NRC Final Rule Lets Reactor Developers Use Energy and War Department Test Data in License Applications

The Nuclear Regulatory Commission finalized a rule on October 22, 2026, that lets companies applying for a commercial reactor license rely on test data and analyses from reactors already authorized by the Department of Energy or the Department of War. The NRC calls it the first major change to its reactor rules finalized under Executive Order 14300.

The rule amends 10 CFR Parts 50 and 53, the two rulebooks a developer can license a power reactor under. It takes effect 30 days after it’s published in the Federal Register, which the NRC expected the week of October 26. The proposal came out on April 2, and the agency received 136 unique comment submissions.

Photo: Nuclear Regulatory Commission, public domain via Wikimedia Commons

What changes for an applicant

Before a commercial reactor of a new design gets a license, the developer has to show the NRC that its safety features work, through testing, analysis or operating experience. The new rule says that evidence can come from a federal demonstration. A new paragraph in Part 50, Section 50.43(f), lets an application draw on information from a reactor previously authorized and tested by DOE or the War Department. A matching change to Section 53.440(a)(1) does the same under Part 53, the newer framework for advanced reactors that the NRC finalized earlier this year.

The rule doesn’t create a separate licensing track, and it doesn’t hand any NRC function to the other departments. Applicants still have to show they meet every NRC requirement. They also have to spell out how the demonstration reactor differs from the commercial one, in design, site or hazards, wherever those differences could affect safety. The final rule text says nothing in it lets the NRC skip an independent review.

The comments changed the wording more than the substance. In response, the NRC clarified that applicants stay responsible for meeting all requirements and added examples of information that can support an application. It didn’t adopt a presumption that DOE or War Department safety conclusions are good enough for similar designs. The degree of credit will be decided case by case.

Why the federal test reactors matter now

The rule matters because there are now federal test reactors to draw on. The President’s May 2025 orders set a goal of three advanced reactors reaching criticality under DOE authorization by July 4, 2026. Four did, at Idaho National Laboratory and in Utah, and a fifth, Oklo’s isotope test reactor in Texas, followed in August. All of these were low-power or zero-power tests. Criticality proves the reactor physics works. It says little about how a plant performs over 40 years of producing electricity.

On the military side, the Army is running its Janus program for microreactors at bases. In August it picked five developers for sites including Fort Bragg and Fort Drum, and plans to commit up to $2.2 billion over fiscal 2027 to 2031. The Army’s own regulatory office will authorize those reactors. That authorization doesn’t replace an NRC license for commercial use, which is the gap this rule is meant to narrow.

The question for developers is how much work the federal data actually saves. The NRC has acknowledged that short federal demonstrations may not settle questions that matter for a commercial plant, like how materials age, how components wear and how fuel holds up over time. A test reactor that ran for weeks at low power won’t answer those. A developer will still have to.

The clock on the wider overhaul

Executive Order 14300, signed May 23, 2025, ordered a wholesale revision of NRC regulations. It set nine months for proposed rules and 18 months for final rules and guidance, which runs out around November 23, 2026. It also told the NRC to set a deadline of no more than 18 months for a final decision on an application to build and run a new reactor. Section 5(d) asked for the expedited pathway for DOE- and Defense-tested designs that this rule provides.

So this is one finished piece of a larger job with about a month left on the order’s timeline. The NRC has other rule changes still in progress, including a September proposal that would end the 15-year expiry on future standard design approvals. Chairman Ho K. Nieh said the new rule “delivers the EO 14300 vision for an expedited path from DOE and DOW projects to NRC commercial licensing.”

The same day, the NRC and the Federal Energy Regulatory Commission held a joint meeting at NRC headquarters on grid reliability, rising electricity demand, existing and new nuclear plants, and cybersecurity. The two regulators have met this way for about two decades. The demand pressure they discussed is the reason both DOE’s lending and the NRC’s rulebook are being pushed to move faster.