Nuclear Regulator Opens Faster Licensing Path for Previously Tested Reactor Designs

The Nuclear Regulatory Commission will allow commercial reactor applicants to cite prior Department of Energy or Department of War authorizations as evidence that their designs can accomplish their safety functions, under a final rule published in the Federal Register on Monday, October 26, 2026. The rule, issued under docket NRC–2025–1503 and document 2026–21801, amends 10 CFR 50.43 and 10 CFR 53.440 and takes effect on November 25, 2026.

The measure implements section 5(d) of Executive Order 14300, “Ordering the Reform of the Nuclear Regulatory Commission,” signed by President Donald J. Trump on May 23, 2025 (90 FR 22587). That provision directed the agency to build an expedited pathway for reactor designs that the Department of Energy or the Department of War have already tested and shown able to function safely, and to concentrate its own review on risks arising from new applications rather than revisiting risks already addressed in the federal authorization process.

The proposal behind the rule was published on April 2, 2026 (91 FR 16584) with a 30-day comment window that closed on May 4, 2026. The commission held a public meeting on April 14, 2026, and received 136 unique comment submissions before finalizing the text.

Two licensing frameworks, one added option

Under 10 CFR 50.43(e), applicants for newer reactor designs already had two ways to show how simplified, inherent, passive or otherwise innovative features accomplish safety functions. The final rule adds a third route, codified at 10 CFR 50.43(f), permitting an applicant to reference information from a prior Department of Energy or Department of War authorization; the pathway covers the part 50 and part 52 licensing frameworks.

For the risk-informed, technology-inclusive framework, the commission revised 10 CFR 53.440(a)(1) so that the bases for demonstrating that design features meet the criteria of 10 CFR 53.410 and 10 CFR 53.420 may include information from a previously authorized and tested utilization facility. A similar provision appears in a separate proposed rule on microreactors and other reactors with comparable risk profiles (91 FR 23628; May 1, 2026), which would apply to a proposed 10 CFR part 57.

What applicants must still prove

• Identify how attributes of the prior authorization satisfy NRC regulations, including paragraph (e) of 10 CFR 50.43.
• Address changes to the design, its functionality, associated hazards, siting information or underlying safety assumptions.
• Justify the applicability and relevance of the referenced information and close any remaining gaps for full compliance.

The commission stated that nothing in the rule delegates to the Department of Energy, the Department of War or any other agency its authority to evaluate a licensing request, and that it retains independent review. Where an applicant relies on prior federal testing, the agency said it may tailor the focus and depth of its own review.

Comment record and safety-standard concerns

Several commenters argued that the proposed 10 CFR 50.43(e)(3) would set a lower safety bar than existing provisions. In response, the commission moved that language to a new 10 CFR 50.43(f) to reaffirm that the safety standard in paragraph (e) is unchanged and that the new pathway is one option among several.

The pathways will be supported by draft interim staff guidance DANU–ISG–2026–XX, published for comment on April 17, 2026 (91 FR 20717), which is intended to facilitate review of future applications, including advanced designs that may not use light-water technology.

Costs, guidance and legal housekeeping

The commission said it does not expect to repeat technical reviews already performed by the Department of Energy or the Department of War where those reviews cover the same scope, and that applications under the new provisions should not require more review work than existing requirements. It declined to quantify the savings, citing dependence on how many applications reference prior authorizations, but anticipated an initial learning curve followed by greater savings for both the agency and applicants.

The rule was certified as having no significant economic impact on a substantial number of small entities, and the commission invoked the categorical exclusion at 10 CFR 51.22(a)(1) under the National Environmental Policy Act. The Office of Information and Regulatory Affairs deemed it a significant regulatory action under section 3(f) of Executive Order 12866 but not economically significant, and the agency classified it as deregulatory under Executive Order 14192; it inserted no conditional sunset dates under Executive Order 14270. New implementation guidance will be announced under docket NRC–2026–0760. The rule was signed on October 22, 2026 by Jody Martin, Secretary of the Commission.

For developers of advanced and demonstration reactors, the change converts years of federal test data into usable licensing evidence, potentially shortening the review path for the first commercial plants built on designs already exercised by the Department of Energy or the Department of War. The commission’s insistence on case-by-case justification means the benefit will depend on how closely each prior authorization matches the commercial configuration an applicant proposes.

Source: Federal Register, Vol. 91, No. 205, October 26, 2026, Rules and Regulations, p. 67195 (official reference: 2026–21801).