Nuclear power’s new rule book: Managing uncertainty in efficiency, safety, and independence

Although much remains unsettled, three questions in particular stand out as both urgent and deeply confusing:

Legally, nuclear regulation and licensing must now be “efficient.” What does “efficient” mean, and what happens if the NRC fails to be efficient?

The NRC has developed both deterministic and probabilistic safety-centric methods, including probabilistic risk assessment (PRA) under risk-informed, performance-based (RIPB) regulation. Will these current safety-centric methods remain applicable under the new regulatory regime?

History suggests that nuclear regulation can be vulnerable to political and industry capture. What is the role of regulatory independence in ensuring nuclear safety?

This article examines each of these questions in light of emerging technological and legal uncertainties and offers recommendations for immediate action. The best window for action is closing, but it is still possible to prevent industry-wide paralysis and ensure that new nuclear power reactors are deployed both safely and efficiently.

Question 1: Legally, nuclear regulation and licensing must now be “efficient.” What does “efficient” mean, and what happens if the NRC fails to be efficient?

On July 9, 2024, the Accelerating Deployment of Versatile, Advanced Nuclear for Clean Energy (ADVANCE) Act—passed weeks earlier by Congress—was signed into law by President Biden. The act included a fundamental change in how the NRC regulates and licenses: For the first time since its establishment in 1974, the NRC’s mission was expanded beyond public health and safety to explicitly include efficiency. More specifically, the ADVANCE Act now requires the NRC to license and regulate “in a manner that is efficient and does not unnecessarily limit – (1) the civilian use of radioactive materials and deployment of nuclear energy; or (2) the benefits of civilian use of radioactive materials and nuclear energy technology to society.”

The NRC initially responded to the change in mission by arguing that “efficiency” in the ADVANCE Act was no different from “efficiency” as the commission defined the term in its Principles of Good Regulation. Notably, these principles were adopted in 1991, more than 30 years before the passage of the ADVANCE Act, at a time when the NRC had no statutory obligations related to efficiency. They were adopted, moreover, in response to a 1989 D.C. Circuit Court decision in Union of Concerned Scientists v. U.S. Nuclear Regulatory Commission and the United States of America, where the court interpreted the statutory mandate of the NRC to preclude consideration of cost in setting a backfit rule.

As a result, the definition of “efficiency” that the commission adopted at that time was not an attempt to interpret what Congress might mean but instead was the NRC’s own view on how to define a word in light of what it believed at that time to be a statutory bar on considerations of economic cost. As a result, it defined “efficiency” in a way that avoided considering economic cost and that focused on management quality and reduction of delay.

Can the NRC’s old definition of “efficiency” be used to interpret its new statutory directives under the ADVANCE Act? Almost certainly not, given another landmark legal event that occurred on June 28, 2024. After Congress passed the ADVANCE Act but before it was signed into law by President Biden, the Supreme Court decided Loper Bright v. Raimondo. This transformational case upended decades of legal precedent and changed how much power agencies across the government have when interpreting laws. Before this decision, under the so-called Chevron doctrine, courts would defer to the NRC’s reasonable interpretations of ambiguous terms. Previously, the NRC’s interpretations of “efficient,” as included in its Principles of Good Regulation, might have survived legal review. Loper Bright v. Raimondo changed that equilibrium. In overruling the Chevron doctrine, the Supreme Court held that courts would no longer defer to agencies’ reasonable interpretations of ambiguous statutory terms, and instead judges would substitute their own “independent judgment”—even on highly technical matters where agencies once held presumptive authority.

The relationship between the ADVANCE Act and the Loper Bright decision is critically important and has been missed by key stakeholders. The ADVANCE Act mandates the NRC to license and regulate in an “efficient” manner, but after Loper Bright, the meaning of “efficiency” will be judged by courts—not the commission. This means that the NRC must now design rules and make licensing decisions that a court sees as efficient. Merely referring to its own preferred view of “efficiency” will no longer suffice. Ignoring this sea change in the law leaves the NRC vulnerable to judicial reversal. Furthermore, any apparent progress it makes by interpreting the law in a way later rejected by the courts, including granting licenses to applicants, is vulnerable to reversal as well.

