The Regulatory Foundation for Small Modular Reactor Deployment

Small Modular Reactors (SMRs) represent a transformative shift in nuclear energy production. Their compact design, factory fabrication potential, and scalability promise lower upfront capital costs and greater siting flexibility compared to traditional large-scale reactors. Over 70 SMR designs are under development globally, spanning light-water, fast neutron, molten salt, and high-temperature gas-cooled technologies. However, the pathway from design to deployment depends critically on a stable, predictable, and technically sound regulatory framework. The U.S. Nuclear Regulatory Commission (NRC) has emerged as a defining force in shaping that framework, influencing not only domestic projects but also serving as a reference point for emerging regulatory systems worldwide.

SMRs differ fundamentally from conventional reactors in ways that challenge legacy regulatory approaches. Their smaller size allows for passive safety systems that rely on natural circulation, gravity, and convection rather than active pumps and backup generators. Many designs incorporate factory-sealed modules that can be transported by rail or truck and assembled on-site. Some operate at higher temperatures or use different coolants such as liquid sodium or molten salt. These innovations require regulators to evaluate new accident sequences, material behaviors, and operational paradigms. The NRC has responded by adapting its regulatory infrastructure, issuing design-specific reviews, and developing new guidance documents that address the unique attributes of SMRs while maintaining rigorous safety standards.

The global significance of NRC regulations extends beyond U.S. borders. Over 30 countries are actively pursuing SMR deployment, and many lack mature nuclear regulatory systems of their own. The NRC's technical reviews, safety evaluation reports, and licensing decisions provide a transparent, technically defensible template that emerging regulators can adapt to their national contexts. International organizations including the International Atomic Energy Agency (IAEA) and the World Nuclear Association have emphasized the importance of regulatory harmonization to reduce duplication, speed deployment, and maintain safety across jurisdictions. The NRC's leadership in this space is therefore not merely a domestic matter but a cornerstone of global SMR commercialization.

The NRC's Evolving Approach to SMR Regulation

Historical Context and Regulatory Foundations

The NRC was established in 1974 as an independent agency responsible for regulating commercial nuclear power plants and other uses of nuclear materials. Its regulatory framework was built around large light-water reactors with active safety systems, multi-year construction timelines, and site-specific licensing. For decades, this framework served the industry well, ensuring that operating plants met rigorous safety criteria. However, the emergence of SMRs revealed gaps between legacy assumptions and the characteristics of advanced, modular designs. Single-unit thermal outputs of 300 MWe or less, combined with factory fabrication and transportable modules, did not fit neatly into the existing regulatory structure.

In response, the NRC initiated a series of policy studies, white papers, and rulemakings beginning in the late 2000s. The agency issued a policy statement in 2019 affirming that SMRs could be licensed under existing regulations, but that specific technical and procedural adjustments were necessary. This pragmatically allowed applicants to proceed with licensing without awaiting comprehensive new rulemaking while the agency developed targeted guidance. The result has been a hybrid approach that leverages the proven safety philosophy of the current framework while introducing flexibility where SMR designs depart from conventional paradigms.

Scope of Design Certification and Licensing Reviews

The NRC's most direct mechanism for supporting SMR deployment is the design certification process, which evaluates a reactor design's safety case independently of any specific site. Once certified, the design can be referenced in subsequent combined license applications, reducing repetitive review. The agency has completed or is actively reviewing several SMR designs, including the NuScale Power Module, a pressurized water SMR that received the first-ever NRC design certification for an SMR in January 2023. This milestone provided a proof-of-concept for the regulator's ability to handle non-traditional configurations and set a precedent for subsequent designs.

