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Nuclear energy developers have historically operated by a simple principle: Go big.
Reactors cost a lot of money to build, so the logic has been that it’s easier to recoup that investment if the project produces more electricity. Of late, a new generation of companies has made waves by bucking that conventional wisdom and instead aiming to build smaller reactors that can be made cheaper through bulk orders and mass production.
But with few advanced reactors built to date, that argument remains theoretical — and a new report shared exclusively with Canary Media suggests the path to proving it out is harder than many in the industry acknowledge.
It’s a chicken-and-egg situation. Next-gen nuclear startups must establish supplies of rare and legally sensitive types of fuel while also competing for a small pool of skilled workers and a limited output of valves, pumps, heat exchangers, and other equipment. Manufacturers are hesitant to ramp up production without a clear signal that advanced reactors will pan out. Investors, in turn, are leery of reactors meant for mass production that rely on unprepared supply chains.
That’s the core takeaway from the new analysis by the Nuclear Scaling Initiative, a campaign by the nonprofits Clean Air Task Force, the EFI Foundation, and the Nuclear Threat Initiative. The Nuclear Scaling Initiative launched in 2024 and aims to promote fleet-scale construction of reactors in a bid to start bringing at least 50 gigawatts of atomic power capacity online worldwide every year at some point in the 2030s.
The study, conducted by the nuclear consultancy Solestiss, highlights two paths it says are promising for the industry: either sticking to proven designs or simplifying supply chains to tap into the traditional nuclear business’ existing materials and know-how.
It comes as the Trump administration pumps billions of dollars into advanced reactors while also courting developers of more conventional large-scale reactors — and amid a high-stakes debate over which approach is best.
Earlier this month, the Bill Gates-backed TerraPower won the Nuclear Regulatory Commission’s approval to begin construction on the country’s first commercial plant with sodium-cooled fast reactors in Wyoming. In December, the decommissioner-turned-developer Holtec International won a $400 million Department of Energy grant to build its first 300-megawatt small modular reactors in Michigan, using a pressurized-water-cooled design. The DOE awarded another $400 million grant to help American-Japanese joint venture GE Vernova Hitachi Nuclear Energy build its first 300-megawatt SMR in Tennessee, based on a traditional boiling water design.
The Trump administration, meanwhile, is trying to get developers to commit to building more AP1000s — the flagship large-scale reactor from Westinghouse Electric Co. The only two nuclear reactors designed and constructed in the U.S. this century used the Westinghouse design. (A third came online in 2016 but first started construction in 1973.)
The variety of designs racing to become the nation’s fourth new reactor in decades calls into question the feasibility of rapidly scaling up production of any one model.
“We can do any one of these first projects all at once. But can we sustain a build-out of TerraPower, GE, Westinghouse, and Holtec? All the ones that are just moving forward right now? The answer to that is not yet,” said Dillon Allen, president of the advisory services division at Solestiss, who started his career working on nuclear propulsion in the U.S. Navy before moving into the utility business. “Once you’re building four to eight AP1000s and a handful of SMRs of other sizes, you start to run into smaller component bottlenecks.”
Those bottlenecks would worsen if microreactor companies succeed in their objective of securing dozens and dozens of orders for their designs.
“While small reactors have been tried before, mass-manufactured small reactors have not,” Aalo Atomics CEO Matt Loszak, whose 10-megawatt reactors also use liquid sodium as a coolant, wrote in a post on X this week. “Small is more expensive than large, if you only make one reactor. But if you make 1000s per year, small could be cheaper than large. This is what Aalo is setting out to prove.”
One major obstacle to this plan is transportation. To build something and send it without prior testing is no problem, since a reactor that hasn’t been fired up and irradiated “is just a big hunk of metal,” Allen said. But once it’s irradiated, it’s subject to different considerations.
National laboratory researchers have started to discuss a framework for a U.S.-wide transportation network with established logistics and safety standards, the report notes, but no such rules have yet materialized.
