The U.S. Nuclear Regulatory Commission (NRC) has proposed a sweeping new licensing framework designed to push microreactors out of the lab and onto the grid at unprecedented speed. The proposed rule, called Part 57, is paired with a broader agency overhaul that earlier this year created the Office of Advanced Reactors (OAR), headed by longtime NRC official Jeremy S. Bowen. Together, the two moves represent the most significant shift in U.S. nuclear regulation in a generation—a direct response to White House Executive Order 14300 (Ordering the Reform of the Nuclear Regulatory Commission) and the bipartisan Accelerating Deployment of Versatile, Advanced Nuclear for Clean Energy (ADVANCE) Act.
A Framework Built for ‘Safety, Scale, and Speed’
Announced April 24, the proposed Part 57 rule creates a streamlined, risk-informed pathway for licensing microreactors and other reactors with comparable risk profiles. The NRC and industry estimate it will save between $3.76 billion and $11.84 billion, depending on discount rate, largely by “reducing exemption requests and streamlining reviews.” Construction permit and operating license timelines could shrink to six months to a year.
“Part 57 is designed to deploy microreactors with safety, scale, and speed,” NRC Chairman Ho K. Nieh said in announcing the rule.
Key features of the proposal include:
- Requesting approval of fleets of identical reactors.
- Allowing appropriate use of alternative design standards and programs for novel reactor operation.
- Streamlining environmental reviews for projects with demonstrated minimal impacts.
- Providing a pathway for limited construction prior to receiving an NRC permit.
The Federal Register notice is tentatively scheduled for May 6. The NRC intends to hold a public meeting on the proposed rule soon.
‘Regulatory Uncertainty Is Capital Risk’
In a media roundtable to provide more detail around the announcement, Nieh framed the rule as a response to a transformed energy landscape. America, he said, urgently needs more power to feed artificial intelligence (AI), data centers, and industrial growth. Nuclear power has emerged as an important solution.
“It used to be the question about nuclear was whether it has a role in our energy future. That question is settled,” Nieh declared. “Now, the question is really execution. Can America build at scale on schedule and at lower cost?”
Nieh was blunt about the NRC’s role in that calculus. “Regulatory uncertainty is capital risk,” he explained. “Capital will go elsewhere if the risks are too high.” Part 57, he argued, is the agency’s answer to that risk—a framework that prioritizes credible, predictable, and timely safety decisions without compromising safety itself.
How Part 57 Fits In
Part 57 doesn’t replace existing rules; it slots into a growing menu of options, which include:
- Part 50. The traditional framework used by today’s operating fleet.
- Part 52. A one-step combined-license process, which includes provisions for standardized designs.
- Part 53. A recently finalized technology-inclusive, risk-informed framework open to all reactor types.
- Part 57. Narrowly tailored for small, simple, low-risk-profile microreactors well-suited to high-volume licensing.
Notably, the NRC chose not to define exactly what fits into the microreactor classification. Instead, the rule sets entry criteria based on a “consequence limit” and a “fuel mass limit,” allowing any design that meets those thresholds to use the framework. The risk profile, Bowen said, is “closer to the current fleet of research and test reactors,” though Part 57 reactors will be fully licensed commercial machines.
“Inherently safe, but not inherently ignored,” as Nieh put it.
Simple Machines, Faster Reviews
The simplicity of the targeted designs is what enables the faster review. Many microreactors rely on passive safety features, including gravity and natural convection, and require little or no operator action during off-normal events. That allows the NRC to use a maximum hypothetical accident approach, focusing analysis on the absolute worst case rather than working through a wide range of licensing basis events.
Part 57 also opens the door to remote and autonomous operation, and could allow a single licensed operator to oversee a fleet of reactors rather than just an individual unit. Transportable microreactors are accommodated as well, working in concert with parallel revisions to the NRC’s Part 71 transportation framework.
Bowen said the rule reflects years of preparation, including technical training of NRC staff on non-light-water technologies, ongoing regulatory research, and early engagement with developers. The agency drew lessons from federal pilot projects, including the Department of War’s Project Pele microreactor program.
A New Office, a Familiar Leader
Steering the work is the new OAR, created as part of the agency reorganization mandated by Executive Order 14300 and slated for completion in September. Bowen, formerly Acting Deputy Director for New Reactors in the Office of Nuclear Reactor Regulation, was named to lead it in March.
A 2007 NRC hire and former Naval submarine officer with a systems engineering degree from the U.S. Naval Academy, Bowen has held senior roles across the agency’s nuclear security, materials safety, and research offices. Nieh, who shares a Navy nuclear background, called him “the right leader at the right time” and “the most qualified person to launch this new office.”
OAR will license and oversee new and advanced reactors, lead the team issuing permits and licenses for new reactor facilities, and serve as the programmatic lead for construction inspection. Asked whether AI will play a role in licensing, Bowen said the NRC is exploring several use cases: comparing new applications against previously approved designs, helping staff focus first-of-a-kind reviews on the areas of greatest safety significance, and analyzing the agency’s own historical decisions to find precedent across the regulatory framework.
Letting the Market Decide
Part 57 will go through a notice-and-comment period before the agency considers a final rule. The NRC also plans additional licensing changes to Parts 50 and 52 later this year, giving applicants a fuller menu of pathways depending on their design’s maturity, deployment model, and use case—from data center microgrids to emergency response to mobile power.
“It’s not for us to choose which technology society ultimately deploys,” Nieh said. “But if there’s a need for it, and if there’s a market for it, and there’s a design that’s viable for licensing, we are going to have a framework ready to produce a safety decision so that America can benefit from it.”
—Aaron Larson is POWER’s executive editor.