Other designs in the NRC pipeline include the GE-Hitachi BWRX-300, an advanced boiling water SMR, and the X-energy Xe-100, a high-temperature gas-cooled reactor. Each review requires the applicant to demonstrate compliance with the agency's safety goals, defense-in-depth philosophy, and performance-based standards. The NRC has established dedicated project offices for each pre-application and formal review, reflecting the resource intensity of these evaluations. The agency has also published design-specific guidance documents, such as Regulatory Guide 1.233, which provides an integrated approach for licensing advanced non-light-water reactors. These documents translate general regulatory principles into design-specific expectations, reducing uncertainty for developers and accelerating the review timeline.

Safety Standards and Technical Requirements for SMRs

Passive Safety Systems and Defense in Depth

A central tenet of NRC safety philosophy is defense in depth: multiple independent layers of protection that prevent accidents and mitigate consequences if they occur. For SMRs, the application of defense in depth requires re-examination because many designs rely more heavily on passive safety features than on active engineered safeguards. The NRC has acknowledged that passive systems may reduce the frequency of certain initiating events while also reducing dependence on operator action and offsite power. However, the agency requires that passive systems be demonstrated with high reliability and that their performance be verifiable under all design-basis conditions.

The NRC's regulatory framework for passive safety includes specific requirements for testing, analysis, and qualification. Passive systems such as natural circulation decay heat removal, gravity-driven emergency core cooling, and passive containment cooling must be designed to function without active components such as pumps, valves, or diesel generators. The NRC evaluates these systems through deterministic analyses supplemented by probabilistic risk assessments. The agency has also developed guidance on the treatment of passive system uncertainties, including the effects of materials degradation, fouling, and manufacturing variability over the reactor's operating life. These technical standards help ensure that passive safety claims are supported by robust evidence.

Security, Safeguards, and Material Control

SMRs present both opportunities and challenges for security regulation. Their smaller physical footprint and potential for underground or below-grade siting can reduce vulnerability to external threats such as aircraft impact or vehicle-borne explosives. Many designs have smaller radioactive inventories, reducing the potential consequences of a malicious event. However, the modular and transportable nature of SMRs introduces new considerations for security during fabrication, transport, and on-site assembly. The NRC has issued regulatory guidance addressing these considerations, including requirements for chain-of-custody control, tamper-indicating devices, and security plans that cover the full lifecycle from factory to end-of-life.

The agency's security requirements for SMRs are codified in 10 CFR Part 73, which covers physical protection of plants and materials. For SMRs, the NRC has allowed licensees to propose alternative security approaches where the design features provide equivalent protection to conventional requirements. This performance-based approach gives developers flexibility to optimize security without reducing effectiveness. For example, some SMR designs incorporate below-grade containment structures that inherently resist aircraft impact, allowing the licensee to reduce the scope of active security features such as armed response forces. The NRC evaluates each alternative security approach through a site-specific or design-specific security assessment that demonstrates compliance with the agency's design-basis threat.

Emergency Preparedness and Siting Flexibility

Traditional large nuclear power plants require extensive emergency planning zones (EPZs) extending approximately 10 miles for ingestion pathways and 50 miles for inhalation pathways, with comprehensive offsite response plans. SMRs, due to their lower source terms and passive safety characteristics, may justify smaller EPZs or reduced emergency planning requirements. The NRC has recognized this potential and has issued guidance for evaluating emergency preparedness for SMRs, including consideration of simplified evacuation plans and reduced reliance on offsite protective actions.

In 2020, the NRC published a draft regulatory basis for a new emergency preparedness framework specifically for SMRs and other advanced reactors. The framework considers factors such as the timing and magnitude of potential releases, the effectiveness of passive mitigation, and the ability of onsite emergency equipment to function without offsite support. For designs that can demonstrate that no offsite protective measures are necessary for public safety, the NRC has indicated that emergency planning zones could be reduced to the site boundary. This flexibility is particularly important for SMR deployment in remote or industrial settings, such as mining operations, petrochemical complexes, or isolated communities, where maintaining a large EPZ may be impractical or unnecessary.

