5 Companies Racing to Build the First Commercial SMR (And Who's Winning)
The nuclear startup era is finally real — and the competition to light up the first small modular reactor is getting very interesting.
The race to commercialize small modular reactors has been “almost there” for so long that a healthy amount of skepticism became the rational default. Reactors on paper. Funding rounds announced. Regulators consulted. Timelines revised. Repeat. But something shifted in 2025. Construction permits got approved. Concrete got poured. Billion-dollar partnerships landed. The SMR industry stopped being a story about promise and started becoming a story about delivery. 🚀
The question now isn’t whether commercial SMRs are coming. It’s who gets there first — and what happens to the stragglers. There are dozens of developers worldwide, but five companies are genuinely close to putting electrons on a grid. They’ve made different technological bets, secured different allies, and chosen different regulatory paths. Some are sprinting. Some are quietly lapping the field. And one, frankly, may have already won.
Here’s where things stand.
GE Vernova Hitachi: the first mover in the West
If you want to know which company is actually building an SMR right now in the Western world, the answer is GE Vernova Hitachi Nuclear Energy, and the reactor is the BWRX-300. Construction began in May 2025 at Ontario Power Generation’s Darlington site, less than 50 miles east of Toronto. That makes Ontario the first G7 jurisdiction to approve and begin construction of a grid-scale SMR. Not a demonstration. Not a prototype. A full 300 MW commercial unit. 🔬
The BWRX-300 is a 10th-generation boiling water reactor design that leans hard on something most advanced reactor startups can’t claim: a massive body of real-world operating experience. GE has been building boiling water reactors for more than six decades. The BWRX-300 uses natural circulation cooling, meaning the reactor stays safe without active pumps, external power, or operator intervention — even in extreme circumstances. BWX Technologies has already started manufacturing the reactor pressure vessel, the largest single component in the machine, making it the first manufacturer in North America to do so for an SMR design.
The numbers are significant enough to pay attention to:
$7.7 billion Canadian for the first unit at Darlington (about US$5.6 billion)
First unit scheduled to be operational by end of 2029
Four units planned for the site, capable of powering over 1 million homes and businesses
A $400 million DOE grant to Tennessee Valley Authority to advance a BWRX-300 at Clinch River, Tennessee
TVA filed a construction permit application with the NRC in May 2025. The UK completed Step 2 of its Generic Design Assessment for the BWRX-300 in December 2025. Poland, Sweden, Finland, Hungary, and Bulgaria are all in active discussions. Samsung C&T signed a strategic alliance in October 2025 to advance deployments in global markets outside North America. 🌍
The obvious concern? Cost. OPG estimated power from the four-reactor fleet at $0.149 Canadian per kilowatt-hour, and the International Energy Agency noted in a January report that SMRs need to reach $4,500 per kilowatt by 2040 to compete seriously. The first-of-a-kind unit at Darlington comes in well above that. But that’s the whole point of a first mover: you absorb the expensive lesson so subsequent units get cheaper. Whether GVH can actually achieve those economies of scale is the open question hanging over everything.
What year does the western world’s first SMR flip on? If Darlington stays on schedule, it’s 2029. That’s a real date with real concrete being poured.
TerraPower: Bill Gates’ sodium bet just became a construction site
TerraPower, the nuclear innovation company founded by Bill Gates, received something remarkable on March 4, 2026: the U.S. Nuclear Regulatory Commission voted to issue a construction permit for Kemmerer Unit 1, the company’s Natrium reactor in Wyoming. It is the first commercial-scale advanced nuclear plant to ever receive that permit — and the first NRC approval for a non-light-water commercial reactor in more than 40 years. ⚡
The Natrium is a 345 MW sodium-cooled fast reactor paired with a molten salt thermal storage system. That storage system is not a gimmick. It can boost the plant’s total output to 500 MW for more than five hours when grid demand peaks — essentially giving you a dispatchable battery built into your nuclear plant. No other advanced reactor design on earth does that. TerraPower’s CEO Chris Levesque described the permit approval as “a historic day for the U.S. nuclear industry.” That description isn’t hyperbole. According to the Department of Energy, TerraPower plans to start construction in “the coming weeks” from the permit date.
