NRC introduces microreactor regulatory framework

The Nuclear Regulatory Commission has released a new licensing framework for microreactors and similar reactor designs that may provide a more suitable pathway for applicants with simpler technologies.

The proposed rule-known as Part 57-is the latest to come out of the NRC's rules review and overhaul stemming from the ADVANCE Act and 2025 nuclear-related executive orders. It is also the latest framework developed for advanced reactor designs shifting away from light water reactor technology, such as the Part 53 rule finalized in March.

"We are developing new licensing frameworks that are designed for safety, scale, and speed-Part 57 is one of those examples," NRC Chairman Ho Nieh said on Friday.

Made for microreactors: The proposed rule includes language to do the following:

• Request approval of fleets of identical reactors.
• Allow appropriate use of alternative design standards and programs for novel reactor operation.
• Streamline environmental reviews of projects with limited environmental impacts.
• Provide pathways for limited construction ahead of NRC permitting.

While the proposed rule doesn't spell it out, Part 57 is intended for reactors that are 100 MWe or smaller, Nieh said. (By comparison, a small modular reactor is commonly understood to have a capacity of around 50 MWe-300 MWe, and the NRC has licensed numerous gigawatt-scale LWRs.)

Evaluating a large reactor requires lengthy reviews of technology and siting. Microreactors are at the opposite end of the spectrum, by size.

"They're small machines, they're simple machines. They're just simple and conducive to higher-volume licensing," Nieh said.

"We are looking at designs here that have very simple safety cases, where there's not a lot of complex safety equipment that needs to activate during an event that would occur in a facility," he added. "This is really geared toward very simple machines, simple safety systems."

According to the NRC, Part 57 will save the agency and industry anywhere from $3.76 billion to $11.84 billion. Furthermore, the NRC projects licensing and deployment to take 6-12 months, accelerating the timeline for permitting and licensing.

Overall, the framework aims to address how developers want to meet customer needs, such as whether a microreactor will be mobile or stationary. If there's a need for new and different nuclear technology, the NRC wants to be there, said Nieh.

"It used to be the main need for nuclear power was baseload electric utility generators," said Nieh. "Now, this whole landscape is completely different. Because of this completely different landscape, innovators are coming to the market with new designs . . . We're trying to adapt our frameworks as the energy landscape adapts."

The timeline: While the NRC has been engaged in microreactor regulation and policy considerations since at least 2020, work began on the proposed rule last year, following the ADVANCE Act and executive orders. Jeremy Bowen, who will head the newly created Office of Advanced Reactors, said technical staff took about six months to develop the rule language.

"A lot of benefit of interactions over the past several years, both with direction from Congress and the interactions from the industry, have allowed us to inform what has gone into the rule," said Bowen. "It's not like we were starting from scratch; we had a lot of ideas before we even started."

According to the NRC, Part 57 is tentatively scheduled to be published in the Federal Register on May 6. The agency intends to hold a public meeting on the proposed rule soon.