Licensing Innovations and Process Efficiency

Standard Design Approvals and Modular Licensing

One of the most impactful regulatory innovations for SMR deployment is the concept of standardized design certification combined with modular licensing. The NRC has developed processes that allow a single design certification to be referenced for multiple units at multiple sites, significantly reducing licensing costs and timelines. This approach mirrors the factory fabrication model on which SMR economics depend: if each unit is identical, regulators need not re-review the design for every site. The NRC's Part 52 licensing framework, which governs design certifications, combined licenses, and early site permits, provides the legal foundation for this approach.

The agency has also explored the concept of a "standard design approval" that would allow a design to be used in multiple countries through bilateral or multilateral agreements. While the NRC cannot issue licenses for foreign facilities, it can provide technical evaluations that foreign regulators incorporate into their own licensing decisions. The NRC has technical assistance programs with several countries, including Canada, the United Kingdom, and Japan, under which the agency shares its review methodology and findings. These collaborations reduce duplication and accelerate the global deployment of designs that have already undergone rigorous NRC review.

Timeline Predictability and Resource Planning

Predictable licensing timelines are essential for SMR project financing. Investors need confidence that regulatory review will be completed within a known timeframe to avoid cost overruns and project delays. The NRC has taken steps to improve timeline predictability through milestone schedules, phased review approaches, and dedicated resource allocation. The agency established an Office of Nuclear Reactor Regulation-led SMR task force that coordinates reviews across technical disciplines and ensures alignment between applicants and reviewers.

The NRC's internal goal for completing a design certification review is approximately 42 months, though actual timelines vary depending on design complexity and applicant responsiveness. The agency has implemented a pre-application engagement process that allows developers to submit white papers, topical reports, and preliminary safety analyses before formal docketing. This proactive engagement identifies potential issues early, reducing the likelihood of major surprises during formal review. The NRC has also issued guidance on the format and content of SMR license applications, including recommended level of detail, analysis methods, and supporting documentation, which helps applicants submit complete and high-quality applications the first time.

Global Harmonization and International Regulatory Collaboration

The NRC as a Benchmark for Emerging Regulators

For countries considering SMR deployment that lack extensive nuclear regulatory experience, the NRC's framework serves as a natural starting point. The NRC's regulations are publicly available, technically comprehensive, and have been tested through decades of application to operating reactors. Emerging regulators often adopt NRC standards wholesale or adapt them to their national legal and administrative systems. This pattern is visible in countries such as Jordan, Ghana, and Kenya, which are developing nuclear power programs and have requested NRC technical assistance under the U.S. Department of Energy's regulatory infrastructure development program.

The NRC also participates actively in the IAEA's standards-setting process, contributing to the development of safety standards, design requirements, and security guidelines that apply to SMRs. The IAEA's SMR Regulators' Forum, established in 2015, brings together regulators from countries with active SMR programs to share experiences, identify common challenges, and develop harmonized approaches. The NRC has been a leading contributor to this forum, providing technical papers, hosting workshops, and serving as a reference for other members. This engagement ensures that international standards remain informed by the most advanced regulatory thinking and that NRC practices evolve in step with global best practices.

Bilateral Agreements and Mutual Recognition

Bilateral regulatory cooperation agreements have emerged as a key mechanism for reducing duplication and accelerating SMR deployment. The NRC has signed memoranda of understanding (MoUs) with regulators in Canada, the United Kingdom, Japan, South Korea, and other countries that include provisions for information sharing, joint reviews, and mutual recognition of technical evaluations. Under these agreements, a design certified by the NRC may be able to reference NRC safety findings in subsequent licensing abroad, contingent on the foreign regulator's review of any site-specific or national-legal considerations.

The NRC-Canadian Nuclear Safety Commission (CNSC) agreement, signed in 2019, is particularly significant given the overlapping interest in SMR development between the two countries. Both regulators have committed to sharing pre-application information, coordinating review schedules, and exploring the possibility of joint technical reviews. Work-sharing arrangements can reduce the total regulatory burden on developers who seek licenses in both countries. The NRC has also engaged with the UK Office for Nuclear Regulation (ONR) and the UK Environment Agency on SMR generic design assessment, sharing methodologies and findings to streamline the process for designs that seek approval in both jurisdictions.

