Making Part 53 Work for Advanced Reactors

The staff of the Nuclear Regulatory Commission is giving another try at a difficult task: creating a new licensing pathway for advanced reactors. This avenue is intended to be more appropriate for emerging technologies than the existing regulatory structures, which assume the use of the light-water technologies that have dominated for the last sixty years. The Breakthrough Institute has followed this process since the rulemaking started several years ago. BTI has moved this process forward over the past four months during the public comment period by conducting workshops with 15 organizations involved in new reactor development to create consensus comments, in addition to submitting comments of our own.

Congress told the Commission in two recent laws—the Nuclear Energy Innovation and Modernization Act and the Accelerating Deployment of Versatile, Advanced Nuclear for Clean Energy (ADVANCE) Act—to develop a framework that is based on performance, so the focus is on achieving safety objective, not ticking boxes that list rigid, predetermined criteria that may or may not be important for safety. The rule is supposed to be technology neutral and applicable to all the various emerging technologies. The change is necessary, partly because the new reactor designs vary widely. Without an advanced licensing framework in place, developers of reactors that are cooled by molten salt or by inert gas must use the rules designed for conventional water cooling and seek numerous exemptions from regulations that aren’t appropriate to them.

Unless the new rules, known as Part 53, are drafted in a way that makes their use practical, developers will continue using old, inappropriate rules, wasting both their time and the NRC’s with dozens of requests for exemptions. If Part 53 goes into effect, but it doesn’t have a usable provision for an applicant to switch from the older system, then Part 53 will not come near achieving its potential. Transferability between older frameworks and Part 53 is stressed in both the consensus document and in BTI’s own comment.

A year ago this week, the Commission sent the staff’s rule draft back for further work. The Commissioners said that the rule should be predictable, flexible, and scalable, and enable innovation.

The new draft is an improvement, but it still needs work. Among the key areas is the requirement for a “comprehensive risk metric.” The applicant is supposed to assure an “appropriate level of safety,” according to the rule’s preamble, but the NRC doesn’t define the term. Applicants are supposed to create comprehensive risk metrics for their designs, but the rule doesn’t give guidance on what the staff would find appropriate. In contrast to existing risk metrics—like the frequency of accidents that damage the core, or that cause large radiation releases quickly, or that the containment will fail—a new comprehensive risk metric would lack the decades of regulatory precedent that the older metrics have, creating regulatory uncertainty.

The terms “comprehensive risk,” “overall risk,” and “appropriate level of safety” seem to be used interchangeably, but elsewhere in the rule, it states that they are not the same. The comprehensive risk metrics are central to the proposed rule. This lack of clarity and mixing conceptions of risk presents a barrier to applicants defining their own metrics and lowers the viability of the Part 53 framework as proposed.

The rule’s confusion on this point is especially worrisome because advanced reactors, by their nature, function differently than current-generation models, making existing risk metrics less suitable. In general, they run at far lower operating pressures, making leaks less likely, and less consequential if they occur. In general, they rely on forces that cannot fail, like gravity and natural heat dissipation, to prevent dangerous conditions. A system of rules that favors older technologies is not what the industry needs, and not what Congress or the NRC itself wants. To achieve that, the rule should move past a narrow metric of risk and refocus on an integrated view of safety.

Similarly, the commission, and separately the ADVANCE Act, told the NRC staff to avoid the pitfall of requiring strict application of probabilistic risk assessment (PRA) as the only approach. However, in the proposed rule, PRA was required in several places. To enable innovative approaches that are more appropriate for the wide range of new technologies, requirements for a PRA should be changed to “risk evaluation methods” to better align with the commission’s direction, and the intent of Congress.

Risk is only one major aspect of the rule. The stakes for Part 53 couldn’t be higher. The NRC has the opportunity to create a modern, predictable, and practical licensing framework that meets the intent of Congress and supports advanced nuclear energy. But that depends on getting the rule right—making it technology-inclusive, risk-informed, and truly usable for the innovative reactor designs it’s meant to serve.

We encourage everyone following this process to review BTI’s detailed comment, the Stakeholder Consensus Comment we facilitated, and the high-level comment in collaboration with other organizations, to understand the practical, consensus-driven changes needed to ensure Part 53 can deliver on its promise.