NRC Proposes Part 57 Framework for Microreactor Licensing

Consistent with this deployment model, Part 57 would allow companies to submit a single joint application covering a construction permit (CP) and any number of operating licenses (OL) for reactors of essentially the same design at one or more sites or within designated geographic areas, rather than treating each reactor as a separate licensing exercise. The initial application may also incorporate a manufacturing license (authorizing fabrication, fueling and testing at a factory), a standard design approval and provisions for regulatory finality over plant designs and substantially complete, standardized operational programs. These elements could be reused in subsequent deployments of reactors that conform to previously approved applications.

Part 57 is structured around the premise that micro and other low-consequence reactors may be deployed differently than traditional nuclear plants, based on their lower risk of radiological consequences. The proposal is part of a broader effort to modernize the agency’s regulatory approach and facilitate the deployment of advanced nuclear technologies, including the recent Part 53 final rule that created an alternative regulatory framework for licensing commercial nuclear plants. Part 57 would not replace Parts 50, 52 or 53. Instead, it would provide an additional pathway for qualifying lower-consequence designs, combining elements of the NRC’s non-power reactor licensing approach with concepts from Parts 52 and 53 in a framework tailored to high-volume deployment.

Part 57 implements Congressional and executive direction, including the Accelerating Deployment of Versatile, Advanced Nuclear for Clean Energy (ADVANCE) Act of 2024 and Executive Order 14300, which call for more efficient and scalable licensing pathways for advanced reactors. In contrast to existing frameworks like Part 50 and Part 52, which were developed primarily for large light water reactors, Part 57 is specifically tailored to smaller, simpler and lower-risk reactor designs.

Eligibility for Part 57 and Considerations for Licensing Strategy
Notably, Part 57 would not define eligible reactors by thermal power level. Instead, the NRC proposes an attribute-based approach focused on whether a design presents sufficiently low potential radiological consequences to support streamlined licensing. This approach reflects the NRC’s view that eligibility should turn on overall risk.

To qualify, applicants would need to satisfy a dose-based entry criterion limiting offsite radiological consequences in the event of an accident, a fuel inventory limit and design attributes related to reactivity control, heat removal, fission product retention, shielding, effluent control and security by design. For developers, Part 57 eligibility will likely drive early design and licensing strategy decisions. Design choices affecting source term, passive safety performance, fuel inventory, transportability, site boundary and security requirements may determine whether a project can use Part 57 or must proceed under another framework.

The proposed rule gives applicants flexibility in how they show they meet the entry criteria, potentially affecting decisions on where projects are sited, how they are deployed and overall project costs. This flexibility should help accommodate the range of deployment models emerging in the microreactor sector, from factory-built, transportable units to site-specific installations. It also reflects the variation in design approaches among developers, allowing different technologies to qualify under a common framework without forcing a single analytical method or deployment strategy.

Key Features of the Proposed Framework: 
The proposed Part 57 framework introduces several structural changes intended to streamline licensing and support scalable deployment of microreactors.

Joint Applications and Fleet Deployment
As noted above, Part 57 would allow an application to encompass a single CP and any number of OLs for reactors of essentially the same design at one or more sites or within designated large geographic areas. This approach is designed to support fleet-based deployment and reduce duplication across licensing proceedings. Part 57 would also authorize manufacturing licenses for reactor fabrication, fueling and testing at a dedicated manufacturing facility.

Further, the applicant can include a request for generic finality. If granted, issues resolved in the first application proceeding would carry forward to future proceedings. This would allow later projects referencing an approved licensing basis to avoid relitigating design and operational issues, narrowing subsequent reviews to site- and applicant-specific matters. For fleet developers, this would help convert a successful first project into a repeatable deployment model based on standardized designs.

Siting Flexibility
In addition, the framework introduces construction and siting flexibilities aimed at accelerating repeat deployments. For example, certain construction activities for “nth-of-a-kind” facilities could proceed under a general license prior to issuance of a construction permit, provided certain conditions are met. Part 57 also incorporates a graded approach to site characterization, scaling the scope and depth of site characterization activities to the facility’s potential radiological consequences. The rule further contemplates the use of categorical exclusions under the National Environmental Policy Act in appropriate circumstances, which could significantly reduce environmental review timelines.

