CoP presentation breaks down reactor licensing frameworks
The American Nuclear Society’s Risk-informed, Performance-based Principles and Policy Committee (RP3C) recently held another presentation in its monthly Community of Practice (CoP) series. Former RP3C chair N. Prasad Kadambi opened the meeting with brief introductory remarks about the RP3C and the need for new approaches to nuclear design that go beyond conventional and deterministic methods. He then welcomed this month’s speaker: Jon Facemire, senior project manager of new nuclear at the Nuclear Energy Institute, who presented “New Regulatory Frameworks: Part 53, Proposed Part 57, and Considerations for Licensing.”
Some background: RP3C is a special committee created by the ANS Standards Board and chaired by Steven Krahn that provides guidance to ANS standards committees on the use of risk-informed, performance-based (RIPB) methods. The CoP is part of RP3C’s charter, which includes training and knowledge-sharing of RIPB principles to exchange ideas outside of the normal management and project processes.
Starting off: Facemire kicked off his presentation by reminding the audience that, for most of his career, 10 CFR Parts 50 and 52 were the two frameworks made available by the Nuclear Regulatory Commission for the licensing of power reactor facilities. In the past year, however, that landscape has rapidly shifted. The new Part 53 is a finalized, currently available rule, and Part 57 is under proposal and is slated to be finalized by the end of the year.
This change has been coming for a while, Facemire explained. The NRC has been talking about how to license small modular or non–light water reactors for decades, but it wasn’t until recently that answering this question has become imperative to the agency, first by way of a legislative push from the Nuclear Energy Innovation and Modernization Act (NEIMA), which passed in 2019. NEIMA directed the NRC to develop a technology-inclusive regulatory framework for optional use by commercial advanced reactor applicants.
According to Facemire, “Parts 50 and 52 are written basically assuming that you are going to be licensing a large light water reactor. If you wanted to license a small modular reactor or non–light water reactor, you needed a lot of exemptions. It was inefficient.” NEIMA, then, represented Congress’s recognition of and attempt to fix this regulatory inefficiency.
The passage of the ADVANCE Act in 2024 pushed for further changes, calling for the NRC to establish RIPB strategies and guidance to license and regulate microreactors, either through Part 53, which was under development at that time, or through a new regulatory pathway.
Finally, President Trump’s Executive Order 14300 in 2025 “built upon what was already there in NEIMA and the ADVANCE Act and basically directed the NRC to go faster and further” in its implementation of new pathways, according to Facemire.
Part 53: On April 29, the final Part 53 rule became effective, coming—from Facemire’s perspective—as a welcome change, compared with the draft that preceded it. “Back in 2024,” he explained, “the proposed rule was put out, and it had a lot of additional requirements” that were burdensome enough to not seem more beneficial than just progressing under Parts 50 or 52. However, after comprehensive feedback from the industry and significant revisions, the NRC “did get it right in the final rule,” according to Facemire.
While there were a number of changes between the proposed and final Part 53, Facemire highlighted the most important difference as the requirements for risk assessment. While the draft rule had stringent requirements requiring probabilistic risk assessment (PRA)—which he called “overkill” for microreactors and other simple designs—the final rule requires the development of systematic risk evaluations (SREs). While there is still some clarification needed about what an SRE is, it is relatively safe to assume this process will be a significantly smaller hurdle than the traditional PRA.
Looking more broadly, Facemire described Part 53 as a rule that “for a while was looking to be so burdensome that it wasn’t worth it, [and] now seems like a pretty big step up in efficiency.” It removes the need for exemptions for many non-LWR and SMR designs, is significantly more flexible than Parts 50 and 52, and caters to applicants looking to pursue pathways that are similar to either Part 50 or Part 52, depending on their design maturity.
Part 57: Looking to the future, Facemire began his exploration of Part 57 by calling it “even more radical than Part 53.” While Part 53 was built on years of engagement, the NRC essentially “invented a whole new framework for microreactor licensing” in 12 months by way of Part 57.
There are two criteria for reactors to qualify for Part 57. The first is a dose limit of 1 rem or less (either at the site boundary or in the unrestricted area—the NRC guidance and the rule itself conflict here). This represents a 25-factor reduction in dose limit, as opposed to what is allowed in 10 CFR 50.34.
The second qualifying criterion is a fuel limit: no more than 10 metric tons of uranium, plutonium, and thorium. This requirement is intended to exclude any possibility of large LWRs with large site boundaries “gaming” the dose limit. Facemire explained that the NRC doesn’t want large LWRs licensed through Part 57; it is instead tailored to “rapid, high-volume licensing for smaller, simpler reactors.” In terms of speed, the NRC hopes to approve new reactor designs under this framework in six to nine months and subsequent deployments of previously approved designs within weeks.
Facemire also highlighted the prescriptive design criteria laid out in the rule as a sharp contrast to prior rules. While 10 CFR 50 lists about 70 design criteria, Part 57 lists only six: reactivity control, heat removal, fission product retention, shielding, radioactive effluents control, and security by design.
There is another significant requirement to progress through Part 57. As currently written, the rule requires an applicant to have final design and operational information included up front in the initial license application. Consequently, “Part 57 is really not built for first-of-a-kind reactors. It is built for a final design” with which an applicant will “basically set up a manufacturing facility and have these reactors come off an assembly line.”
Go much deeper: In his full presentation, Facemire dives into the details of Parts 53 and 57. In his concluding words, he also provides some final comparisons of which applicants, design maturity levels, and deployment models will be best suited to Parts 50, 52, 53, and 57. The presentation is available on the American Nuclear Society Standards YouTube channel.
