Nuclear Regulatory Commission Charts a Path Forward on Part 53

The NRC Commissioners released their decision on the draft proposed rule. The results are mostly positive

Nuclear Regulatory Commission Charts a Path Forward on Part 53

Today, the Nuclear Regulatory Commission (NRC) released its votes and instructions for the initial draft of Part 53. The Part 53 rule should be predictable, flexible, scalable, and enable innovation. The Commission's decision on the draft Part 53 is a step in the right direction. The Staff Requirements Memorandum (SRM) addresses many of the key concerns of stakeholders. In doing so, the Commission may have taken a draft rule that was unlikely to be used, and set it on a path to be a modern performance-based pathway for licensing new reactors.

There is still a lot of work to do to form the NRC staff’s draft and the Commission’s direction into a viable rule. While the SRM provides a lot of information on the Commission’s decision, it will take some time to complete an in-depth review of the 1,300+ pages in the SRM package.


“Part 53” is an unassuming name for an exciting concept: a licensing framework that is suitable for a new generation of reactors that are fundamentally different from the reactors currently in operation now, and that the current rules are drafted to regulate. Congress gave clear instructions to the NRC in the Nuclear Energy Innovation and Modernization Act of 2019 (NEIMA), but the Commission and its staff have had trouble meeting the Congressional mandate. To regulate these new designs in an efficient and practical way, the new rules are supposed to be “technology-neutral,” meaning that they can be applied to different types of reactors, and are supposed to set requirements but not prescribe how they are to be met.

The initial draft of Part 53 was sent to the Commission on March 1, 2023. This draft was substantially similar to the one sent to the Advisory Committee on Reactor Safeguards in September 2022. In December of 2022, The Breakthrough Institute released a Whitepaper detailing major issues in that initial draft. Other stakeholders have also been less than pleased with the initial draft of Part 53. Last year, The Breakthrough Institute convened a diverse group of stakeholders to discuss specific issues with the current state of Part 53, which resulted in a consensus document detailing some of the most prominent issues.

Now the Commissioners have released their input to a revised version and directed that it be issued as a draft rule later this year. As is usual in these policy decisions, rather than simply voting yea or nay, each Commissioner has released a detailed vote, giving his or her views on different aspects of the draft: see the votes of Chair Hanson and Commissioners Caputo, Crowell, and Wright.

The votes released today show that the majority of the four Commissioners (one seat is vacant) have recognized many of the critical issues. These include

Comprehensive Risk Metrics

The initial draft rule contains a criterion called Quantitative Health Objectives (QHOs), that was previously only used as goals in policy. The QHOs are not a viable metric in a performance-based rule. The requirement is meant to assure that there is no significant health impact from the operation of the plant, but the effects that the NRC staff’s submitted draft of the rule seeks to measure are too small to be measured in real-time, as required, and therefore could not be complied with. There was a consensus among stakeholders that the QHOs should be removed.

The Commission appropriately directed the staff to remove the QHOs from Part 53.

Instead of QHOs, or any single metric defined by the NRC, developers will have to provide their own metric that is specifically not intended as a real-time requirement—a major legal flaw with the draft. This approach creates more flexibility for new technologies but has less regulatory predictability. The NRC uses this approach with existing reactors in the form of surrogate metrics, which took many years to develop. Clear guidance will be the key—along with clear communication by both applicants and the NRC—to making this approach work.

The Commission acknowledged the need for some other risk assessment in conjunction with an applicant-proposed metric but avoided the pitfall of requiring strict application of probabilistic risk assessment (PRA) standards. This is the flexibility needed to enable developers to propose alternative approaches to considering how risk insights are relied upon to support the overall licensing application. It will be critical how this flexibility is defined. The Commission directed the staff to seek feedback from stakeholders on this when the proposed rule is published for comment.

Two Frameworks

The NRC’s first draft of the new Part 53 included two frameworks for licensing. One (Framework A) determines risk using a PRA, a mathematical technique for determining what sequence of failures would be required to cause a release of radioactive material, and then calculating the actual probability that all the component failures required for that sequence to occur would actually happen.

The NRC staff envisioned Framework B as a technology-neutral and risk-informed version of the existing licensing frameworks. They started to add this approach in response to stakeholder feedback that it would be beneficial to have an option that aligns with international standards. Instead of enabling that alignment as an optional approach to meeting the requirements in Part 53 using regulatory guidance, the NRC made a second framework inside the Part 53 rule. That meant that Framework B was a traditional deterministic and prescriptive approach instead of the risk-informed and performance-based approach required by NEIMA.

The Commission did not approve Framework B’s inclusion in Part 53.

