ProjectsPlenty of SMR coverage is still speculative. This roundup isn’t. Every project below has a signed permit, a construction crew, or a regulator’s stamp attached to it right now, in 2026, not a hoped-for date five years out. 🏗️ Some are sodium-cooled, some run on molten salt, one is a familiar boiling-water design shrunk down and factory-built. What they share is dirt actually moving.
Pick any one of these and you’re watching a different bet on how nuclear gets built cheaper and faster. Here are the five worth tracking this year, with the numbers that actually matter. ⚛️
TerraPower’s Natrium reactor breaks ground in Kemmerer, Wyoming
TerraPower started construction on April 23, 2026, at Kemmerer Unit 1, its flagship Natrium plant in southwestern Wyoming. The design is a 345-MWe sodium-cooled fast reactor paired with a molten salt heat storage system that can push output to 500 MWe on demand, essentially letting the plant behave like a dispatchable battery. 🔋
The Nuclear Regulatory Commission issued the construction permit in early March 2026, its first approval for a commercial non-light-water reactor in more than 40 years and its first commercial reactor approval of any kind in nearly a decade. Bechtel is the engineering and construction partner, and TerraPower CEO Chris Levesque said the company is “building the next generation of America’s energy infrastructure.” The site sits next to a retiring coal plant, which is deliberate: TerraPower wants to reuse grid connections and a trained workforce rather than start from a blank field, a much cheaper first-mover strategy than it sounds. 📈⚡
What makes Kemmerer worth tracking:
First utility-scale advanced reactor construction in the US, not a demonstration unit
Sodium coolant runs at low pressure and high temperature, a genuine departure from light water
Integrated molten salt storage decouples heat generation from electricity output
Bill Gates-founded TerraPower is self-funding a large share of the project alongside Department of Energy support
Kairos Power’s Hermes goes from salt tanks to poured concrete in Oak Ridge
Kairos Power’s Hermes reactor, a 35-MWt demonstration unit cooling TRISO fuel pebbles with FLiBe, a molten mixture of lithium and beryllium fluoride salts, has moved well past paperwork. 🧪 The company has completed its first safety-related concrete pour at the Oak Ridge, Tennessee, site, anchored on 51 large-diameter piers drilled roughly 40 feet into bedrock, which is a very unglamorous way to describe a genuinely novel reactor. 🧊
Hermes received its construction permit from the NRC in December 2023, the first approval for a non-light-water reactor design in the US in decades, and the company has spent the years since proving out the technology at full scale before pouring a single yard of concrete on the actual reactor. 🔬 Its Engineering Test Unit in Albuquerque logged more than 2,000 hours of pumped salt operations, the largest FLiBe system ever built, before Hermes construction even began.
Why Hermes matters beyond Oak Ridge:
Non-power demonstration reactor, so no grid connection risk clouds the safety case
Near-atmospheric pressure operation means a much lighter, cheaper containment structure
FLiBe production has its own dedicated Kairos facility in Ohio, a first for the US supply chain
Success here directly informs Kairos’s planned commercial KP-FHR fleet
Which of these five reactors do you think has the toughest remaining hurdle: fuel supply, financing, or the regulator’s final sign-off?
OPG’s BWRX-300 lowers its first reactor foundation in Ontario
Ontario Power Generation is arguably ahead of everyone on this list. Its first GE Vernova Hitachi BWRX-300, a 300 MWe boiling-water SMR, is under construction at the Darlington site east of Toronto, and in May 2026 crews lowered the reactor’s basemat into a 35-meter-deep excavated shaft, a genuinely photogenic milestone for an industry not known for them. 🇨🇦🏗️ The Canadian Nuclear Safety Commission granted the construction license in April 2025, and OPG reached its final investment decision the following month.