The biggest barrier for next-gen nuclear, however, is likely to be the fuel supply. Some small reactor companies have been proactive here. Aalo, for example, has opted for the most commonly used reactor fuel on the planet, low-enriched uranium, so it can tap into the existing global supply chain.
But most advanced nuclear startups are banking on what’s known as fourth-generation reactors. These designs rely on coolants other than water and mostly aim to use one of two types of fuel: high-assay low-enriched uranium, commonly known as HALEU (pronounced HAY-loo), or tristructural isotropic fuel, for which HALEU is typically an input. Tristructural isotropic fuel is also known as TRISO.
HALEU, which firms like TerraPower and microreactor developer Oklo plan to use, is only really produced at a commercial scale by Russian and Chinese state-owned companies. Efforts to bring new centrifuges online in America are slow-going. Meanwhile, the TRISO fuel that startups such as Valar Atomics or Radiant need requires not only securing HALEU but also separating that enriched uranium into ceramic-coated pellets the size of poppy seeds. Manufacturers admit that TRISO may never cost less than low-enriched uranium.
The complications don’t stop there. Because HALEU is up to four times more enriched than traditional reactor fuel, it comes with stricter regulations. On the Nuclear Regulatory Commission’s security-clearance scale of category one, which allows for handling normal reactor fuel, to three, which includes military-grade enrichment levels, facilities with HALEU need to be rated at a category two. No such facilities exist in the U.S. today, though the commission just issued its debut permit for one last month.
As for traditional fuel, the existing supply of low-enriched uranium falls short of what would be required to meet the U.S. goal of quadrupling the nation’s nuclear capacity to 400 gigawatts by 2050.
“The supply chain is pretty well suited to support a fleet of 100 operating reactors,” Allen said, referring to the 94 commercial reactors in service in the U.S. “But then you can have 150, then 180, and pretty soon 200 after that. If you double that demand on the LEU supply, it’s not just the enrichment” that’s a limiting factor.
It’s also, he said, the production of raw uranium and the facilities to carry out conversion, where purified uranium ore is turned into a gas, and deconversion, where it’s solidified once again.
Expanding these upstream operations may be challenging, but it isn’t impossible. In fact, Allen said he came away from writing the report with the impression that supply chains are more capable of scaling up than he previously thought. But his team’s work demonstrates the steep obstacles faced by the entire industry — not only advanced reactor firms — as it attempts to bolt into action following decades of anemic construction in America.
The biggest impression the research left on Allen, he said, is that the AP1000 has a good shot at becoming the next reactor built in the U.S. Its costs are more predictable — and thus easier to finance — thanks to the lessons learned during construction of the two units that came online at Southern Co.’s Alvin W. Vogtle Electric Generating Plant in central Georgia in 2023 and 2024.
“I’m more bullish on the AP1000 than I was when I started this effort,” he said. “I’m broadly bullish on the supply chain.”
The DOE is considering alternatives to the AP1000 to satisfy President Donald Trump’s order to facilitate construction on at least 10 large-scale reactors by the end of the decade. In response to the news that the administration held talks with its rivals, Westinghouse said the AP1000 is“the only construction-ready, gigawatt-scale, advanced modular reactor that is fully licensed and operating in the U.S.”
The U.S. ultimately should focus on designs it can scale up rather than spreading its efforts in many different directions, said Stephen Comello, the executive director of the Nuclear Scaling Initiative. At that point, nuclear power will become cheap enough to be “boring.”
“Once you start accumulating that knowledge from repetition, nuclear construction becomes boring — just like natural gas combined-cycle plants, just like all other complex megaprojects and energy infrastructure that’s out there,” he said.
There’s little doubt that the AP1000 has a well-established supply chain and data showing it runs well, he said.
The question is, “Can you do it in a repeatable, cost-effective way? That’s where the risk lies with the AP1000,” Comello said. “It runs, the technology is great. But we have to prove to investors that we can overcome the execution risk. But here’s the thing: All reactors share execution risk to some extent. Others have a technology risk because they are still not proven at scale.”
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