NRC finalizes new licensing framework for advanced reactors and proposes streamlined path for DOE- and DOW-authorized designs

A new optional licensing framework: Finalization of Part 53

10 CFR Part 53 is the first new NRC reactor licensing framework since the adoption of Part 52 in 1989 and represents the most substantial re-thinking of reactor licensing since the original Part 50 regulations were issued in the 1950s.

Scope: Rather than limiting the scope of Part 53 to advanced reactors, the NRC has framed the regulation as applicable to commercial nuclear plants more broadly. The Commission explained that this formulation avoids implying enhanced safety where technological improvements may instead relate to cost, deployment model, or operational flexibility, and ensures the framework can accommodate a wide variety of reactor designs and uses.

Part 53 is optional. Applicants may continue to pursue licensing under Parts 50 or 52 where appropriate.

Key features: Part 53 reorganizes the licensing framework around three core regulatory concepts: risk-informed regulation; performance-based requirements; and technology inclusivity. Within that structure, the rule introduces flexibility in areas that have historically constrained non-light-water and smaller reactors, including siting considerations, staffing models, physical security, emergency planning, use of industry codes and standards, and lifecycle licensing strategies.

Building a rigorous safety case remains central: While Part 53 provides increased flexibility, the NRC has made clear that this flexibility is paired with heightened expectations for analytical rigour. Applicants will be expected to present a defensible safety case supported by well-developed risk metrics, maintain risk analyses over the life of the facility, and robust change-control processes to preserve approved safety margins.

In this respect, Part 53 represents a shifting emphasis away from prescriptive design rules toward a more holistic evaluation of safety performance.

Proposed rule to leverage DOE and DOW reactor authorizations

DOE and DOW have statutory authority, in limited contexts, to authorize the construction and operation of certain reactors outside the NRC licensing regime, particularly for research, demonstration, and national security purposes. Recent executive directives such as Executive Order 14299 and Executive Order 14300 have encouraged use of those authorities to accelerate reactor development.

The NRC's proposed rule seeks to address the transition point: how, and to what extent, work performed under DOE or DOW authorization can be credited in subsequent NRC licensing reviews for commercial use.

Effect of the Proposed Rule: The proposal would amend 10 CFR 50.43, applicable to licensing under Parts 50 and 52, and 10 CFR 53.440, governing design requirements under the new Part 53 framework. Under the proposed amendments, an applicant could reference a prior DOE or DOW authorization—and associated testing and demonstration—to support that a reactor design can perform its required safety functions, provided the applicant demonstrates how that prior work satisfies NRC regulatory requirements.

Limits on reliance: The NRC emphasized that prior DOE or DOW authorization would not substitute for NRC review. Applicants would remain responsible for mapping DOE/DOW findings to NRC safety requirements; addressing differences between the demonstrated design and the proposed commercial configuration; and evaluating site-specific and operational factors not previously considered.

The proposal is intended to reduce duplicative review, not to diminish NRC oversight. The NRC has indicated that additional guidance will be issued to support implementation of this pathway, though that guidance is not part of the current proposal.

What this means for reactor developers and investors

These two rulemakings together provide new strategic options for reactor developers:

Greater licensing optionality: Developers can evaluate whether Part 53's risk-informed framework better aligns with their technology and deployment model than existing pathways.

Earlier value from demonstration projects: Where a design is authorized and tested under DOE or DOW authority, the proposed rule offers a potential mechanism to carry aspects of that work forward into NRC licensing.

Advanced planning is critical: The ability to benefit from either Part 53 or the DOE/DOW leveraging pathway will depend heavily on early alignment of design assumptions, safety analyses, and documentation with NRC expectations.

Stakeholders considering use of the proposed DOE/DOW pathway may wish to engage with the NRC during the comment period to help shape how the agency defines the scope and limits of acceptable reliance.

Closing

Hogan Lovells will continue to monitor developments in advanced reactor licensing and federal reactor authorization authorities. We regularly advise reactor developers, investors, utilities, and technology partners on navigating NRC licensing strategy, inter-agency coordination, and regulatory risk across the project lifecycle.

Authored by Dan Stenger, Stewart Forbes, and Érida Tosini-Corea.