NRC Launches Fresh Licensing Framework for New Reactors

The Nuclear Regulatory Commission (NRC) has published its long-awaited final rule codifying the new 10 CFR Part 53, Risk-Informed, Technology-Inclusive Regulatory Framework for Commercial Nuclear Plants (Part 53). The rule establishes a new optional pathway for the licensing of new—and existing—reactor technologies. It is lauded as “risk-informed,” “performance-based,” and “technology-inclusive.” In other words, it is less prescriptive than the existing licensing frameworks in Parts 50 and 52.

The new rule does not eliminate those pathways; rather, it provides applicants with a far more flexible regulatory framework adaptable to nuclear technologies beyond traditional light water reactors. In practice, this means that project developers will not need to seek specific regulatory exemptions from inapt requirements that were intended for different technologies, and it fully embraces modern, state-of-the-art risk analysis approaches. Ultimately, the rule acknowledges the vast diversity of reactor technologies, sizes, end-users, and deployment scenarios that are being considered in the commercial marketplace while continuing to ensure an equivalent level of radiological safety.

THE PATH TO PART 53

The NRC developed the existing commercial nuclear power regulatory framework mainly for the licensing of light-water reactor technologies. As the regulatory framework for the existing fleet of light-water reactors matured, the NRC continued to refine its regulatory scheme for the licensing of non-light-water reactor technologies and make strides towards the creation of a regulatory framework that is adaptable to advanced reactor technologies (i.e., non-light-water reactors and small modular reactors).

Part 53 is the result of efforts undertaken for decades, including, but not limited to: the NRC’s 1986 Policy Statement on the Regulation of Advanced Nuclear Power Plants; NUREG-1860, Feasibility Study for a Risk-Informed and Performance-Based Regulatory Structure for Future Plant Licensing (2007); and Regulatory Guide (RG) 1.233, Guidance for a Technology-Inclusive, Risk-Informed, and Performance-Based Methodology to Inform the Licensing Basis and Content Of Applications for Licenses, Certifications, and Approvals for Non-Light-Water Reactors (2020) (endorsing NEI 18-04, Rev. 1, Risk-Informed Performance-Based Guidance for Non-Light Water Reactor Licensing Basis Development), known as the Licensing Modernization Project (LMP) approach.

Direction from Congress was a driving force for the rule. Specifically, in 2019 the Nuclear Energy Innovation and Modernization Act (NEIMA) directed the NRC to “complete a rulemaking to establish a technology-inclusive, regulatory framework for optional use by commercial advanced nuclear reactor applicants for new reactor license applications” no later than December 31, 2027.[1] Building on NEIMA, in 2024, the Accelerating Deployment of Versatile, Advanced Nuclear for Clean Energy Act of 2024 (ADVANCE Act),[2] directed the NRC to improve efficiency in the licensing review process, establish an expedited process for reviewing new reactor license applications, and advance regulatory strategies for microreactors.

Most recently, Executive Order 14300, Ordering the Reform of the Nuclear Regulatory Commission directed the NRC to perform a wholesale review of its regulations, including establishing a process for high-volume licensing of microreactors and modular reactors.[3]

Throughout the development of Part 53, the NRC maintained frequent engagement with both nuclear industry stakeholders and the public. Prior to publication of the proposed rule, the NRC staff held numerous public meetings to discuss proposed rule language and draft guidance, and the NRC’s Advisory Committee on Reactor Safeguards (ACRS) held over a dozen public meetings on Part 53 developments. The rulemaking process involved an extended comment period, from October 2024 to February 2025, resulting in more than 150 written comments on the proposed rule and other stakeholder input provided during public meetings.

WHO CAN PURSUE PART 53 LICENSING PATHWAYS?

While NRC’s development of Part 53 was driven by the need for a risk-informed regulatory framework that is flexible and adaptable to advanced reactors, the scope of Part 53 remains broadly applicable to “commercial nuclear plants,” rather than a more limited subset of advanced reactors. The Part 53 framework is particularly suitable for non-light water reactors and other new technologies that incorporate inherent safety features in design and operation and can implement the risk-informed and performance-based features of Part 53.

Part 53 may also be advantageous to entities pursuing factory-built reactors, as the new rule contemplates an integrated production model for manufacturing reactors, fuel loading, and transport to the place of operation. Additionally, Part 53 includes new and exclusive regulatory provisions that allow load following, which are applicable to nuclear reactor technologies designed for safe commercial operation at varying levels of power output. The Part 53 regulatory framework, however, does not apply to nuclear fusion machines, which are being addressed in a separate rulemaking process.

KEY FEATURES

The Part 53 framework is comprehensive. Below, we identify some of the most noteworthy Part 53 regulatory approaches.

