11 minute read | May.01.2026
For decades, nuclear licensing has been built around a single assumption: reactors are large, site-built, and fundamentally one-off projects.
That assumption is embedded in the NRC’s licensing framework, which centers on site-specific review of construction and operation for a single facility. Even newer pathways for small modular and advanced reactors—while more flexible—continue to rely on variations of this same model.
Microreactors break that paradigm.
Designed for factory fabrication, transportability, and repeat deployment, they are intended to be manufactured and deployed in fleets—not licensed as bespoke infrastructure projects. The existing regulatory framework was not built for that model.
The U.S. Nuclear Regulatory Commission’s proposed rule, issued April 24, 2026, is the first comprehensive attempt to address that gap. It establishes a risk-informed, performance-based licensing framework specifically designed to enable rapid and high-volume deployment of microreactors and other reactors with comparable risk profiles.
This rulemaking has been years in the making, reflecting sustained engagement across industry, government, and other stakeholders on how to move from one-off licensing to scalable deployment. If finalized as proposed, Part 57 would mark a fundamental shift in how nuclear reactors are licensed, financed, and deployed in the United States.
Microreactors are typically defined as nuclear reactors under approximately 20 MW—but their significance is not their size. It is how they are designed, built, and deployed.
Unlike traditional reactors, microreactors are compact, factory-fabricated systems intended for repeat production and transport to a range of deployment sites. They can operate with simplified staffing models, incorporate inherent and passive safety features, and in many cases do not depend on a fixed, large-scale site footprint.
These characteristics fundamentally change the deployment model—from bespoke, site-specific construction projects to standardized, potentially fleet-based deployment.
That shift is precisely what challenges the existing regulatory framework.
Taken together, these characteristics—standardization, manufacturability, transportability, and flexible end use—differentiate microreactors from traditional nuclear technologies and underscore the need for a tailored regulatory approach.
The rise of microreactors exposes a fundamental mismatch between the NRC’s existing licensing framework and the next generation of nuclear technologies. That framework was developed for large, complex, site-built reactors—projects that are designed, constructed, and licensed as one-off facilities tied to a specific location. It is highly structured, resource-intensive, and centered on detailed, site-specific review.
Microreactors are built on a different model.
The NRC has historically licensed nuclear reactors under two primary pathways: 10 CFR Part 50 and 10 CFR Part 52. While these pathways differ procedurally, they are built on the same foundational assumption: a large light water reactor constructed and operated at a fixed, site-specific location.
Both frameworks are inherently prescriptive and site-focused. Compliance is measured against detailed regulatory requirements developed for large, complex facilities with significant on-site construction and operational staffing.
That approach has worked for the existing fleet. It is not well suited to technologies designed for standardization, transportability, and repeat deployment across multiple sites.
The NRC has taken steps to modernize its licensing framework for advanced reactors through 10 CFR Part 53. Part 53 introduces a risk-informed, technology-inclusive approach intended to accommodate a wide range of reactor designs, including small modular reactors and other advanced technologies (as we previously covered).
But Part 53 is not designed for high-volume deployment.
While it provides greater flexibility than Parts 50 and 52, it still contemplates reactor licensing as a project-specific exercise and retains a level of complexity aligned with larger, more traditional facilities.
Microreactors present a different challenge. Their portability, simplified designs, and potential for repeat, fleet-based deployment require a framework that not only accommodates new technologies, but is specifically structured for scale.
On April 24, the NRC published a proposed rule, “Licensing Requirements for Microreactors and Other Reactors with Comparable Risk Profile,” to establish a new 10 CFR Part 57. The rule is specifically targeted at low-consequence reactors, reflecting their reduced radiological risk and smaller source terms relative to traditional nuclear plants.
At its core, Part 57 is not an entirely new construct, drawing from existing licensing approaches under Parts 50, 52, and 53. Rather, it reconfigures them to align with how microreactors are designed, manufactured, and deployed.
The result is a risk-informed, performance-based licensing framework explicitly intended to support high-volume deployment.
Part 57 provides a set of licensing pathways that applicants can select based on their deployment strategy. Rather than a single prescribed process, the rule is structured to support different commercialization models, from site-specific deployment to manufacturing and fleet rollout.
Notably, the NRC declined to adopt a true “general license” framework that would authorize the fabrication, deployment, and operation of multiple reactors under a single license. The agency concluded that such an approach is constrained by the Atomic Energy Act—particularly §§ 11(cc) and 109(a)—which limit the Commission’s authority to issue general licenses for utilization facilities.
That limitation matters. A true general license would represent the most direct pathway to fleet-scale deployment, eliminating the need for repeated licensing actions for standardized reactor designs. Without it, Part 57—while significantly streamlined—still relies on individual licensing decisions, even where designs and operating programs are largely identical.
The proposed rule does, however, introduce a more limited general license for certain construction activities. While narrower in scope, this authority could still provide meaningful flexibility—particularly for “nth-of-a-kind” deployments—by allowing portions of the build process to proceed without full licensing approval.
Layered into these licensing pathways are a series of targeted flexibilities that distinguish Part 57 from the NRC’s traditional frameworks. These are not incremental adjustments—they are designed to align licensing with standardization, mobility, and repeat deployment.
These flexibilities do not alter the NRC’s core safety standard. The Commission must still find reasonable assurance of adequate protection of public health and safety. Instead, Part 57 recalibrates how that standard is met—moving away from prescriptive, one-size-fits-all requirements toward a framework that is commensurate with the risks and deployment models of microreactors.
At a more fundamental level, Part 57 is structured to enable standardization and repeat deployment across fleets of reactors. The rule allows applicants to leverage approved designs, operational programs, and licensing bases across multiple units and locations, reducing the need to relitigate the same issues in each proceeding.
This is most evident in features such as generic finality, multi-site licensing, and manufacturing-based approvals, which collectively shift the licensing model away from one-off project approvals toward a more scalable, programmatic approach.
While the NRC stops short of a true fleet-wide or general license, the framework reflects a clear move in that direction—laying the groundwork for more efficient licensing of standardized reactor deployments over time.
Part 57 represents a meaningful shift in how the NRC is approaching reactor licensing. It reflects a deliberate move toward risk-informed, performance-based regulation that is better aligned with standardized, lower-consequence technologies—and, importantly, with the prospect of repeat deployment at scale.
At the same time, the framework does not fully resolve the tension between traditional licensing processes and high-volume deployment. Key elements of the existing regime remain in place, including Advisory Committee on Reactor Safeguards review and the opportunity for adjudicatory hearings. Some of these requirements are statutory, but others may be subject to Commission discretion. As a result, initial applications are still expected to take on the order of 6–12 months under ideal conditions—faster than traditional timelines, but still long relative to the deployment expectations for microreactors.
The proposed rule also leaves open several important questions. The scope of eligibility for Part 57, the potential expansion of general licensing concepts, and the approach to decommissioning and other lifecycle considerations will all be shaped through the notice-and-comment process. The NRC has specifically requested input on these issues, and stakeholder engagement will likely influence how far the final rule goes in enabling true fleet deployment.
Procedurally, this remains a proposed rule. The public have until June 15, 2026 to submit comments, per the May 1st Federal Register notice. Given the significance of the departures from existing licensing frameworks, the rule is likely to receive substantial attention—and potential refinement—before it is finalized.
As proposed, Part 57 lays the groundwork for high-volume microreactor deployment. Whether it ultimately achieves that objective will depend on how the NRC resolves the remaining procedural constraints and how the final rule balances flexibility with statutory requirements.