The regulatory timeline for Kemmerer tells a story of what streamlined licensing actually looks like when a company shows up with a complete application:
March 2024: Construction permit application submitted to NRC
May 2024: Application docketed — first commercial advanced reactor ever docketed
December 2025: Safety evaluation completed, ahead of schedule and 11% under budget
March 2026: Construction permit issued — five months ahead of original schedule
TerraPower aims to pour its first nuclear-related concrete in 2027, load fuel in 2030, and reach commercial operation by 2031. That’s five years behind the original DOE target, but the delays were caused by a Russian fuel supply disruption that forced a redesign around domestic high-assay low-enriched uranium. Not a technology failure. A geopolitical one.
The company also has tech giant Meta on board, with an agreement that could see TerraPower deploy up to eight Natrium reactors to support Meta’s energy needs. That’s a serious commercial anchor for the fleet deployment that has to follow the Kemmerer demonstration. 🔋
X-energy: the industrial heat specialist with a $700 million war chest
Most SMR developers are chasing the electricity market. X-energy is thinking a layer deeper. Its Xe-100 reactor — an 80 MW high-temperature, gas-cooled reactor using pebble-bed fuel — can reach temperatures over 750°C, making it suitable for something large light-water reactors simply cannot do: supplying industrial process heat. That means chemical plants, steel mills, hydrogen production, and other industries that run on enormous quantities of thermal energy, not just electricity.
The Xe-100’s first commercial deployment is with Dow Inc. at its Seadrift, Texas chemical plant, where four units will supply both power and high-temperature steam. That project is the furthest along in its NRC approval process, with the construction permit docketed in May 2025. X-energy uses proprietary TRISO-X fuel — uranium particles encased in graphite — which is physically designed to prevent meltdown even in worst-case scenarios. The company is building a $300 million TRISO-X fuel fabrication facility in Oak Ridge, Tennessee that will produce 700,000 fuel pebbles annually. 💡
Beyond Dow, the pipeline is substantial:
Amazon committed to helping deploy more than 5 GW of Xe-100 capacity by 2039, starting with the Cascade Advanced Energy Facility in Washington state with Energy Northwest
Centrica signed a joint development agreement in September 2025 to deploy up to 6 GW across 12 units in the UK, at Hartlepool — next to a site that was a nuclear plant until 2028
X-energy closed a $700 million Series D financing round in November 2025
A letter of intent with Talen Energy in March 2026 to evaluate three or more four-unit plants in Pennsylvania’s PJM market
In total, X-energy is actively developing more than 11 GW of new nuclear capacity across commercial partnerships. The company is developing more capacity than most national grid operators manage. Whether it can build that out on time is a different conversation — but the commercial demand is real and growing fast.
Think about which company in the SMR space has the most direct answer to the AI data center power crisis right now, and X-energy is a serious candidate. What other use case would you prioritize if you were in their position?
Rolls-Royce SMR: the UK’s government-backed national champion
Rolls-Royce SMR is not building the same kind of advanced reactor as X-energy or TerraPower. Its design is a 470 MW pressurized water reactor — proven technology, not a first-of-a-kind gamble. That’s the point. Rolls-Royce explicitly bets on a mature PWR design with modular factory construction as the route to predictable cost and reliable deployment. The company argues that “novel” is the enemy of “on budget.”
In November 2025, the UK government selected Wylfa on the island of Anglesey, North Wales, as the site for the country’s first SMR fleet — three Rolls-Royce SMRs, with the potential to expand to eight. According to the UK Parliament, the project is backed by more than £2.5 billion in government funding and is expected to create up to 3,000 jobs at peak construction. Site activity starts in 2026. First power to the grid is targeted for the mid-2030s. 🌱
The company also has:
ČEZ Group of the Czech Republic as a strategic investor, with plans for up to 3 GW of SMR capacity and an Early Works Agreement at the Temelín site signed in July 2025
Rolls-Royce SMR advancing through the final stage of the UK’s Generic Design Assessment, expected to conclude by December 2026
A potential export program reaching into Sweden, Hungary, and beyond
What’s distinctive about Rolls-Royce’s position is the government partnership model. Great British Energy — Nuclear, a publicly owned body, is leading the Wylfa project. That’s less startup-style risk and more state-backed industrial program. For a technology that still needs to prove its cost competitiveness, that backing matters.