Multiple Licensing Pathways

Like 10 CFR Part 52, Part 53 provides a wide range of licensing options for nuclear power developers at different stages. The licensing framework includes limited work authorizations (LWAs), early site permits (ESPs), standard design approvals (SDAs), standard design certifications (SDCs), manufacturing licenses (MLs), construction permits (CPs), operating licenses (OLs), and combined licenses (COLs).[4]

Separating Requirements for Safety-Related (SR) Structures, Systems, and Components (SSCs) and Non-Safety-Related but Safety-Significant (NSRSS) SSCs

Part 53 introduces the concept of NSRSS, which refers to SSCs that are not relied upon to meet design-basis accident (DBA) scenarios but are relied upon as part of defense-in-depth measures or other risk-significant functions. Part 53 affords flexibility in the design parameters applicable to NSRSS SSCs through high-level safety criteria. The Part 53 regulatory framework distinguishes SR SSCs and NSRSS SSCs and bundles both sets of SSCs through the regulations as applicable.[5]

Scope of Construction

The definition of “construction” in Part 53 includes on-site activities that are applicable to SRSSCs and NSRSS SSCs with special treatment in design or installation; SSCs required for security purposes under 10 CFR Part 73; and emergency on-site facilities pursuant to § 53.855. Special treatment requirements include quality assurance, design criteria, and programmatic controls.[6] This limited scope allows reactor developers to pursue a commercial-grade construction approach for non-safety-significant and NSRSS SSCs that do not require special treatment while remaining subject to NRC regulatory oversight during the operations phase.

Risk-Informed Safety Criteria

Safety criteria for the design and analysis of nuclear power reactors incorporate risk-based components. Broadly, the design-basis accident (DBA) requirements include a total effective dose equivalent limit of 25 rem for two hours at any point in the exclusion area or at any point on the outer boundary of the low population zone.[7] Specifically, for licensing basis events (LBEs) other than DBAs, Part 53 requires applicants to demonstrate that design features and programmatic controls provide defense-in-depth and an appropriate level of safety, based on comprehensive risk metrics that are acceptable to the NRC.[8]

The regulations also provide that such LBEs must address “risk-informed combinations of malfunctions of plant SSCs, human errors, facility hazards, and the effects of external hazards,” thus tailoring the scope of LBEs and corresponding analyses to the risk objectives associated with any given type of reactor technology.[9]

Defense-in-Depth

Part 53 affords applicants flexibility in the demonstration of compliance with high-level safety criteria. Part 53 does not allow the applicant to rely exclusively upon a single engineered design feature, human action, or programmatic control to address LBEs other than design-basis accidents. The applicant, therefore, does not need to accommodate single failures to ensure defense-in-depth where other measures can be accounted for for this purpose, including crediting inherent characteristics of the reactor design.[10]

Performance-Based Considerations

Part 53 allows for performance-based demonstrations of how a reactor design or plant operations meet associated risk objectives. For example, Part 53 allows:

• Implementation of functional design criteria, including a functional containment approach;[11]
• Right-sizing staff levels for a reactor technology;[12] and
• Credit for self-reliant mitigation in operations.[13]

Elimination of Certain Prescriptive Criteria

Consistent with Part 53’s performance-based and functional design criteria approach, the Part 53 framework eliminates certain prescriptive licensing criteria, such as the following:

• General design criteria: Part 53 excludes the general design criteria listed under Appendix A to 10 CFR Part 50 and instead requires applicants to perform an assessment of potential failures, susceptibility to internal and external hazards, and other contributing factors that could pose a risk to public health and safety for their reactor design[14]
• Aircraft impact assessment: Part 53 does not include the specific aircraft impact assessment requirements that the NRC is sunsetting in Part 50; rather, the applicant performs broader hazard evaluation analyses that include a spectrum of unplanned events[15]

Generally Licensed Reactor Operators

The new regulatory framework under Part 53 accounts for new technologies with self-reliant mitigation, allowing generally licensed reactor operators (GLROs), subject to specific training, examination, and proficiency requirements, to manipulate controls at such facilities, including from remote locations; however, GLROs are supplemental positions and are not expected to have significant safety roles.[16]

Load Following

Under a load-following approach, power plants adjust their output in real-time to match electricity demand. This is particularly advantageous for advanced reactors, as traditional light water reactors are less suitable for load following due to technical specifications’ restrictions and procedural steps required to fluctuate between power levels. Part 53 enables new reactors to implement load-following operations, subject to protection, control, or operator measures that can immediately refuse demands that may challenge safe reactor operation or plant equipment conditions.[17]

Technology-Inclusive Security Requirements

The new Part 53 framework allows applicants to meet the regulatory requirements for physical and digital security through the existing prescriptive criteria[18] or through a new performance-based approach for physical security and a consequence-based approach for cybersecurity under Part 73.[19] Part 53 also allows possession of unirradiated fuel onsite in accordance with the protection requirements for special nuclear material of moderate and low strategic significance under § 73.67 until initial fuel loading of the reactor.

• The physical protection requirements under § 73.100 are graded based on the achievability of target sets and reliance on active measures.
• For cybersecurity, § 73.110 requires license applicants to demonstrate protection against cyberattacks commensurate with the risk level for their reactor technology and potential consequences of such attacks for that technology.

