NRC Finalizes a New Risk-Informed, Technology-Inclusive Regulatory Framework for Advanced Reactors

Key Takeaways

• On March 25, 2026, the U.S. Nuclear Regulatory Commission (NRC) approved a final rule establishing a new risk-informed, performance-based, and technology-inclusive regulatory framework for licensing commercial nuclear plants.
• This is the first new set of regulations to address initial reactor licensing since 1989, when the NRC created Part 52, and the first major update to reactor licensing standards since 1956, when the Atomic Energy Commission issued Part 50.
• Part 53 is an optional alternative to the existing frameworks in 10 CFR Parts 50 and 52, designed to accommodate advanced reactor technologies—including non-light-water reactors, small modular reactors (SMRs), and microreactors—that do not fit neatly within the current light-water-cooled reactor (LWR)-focused regulatory structure.
• The rule replaces prescriptive, technology-specific requirements with high-level performance criteria that allow applicants to use probabilistic risk assessments (PRAs) and other systematic risk evaluations to demonstrate compliance, offering significant design and operational flexibility.
• Alongside Part 53, the NRC finalized a separate rule updating its categorical exclusions from environmental review under 10 CFR Part 51, streamlining environmental assessment processes for routine licensing actions.

Introduction

On March 25, 2026, the NRC announced the issuance of two final rules of significant consequence to the nuclear industry. The first rule adds a new Part 53 to Title 10 of the Code of Federal Regulations, establishing a risk-informed, performance-based, and technology-inclusive regulatory framework for licensing and regulating commercial nuclear plants. The second amends the NRC's categorical exclusion regulations under 10 CFR Part 51, streamlining environmental review processes for routine licensing, regulatory, and administrative actions that do not significantly affect the quality of the human environment.

The Part 53 rulemaking has been years in the making. Congress laid the groundwork with the passage of the Nuclear Energy Innovation and Modernization Act in January 2019, which 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.” Congress reinforced this direction with the ADVANCE Act of 2024, which further defined "advanced nuclear reactor" to include "a nuclear fission reactor or fusion machine . . . with significant improvements compared to commercial nuclear reactors under construction." 

These legislative initiatives have been accompanied by an increasingly robust suite of executive actions. The Trump administration signed four Executive Orders in May 2025, three of which seek to expedite approval processes for permitting new nuclear reactors. The orders are aimed at reinvigorating the nuclear power sector, through collectively seeking to harness the resources of executive agencies to promote advanced nuclear energy in support of national security objectives, including powering AI computing infrastructure.[1]

The U.S. Department of Energy (DOE) has actively advanced the administration’s priorities through solicitations to co-locate large AI data center complexes and new generation sources on federal lands, with an emphasis on using existing federal nuclear sites. This initiative includes launching the Nuclear Reactor Pilot Program with the selection of 11 advanced reactor projects to move their technologies towards deployment,[2] supporting two teams to develop and construct the first Gen III+ small modular reactor (Gen III+ SMR) plants, and announcing a $2.7 billion investment in strengthening domestic uranium enrichment capabilities over the next decade. On the industry side, hyperscalers have executed multibillion-dollar offtake agreements and power purchase agreements for nuclear energy, underscoring the private sector's growing appetite for reliable, clean baseload power to fuel data centers and AI operations.[3]

Against this backdrop, the finalization of Part 53 represents a milestone in the federal government's effort to modernize the regulatory infrastructure for nuclear energy and clear the path for the next generation of reactor technologies.[4]

Overview: Technologies and Scope

Part 53 is expressly designed to be technology-inclusive, unlike the existing regulatory frameworks that were primarily developed to address light-water-cooled reactors, which make up the U.S. commercial operating fleet. While the NRC can license non-LWR technologies under the existing framework through exemptions and regulatory flexibilities, the process is ill-suited to the emerging generation of reactor technologies.

Part 53 uses the broader term "commercial nuclear plant," rather than "advanced nuclear reactor," to define its scope. The NRC determined that the Nuclear Energy Innovation and Modernization Act (NEIMA) definition of "advanced nuclear reactor," while broad, did not define "significant improvements" with enough specificity for regulatory purposes and that the descriptor "advanced" could be misconstrued as implying enhanced safety rather than general technological improvement. As a result, the new framework is available for any reactor technology, size, and end use. This includes, but is not limited to, high-temperature gas-cooled reactors, liquid metal reactors, molten salt reactors, small modular reactors, and microreactors, as well as innovative LWR designs.

Importantly, the rule is optional, so applicants may continue to seek licenses under Parts 50 or 52. 

Summary of Key Provisions

Subpart B: Technology-Inclusive Safety Requirements

Subpart B establishes high-level, technology-neutral safety standards that serve as the basis for the Part 53 framework. Subpart B also sets safety criteria for accidents and licensing-basis events (LBEs), requires risk-based performance objectives, emphasizes limiting radioactive releases, and mandates defense-in-depth measures with flexible safety margins.

