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NUCLEAR power is meant to play a key role in holding global warming below a rise of 1.5掳C, but the world鈥檚 nuclear plants are quietly starting to show their age 鈥� and some people are wondering if we should give up on them altogether.

The UK has eight nuclear plants, a cornerstone of the country鈥檚 energy system, but two 鈥� Hunterston B on the west coast of Scotland and Dungeness B in south-east England 鈥� have been silent since 2018.

Hunterston, which started generating electricity in 1976, has been offline because of concerns over cracks in the graphite bricks that control the nuclear reaction, although one reactor . Dungeness, generating since 1983, has been down for repairs to pipes carrying steam, and isn鈥檛 due back until April at best.

鈥淣uclear is effectively infinite, scalable. It is the only thing that鈥檚 going to work for climate change鈥�

This picture isn鈥檛 confined to the UK. There are 415 reactors operating around the world, supplying 10 per cent of the world鈥檚 electricity supply, but that is down from a high of around 17.5 per cent in 1996, according to a .

For the first time, the average reactor age passed the 30-year mark. Five reactors shut down last year, while construction started on just two new reactors. The number being built globally stood at 46 by mid-2019, a decadal low, with 10 of them in China.鈥漈o me it鈥檚 very clear now that the renewal rate of nuclear power is too small to be sustainable. So this species will die out,鈥� says Mycle Schneider, a Paris-based nuclear consultant and a lead author of the report, the World Nuclear Industry Status Report 2019.

The hiatus is likely to be a foretaste of the next few years. Seven of the UK鈥檚 plants will have been retired by 2030, stalling the carbon savings from a rapid growth in renewables. Theoretically, a big new nuclear plant 鈥� Hinkley Point C 鈥� will come online in 2025, but EDF, the company behind it, has .

So should the world double down on nuclear power and do whatever it takes to get more plants built? Or is time to abandon the idea of nuclear as an important tool for fighting climate change?

鈥淚 would frame the question differently,鈥� says Michael Shellenberger at Environmental Progress, a US-based non-profit organisation. 鈥淐an renewables be part of the climate fight? Look, there鈥檚 just these inherent physical limits to renewables because of the dilute nature of sunlight and wind, and their inherent unreliability, whereas nuclear is effectively infinite, scalable. Nuclear is really the only thing that鈥檚 going to work for climate.鈥�

In a letter sent to US president Donald Trump last month, Shellenberger and other nuclear advocates complained that the US is building only one nuclear plant at home and none abroad, and that two-thirds of current US plants may retire within two decades. 鈥淭he US nuclear industry needs your leadership to grow nuclear at home and sell American nuclear plants abroad,鈥� they said.

Matt Bowen at Columbia University in New York says that while Trump backs nuclear power, he has done little to help it. The president鈥檚 decision to pull the US out of the Paris climate agreement means the country has no policies that would improve the economics of nuclear, such as putting a price on carbon. 鈥淚 want to believe the US will have some sort of climate policy. I think that鈥檚 key to nuclear energy鈥檚 future,鈥� says Bowen.

Competition from the falling cost of renewables is another reason that new nuclear plants face an uphill challenge in some countries. The cost per megawatt hour of subsidising offshore wind farms in the UK is now half of that agreed for Hinkley Point C, meaning even accounting for the costs to the grid of their variable nature, they are still much cheaper than nuclear.

Antony Froggatt at UK think tank Chatham House says there used to be a clear contrast on cost between nuclear and renewables. 鈥淏ut now I think what we are seeing is the cost of renewables is going below that of all [forms of electricity] generation.鈥�

Europe has meanwhile seen a political backlash against nuclear power following the disaster that struck the Fukushima plant in Japan in 2011. Germany opted to close its own plants, and the last will be retired in 2022. As a result, Germany鈥檚 emissions grew by about 100 million tonnes of carbon dioxide a year, roughly a quarter of the UK鈥檚 annual emissions, according to healthcare and social cost at $12 billion a year because of the air pollution from coal plants filling the gap left by nuclear.

Switzerland has also voted to phase nuclear out and Belgium will shut its reactors by 2025. Even atomic stronghold France is planning to drop nuclear from 75 per cent of the country鈥檚 electricity to 50 per cent through installing more wind and solar power.

Such phase-outs mostly work by letting plants come to the natural end of their life. But Amory Lovins at the Rocky Mountain Institute in Colorado takes a more extreme view that .

鈥淭oday鈥檚 hot question is whether existing reactors should keep operating,鈥� he says. 鈥淢ost of them cost more to run than their output can earn, and more than it would cost to provide the same services by building and operating new renewables or by using electricity more efficiently.鈥�

Shellenberger disagrees with how Lovins counts the costs of nuclear, and many observers think nuclear plants should have their lives extended rather than being retired. Catherine Mitchell at the University of Exeter, UK, a critic of nuclear power, says she doesn鈥檛 mind extensions so long as they are safe, don鈥檛 last too long and are overseen by a good regulator.

This is the approach being taken in Florida, where the US , up from 60 years. 鈥淚t鈥檚 the way to go,鈥� says Bowen. The UK鈥檚 regulator could in theory make a similar decision, but whether it would be economical for EDF, which owns all of the UK鈥檚 nuclear plants, to do so is another matter, given the ageing problems at Hunterston and Dungeness.

Some are looking to other forms of nuclear power instead. Mini plants known as small modular reactors, such as those being developed by US firm NuScale, are one possibility, but Shellenberger says going smaller won鈥檛 make nuclear more economical in the face of the rise of renewables.

鈥�415
The number of nuclear reactors operating around the world鈥�

Then there is nuclear fusion, a cleaner source of energy than current nuclear fission plants. Unfortunately, it is still too far off to help us prevent the globe warming by more than 1.5掳C, which requires halving global emissions by 2030.

A UK government-backed fusion project is trying to build a commercial fusion power station by 2040, and . None are guaranteed to succeed, though.

In the meantime, the nuclear industry will keep making its case for being crucial to tackling climate change by reducing emissions to net zero. 鈥淣et zero needs nuclear NOW,鈥� the UK nuclear trade body .

Shellenberger says he is bullish about nuclear鈥檚 long-term prospects, and China鈥檚 efforts both domestically and abroad will be key. But nuclear power鈥檚 prospects in the short term are chaotic and unpredictable, he says. 鈥淚n the short-term, it鈥檚 a knife fight in a phone booth. It鈥檚 everywhere, it鈥檚 difficult, it鈥檚 complicated.鈥�

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