Regulatory Stability and Investment Confidence

Regulatory stability is perhaps the most critical factor for attracting private investment in SMR projects. Developers and financiers need confidence that the regulatory framework will not change in ways that invalidate prior approvals or impose unanticipated costs. The NRC's rulemaking process, which includes public notice, comment periods, and formal hearings, provides procedural stability and predictability. The agency also has a well-established process for amending regulations, including environmental assessments and cost-benefit analyses, which limits the risk of arbitrary changes.

The NRC's track record of finalizing design certification reviews and issuing combined licenses demonstrates its commitment to completing regulatory processes once initiated. This reliability is especially important for SMRs, where factory production lines and supply chain investments depend on a clear regulatory pathway. The first-mover advantage goes to designs that successfully navigate regulatory review, not only in the United States but also in jurisdictions that reference NRC findings. The agency's role in building investor confidence cannot be overstated: a design that holds an NRC certificate has a credibility advantage that extends well beyond U.S. borders.

Challenges and Areas for Continued Regulatory Development

Advanced Technology and Non-Light-Water Reactors

While light-water SMRs have made the most regulatory progress, many of the most innovative SMR designs use non-water coolants such as molten salt, liquid sodium, or helium gas. These designs pose fundamental regulatory challenges because the NRC's existing regulations were written specifically for light-water reactors. Accident phenomena, materials behavior, and operational characteristics differ substantially, requiring new analytical tools, experimental data, and regulatory guidance. The NRC has initiated several activities to address these gaps, including the development of a non-light-water reactor regulatory framework and the issuance of a policy statement on advanced reactor licensing.

The agency's regulatory framework for non-light-water reactors, known as "Part 53," is under development and will establish technology-inclusive safety requirements that can be applied to any reactor type. The proposed rule would replace prescriptive requirements with performance-based criteria, allowing designers to demonstrate safety using methods appropriate to their technology. The NRC has published draft regulatory guides, white papers, and a proposed rule for public comment, with a target for finalization in 2025 or 2026. Until Part 53 is finalized, applicants for non-light-water SMRs must use the existing framework with exemptions and alternative approaches, which adds uncertainty and lengthens review times.

Public Confidence and Stakeholder Engagement

Regulatory approval alone does not ensure SMR deployment; public acceptance at proposed sites is equally essential. The NRC's public meeting requirements, environmental impact statement process, and mandatory hearings provide formal channels for stakeholder input. However, SMR proponents and regulators must also address broader concerns about nuclear waste, security, and community impacts. The NRC has supported public outreach initiatives through its Office of Public Affairs and regional offices, including workshops and webinars that explain SMR technology and regulatory processes in accessible terms.

One challenge specific to SMRs is the potential for deployment in communities with no prior nuclear experience. For example, a factory-fabricated SMR trucked to a remote mining site introduces safety and security considerations that differ from those at established nuclear power plant sites. The NRC's regulatory framework addresses these considerations, but effective communication is required to build confidence. The agency has issued guidance on how SMR licensees should engage with local stakeholders, including emergency response organizations, state and local governments, and community groups. The NRC also participates in regional workshops organized by the IAEA and the World Nuclear Association to share lessons learned from community engagement in early adopter countries.

Workforce and Technical Capability

The NRC faces ongoing challenges in recruiting, training, and retaining the technical workforce necessary to review SMR designs, particularly those involving novel technologies. The agency's staff have deep expertise in light-water reactor systems, but non-light-water coolants, advanced materials, and new fuel forms require additional capabilities. The NRC has invested in training programs, university partnerships, and recruitment campaigns to build expertise in areas such as high-temperature materials chemistry, molten salt corrosion, and tritium management. The agency also participates in international research programs and exchanges to keep its technical staff current with cutting-edge developments.

