NRC Proposes New Licensing Framework for Microreactors

What Happened: The Nuclear Regulatory Commission (NRC) proposed a new regulation to be located at 10 CFR part 57 to create a risk-informed, performance-based framework for rapid licensing and high-volume deployment of microreactors and other reactors with comparable risk profiles. Comments are due by June 15, 2026.

Who’s Impacted: Reactor developers, manufacturers, utilities, industrial energy users, remote-site operators, companies pursuing modular or transportable reactor business models, fuel-cycle participants, and entities planning to comment on the NRC’s approach.

What Should They Consider Doing in Response: Stakeholders should evaluate whether their designs meet the proposed eligibility criteria, assess how the proposed pathways align with planned deployment models, and consider commenting on NRC’s specific questions regarding entry criteria, general licensing, remote and autonomous operations, fitness-for-duty requirements, transportation, decommissioning, and hearing procedures.

By When Should They Act: Comments must be submitted by 11:59 p.m. Eastern time on June 15, 2026, under Docket ID NRC–2025–0379.

Background

NRC’s proposed rule would create a new licensing framework for “microreactors and other reactors with comparable risk profiles.” NRC explains that these reactors may be smaller, simpler, potentially transportable, and designed with inherent or passive safety features that differ from the current fleet of large light-water reactors. The agency identifies possible uses, including remote communities, industrial process heat, military bases, maritime applications, disaster relief, and locations where a grid connection is unreliable or unavailable.

NRC considered using parts 50, 52, or 53 as the primary framework for this initiative, but ultimately rejected those in favor of a new licensing scheme. According to the Commission, parts 50 and 52 were developed for large light-water reactors, while part 53 would cover a broader class of reactors, including large and complex designs. NRC instead proposes a separate part 57 focused on rapid licensing, leveraging standardization, and high-volume deployment for lower-risk reactors.

Core Eligibility Criteria

This new licensing framework would not apply to every advanced reactor. Applicants would need to satisfy certain entry criteria designed to screen for lower-consequence designs.

First, an applicant would need to demonstrate that the reactor satisfies a 1 rem total effective dose equivalent criterion at the site boundary under accident conditions. Applicants may use either the maximum hypothetical accident or the maximum credible accident methodology to conduct this demonstration. The maximum hypothetical accident approach would allow a conservative bounding analysis. The maximum credible accident approach would allow a more risk-informed analysis that excludes physically unrealistic or excessively conservative assumptions.

Second, NRC proposes a 10 metric ton fuel mass limit on the total inventory of thorium, uranium, and plutonium in the nuclear reactor. NRC describes this limit as an additional defense-in-depth measure intended to shepherd in smaller designs with limited material available for release and limited decay heat challenges. The agency specifically requests comments on whether it should use an alternative performance-based entry criterion instead of a deterministic material limit.

The proposed rule also identifies six design criteria attributes that would assist with determining applicability: reactivity control, heat removal, fission product retention, shielding, radioactive effluent control, and security by design. These attributes focus on a reactor’s ability to control power, shut down, remove heat, retain radioactive materials, protect workers and the public, control releases, and address security risks through design features where possible.

Licensing Pathways and Standardization

Under the proposed rule, several licensing and approval pathways would be available to applicants, including joint applications for construction permits and operating licenses, manufacturing licenses, and standard design approvals.

For joint applications, an applicant would submit final design information and complete operational programs at the outset. NRC would conduct a single comprehensive safety review and have the option to hold one adjudicatory hearing. The Commission states that this structure should support issuance of an operating license within 6 to 12 months after accepting an application, assuming the application is complete, does not require additional information requests, construction proceeds on time, and any hearing contentions are resolved quickly.

The proposal emphasizes standardization to ensure efficiency and expedience. An applicant could request a single construction permit and multiple operating licenses for reactors of essentially the same design at one or more sites or within designated large geographic areas. Multiple applicants using essentially the same design could reference common non-site-specific information. Additionally, the proposed rule would also allow applicants to request generic finality for designs and certain operational matters, limiting later proceedings that reference the approval to site- and applicant-specific issues. This would mean that matters resolved during the application process where the applicant has requested generic finality would be considered resolved in proceedings on other joint applications that reference the construction permit and associated operating licenses.

Manufacturing Licenses and Transportable Reactor Models

The manufacturing license provisions could prove especially important for developers pursuing factory-built or transportable reactor models. Proposed part 57 would allow standardized reactors to be manufactured under an NRC manufacturing license, then installed at deployment sites under related construction permits and operating licenses.

NRC also proposes to allow fuel loading at the manufacturing facility under appropriate part 70 controls, provided the manufacturing license includes features to prevent criticality during storage and transport. The proposal contemplates that some reactors may be fabricated, fueled, tested, transported to a deployment site, operated, removed, refurbished, refueled, decommissioned, or redeployed under various licensing combinations.

For transportation, NRC proposes to rely primarily on 10 CFR part 71 but would add a pathway for applicants to use a risk methodology for evaluating normal or accident transportation conditions if they cannot meet existing testing and performance requirements. The Commission requests comments on whether alternative transportation dose rates may be appropriate for transportable microreactors.

General License for Certain Construction Activities

The proposed rule would not create a general license for the construction of an entire reactor. NRC concluded that the Atomic Energy Act does not authorize general licensing of a nuclear reactor under the current statutory framework. Instead, NRC proposes a narrower general license for certain construction activities for nth-of-a-kind facilities before issuance of a construction permit.