Notably, the proposed framework does not require a traditional emergency planning zone, reflecting the lower risk profile associated with eligible reactor designs.

Quality Assurance Flexibility
Part 57 departs from the prescriptive quality assurance requirements in Appendix B to Part 50 by allowing applicants to propose alternative QA programs tailored to their specific designs and risk profiles. This approach is intended to expand the pool of qualified suppliers and reduce barriers associated with traditional nuclear QA standards, which have historically limited participation and increased costs. Applicants would still be required to demonstrate that their QA programs provide adequate confidence in the performance of safety-related structures, systems and components, but the rule affords greater flexibility in how those programs are structured and implemented.

Codes and Standards
Part 57 further adopts a more flexible approach to codes and standards, permitting applicants to select applicable frameworks—including generally recognized consensus codes, international codes and standards not previously used in NRC licensing—subject to NRC review for adequacy and applicability. This could potentially enable the use of American Society of Mechanical Engineers (ASME) codes and standards and other code sections not traditionally used in the nuclear industry.

Operational Model
The proposed rule expressly contemplates modernized operational models, including remote monitoring, remote operation and autonomous operation. These provisions could allow a single licensed operator to oversee multiple reactors across a fleet. Additionally, NRC oversight would emphasize risk-informed, performance-based inspections in place of on-site resident inspectors.

Financial Protection
Finally, Part 57 proposes changes to financial protection requirements set forth in the Price-Anderson Act. The NRC may reduce required levels of financial protection and indemnification based on the facility’s risk profile—a cost advantage for qualifying projects.

Practical Considerations
The proposed Part 57 rule represents a significant evolution in the NRC’s regulatory approach, aimed at aligning licensing requirements with the characteristics of emerging reactor technologies. By emphasizing flexibility, standardization and scalability, the framework is designed to address longstanding concerns regarding the cost, complexity and duration of nuclear licensing processes. Construction permit and operating license timelines could also shrink to 6–12 months. These efficiencies could improve the commercial viability of microreactors and other advanced reactor technologies.

• Developers: Developers should evaluate whether their designs and deployment strategies are structured to meet Part 57’s entry criteria and take advantage of its scalability features. Designs that support standardization, manufacturing and repeat deployment are more likely to benefit from the framework.
• Investors: For investors, the key diligence questions will extend beyond licensing timelines to include whether a developer can qualify for Part 57, whether its licensing basis is reusable and whether its manufacturing, fuel and deployment strategies support scalable growth.
• Customers and End Users: For potential customers—such as data center developers—Part 57 may make microreactors more viable as repeatable, on-site or near-site power solutions. However, project execution will still depend on site control, environmental review, state and local approvals, fuel supply and integration with broader infrastructure.

Requests for Comments
The NRC has also issued a request for comments on the proposed rule and is seeking stakeholder input on a range of issues, including the following:

• Whether the proposed eligibility criteria appropriately define the scope of the framework, including the use of both dose-based and material limits;
• The extent to which risk-informed approaches should complement or balance traditional deterministic requirements;
• The treatment of remote and autonomous operations and whether additional regulatory guidance is needed;
• Whether additional license tools, such as general licensing approaches and expedited hearing procedures, are needed; and
• Whether aspects of existing frameworks (e.g., Parts 50 or 52) could be adapted in lieu of establishing a new regulatory regime.

Developers, investors and potential customers may wish to submit comments to ensure the final rule accommodates their specific design approaches and deployment models and does not introduce unintended constraints or opportunities for further licensing innovation. The senior leadership of the NRC has indicated that they are very interested in receiving comments on the proposed rule, so interested parties should not hesitate to share constructive comments with the Agency. Early engagement can also help shape key aspects of the framework—such as eligibility criteria, finality, and operational flexibility—that will directly affect project timelines, costs and scalability.

Comments are due June 15, 2026.

Looking Ahead
Part 57 has the potential to shape the regulatory landscape for advanced nuclear technologies in the United States, providing a pathway for faster, more predictable licensing of microreactors and similar designs. Developers, investors and other stakeholders should closely evaluate the proposed rule and consider participating in the rulemaking process. Pillsbury’s Nuclear Energy team is closely monitoring this rulemaking and is available to assist clients with comment preparation and, looking ahead, entry criteria analysis and licensing and deployment strategies.