Therefore, much rests on the NRC changing its approach to align with what courts will require. Unfortunately, predicting how a court will interpret statutory meaning is complex, as it involves consideration of both judicial precedent and what are called “canons of construction,” or decision-making strategies traditionally used by courts. For those who specialize in such matters, there are clues to look for, and in some cases there are strategies that can secure NRC action against reversal.

Figure 1. Example of a cost-benefit analysis for efficient and safe nuclear licensing. This framework illustrates how safety risk, traditionally quantified through PRA, must be combined with other relevant cost and benefit dimensions to meet statutory expectations of efficiency.

This is the case especially for language on efficiency, which courts generally interpret to require a cost-benefit analysis (such as in the 2011 case of Business Roundtable v. SEC). Under this interpretation of efficiency, any NRC rulemaking or licensing action needs to be benefit-justified, and the fact that benefits justify costs must be established by a cost-benefit analysis.

While adjusting to judicial understandings of efficiency will require significant work, failing to adapt to the new requirements risks wasting resources and generating uncertainty. For example, the proposed licensing pathway under Part 53 will need to be revised to address efficiency, or action taken by the NRC can be overturned by a court. Any interested party, whether an affected member of the public or a representative from competing energy industries, could bring such a challenge.

As the NRC considers developing new methods to satisfy efficiency requirements as well as the mandate for adequate protection, we think cost-benefit analysis offers the best path forward. Although there are nuances in how such analyses can be done, Fig. 1 is our conceptualization of a cost-benefit analysis for efficient and safe nuclear licensing. By abandoning its attempt to define efficiency according to its own past guidance (acknowledging the historical limitations on its use of cost-benefit analysis) and adopting a more comprehensive cost-benefit analysis framework to justify its regulatory and licensing decisions, the NRC has the opportunity to prevent the risk of judicial reversal and eliminate the uncertainty such a reversal would create for the entire industry while still respecting its core safety mission.

Question 2: The NRC has developed both deterministic and probabilistic safety-centric methods, including PRA under the RIPB regulation. Will these current safety-centric methods remain applicable under the new regulatory regime?

Just as courts must now determine for themselves what it means for an agency to license and regulate in an efficient manner, they must also interpret other ambiguous terms in the ADVANCE Act, including requirements for RIPB licensing and regulation.

The term “risk-informed, performance-based” is not defined in the statute, and there is no established judicial tradition regarding this term. While predicting likely interpretations of the term is uncertain, a court can be expected to look skeptically on any interpretation that is inconsistent with the mission requirement of regulating and licensing in an “efficient” manner.

This matters because the NRC’s traditional interpretation of RIPB regulation—defining it as the integration of risk insights, engineering judgment (particularly the principle of defense-in-depth and the incorporation of safety margins), and performance history to achieve safety—is in partial tension with efficiency, and thus, with cost-benefit analysis. Defense-in-depth and safety margins, by design, impose extra layers of conservatism. In many cases, this conservatism dictates inefficient requirements where the marginal increase in benefits does not outweigh the expected marginal increase in costs.

In a world where the commission’s only goal is safety, adding safety margins may make sense—but in a world where it must also act efficiently, extra margins may not be justified. This presents the NRC with both challenges and opportunities. Without a clear statutory framework, the commission may face challenges if RIPB implementation is viewed as inconsistent with the efficiency mandates of the ADVANCE Act. That said, it has an opportunity to refine its RIPB framework to align with efficiency requirements, removing internal contradictions. By doing so, it can strengthen both regulatory defensibility and long-term sustainability of RIPB as a robust licensing approach.

