2026 is the year small modular reactors stopped being a slide deck and started being a construction site. For a decade, the SMR pitch was always “five years out.” Now the U.S. Nuclear Regulatory Commission has issued its first construction permit for a commercial non-light-water reactor in more than 40 years, Ontario’s BWRX-300 has steel going into the ground, and the U.K. has picked a winner for its first fleet. Even China’s Linglong One is racing to become the world’s first land-based commercial SMR, a reminder that the West isn’t the only one pouring concrete. 🏗️
None of this happened by accident. AI data centers need firm, round-the-clock power that wind and solar alone can’t promise, and utilities are done waiting on transmission queues. That demand pulled billions of dollars of private and government capital into a handful of companies that actually have dockets, permits, and shovels in the ground, not just renderings. Here are the five that pulled ahead this year, and why.
X-energy is turning a chemical plant into a nuclear testbed
X-energy is building four Xe-100 reactors, an 80 MW high-temperature gas-cooled design, at Dow’s UCC Seadrift petrochemical site on the Texas Gulf Coast. Combined, the four-pack adds up to 320 MWe, enough to replace the fossil-fuel cogeration plant currently running the site. The NRC completed its Environmental Assessment in May 2026 with a Finding of No Significant Impact, and a construction permit is expected in the first quarter of 2027. ⚛️
What sets X-energy apart isn’t just Dow. It’s the pipeline: contracts with Dow, Amazon, and the U.K.’s Centrica add up to more than 11.5 gigawatts across 144 reactors. The company backed that pipeline with real money in 2026:
An upsized IPO in April at $23 a share, now trading on Nasdaq as XE
An additional $1 billion in DOE cost-shared funding for the Seadrift project, bringing the government’s total commitment there to roughly $2.15 billion
The first-ever NRC Category II license for TRISO-X to manufacture advanced fuel, granted in February 2026
A March MOU with Japan’s IHI to expand U.S.-Japan supply chain capacity for the Xe-100
Dow expects to receive its first commercial reactor delivery in the early 2030s, but the fuel fabrication and licensing groundwork happening right now is what X-energy says makes Seadrift the template for every industrial site that follows it.
TerraPower broke ground on America’s first advanced reactor
TerraPower, the Bill Gates-backed developer, hit the milestone the whole sector has been chasing: an actual NRC construction permit. On March 4, 2026, commissioners unanimously approved the permit for Kemmerer Unit 1 in Wyoming, home to TerraPower’s Natrium reactor, a 345 MW sodium-cooled fast reactor paired with a molten salt storage system that can push output to 500 MW on demand. Construction officially began April 23, 2026, according to the company, less than seven weeks after the permit came through. 🔧
The historical weight here is hard to overstate without sounding like a press release, so let’s just stick to facts: it’s the first construction permit the NRC has granted a commercial reactor in nearly a decade, and the first ever for a non-light-water design. A few numbers that matter:
Project cost projected at up to $4 billion
Sodium-cooled fast reactor rated at 345 MW, boostable to 500 MW
Site sits next to a retiring coal plant, replacing jobs the closure would have cut
Targeted completion in 2030
TerraPower’s sister project, the Hermes test reactor built with fellow ARDP recipient X-energy’s peer Kairos Power (more on them below), shows how tightly the DOE’s original 2020 bet on these two companies has paid off. Both were long-shots five years ago. Neither is anymore.
