TVA got the first US construction permit for a commercial SMR — in 14 months, four ahead of schedule

The Nuclear Regulatory Commission issued the Tennessee Valley Authority a construction permit for a BWRX-300 small modular reactor at its Clinch River site in Oak Ridge, Tennessee, at the end of September. It is the first US construction authorisation for a commercial SMR. The 300 MW boiling-water design from GE Vernova Hitachi relies on passive safety, needing neither external power nor operator action to stay in a safe state. TVA applied in April 2025; the review took 14 months, about four months ahead of the NRC's schedule, after staff recommended the permit in July. TVA must still build the plant and obtain a separate operating licence before loading fuel, and has said the site could eventually hold four units. The tracker records the permit.

Why it matters

Earlier US advanced-reactor permits — for Kairos's Hermes reactors and TerraPower's Natrium — went to developers building their own first plants. This one went to a utility, for a design it is buying rather than inventing, on a site it already owns. That is the shape the SMR business case has always depended on: utilities ordering standard units, not every project being a first of a kind. The permit is the first time that shape has reached this stage in the US.

The 14 months is the other half of the story, and it should be read carefully. It shows the NRC can review a light-water SMR faster than its reputation suggests — partly because the design is a simplified version of boiling-water technology the agency has licensed for decades, and partly under political pressure to move faster. It does not show that construction will be fast, which is where nuclear schedules have actually failed. The lead contractor walked off TerraPower's Natrium a fortnight ago, after it had a permit. The licence was never the hard part of Vogtle either.

The useful comparison is Darlington. Ontario Power Generation is already building the first BWRX-300 and targets 2030. Clinch River will be judged against it: same reactor, different owner, different regulator. If the second unit of a design comes in cheaper and faster than the first, the SMR thesis starts to look like what it promised; if not, the first US permit is mostly a regulatory achievement.

What to watch

TVA's final investment decision and the cost estimate that comes with it, Darlington's progress against its 2030 date, and whether TVA files for a second Clinch River unit.