The One Regulatory Change That Could Accelerate SMRs by a Decade
After 70 years of licensing rules built for a different era, the NRC just rewrote the rulebook — and the implications for small modular reactors are enormous.
The date March 25, 2026 will probably not make it into many history books. No explosions, no ribbon cuttings, no president at a podium. Just four commissioners voting to finalize a regulatory rule, the way regulatory rules get finalized — quietly, in a meeting room, buried in technical language. And yet if small modular reactors actually get built at scale in this country, that date is where the story really begins.
What the U.S. Nuclear Regulatory Commission approved that Tuesday was 10 CFR Part 53, a new framework for licensing commercial nuclear plants. It is, without hyperbole, the most consequential regulatory reform in American nuclear history in living memory. The previous licensing framework — Part 50 — dates to 1956. The Suez Crisis was happening. Elvis had just released “Heartbreak Hotel.” The rules governing how the United States approves new nuclear reactors are, functionally, older than the interstate highway system, and they were written for reactors that look nothing like the ones developers are racing to build today.
Part 53 changes that. Completely. Whether it changes it fast enough is a different question.
What the old rules actually required
To appreciate why Part 53 matters, you need to understand what came before it — and why it was such a problem for SMR developers specifically. 🔬
The existing Part 50 and Part 52 frameworks were written around light-water reactor technology. That means pressurized or boiling water that cools a conventional uranium core. Makes sense: that’s what America built for 60 years. But the SMR designs drawing billions in investment today are wildly diverse. TerraPower’s Natrium uses liquid sodium as a coolant. Kairos Power’s Hermes runs on molten fluoride salt. Oklo’s Aurora is a compact sodium-cooled fast reactor. Not one of these fits neatly into rules written when “advanced reactor” meant slightly bigger version of the last one.
The consequence was brutal for developers. Every time an SMR company tried to license a design that deviated from light-water norms, it had to apply for individual exemptions — sometimes dozens of them — from specific regulatory requirements that simply didn’t apply to their technology. This process added:
Years to the review timeline
Millions of dollars in legal and engineering costs
Fundamental uncertainty, because NRC had no clear precedent
The discouraging feeling that you were basically making it up as you went
NuScale, which designs a light-water SMR and is the only company with an approved design in the U.S., still took more than 41 months for its first certification review. Its second design got through in 22 months — a record, and even then it required working closely with NRC staff for years beforehand. For non-light-water developers, those timelines would have been considerably longer without exemptions. Part 53 is the fix.
What Part 53 actually does ⚡
The new rule, which takes effect April 29, 2026, is designed around one core principle: instead of prescribing how a reactor must be built, it sets performance targets and lets developers demonstrate — using probabilistic risk assessments — that their design meets those targets. This is the difference between a building code that says “use these exact materials” and one that says “the building must survive these specified loads.”
The practical changes are significant:
No more technology-specific exemptions for non-light-water designs, meaning TerraPower, Kairos, and others get a genuine pathway rather than a workaround
Factory fuel loading is now explicitly authorized, allowing manufacturers to fuel reactors at the production facility before shipping them to a site — a massive logistics advantage for modular, repeat-build strategies
Alternative siting criteria allow reactors to be placed closer to population centers, industrial facilities, and data centers, which is exactly where the demand is
Generally licensed reactor operators (GLROs) for certain “self-reliant mitigation” facilities, reducing ongoing staffing costs
Staged licensing lets developers complete reviews in phases rather than waiting for full approval before starting the next step
According to Perkins Coie’s analysis of the rule, NRC officials estimate Part 53 could cut design review timelines to 18 months or less — and reduce application costs by half or more. A 2023 NRC draft analysis put the avoided costs at between $53.6 million and $68.2 million per applicant. 💡 That is not nothing.
NRC Chairman Ho Nieh put it plainly: “This final rule is a major NRC action that provides a clear risk-informed, technology-inclusive licensing framework to enable new nuclear to safely move faster from concept to construction.” The American Nuclear Society called it historic, and for once that word seems justified.
Why this lands now 🚀
Part 53 didn’t happen in a vacuum. A few converging pressures forced it to the finish line earlier than anyone expected — the rule was completed more than a year ahead of the end-of-2027 deadline set by the Nuclear Energy Innovation and Modernization Act of 2019.