The risk (or safety risk) insights of the RIPB approach, as currently informed by PRA and its foundational “risk triplet”— what can go wrong, how likely it is to happen, and what are the consequences—are well aligned with cost-benefit analysis in support of efficiency. Safety risk assessment for nuclear accidents, which is fundamental to RIPB regulation at the NRC, is also crucial for estimating the safety cost input in cost-benefit analysis for efficient licensing (Fig. 1). In the nuclear industry, particularly for large light water reactors, safety risk assessment has evolved into three levels of PRA. Level 1 quantifies accident initiators and core damage frequencies, level 2 models containment response and radionuclide releases, and level 3 assesses off-site consequences, including health and economic impacts on the public. PRA can quantify both the probability and consequences of an LWR nuclear accident, which is well-suited for determining the expected value of safety cost (C_s × P_s in Fig. 1) in cost-benefit analysis. However, the PRA methods the NRC currently uses, which rely on LWR operational data, are not adequate for advanced reactors because of the limited experiential data available. As highlighted by Zahra Mohaghegh in “Lighting the Path for Next-Generation PRA Leaders in Nuclear Engineering” (Nuclear News, Sep. 2021, p. 10), advancing PRA methods is essential to address this limitation. For example, such advancements include the integration of modeling and simulation of underlying phenomena and expanded use of probabilistic physics‑of‑failure approaches to generate simulation data and compensate for sparse experiential data; application of AI techniques to accelerate simulation data analysis and efficient computing; and enhanced uncertainty quantification and validation. These directions, emphasized by both the NRC staff (e.g., in the Part 53 proposed rule “Risk-Informed, Technology-Inclusive Regulatory Framework for Advanced Reactors”) and the PRA research community, will ensure PRA can remain credible and defensible in supporting safe and efficiency‑driven regulatory decisions for advanced nuclear technologies.

Some stakeholders have proposed deterministic safety assessments, such as the maximum hypothetical accident (MHA), as alternatives to advancing PRA methods for new reactors. While deterministic approaches may serve as a potential starting point, methods like the existing MHAs are poorly suited for efficiency-driven cost-benefit analysis because they lack the essential probability component needed to estimate the expected value of safety cost (C_s × P_s in Fig. 1). However, there may be ways to adjust current deterministic methods to align with efficiency objectives. One possible way is to use only two elements of the risk triplet—accident scenarios and their consequences—while assuming a probability of one for the worst-case accident, thus avoiding the need to estimate probabilities altogether. This would allow deterministic safety assessments to be used in cost-benefit analysis, though in a highly conservative manner. For such an approach to be theoretically sound and legally justifiable, the worst-case scenario must assume simultaneous failure of all safety protection systems—both active and passive—within the plant, along with the failure of all external emergency response systems, resulting in maximum possible consequences, which the current MHA approach does not capture. In practice, other high-consequence industries rarely rely solely on deterministic safety assessments when regulatory efficiency is a goal, because credible and legally defensible worst-case scenarios often lead to cost estimates too inflated for meaningful analysis.

The transition from strictly worst-case assumptions to probabilistic safety methods can be gradual and deliberate. Initially, strictly conservative worst-case assumptions may be employed. If the design does not meet cost-benefit criteria under these assumptions, more refined probabilistic methods should be introduced. For components with insufficient data, some may be analyzed using advanced modeling and simulation techniques, while others can be conservatively treated as guaranteed failures. If, after these refinements, the estimated safety risk still does not satisfy cost-benefit thresholds, applicants have several options to strengthen their case for licensing approval. These include expanding the use of advanced modeling and simulation to additional critical components, generating new experimental data to better estimate failure probabilities (rather than assuming guaranteed failure), or modifying the design to reduce overall safety risk. A step-by-step algorithm^[1] previously proposed by some of this article’s authors follows a similar transitional approach, though that framework relied solely on safety risk to guide decisions. Under the new regulatory regime focused on efficiency, a more balanced transitional algorithm is needed—one in which cost-benefit justification, including safety risk, becomes the central principle for determining when and to what extent modeling and simulation should be applied.

Given the challenges associated with worst-case-based methods and the fact that not all designs are benefit-justified under such an approach, there is a need to invest in advancing PRA methods for new reactors. Figure 1 makes clear these risk methods should also extend beyond safety risk. Efficiency-driven cost-benefit analyses require probabilistic inputs for multiple domains, for example, nuclear waste risk, climate risk, and even security-related risks. This multidimensional perspective is critical to building a defensible, future-oriented regulatory framework.

