Small Modular Reactors

World's first commercial pebble-bed high-temperature gas-cooled SMR.

After a four-year evaluation of 70+ options, Sweden's Videberg Kraft (Vattenfall + Industrikraft) picked Rolls-Royce SMR over GE Vernova to supply three 470 MWe reactors (~12 TWh/yr) at the Värö Peninsula — Rolls-Royce SMR's first international selection and Sweden's first new nuclear in over 40 years. Detailed planning begins now; the first reactor is targeted for the mid-2030s.

Antares' Mark 0 test reactor at Idaho National Laboratory achieved first criticality — a self-sustaining nuclear reaction and the first new US advanced-reactor design to cross the threshold (it is not yet generating power).

Oklo broke ground (22 Sep 2025) on Aurora-INL — its first Aurora Powerhouse, a 75-MWe liquid-metal-cooled, metal-fueled fast reactor at Idaho National Laboratory (building on EBR-II heritage) under DOE's Reactor Pilot Program, with Kiewit as lead constructor.

Westinghouse's eVinci test article reached zero-power criticality at 10:39 a.m. PT on 24 Aug 2026 at the National Criticality Experiments Research Center in Nevada, with Los Alamos and Idaho National Laboratory. Zero-power criticality confirms the core's nuclear design — the reaction is self-sustaining — without generating usable heat or power, so it validates physics rather than demonstrating a working reactor. Westinghouse's 15 Sep release added the temperatures: the test article went critical at 663°C (1,225°F) and researchers measured a peak core temperature of 1,011°C (1,852°F), a record high for a reactivity measurement at NCERC — a facility record, not a technology one. Read the pair carefully: at zero power the core is not making that heat, it is held at those temperatures so the team can measure how reactivity responds to them, which is the data the prototype design needs. eVinci is a heat-pipe-cooled design with no pumps or coolant loops, sized at 5 MWe for remote sites and data centers; it was separately selected for the US Army's Janus Program at Fort Drum.

Oklo's Groves reactor reached first criticality at 9:19 p.m. ET on 5 Aug 2026 — a controlled, self-sustaining chain reaction less than a year after groundbreaking. It is the fifth reactor to go critical under DOE's Reactor Pilot Program and the first to do so on private land, built from scratch on a greenfield site rather than a federal laboratory campus. Groves is a low-power isotope test reactor, not a power plant: it establishes the operating base for commercial isotope production, while Oklo's Aurora power reactors remain a separate track.

DOE's Idaho office approved the Preliminary Documented Safety Analysis (PDSA) for Oklo's Aurora-INL under the Reactor Pilot Program — a staged framework letting advanced reactors build on a federal site under DOE oversight instead of waiting on full NRC licensing. It clears the safety basis for construction (not commercial operation); Oklo pursues NRC licensing separately for commercial units.

The NRC issued a construction permit for TerraPower's Natrium plant (Kemmerer, Wyoming) — the first US commercial advanced-reactor approval in ~a decade and the first non-light-water reactor approval in over 40 years. 345 MWe sodium-cooled fast reactor with molten-salt storage boosting to 500 MW; completion targeted 2030.

Weeks after winning its NRC construction permit, TerraPower started safety-related construction on Kemmerer Unit 1 — on track to be the first utility-scale advanced (non-light-water) nuclear plant built in the US. The 345 MWe sodium-cooled fast reactor (molten-salt storage boosting to 500 MWe) will take ~1,600 workers and is targeted for completion by 2030; a January deal commits up to eight Natrium units to Meta by 2035. In September the lead contractor left: Bechtel, which had been TerraPower's engineering and construction partner since the project's start, filed a WARN notice on 15 Sep covering about 200 positions after the two companies were "unable to reach an agreement on the next phase of the project". TerraPower will rebid the EPC contract and says the schedule — construction complete in 2030, commercial operation in 2031 — is unchanged. A month earlier it had signed Hyundai E&C for up to eight later units, with price and completion guarantees; unit 1 has no such contractor today.

The NRC issued a Finding of No Significant Impact for X-energy's plan to build four 80 MWe Xe-100 reactors at Dow's Seadrift site on the Texas Gulf Coast — the first commercial nuclear project in the NRC's 52-year history cleared through a streamlined environmental assessment rather than a full environmental impact statement. The Amazon-backed developer still faces the separate safety review next.

Kairos broke ground on Hermes 2 in Oak Ridge — the first power-producing Gen IV reactor with an NRC construction permit. The molten-salt-cooled plant will feed up to 50 MW to TVA, powering Google data centers. On 21 Sep 2026 Samsung C&T committed up to $100M — about $70M in equity, the rest as engineering services — and joined the build as a construction partner.

After ~6 years, the NRC finalized Part 53 (effective 29 Apr 2026) — a risk-informed, technology-inclusive licensing framework targeting design approvals in 18 months or less at roughly half the cost. A structural unlock for the entire US advanced-reactor field, independent of any single project.

US Energy Secretary Chris Wright signed authorization (25 Jun 2026, at Idaho National Laboratory) for Aalo Atomics to proceed with criticality testing of its Aalo-X critical test reactor under the DOE Reactor Pilot Program (EO 14301) — following DSA approval and an operational readiness review. The signed go-ahead is the milestone; criticality itself was expected within days (July 4 program target). Aalo-X tests the full core for the ~10 MWe Aalo-1 design.

The NRC issued the Tennessee Valley Authority a construction permit for a 300 MW BWRX-300 at its Clinch River site in Oak Ridge at the end of September 2026 — the first US construction authorisation for a commercial small modular reactor, and the first held by a utility rather than a reactor developer. The review took 14 months from TVA's April 2025 application, about four months ahead of the NRC's own schedule. A construction permit is not an operating licence: TVA must build the plant and obtain a separate licence before loading fuel. TVA has said the site could host up to four units; the design's first unit anywhere is Ontario Power Generation's Darlington project, targeted for 2030.