First, there’s the AI data center buildout. Meta, Google, Amazon, and Microsoft have all signed nuclear power agreements or made direct investments in reactor development. OpenAI has floated needing as much as 20 gigawatts of dedicated power for its operations. These companies don’t want variable renewable energy with storage kludges; they want always-on baseload, and they’re willing to pay for it. That commercial pressure has political weight.
Second, the Trump administration issued four executive orders in May 2025 specifically aimed at expediting nuclear permitting. One required NRC to review new reactor applications within 18 months — a mandate that Part 53 is now designed to meet. Another expanded the roles of the Departments of Energy and Defense in licensing, potentially creating new fast-tracks for reactors on federal land. 📈
Third, the pipeline of actual projects is real and growing. The Tennessee Valley Authority submitted its full construction permit application in May 2025 for a BWRX-300 small modular reactor at the Clinch River site in Oak Ridge. TerraPower’s Natrium reactor in Kemmerer, Wyoming completed its final environmental impact statement — the first advanced reactor technology to do so. The DOE selected 11 companies for its Nuclear Reactor Pilot Program. The demand is here. The projects are real. What was missing was a regulatory path that didn’t feel like hiking through a swamp with a compass from 1956.
What do you think is the bigger barrier to SMR deployment right now — regulatory uncertainty, or the cost of financing first-of-a-kind projects? That distinction probably shapes whether Part 53 is the unlock people hope it is.
The complications worth being honest about 🔬
Part 53 is not a magic wand. The Information Technology and Innovation Foundation’s realist assessment makes this clear: NRC reform is under way, but more is needed. Innovation requires iteration, and Part 53 still leaves open the question of what happens when a developer needs to make significant design changes after initial approval. The “design once, build often” model that the new rules encourage doesn’t obviously accommodate the kind of rapid iteration that characterizes successful technology development.
There are also real concerns about NEPA — the National Environmental Policy Act — which governs environmental review and can add years to infrastructure projects independent of NRC licensing. The Part 51 companion rule finalized alongside Part 53 streamlines environmental review for routine licensing actions, but major new reactor projects still face full NEPA review, including potentially full environmental impact statements. That’s not a small caveat.
And then there’s the practical first-mover problem that the Perkins Coie analysis flags directly: because Part 53 replaces prescriptive rules with high-level performance criteria, the first applicant under the new framework has to blaze the trail. There’s no established regulatory precedent, no well-worn path. The first company to use Part 53 will bear the full burden of demonstrating, through probabilistic risk assessments, that their novel approach meets the safety criteria. That is expensive, slow, and genuinely uncertain. The fifth company will have a much easier time.
Key obstacles that remain, even with Part 53 in place:
HALEU fuel supply — many advanced reactor designs require high-assay low-enriched uranium that the U.S. simply doesn’t produce at scale yet
NEPA reform still needed for full environmental review streamlining
First-of-a-kind construction costs remain high, and no amount of regulatory reform fixes the economics of building reactors that have never been built before
NRC staffing and guidance — the rule exists, but companion technical guidance is still being developed and NRC needs to actually staff for the new review processes
What comes next 💊
Part 53 goes live on April 29, 2026 — roughly two weeks from now. The next move is on the developers. Several companies, including those in DOE’s Reactor Pilot Program, have signaled interest in using the new framework, but “interest” is a long way from a filed application. The real test of Part 53 isn’t the rule itself; it’s whether any company is brave enough — or well-capitalized enough — to be the first through the door.
There’s also an international dimension to keep in mind. Russia and China have already deployed operational SMRs. China brought its ACP-100 online 58 months after breaking ground. The U.S. has superior reactor designs by most technical assessments, but superior designs sitting in regulatory purgatory don’t power anything. Part 53 is, at least in part, a geopolitical response to the reality that American SMR companies are racing against state-backed competitors who don’t have to file exemptions.
The ConstructConnect analysis noted that construction starts in the power infrastructure category surpassed $36 billion for the first time on record in 2026. That capital is looking for a home. Part 53 gives it a cleaner path to nuclear than existed yesterday.
Whether 18-month reviews actually materialize, whether factory fuel loading enables the assembly-line economics SMR proponents have promised, whether the first applicants under the new framework survive the pioneer’s burden — none of that is settled yet. But the door is open in a way it has never been. After 70 years of rules designed for a world that no longer exists, that is not nothing.
The question worth sitting with: if Part 53 cuts licensing time by even half of what officials are promising, which of today’s SMR developers actually has the technology, the supply chain, and the capital to sprint through that open door first?