Kairos Power is racing a molten-salt reactor into Tennessee
Kairos Power builds a fluoride salt-cooled high-temperature reactor (KP-FHR) that runs on TRISO pebble fuel, technology with roots in 1960s Oak Ridge research reborn for a 2026 grid. The company’s Hermes 1 test unit is, right now, the only Gen IV reactor under active nuclear construction in the United States. Behind it comes Hermes 2, a 50 MWe commercial-scale demonstration plant that broke ground this year on the same Oak Ridge campus. 🧪
Hermes 2 exists because of a deal that turned heads in the industry: Kairos, the Tennessee Valley Authority, and Google agreed in 2025 to put the reactor’s output directly onto TVA’s grid, making it the first commercial deployment tied to Google’s advanced nuclear procurement push. A few specifics worth flagging for anyone tracking the fuel side of this story:
Kairos finalized a DOE contract for HALEU in January 2026 to fuel the Hermes demonstration reactor
A September 2025 agreement with BWXT targets commercial-scale TRISO manufacturing for Hermes 2 and future units
Hermes 2 components are fabricated at Kairos’s Albuquerque manufacturing campus and shipped to Tennessee for assembly, a factory-build approach the company is betting will cut costs
Commercial operation is targeted for 2030
If you’re wondering how this compares to the more established light-water designs below, SMRbrief Pro members can search, filter, and export the full intelligence picture behind developments like this one, including fuel supply timelines that don’t always make the press release.
GE Vernova Hitachi’s BWRX-300 is going global fast
Of everyone on this list, GE Vernova Hitachi Nuclear Energy has the least to prove technically. Its BWRX-300, a 300 MWe boiling water reactor built on the NRC-certified ESBWR design, is under construction right now at Ontario Power Generation’s Darlington site in Canada, the first SMR construction project in the Western world, with completion expected by decade’s end. 🌍
The bigger story this year is reach. GE Vernova and Poland’s Orlen Synthos Green Energy (OSGE) signed a Poland Generic Design Agreement in February 2026 to develop a detailed BWRX-300 reference design for the Polish market, backed by up to $4 billion in U.S. Export-Import Bank and International Development Finance Corporation support. That’s a lot of acronyms for one deal, so here’s the shape of it:
Poland is targeting a first unit at Włocławek by 2032, with up to 24 reactors planned across six sites
The NRC is separately reviewing the Tennessee Valley Authority’s application to build a BWRX-300 at Clinch River, Tennessee
Darlington’s reactor pressure vessel is already in manufacturing, per GE Vernova
Poland still generates roughly 70% of its electricity from coal, which is the real reason this deal matters
Which of these five reactors do you think reaches commercial operation first, Darlington’s BWRX-300 or TerraPower’s Natrium? Worth arguing about in the comments, because the smart money keeps splitting on that question. 💬
Rolls-Royce SMR won the UK, then went to Sweden
Rolls-Royce SMR spent years as the perpetual bridesmaid of the sector, and 2026 is when that changed. Great British Energy - Nuclear named Rolls-Royce SMR the preferred technology for the U.K.’s first SMR fleet after a two-year competition against GE Hitachi, Holtec, and Westinghouse, World Nuclear News reported. The reactor itself is a 470 MWe pressurized water reactor, derived from decades of Royal Navy submarine engineering, and it’s going up first at Wylfa on Anglesey in North Wales. ☢️
The contract, backed by £2.5 billion in government funding, was formally signed this year and lets Rolls-Royce SMR start ordering long-lead equipment. A few numbers to anchor the scale of this bet:
Wylfa’s first three reactors are expected to support around 3,000 jobs at peak construction
In June 2026, Sweden’s Videberg Kraft picked Rolls-Royce SMR to build three reactors on the Värö peninsula, up to 1,500 MWe total
Rolls-Royce SMR is now the only developer with multiple firm commitments in Europe
Backers include the Qatar Investment Authority, Constellation Energy, and a 20% equity stake held by the Czech utility CEZ
That combination, a domestic anchor customer plus an export order landed in the same year, is what separates a chosen technology from a company that’s merely hopeful. Rolls-Royce SMR’s own progress page reads less like a pitch deck now and more like a project schedule.
Five companies, five very different bets on reactor chemistry, and all five now have something in common they didn’t have two years ago: dirt moving, permits signed, or a customer with skin in the game. The next twelve months will separate the ones that stay on schedule from the ones that quietly slip into “early 2030s.” Which of these five would you put your money on to actually flip the switch first?