That general license would apply only if several conditions are met, including the docketing of a joint construction and operations application, reference to an NRC-issued manufacturing license, reference to a construction permit and operating license already afforded generic finality for the same manufacturing license, satisfaction of categorical exclusion criteria, completion of relevant environmental consultations, and compliance with inspection and other requirements. The general licensee could not bring special nuclear material or operational radioactive material to the site under the general license.

Environmental Review and Categorical Exclusions

In accordance with Executive Order 14300, Ordering the Reform of the Nuclear Regulatory Commission, part 57 would create a categorical exclusion from the requirement to prepare an environmental assessment or environmental impact statement when specified criteria are met. The categorical exclusion would rely in part on plant and site parameter envelope values from the NRC’s generic environmental impact statement for licensing new nuclear reactors.

The proposed criteria focus on environmental conditions such as whether the site lies within a previously disturbed area, whether cooling systems avoid direct withdrawal from or discharge to surface water or groundwater sources, whether air emissions fall below specified de minimis thresholds, and whether the licensed activity complies with applicable state and local requirements, including land use, zoning, and coastal zone management requirements.

If the licensed action does not meet the criteria for the categorical exclusion, the applicant must prepare an environmental assessment or environmental impact statement in accordance with part 51.  

Operational Programs, Staffing, Security, and Fitness for Duty

The proposed rule would allow operational programs for covered reactors to be standardized and administered either onsite or at a corporate or institutional level. These programs could include emergency preparedness, security, training, quality assurance, fire protection, radiation protection, remote operation, remote monitoring, and staffing plans. NRC would not define an emergency planning zone for facilities licensed under proposed part 57, citing the low-consequence characteristics of eligible facilities.

For operator licensing, the proposed regulations distinguish between operator-dependent and operator-independent facilities. Operator-dependent facilities would require specifically licensed operators and senior operators. Operator-independent facilities, where no operator action is required to maintain the reactor within the proposed dose criterion, could use generally licensed reactor operators. The proposed rule would also allow remote monitoring, remote operation, and autonomous operation, and it asks whether additional requirements or guidance are needed for those approaches.

The proposal would also revise fitness-for-duty rules in 10 CFR part 26. A new subpart P would apply to part 57 facilities during both construction and operation and would allow flexibility for drug and alcohol testing, including oral, fluid, urine, and hair testing for certain purposes, and potential future portal screening technologies. In some circumstances, licensees could implement a fitness-for-duty program of their own specification if operator action is not needed to maintain the reactor within the dose criterion or if credible operator or maintenance error could not exceed that criterion.

On physical security, the proposal would take a consequence-based approach. If an applicant can show that a design basis threat-initiated event would not exceed specified offsite dose values even without mitigation or operator action, the applicant would not need to protect against the design basis threat of radiological sabotage in the same way as higher-consequence facilities. NRC also proposes a technology-inclusive cybersecurity framework in part 73.

Decommissioning and Fuel Storage

The proposal would let applicants submit decommissioning plans during initial licensing. The NRC describes this approach as flexible enough to address individual reactor decommissioning, transport of reactors to another facility for decommissioning or refurbishment, and decommissioning of larger sites with multiple reactors or shared systems. Licensees would not need to submit the post-shutdown decommissioning reports required for large light-water reactors but would need to complete decommissioning without significant delay under NRC-approved schedules.

For irradiated fuel storage, the proposed rule would use a combination of part 70, part 72 general or site-specific licenses, and certified dry storage systems. The proposal would allow operating license holders to store irradiated fuel at the operating site within the reactor or in a certified storage system, subject to the applicable licensing framework.

Key Comment Issues

The NRC asks for comments on several issues that could shape the final rule, including:

• Whether the NRC should replace the 10 metric ton material limit with a performance-based entry criterion.
• Whether additional general licensing approaches could support high-volume deployment.
• Whether proposed part 57 should eliminate, narrow, or further streamline any requirements.
• Whether the NRC should create a part 57-compatible early site permit process.
• How the rule should address refurbishment, decommissioning, partial site release, and access to decommissioning funds.
• Whether alternate transportation dose rates are appropriate for transportable microreactors.
• What core elements should apply to fitness-for-duty programs developed by licensees.
• Whether certain part 57 proceedings should receive highly expedited hearing treatment.
• Whether the NRC should allow remote and autonomous operation, and what additional safeguards or guidance may be needed.
• How implementation guidance should balance the single failure criterion with risk-informed methods.

Takeaways

The proposed rule would substantially change the licensing strategy for microreactor developers and companies seeking standardized, repeatable deployment models. It would shift much of the regulatory value to early decisions about design standardization, site parameter envelopes, operational program standardization, manufacturing controls, transportation planning, and whether applicants can satisfy the proposed entry criteria.

Companies considering pursuing future licensing under part 57 should assess whether their designs fit the dose and fuel-mass thresholds, whether their deployment plans depend on manufacturing licenses or generic finality, and whether the proposed categorical exclusion, staffing, security, fitness-for-duty, and transportation provisions support their business model. Stakeholders should also consider filing comments where NRC’s specific questions intersect with planned designs, siting strategies, or commercial deployment models.

Beveridge & Diamond’s nuclear, energy, and environmental teams help clients navigate evolving regulatory frameworks, secure permits and approvals, and manage risk across the full life cycle of advanced energy projects. In addition, our Infrastructure, Project Development, and Permitting, and Renewable Energy practices offer a full range of counseling, permitting, and litigation services for developers of energy, data centers, and manufacturing projects. We advise developers, utilities, manufacturers, and investors on licensing strategy, compliance, and stakeholder engagement for next-generation reactor technologies. For more information, please contact the authors.