues that renewables, paired with energy efficiency measures and grid innovations like battery storage and improved interconnectors, can help build a more resilient power system.

“It’s looking like a significant investment in renewables of all kinds – and in energy efficiency – is urgently needed,” said Dorfman.​​​​​​​

Czyzak added that solar power is a particularly strong ally during heat waves.

“This year, pretty much every year, we're seeing more solar power deployed and record generation volumes,” he added.

Still, he acknowledges the transition will not happen overnight. “I think maybe the next five years are a bit difficult, and then it will get better,” he said. “Generally, the countries that don’t have very flexible and diversified power systems are at most risk.”