SMRs: where the field actually stands

The small modular reactor field carries two metrics and 26 milestones here, and the contrast between them is the story.

The metric that counts grid-connected commercial SMR units worldwide reads 4, and it has read 4 since 2023. Russia's Akademik Lomonosov contributes two floating 35 MWe KLT-40S reactors, operating since 2020; China's HTR-PM pebble-bed plant contributes two modules, commercial since December 2023. No Western SMR is generating power. Published research runs about 880 papers a year.

Against that stationary number, 2026 was extraordinarily busy. The NRC issued TerraPower a construction permit for its Natrium plant at Kemmerer, Wyoming in March — the first US commercial advanced-reactor approval in about a decade and the first non-light-water approval in over forty years — and safety-related construction began weeks later. The NRC finalized Part 53 in March, a risk-informed, technology-inclusive licensing framework targeting design approvals in eighteen months at roughly half the cost; that is a structural unlock independent of any single project. Kairos broke ground on Hermes 2 at Oak Ridge, the first power-producing Gen IV reactor with an NRC construction permit. X-energy became the first commercial nuclear project in the regulator's 52-year history cleared through a streamlined environmental assessment.

Several reactors also went critical. Antares' Mark 0 at Idaho National Laboratory reached first criticality in June, the first new US advanced-reactor design to cross the threshold. Oklo's Groves reactor went critical in August, the first under the DOE pilot program to do so on private land. Westinghouse's eVinci heat-pipe microreactor reached zero-power criticality in Nevada in August. Each of these confirms a nuclear design works; none of them generates useful power. Zero-power criticality validates physics, not a working plant.

Outside the US, OPG set the first North American SMR basemat at Darlington in May, targeting grid connection by 2030. Rosatom poured first concrete in Uzbekistan in June — the first plant built anywhere under an export SMR contract. Rolls-Royce SMR won Sweden in June, its first international selection, with the first reactor targeted for the mid-2030s, and holds the UK's Wylfa programme. China's Linglong One, a 125 MWe land-based ACP100 on Hainan, is the nearest-term candidate to move the operating count.

The honest summary is that this field converted regulatory risk into regulatory progress at remarkable speed in 2026 while converting almost none of it into electricity. The tracker's locked milestone — first Western SMR online — sits at 2030. Watch the operating-units metric: it is the one number here that has not moved, and the one that will say the field arrived.