The honest caveat: “mid-2030s” means this race, at least for Rolls-Royce, runs long. The Wylfa units won’t be on the grid until nearly a decade after GVH’s Darlington unit. Whether Britain’s nuclear ambitions stay funded and politically consistent across two or three elections is a genuine open question. ♻️
NuScale: the regulatory pioneer with a deal that rewrote the record books
NuScale Power deserves a seat at this table for one reason no other company can claim: the VOYGR is the only SMR design to have received design approval from the U.S. Nuclear Regulatory Commission. NuScale has been through the full NRC licensing process. That is an extraordinary thing to accomplish, and it took years. The company went public in 2022, and it has spent the time since trying to convert that regulatory lead into actual commercial contracts.
The biggest signal came in September 2025, when NuScale’s exclusive global strategic partner ENTRA1 Energy signed a landmark agreement with the Tennessee Valley Authority to deploy up to 6 GW of NuScale SMR capacity — the largest SMR deployment program in U.S. history. NuScale CEO John Hopkins called TVA “ready for commercial deployment.” Each VOYGR power module produces 77 MW, designed for passive cooling via natural convection — no pumps required. A full 12-module plant produces 924 MW.
NuScale’s current targets:
Standard Design Approval for the uprated 77 MWe design from NRC, expected by July 2025
12 modules already in the manufacturing process as of early 2025
First NuScale Power Module delivery targeted for 2030
A Front-End Engineering and Design study for a project in Romania continues with Fluor
The company ended Q3 2025 with $753.8 million in cash, giving it runway. But NuScale’s path has had real bumps. A Utah utility project was canceled in 2023 due to cost concerns, and the company has had to pivot toward industrial customers, data centers, and government partners rather than traditional utilities. The TVA deal via ENTRA1 is the biggest positive development since NRC approval, but a letter of intent is not concrete in the ground.
If NuScale executes on the TVA program, it becomes a dominant player. If the economics don’t close — the IEA’s $4,500/kW threshold is a tough target — the regulatory first-mover advantage alone won’t be enough. That tension is worth watching closely. 📈
The wild card: China is already winning
Here is the uncomfortable truth about this race: China may have already crossed the finish line.
China National Nuclear Corporation’s Linglong One — also known as the ACP100 — is a 125 MW pressurized water reactor at the Changjiang site on Hainan Island. It completed cold functional testing in October 2025 and non-nuclear turbine testing in December 2025. According to Reuters, CNNC officials confirmed in December 2025 that commercial operation is targeted for the first half of 2026 — meaning right now, or within weeks of this article. It was also the first SMR globally to pass an IAEA safety review, back in 2016. Construction started in July 2021. That’s a 58-month build time, from first concrete to commercial operation, for a first-of-a-kind reactor. 🧬
Western SMR developers aren’t close to that pace. The Darlington unit in Canada won’t be operational until 2029 at the earliest. TerraPower’s Kemmerer unit targets 2031. The Rolls-Royce units at Wylfa won’t light up until the mid-2030s.
None of that makes Western SMRs uncompetitive. Different markets, different regulatory environments, different technology choices. But anyone seriously thinking about the global SMR race has to grapple with the fact that China built one first, built it on schedule, and is already positioning the ACP100 design for export to Indonesia, Thailand, Malaysia, and Saudi Arabia under its Belt and Road strategy. That’s the race within the race — and it’s already producing real outcomes.
The question for policymakers, investors, and energy planners isn’t just who builds the first SMR in their country. It’s whether Western developers can build the second and third fast enough to matter.
So who’s winning? GE Vernova Hitachi has real concrete being poured in Canada, making it the leader among Western developers by almost any honest measure. TerraPower’s construction permit is historic and its timeline is credible. X-energy has the commercial pipeline and the industrial use case. Rolls-Royce has the government money. NuScale has the regulatory approval and a record-breaking deployment commitment. And China, quietly, may have already answered the question the rest of the world is still debating.
Which of these five companies do you think has the strongest long-term position — and does it matter if China starts exporting ACP100s before the West deploys its first commercial unit?