NRC unveils Part 53 final rule

The Nuclear Regulatory Commission has finalized its new regulatory framework for advanced reactors that officials believe will accelerate, simplify, and reduce burdens in the new reactor licensing process.

The final rule arrives more than a year ahead of an end-of-2027 deadline set in the Nuclear Energy Innovation and Modernization Act (NEIMA), the 2019 law that formally directed the NRC to develop a new, technology-inclusive regulatory approach. The resulting rule-10 CFR Part 53, "Risk-Informed, Technology-Inclusive Regulatory Framework for Advanced Reactors"-is commonly referred to as Part 53.

"This is really a historic milestone," NRC Chairman Ho Nieh said on a call Wednesday. "With the addition of Part 53 to Part 50 and 52-and I believe some of you know that we're working on a microreactor licensing framework-America now has many options available to applicants and licensees that want to pursue the development and deployment of new nuclear technologies."

In a separate news release issued Wednesday afternoon, Nieh said, "This final rule is a major NRC action that provides a clear risk-informed, technology-inclusive licensing framework to enable new nuclear to safely move faster from concept to construction."

What's in Part 53: The final rule introduces, among other things:

• Technology-inclusive safety standards.
• Flexibility for reactor design and operation based on risk analyses.
• Graded security requirements.
• Innovative features to accelerate deployment.

Part 53's shift from a technology-specific to a technology-neutral approach to reactor licensing is intended to address a long-standing issue in regulatory frameworks that were developed for light water reactor technology. Licensing reactors that do not use LWR technology has required applicants to seek regulatory exemptions, leading to a cumbersome licensing process.

"Part 53 offers a comprehensive new approach to license advanced reactors, including non-light-water reactors, across their life cycles," according to the NRC release. "It provides designers and operators with more flexibility in how they build and run their plants while continuing to ensure safety."

Updates: This week's announcement comes more than a year after the NRC published the Part 53 proposed rule. Public comments were accepted from October 31, 2024, through February 28, 2025, a comment period that included a 60-day extension.

According to Federal Register document details for the proposed rule, 158 comments were submitted in the public comment period; comments came from interested parties including Westinghouse, The Breakthrough Institute, the Nuclear Energy Institute, and Idaho National Laboratory. While some comments were supportive, other comments pointed out more work needed to be done. Some said previous draft rules were too rigid.

On Wednesday's call, NRC officials highlighted some examples of changes incorporated in the final rule. A proposal regarding different types of programs to evaluate plant licensing for natural hazard information was changed, as was a proposal regarding health objectives. The final rule also expands upon consensus codes and standards and on language regarding alternative risk approaches.

Nieh said the final version of Part 53 addresses many of the complaints and comments he and the NRC heard regarding earlier versions of the rule, which some parties deemed unusable.

"I do believe this framework does provide the appropriate flexibility and risk-informed approaches that will make it a usable tool among the other options that are already available," said Nieh.

"We've already had communications from several advanced reactor developers and potential applicants that have indicated their interest in using Part 53 once it is available," added Acting Deputy Office Director for New Reactors Jeremy Bowen.

Under Part 53, Bowen expects reactor designs to receive approval in 18 months or less. The cost of the application could be reduced by half or more, given the shorter review and the added flexibility of Part 53, he added.

A 2023 draft regulatory analysis by the NRC estimated the net averted costs to the industry and the agency for just one applicant could range from $53.6 million to $68.2 million.

A long time coming: Part 53 is the first new reactor licensing framework issued by the NRC since 1989, when the agency introduced Part 52. NRC officials added that it is the first major update to reactor licensing standards since 1956, when the Atomic Energy Commission (the NRC's predecessor) issued Part 50.

The final rule's imminent publishing is noteworthy given that it comes well ahead of the 2027 deadline ordered by NEIMA, despite a start-to-finish timeline that stretched more than five years.

To some, the Part 53 turnaround may be seen as another example of a nuclear power-related initiative getting an accelerated push. Nieh said he doesn't see it like that.

"We are looking at rules that were put in place many, many decades ago that were being used to license the first wave of nuclear reactors built in the United States in the '60s and '70s, where we did not know as much about the technology that we know today, where we [did] not have the sophistication and analytical tools to evaluate safety cases that we have today. . . . To me, I see this as removing the friction in legacy frameworks that are no longer needed today," he said.

What's next: According to the NRC website, the Part 53 final rule will be published on April 3, and the rule will go into effect 30 days after it appears in the Federal Register. As part of the posting, the NRC will publish nine additional guidance documents, with additional guidance to follow.