Alternate Approach to Access Authorization

The new Part 53 framework provides an alternative to existing access authorization requirements,[20] using an approach commensurate with the risks associated with a given reactor technology, like § 73.100.[21] This alternate approach still requires individuals subject to the access authorization program to complete background investigations, undergo behavioral observation, and disclose certain legal actions.

Flexible Testing of Fitness-for-Duty Requirements

The final rule includes a new 10 CFR Part 26, Subpart M, defining the regulatory requirements applicable to fitness-for-duty demonstration during construction, operations, and decommissioning. Part 26, Subpart M, accounts for facilities that may have a limited staff or be located in remote locations by providing a flexible approach to drug and alcohol testing that incorporates a variety of biological specimens and allows remote behavioral observation.[22]

Financial Qualification Requirements

Part 53 loosens the financial qualification requirements applicable to estimated construction costs, related fuel cycle costs, and operation costs through the license term.[23] The NRC adopted the standard long used for Part 70 applicants, which allows applicants without fully committed financing at the application stage to rely on a license condition (requiring a later financial demonstration) to satisfy the requirements for receiving a license or permit. The financial assurance requirements for decommissioning remain largely unchanged.[24]

Factory Loading of Fuel into Manufactured Reactors

In addition to allowing factory manufacturing of new reactors, Part 53 provides the flexibility to load fuel into newly manufactured reactors and transport the loaded reactor to another location for operation, subject to the implementation of criticality prevention measures.[25]

Alternative Siting Criteria

Part 53 provides an alternative to the current siting criteria in Part 100; the new criteria require identification of site characteristics, including geology, hydrology, meteorology, and other information necessary to meet applicable design and analysis requirements. Part 53 retains a preference for siting reactors in areas of low population density but provides applicants an option to justify siting a reactor in areas with higher population density, subject to consideration of societal risks and benefits.[26]

Broad Approach to Codes and Standards

Part 53 allows the use of generally accepted codes and standards for in-service inspection (ISI) and in-service testing (IST), consistent with the safety significance of the applicable SSC. (§ 53.880) The existing regulatory framework for ISI and IST programs under Part 50 is less flexible—it is based on specific codes and standards from the American Society of Mechanical Engineers (ASME).[27]

Unlike Part 50, Part 53 does not incorporate by reference specific codes and standards. Instead, Part 53 provides new license applicants with the flexibility to develop ISI and IST programs complementary to the reactor design and its inherent uncertainties and allows the use of commercial codes and standards beyond those specific to the nuclear industry, depending on the safety significance of the corresponding SSC.

NEXT STEPS IN IMPLEMENTATION

Part 53 becomes effective on April 29, 2026. Concurrently with the release of Part 53, the NRC is issuing guidance for its implementation, including

• RG 1.254, Technology-Inclusive Identification of Licensing Events for Commercial Nuclear Plants;
• RG 5.95, Access Authorization Program for Commercial Nuclear Plants;
• RG 5.96, Establishing Cybersecurity Programs for Commercial Nuclear Plants Licensed under 10 CFR Part 53;
• RG 5.97, Guidance for Technology-Inclusive Requirements for Physical Protection of Licensed Activities at Commercial Nuclear Plants;
• RG 5.99, Fatigue Management for Nuclear Power Plant Personnel at Commercial Nuclear Plants Licensed under 10 CFR Part 53;
• DRO-ISG-2023-01, Operator Licensing Programs;
• DRO-ISG-2023-02, Interim Staff Guidance Augmenting NUREG-1791, ‘Guidance for Assessing Exemption Requests from the Nuclear Power Plant Licensed Operator Staffing Requirements Specified in 10 CFR 50.54(m),’ for Licensing Commercial Nuclear Plants under 10 CFR Part 53; and
• DRO-ISG-2023-03, Development of Scalable Human Factors Engineering Review Plans.

Although Part 53 codifies a comprehensive, risk-informed, performance-based, technology-inclusive licensing framework for the first time, many of its core concepts are rooted in approaches that have been used before and are well understood. For example, many of its processes are derived from the existing processes under Part 52 (i.e., LWAs, SDAs, CPs, OLs, COLS, etc.).

Likewise, PRA has been used, on a voluntary basis, across the nuclear industry for many years. And various applications using the LMP approach—which lies at the heart of Part 53—already have been approved or are currently under review by the NRC. A key benefit of Part 53 is that specific regulatory exemptions are no longer required to pursue these approaches.

HOW WE CAN HELP

Our lawyers stand ready to advise clients on new nuclear project needs, including navigating NRC’s revisions to the regulatory framework for commercial nuclear power reactors and new licensing pathways. We are closely monitoring the evolution of the NRC’s licensing and oversight framework, and our nuclear team stands ready to assist with questions on government approval pathways and acceleration of commercial nuclear deployments.