Leveraging the draft Part 53 for other frameworks

So, what happened to Framework B if it was cut from Part 53? There are many technology-specific requirements in the existing licensing frameworks that require exemptions for new designs. Multiple rulemakings are underway to slowly resolve those barriers. Although stakeholders generally agreed that Framework B shouldn't be in the draft Part 53, it raised the question of how the effort to develop the technology-inclusive approach in Framework B could be leveraged to improve the existing frameworks. The Commission voted to remove Framework B from Part 53, but to further explore that question. The staff has one year to provide the Commission with options on how to leverage that work to either update the existing licensing frameworks or possibly create another standalone framework.

Framework B involves an “alternative evaluation for risk insights (AERI),” which was unrealistic. The initial draft of AERI had major flaws but also showed potential if those flaws were fixed. It was removed from Part 53 because it was only included in Framework B, which was also removed. Acknowledging stakeholder feedback on the potential for AERI, the Commission directed the staff to work with stakeholders to adapt the AERI guidance as an acceptable form of risk evaluation for use under part 53.

What was removed from the rule

In several provisions in the draft Part 53, the staff considered policy decisions, which they expected the Commission to weigh in on. The staff often put off stakeholder questions and feedback by saying they will wait for Commission direction. In its instructions, the Commission provided such feedback very clearly regarding several topics.

The Commission completely removed several of the sections in question. The newly introduced Facility Safety Program was removed from the rule. This program is not consistent with the other licensing frameworks, but the staff considered it important for oversight. The Commission’s decision took the path with more regulatory predictability, requiring clarification that the NRC will continue to perform oversight of external hazards and changes to plant risk as it currently does, instead of adding a new oversight program.

In the initial draft, the staff proposed to expand the application of ‘As low as reasonably achievable’ (ALARA) requirements from just overall plant operation, to also include the design of the facility. The Commission directed the staff not to expand the use of ALARA and to maintain consistency with existing rules.

The ‘safety objective’ definitions included in the draft Part 53 potentially added confusion between the proposed rule and the Atomic Energy Act, and were deemed unnecessary to maintain safety.

The initial draft submitted by the staff included separate quality assurance requirements that were similar but differed slightly, from the existing frameworks. This had the potential to unnecessarily create supply chain confusion without benefit to public safety. The Commission addressed this issue by directing the staff to update the existing regulations to harmonize the rules and avoid unnecessary problems.

Other Provisions

The Commission directed the staff to consider and include other rulemakings that have been finalized or have made progress while Part 53 was being developed. This includes the Emergency Preparedness for Small Modular Reactors and Other New Technologies (that was approved in August 2023), the Advanced Reactor Generic Environmental Impact Statement (that has been awaiting Commission direction on the draft rule for over 2 years now), and the recently released paper on micro-reactor licensing.

In the initial draft sent to the Commission, the staff opted to push the topic of manufacturing licenses to the future. These licenses relate to manufacturing (and loading fuel into) reactors at a factory, instead of on the site where the reactor will eventually be located. In their instructions, the Commission specifically instructed the staff to include factory fuel load provisions in the proposed rule. Manufacturing licenses are being strongly considered by microreactor developers, many of whom are hoping to mass-produce reactors at factories and then ship them to their ultimate destinations. As such, these licenses will likely be key to mass micro-reactor deployment.

Next Steps

Now that the Commission has released its votes and instructions, the Staff will need to “make conforming changes to the proposed rule text, regulatory analysis, and Federal Register notice to be consistent with the direction in this SRM before proceeding with the rulemaking process.”

The Commission also provided over 1,300 pages of direction across four enclosures for the staff to reference when making adjustments. Some of the provided references potentially conflict and will be difficult for the staff to reconcile.

The NRC staff have 6 months to make the required changes before publishing the proposed rule in the Federal Register. The Commission also specified that the staff does not need to delay the proposed rule for updated guidance.

The Commission required the staff to provide monthly updates to their offices but did not direct the staff to engage with stakeholders prior to issuing the updated proposed rule. That is an unfortunate oversight considering every major provision in the SRM was related to stakeholder engagement and research. Stakeholders have been a critical part of improving the Part 53 rule.

Chairman Hanson hopes to have Part 53 finalized just 12-18 months after the proposed rule is published. The NRC staff previously planned for 2 years between publishing the proposed and final rules. If the staff publishes the proposed rule 6 months from now as directed, the final rule could be published in September 2026—ahead of the December 31, 2027 deadline given in NEIMA. There is significant work needed between now and then, but the Commission has addressed many of the issues in the initial draft of Part 53.