Subpart C: Design and Analysis Requirements

Subpart C requires applicants to provide design features and supporting analyses to demonstrate that the performance standards in Subpart B can be satisfied. A central feature of Part 53 is the requirement that applicants perform a probabilistic risk assessment, other systematic risk evaluations, or a combination thereof to identify potential failures, assess risks, and support safety demonstrations. This represents a departure from the traditional deterministic approach in Parts 50 and 52, where design-basis events were analyzed using bounding assessments and standard design rules such as single failure assumptions.

Structures, systems, and components (SSCs) must be classified according to their safety significance into three categories: safety-related (SR), non-safety-related but safety-significant, and non-safety-significant. Special treatment requirements are then tailored based on the SSC's classification and its role in preventing or mitigating LBEs. The NRC concluded that the comprehensive, full-spectrum risk assessments required under Part 53 sufficiently address the potential consequences of beyond-design-basis events, including large fires and explosions, making a separate aircraft impact assessment unnecessary.

Subpart D: Siting Requirements

Part 53 maintains the NRC's long-standing preference for siting reactors in areas of low population density but introduces an important new option: Applicants may propose sites in areas of higher population density if they can demonstrate that the societal benefits of the specific site outweigh the additional societal risks. This flexibility could be significant for commercial nuclear plants intended to serve data centers, industrial facilities, or other loads located near population centers.

Subpart E: Construction and Manufacturing Requirements

The construction-related provisions in Part 53 largely reflect current requirements in Part 50 without fundamental changes, adapted to be technology-neutral. A notable addition is the expanded treatment of manufacturing licenses, including provisions that would allow the factory loading of fuel into manufactured reactors with appropriate features to prevent criticality, enabling transport to another location for operation.

Subpart F: Requirements for Operation

Subpart F addresses staffing, training, personnel qualifications, and human factors engineering in a risk-informed, technology-inclusive, and performance-based manner. A significant innovation is the concept of "self-reliant-mitigation facilities"—commercial nuclear plants whose designs demonstrate compliance with safety performance criteria without reliance on human action for credited event mitigation. For such facilities, Part 53 introduces "generally licensed reactor operators" (GLROs), which replace the traditionally individually licensed operators required under Part 55. This provides flexibility for staffing levels and the types and locations of staffing needed.

Technical specifications under Part 53 are generally similar to those under Part 50 but do not carry over safety limits or associated limiting safety system settings, reflecting the alternative, more mechanistic approaches to evaluating source terms available under Part 53.

Subpart G: Decommissioning Requirements

Subpart G provides decommissioning requirements, including that decommissioning must be completed within 60 years of permanent cessation of operations. The NRC is currently pursuing a separate rulemaking on decommissioning improvements and has indicated it will consider revisions to Part 53 to align the two efforts.

Subpart H: Licenses, Certifications, and Approvals

Part 53 carries over and consolidates all existing licensing, certification, and approval processes currently available under Parts 50 and 52, including construction permits, operating licenses, combined licenses, early site permits, standard design approvals, standard design certifications, and manufacturing licenses. The rule also provides that a first-of-a-kind reactor may be licensed for operation prior to seeking generic approval or certification of its standard design—a flexibility not available under the existing framework. 

The financial qualification standard under Part 53 differs from Parts 50 and 52. Part 53 replaces the existing requirement to demonstrate that the applicant "possesses or has reasonable assurance of obtaining" necessary funds with a standard that the applicant "appears to be financially qualified."

Subpart I: Maintaining and Revising Licensing-Basis Information

Subpart I establishes a risk-informed process for evaluating changes to a facility and determining whether NRC approval is required. Section 53.1550 provides the equivalent of Section 50.59 but reflects the central role of PRAs in Part 53, including criteria tied to changes in risk-significant event sequences, changes in comprehensive risk metrics, changes in SSC safety classification, and reductions in defense in depth.

Environmental Review

The companion final rule on categorical exclusions amends 10 CFR Part 51 to streamline environmental review by reorganizing and adding categorical exclusions for licensing, regulatory, and administrative actions that do not significantly affect the environment. Key changes include eliminating the "no significant hazards consideration" criterion as a threshold for categorical exclusion; replacing the "no significant construction impact" criterion with a requirement that "any ground disturbance is limited to previously disturbed areas;" and adding new categorical exclusions for actions such as certificates of compliance for spent fuel storage cask designs and changes to fire protection, emergency planning, physical security, cybersecurity, or quality assurance requirements. 