Industry stakeholders have expressed concern about the NRC's capacity to review multiple SMR designs simultaneously, given the resource intensity of each review. The agency has responded by scaling its advanced reactor licensing team, establishing dedicated project offices, and prioritizing designs that are furthest along in development. The NRC's budget for advanced reactor licensing has increased in recent years, reflecting congressional and administration support. However, the pace of review remains constrained by the availability of qualified staff and the complexity of the designs under review. Continued investment in workforce development is essential to maintain the NRC's capacity to support SMR deployment at scale.

The technical demands of SMR review also extend to the applicant community. Developers must produce high-quality safety analyses, design descriptions, and supporting documentation that meet NRC standards. The agency has provided extensive guidance on expectations, including example calculations, template formats, and accepted codes and standards. The NRC's Office of Nuclear Regulatory Research conducts and sponsors experimental programs that generate data relevant to safety analyses, such as separate effects tests, integral effects tests, and thermal-hydraulic code validation. This research reduces uncertainty and provides a technical basis for regulatory decisions that support both domestic and international SMR deployment.

The Future of NRC Regulations in Global SMR Deployment

Harmonization Through and the Path Forward

As more countries pursue SMR deployment, the pressure for regulatory harmonization will intensify. The NRC is well-positioned to lead this effort given the depth of its technical expertise, the maturity of its regulatory processes, and its established relationships with foreign regulators. The agency's ongoing work on Part 53, the non-light-water reactor framework, will provide a technology-inclusive template that other regulators can adapt to their national contexts. The NRC's experience with standard design certification, modular licensing, and alternative approaches to emergency preparedness and security will inform global standards development.

International harmonization does not mean uniform regulation; national legal systems, resource availability, and public expectations will continue to produce differences. However, mutual recognition of technical findings, joint reviews, and work-sharing arrangements can reduce duplication while maintaining safety. The NRC's collaboration with the CNSC on common technical reviews for SMR designs that seek approval in both countries provides a model that could be extended to other bilateral and multilateral relationships. The agency's participation in the IAEA SMR Regulators' Forum and the Generation IV International Forum provides additional channels for developing common regulatory approaches for next-generation reactors.

Regulatory Predictability as a Catalyst for Investment

The most important contribution the NRC can make to global SMR deployment is to maintain a stable, predictable, and technically rigorous regulatory environment. Developers and financiers require regulatory certainty to commit the billions of dollars needed to build SMR factories, establish supply chains, and construct first-of-a-kind projects. The NRC's track record of issuing design certifications, combined licenses, and early site permits demonstrates its operational capability and commitment to regulatory completion. The agency's continued engagement with international counterparts extends this predictability globally.

For countries seeking to deploy SMRs quickly to meet decarbonization goals, the NRC's regulatory framework offers a proven foundation. By referencing NRC-certified designs, adopting NRC-derived safety standards, and leveraging bilateral agreements, emerging nuclear nations can reduce their own regulatory development time and cost. The NRC's technical cooperation programs, training initiatives, and knowledge transfer mechanisms provide the tools these countries need to build their regulatory capacity. The result is a virtuous cycle: strong NRC regulations support domestic deployment, which builds international confidence, which in turn supports market formation and cost reduction for subsequent projects worldwide.

The global SMR industry stands at a critical juncture. Designs are maturing, first mover licensing is underway, and national climate commitments are creating demand for clean, dispatchable power. Regulatory frameworks will determine which designs succeed, how quickly they can scale, and which countries benefit from this emerging technology. The NRC, through its evolving standards, licensing innovations, and international engagement, is playing a defining role in shaping the regulatory landscape for SMRs worldwide. Continued investment in regulatory capacity, technology-inclusive rulemaking, and international collaboration will ensure that the NRC remains a cornerstone of safe, responsible, and efficient SMR deployment for decades to come.