The U.K. was the birthplace of commercial nuclear energy, but now generates just a fraction of its power from it — big investments are underway to change that.

The country once had more nuclear power stations than the U.S., USSR and France — combined. It was a global producer until 1970 but hasn’t completed a new reactor since Sizewell B in 1995.

Today, the country takes the crown not for being a leader in atomic energy, but for being the most expensive place in the world to build nuclear projects.

Nuclear energy accounted for just 14% of the U.K.’s power supply in 2023, according to the most recent data from the International Energy Agency, trailing its European peers and well behind frontrunner France at 65%.

There is ambition to change that and have a quarter of the U.K.’s power come from nuclear by 2050. Nuclear is considered an attractive bet gas it’s a low-carbon, constant energy source that can act as a baseload to complement intermittent sources like renewables.

“There’s a very clear momentum that has been observed,” Doreen Abeysundra, founder of consultancy Fresco Cleantech, told CNBC. It’s in part due to geopolitical tensions, which pushed energy security and independence onto public agendas.

However, the U.K.’s Nuclear Regulatory Taskforce called for urgent reforms after identifying “systemic failures” in the country’s nuclear framework. It found that fragmented regulation, flawed legislation and weak incentives led the U.K. to fall behind as a nuclear powerhouse. The government committed to implementing the taskforce’s guidance and is expected to present a plan to do so within three months.  

In September, the country signed a deal with the U.S. to enable stronger commercial ties on nuclear power and streamline licensing for firms that want to build on the opposite side of the Atlantic. 

However, “the first thing is, there is not, at the moment, a single SMR actively producing electricity under four revenues. They will all come at best in the 30s,” Ludovico Cappelli, portfolio manager of Listed Infrastructure at Van Lanschot Kempen, told CNBC. 

While SMRs are a “game changer” thanks to their ability to power individual factories or small towns, their days of commercial operation are too far away, he said. From an investment standpoint, “that is still a bit scary,” he added. 

To secure the large baseloads needed to offset the intermittency of renewables, “we’re still looking at big power stations,” added Paul Jackson, Invesco’s EMEA global market strategist.  

SMRs “probably” do have a role — “they can clearly be more nimble” — but it will take time to roll them out, Jackson said, casting doubt on the U.K.’s ability to be a leader in nuclear, as France and China are already miles ahead.

The U.K. government body Great British Energy-Nuclear is set to identify sites for an additional large-scale plant, having already acquired one in Gloucestershire, in the west of England, as well as the site in Wales. 

“We are reversing a legacy of no new nuclear power being delivered to unlock a golden age of nuclear, securing thousands of good, skilled jobs and billions in investment,” a spokesperson for the U.K. government’s Department for Energy Security and Net Zero told CNBC.

“Sizewell C will deliver clean electricity for the equivalent of six million of today’s households for at least six decades, and the UK’s first small modular reactors at Wylfa will power the equivalent of three million homes, bringing energy security,” they added.

Meanwhile, Tokamak Energy and First Light Fusion call the U.K. home. They both focus on nuclear fusion, the process of generating power by combining atoms, though this technology is yet to get out of the lab. All of today’s nuclear power comes from fission, where atoms are spit. The U.K. announced £2.5 billion for a world-first fusion prototype in June. 

Perhaps the toughest issue, however, is the supply chain.  

Uranium, the fuel used to make a nuclear reaction, is dominated by just four countries, including Russia. Global demand for uranium could rise by nearly a third by 2030 and more than double by 2040, according to the World Nuclear Association, adding further reliance on a select few countries and pressure on developers.  

The U.K. government has allocated funding to build up the supply chain and has committed to preventing the import of nuclear fuel from Russia by 2028. Fuel for Sizewell C will come from European or “Western suppliers,” Cappelli noted. 

However, for him, it poses the question: How secure is nuclear energy really? “We have to build nuclear power plants, but we need to build the value chain,” Cappelli added. 

Workers, expertise and funding are required for nuclear energy, but the supply chain is also key, he said. Otherwise, there will be “the same issues that we had with gas,” a nod to the U.K.’s reliance on just one supplier. Instead of gas, it will be with uranium.