RegulationNuScale Power’s first reactor design took the Nuclear Regulatory Commission more than four years to certify, from application acceptance in March 2018 to a final rule on July 29, 2022. Its second design, the uprated 77-megawatt US460 module, cleared the same agency in under two years, “ahead of schedule and under budget,” as the NRC told Utility Dive after the May 2025 approval. That gap is the whole story of SMR regulation right now. The question isn’t whether these designs can clear review. It’s how much faster the process gets each time a developer runs it.
With roughly 100 SMR designs in development worldwide and the NRC expected to hand down several licensing decisions this year, according to a 2026 American Bar Association analysis, it’s worth walking through what regulatory approval actually involves. It isn’t one review. It’s five, and most projects fail or stall somewhere in the middle three.
Step 1: pre-application, the unglamorous years before the paperwork
Nobody walks into the NRC’s Rockville, Maryland offices and files a cold application. Every successful SMR project spends years in informal technical exchanges before a formal submission ever lands. Kairos Power began engaging NRC staff on its fluoride salt-cooled design back in 2018, five years before it filed for a construction permit. That head start is exactly why its second construction permit application, for the Hermes 2 demonstration plant, moved through NRC review in just sixteen months after being filed in July 2023.
This step is where a company decides which of three licensing lanes to take:
10 CFR Part 50 — the traditional two-step process (construction permit, then separate operating license), still the default for first-of-a-kind designs
10 CFR Part 52 — a one-step combined license process built for the large light-water fleet
10 CFR Part 53 — a new, technology-inclusive, risk-informed pathway that takes effect April 29, 2026, giving non-light-water designs like molten salt and gas-cooled reactors an alternative that doesn’t force them into rules written for 1970s pressurized water plants
The NRC’s own Part 53 rulemaking page traces the pathway back to a 2019 congressional mandate; it’s the first new reactor licensing framework the agency has issued since 1989. Companies that lean on national lab support and Department of Energy cost-sharing tend to move faster here. DOE has put more than $600 million into NuScale’s design and licensing work alone since 2014, and that kind of backing shows up later as fewer surprises during technical review.
Step 2: design certification, the technical marathon
This is the part people picture when they think “nuclear regulation”: engineers picking apart thermal-hydraulics models, seismic assumptions, and accident scenarios line by line. The NRC’s Advisory Committee on Reactor Safety reviews the safety case independently of NRC staff, and either body can send an applicant back to redo work.
NuScale’s history shows how much this step compresses with repetition. The company’s first design certification, a 50-megawatt module packaged into its VOYGR plant, took from March 2018 acceptance to July 2022 certification, becoming the seventh reactor design ever cleared for use in the United States, per the Department of Energy’s account. The second application, for the uprated 77-MWe module powering a six-module, 462-MWe plant, was submitted January 1, 2023, and approved in under two years, as DOE later confirmed, with NuScale VP Carrie Fosaaen crediting the streamlined process for a “second design approval” built on the first one’s foundation.
What determines the timeline here:
Whether the design reuses a previously certified safety case, or is genuinely novel
How complete the pre-application data package is (test results, computer code validation, materials data)
Political and administrative pressure on the agency; a May 2025 executive order pushed the NRC toward reviewing new reactor applications within 18 months, down from the roughly 30 months the agency itself says is typical today
Whether the applicant chooses Part 50, Part 52, or the new Part 53 track
If you’re tracking the nuclear market professionally, SMRbrief Pro gives you the structured database to go deeper than any single article can, including every design certification docket currently open at the NRC.
Step 3: construction permit, where shovels meet the safety case
Design certification proves a reactor could be built safely somewhere. A construction permit proves it can be built safely at this specific site, with this specific environmental footprint. That means a fresh environmental review, site-specific seismic and flood analysis, and, increasingly, cybersecurity requirements baked in from the start under the NRC’s new 73.110 rule.
Two live examples show how differently this step can play out. Holtec International filed Part 1 of its construction permit application on December 31, 2025, for two “Pioneer” SMR-300 units at its Palisades site in Michigan, using a staged Part 50 filing designed to let construction start as early as possible. It’s a savvy sequencing play: Holtec is restarting the shuttered 800-megawatt Palisades plant first, which re-establishes the site’s environmental and security credentials before the SMR review even begins, according to reporting on Holtec’s licensing strategy. Kairos Power took a more conventional route: the NRC voted to approve construction permits for its two-unit, 70-megawatt-thermal Hermes 2 facility in November 2024, making it, in Kairos’s own words, the first electricity-producing Gen IV plant ever approved for construction in the United States. Kairos broke ground on the project in April 2026.
A construction permit typically requires:
A completed final safety analysis report, site-specific
An environmental impact statement or environmental assessment from NRC staff
Resolution of any contested issues raised during the mandatory hearing process
Confirmed funding, since regulators won’t sign off on a permit for a project that can’t finish paying for its own review
Step 4: the operating license, the last real gate
Getting a construction permit doesn’t mean flipping a switch when the concrete cures. Under the two-step Part 50 process, Kairos and Holtec both still need a separate operating license before either commercial plant can load fuel and generate power. That review checks whether the as-built plant actually matches what regulators approved on paper, plus final testing of safety systems, emergency planning, and operator training and staffing.
This is also the step where timelines slip most often, because as-built discrepancies and commissioning delays are far more common than paperwork problems. Kairos is targeting 2030 for Hermes 2 to start supplying power, under a deal with Google and the Tennessee Valley Authority to deliver 500 megawatts by 2035. That’s a six-year gap between the construction permit landing and power actually hitting the grid, and Hermes 2 is one of the fastest-moving projects in the country. It’s worth sitting with that number before assuming any SMR developer’s public timeline is the real one.
Step 5: the global race to make one approval count twice
Here’s the part most domestic coverage skips: a design approved by the NRC still has to run the gauntlet again in every other country where it wants to build. The UK’s Office for Nuclear Regulation runs its own three-step Generic Design Assessment, and Rolls-Royce SMR’s 470-MWe pressurized water design offers a useful comparison point. It completed GDA Step 2 in July 2024 and entered the detailed Step 3 assessment immediately after, with the full 53-month process expected to wrap up in August 2026, culminating in a Design Acceptance Confirmation from ONR and a separate Statement of Design Acceptability from the Environment Agency.
Multiply that by every country with SMR ambitions and you get a genuinely absurd amount of duplicated work, reviewing the same neutron physics and containment math under a different flag each time. That’s the problem the IAEA’s Nuclear Harmonization and Standardization Initiative is trying to solve. Its regulatory track is working to get national regulators to share reviews and lean on each other’s technical conclusions instead of starting from zero, while keeping final licensing authority with each country. It’s slow, consensus-driven work involving dozens of member states, and it won’t replace national sign-off anytime soon. But for a sector with upwards of 80 designs chasing licenses across 18-plus countries, it might end up mattering as much as any single NRC decision.
So: which step is actually the bottleneck for the project you’re watching, pre-application groundwork, the technical review itself, or the wait for a second country’s regulator to agree? That’s usually the first question worth answering before you trust anyone’s deployment date.