This is the first-of-a-kind deployment of the BWRX-300, and OPG plans three more units at Darlington after this one, Canada’s first new nuclear build in more than 30 years. OPG chief projects officer Subo Sinnathamby, who previously led Darlington’s CANDU refurbishment, described the pace by saying the team got its construction license in April and its investment decision in May, “and we’ve been off to the races since.” The BWRX-300 has also cleared step two of its UK Generic Design Assessment, and the Tennessee Valley Authority has filed its own construction permit application for a BWRX-300 at Clinch River. 🔧
The specs that make Darlington the pace-setter:
300 MWe per unit, based on GE’s decades-proven boiling-water reactor lineage rather than an unproven coolant
Four units planned at one site, testing whether a repeatable build gets cheaper each time
Ahead-of-schedule, under-budget refurbishment track record from the same OPG team
A design already exported into US, UK, and Polish licensing processes simultaneously
Every project, deal, company, and regulatory event we cover is logged, verified, and searchable in SMRbrief Pro, which is the fastest way to see how Darlington’s timeline stacks up against the other four projects here.
X-energy’s Xe-100 four-pack advances at Dow’s Seadrift plant in Texas
X-energy is building four Xe-100 high-temperature gas reactors, roughly 80 MWe each, at Dow’s UCC Seadrift chemical plant on the Texas Gulf Coast, the first grid-scale advanced reactor deployment at an industrial site in North America. 🏭 Dow subsidiary Long Mott Energy filed the construction permit application with the NRC in March 2025, and in May 2026 the agency completed its environmental review with a Finding of No Significant Impact, ahead of schedule, which is a genuinely rare phrase to type about a first-of-a-kind reactor project. ⚙️
The full construction permit is expected in the first quarter of 2027, with commercial operation targeted for the early 2030s. X-energy itself went public in 2026, raising roughly $1.1 billion in net proceeds on its Nasdaq debut under ticker XE, and CEO J. Clay Sell said the quarter’s results reflect “the progress we are making to commercialize advanced nuclear technology at scale.” The company also secured a Part 70 fuel fabrication license from the NRC this year, letting it manufacture its own TRISO-X fuel commercially rather than depend on outside suppliers. ⚗️
The details that separate Seadrift from a typical SMR pitch:
Dow is eligible for 50% of the construction cost for the first four-pack, a Department of Energy risk-sharing arrangement
The reactor supplies both electricity and industrial process steam, matching Dow’s actual plant needs
Amazon has a parallel Xe-100 deal at Energy Northwest in Washington, part of a pipeline X-energy says could exceed 11 GWe across three customers
Graphite supply is locked in through a new agreement with Germany’s SGL Carbon
Rolls-Royce SMR lands its first UK site at Wylfa
Rolls-Royce SMR finally has a home for its 470 MWe pressurized-water reactor. Great British Energy-Nuclear named Rolls-Royce SMR the preferred technology in June 2025, and in November 2025 the UK government confirmed Wylfa, on Anglesey in North Wales, as the site for the first three units, a combined 1.5 GW. 🇬🇧 A final investment decision is expected in 2029, with grid connection targeted for the mid-2030s, a timeline that’s honestly more aggressive than most of this list.
The design has cleared step two of its Generic Design Assessment with the Office for Nuclear Regulation, and it isn’t just a UK story. 🌍 Czech utility ČEZ selected Rolls-Royce SMR for up to 3 GW of new capacity back in October 2024 and took a 20% equity stake in the company, and in January 2026 Amentum was named delivery partner across the combined 4.5 GW UK and Czech pipeline. Roughly 90% of each plant is meant to be assembled in factory conditions before shipping to site, the core bet behind the whole modular premise. 🔩
What to watch as Wylfa moves forward:
Site is a former Magnox nuclear plant already being decommissioned, with room for up to eight SMRs long-term
Step three of the GDA, the most detailed technical review, is the next major regulatory gate
The Czech and UK programs share one supply chain, so delays or wins in one country ripple into the other
2029’s final investment decision is the real test of whether financing keeps pace with the engineering
Five projects, four countries, three different reactor chemistries, and one shared question: which of them actually delivers first power on schedule?