Security

Part 53 includes a new technology-inclusive, consequence-based approach to physical security, cybersecurity, and access authorization. The physical security framework uses performance objectives rather than the prescriptive requirements, giving licensees flexibility in how they demonstrate compliance. Notably, licensees may rely on law enforcement or other offsite armed responders—rather than exclusively onsite armed responders—to fulfill interdiction and neutralization capabilities, a significant departure from the current framework. The cybersecurity provisions implement a graded approach based on the potential consequences of a cyberattack, requiring licensees to demonstrate protection commensurate with the risk presented.

Implications for Developers

The finalization of Part 53 represents a meaningful step forward for the nuclear industry, particularly for developers of advanced reactor technologies that have struggled to fit within the existing LWR-focused regulatory paradigm. Some practical implications include:

• The technology-inclusive and performance-based nature of Part 53 should reduce the need for exemptions from prescriptive requirements that were designed for LWR technology, which has historically added time and cost to the licensing process.
• However, because the framework relies on high-level performance criteria rather than prescriptive rules, the first applicants under Part 53 will bear the burden of demonstrating through their analyses—particularly PRAs—that their designs meet the safety criteria, without the benefit of well-trodden regulatory precedent.
• The introduction of GLROs and reduced staffing requirements for self-reliant-mitigation facilities could meaningfully reduce operating costs for certain advanced reactor designs, particularly SMRs and microreactors intended for remote or co-located deployment.
• Flexible siting criteria could open new deployment opportunities, particularly for reactors intended to serve industrial loads, data centers, or grid-constrained urban areas.
• Expanded manufacturing license provisions, including factory fuel loading, could accelerate deployment timelines for modular reactor designs by enabling significant factory fabrication and pre-fueling before transport to the operating site.
• The companion categorical exclusions rule will help streamline environmental review for routine licensing actions, but applicants for construction permits, operating licenses, and combined licenses should still anticipate full environmental review under the National Environmental Policy Act, including potentially an environmental impact statement depending on the circumstances.

Potential Issues

The Commission's Staff Requirements Memorandum (SRM) directs NRC staff to provide an information paper by late 2027 outlining plans for alternative licensing approaches. Key companion guidance documents—including those on codes, standards, maintenance, inspection, risk-informed principles, and security—are still in development, contributing to uncertainty regarding Part 53’s practical implementation.

The SRM also calls for reviews of the 15-year design approval validity, updates to site suitability guidance, and revisions related to "as low as reasonably achievable" and effluent requirements. Staff are instructed to prepare guidance on security event dose calculations and to address the removal of aircraft impact assessment requirements. As the NRC notes in its announcement of the rule, Part 53 also sets the stage for several upcoming rules in the next few months under Executive Order 14300.[5] Developers should be aware of ongoing challenges, including permitting, construction, and supply chain risks, especially for first-of-a-kind nuclear projects.

Conclusion

The NRC's finalization of 10 CFR Part 53 marks a significant milestone in the evolution of U.S. nuclear regulation. For the first time, the regulatory framework offers a truly technology-inclusive, risk-informed, and performance-based pathway for licensing the next generation of commercial nuclear plants—from large-scale advanced reactors to factory-built SMRs and microreactors. Paired with the streamlined categorical exclusion rule, strong bipartisan federal support, and growing private sector demand for clean, reliable baseload energy, Part 53 positions the nuclear industry for a period of potential transformation.

The practical realization of Part 53's promise will depend on the development of robust companion guidance, the willingness of applicants to pioneer first-of-a-kind licensing applications under the new framework, and the ability of the NRC to review those applications in a timely manner. Developers, investors, and potential offtakers should begin assessing how Part 53 may benefit their projects now, while remaining attentive to ongoing regulatory developments.

Endnotes

[1] EO 14154, Unleashing American Energy. 90 Fed. Reg. 8353 (Jan. 20, 2025); EO 14156, Declaring a National Energy Emergency, 90 Fed. Reg. 8433 (Jan. 20, 2025); EO 14300, Ordering the Reform of the Nuclear Regulatory Commission (May 23, 2025); EO 14302, Reinvigorating the Nuclear Industrial Base (May 23, 2025). More detail regarding these Executive Orders can be found in our prior Update.

[2] Under this pilot, DOE will work with industry with the goal to construct, operate, and achieve criticality of at least three test reactors using the DOE authorization process by July 4, 2026.

[3] For more information on some of the deals reached by hyperscalers, see our earlier Update.

[4] The final rule also included 10 CFR Part 26, “Fitness for Duty Programs,” developed from existing requirements in Subpart K, “FFD Programs for Construction,” of Part 26 and a new security framework in 10 CFR Part 73, “Physical Protection of Plants and Materials,” that includes requirements for protection of licensed activities at commercial nuclear plants. 

[5] The first of these proposed rules, published on April 2, 2026, creates a new licensing pathway that would allow commercial reactor applicants to reference prior U.S. Department of Energy or Department of Defense authorizations as a basis for demonstrating the safety of their designs.