Question 3: History suggests that nuclear regulation can be vulnerable to political and industry capture. What is the role of regulatory independence in ensuring nuclear safety?

The final source of confusion stems from the question of regulatory independence and how it relates to nuclear safety. Recently, there has been a multitude of executive orders and actions that have challenged the NRC’s independence as a decision maker while expressing political commitment to furthering nuclear energy. It is now becoming increasingly common for the nuclear community to sound alarm bells, warning that threats to the independence of the NRC would lead to reduced safety. Some industry voices, meanwhile, share the assumption that less independence would mean less safety while welcoming the reduction in oversight, because safety regulation is seen as a barrier to timely deployment and innovation.

What these voices share is an assumption that safety oversight stems from regulatory independence. In reality, we believe the relationship between safety and regulatory independence is more complex. Three points in particular have been neglected.

First, regulatory independence is not always necessary to secure safety. Independence is often discussed as if it is the sole determinant of nuclear safety—but this neglects other important socio-technical contributing factors impacting safety. It is true that independent agencies like the NRC are traditionally insulated from political pressures and President Trump has taken multiple actions to increase his control of agencies. But independence does not guarantee a safe or effective regulator, nor does its

absence imply that an agency subverts its safety mission. Some “executive” agencies, which have always been accountable directly to the president, have a strong history of promoting safety. The Environmental Protection Agency, for example, lacks the structural independence of the NRC but has saved many lives while under the direct control of presidents concerned with safety. Simultaneously, independent agencies (e.g., the U.S. Consumer Product Safety Commission) can also fail at securing safety. If our goal is to promote safety, we cannot end our inquiry at independence.

Second, while even executive agencies can promote safety under some circumstances, it is important to recognize that questions about agency independence generate uncertainty. Recent challenges by President Trump to the constitutional validity of independent agencies and attempts to exert greater executive control over the NRC muddy the waters and increase the difficulty of predicting what the commission is legally obligated to do, who is responsible for making decisions, and whether political considerations are appropriate to address.

Resolving the question of whether the NRC is indeed independent—a consistently held view for the past 50 years—or directly accountable to the president would provide much-needed clarity on how the commission should proceed. Unfortunately, the legal status of independent agencies is an increasingly open question in administrative law. Until this status is clarified by the Supreme Court, questions of the status of agency independence generate uncertainty—and potentially stifle industry growth.

Finally, concerns of nuclear independence arise when there is a perception of weakened safety standards, particularly if the NRC is perceived as “rubber-stamping” designs without rigorous review. These concerns are heightened because of a common and inaccurate assumption within the nuclear community that an agency concerned with efficiency will neglect safety. In fact, as shown in Fig. 1, safety is a necessary input in determining the efficiency of a regulatory action. It is important to note that although the uncertainty in the NRC’s independence draws attention towards the executive branch, the NRC must still comply with all legal obligations—including to act in an efficient manner—regardless of whether it is independent or executive.

Call for action

The points above show that the nuclear industry is facing unprecedented uncertainty. We stand at a critical point in time where it is still possible to prevent potential chaos resulting from judicial reversals and to avert stagnation in the sector. Doing this, however, will require swift and decisive action. We recommend the following:

Recommendation 1: Build a robust cost-benefit analysis framework to support efficient regulation and licensing

The NRC should dedicate resources to developing a robust, transparent, and defensible cost-benefit analysis framework that supports efficient regulation and licensing and withstands legal scrutiny. This action should be undertaken in concert with efforts from industry, academia, and other stakeholders, and might even allow the NRC to align its action with recent executive orders mandating cost-benefit analysis. Such a robust framework would help insulate NRC decisions from judicial reversal.

This effort could build on existing cost-benefit practices in use, such as those that have been traditionally used in backfitting analysis, while drawing lessons and best practices from other agencies like the EPA, with decades of cost-benefit analysis experience. Within the NRC itself, institutional culture must evolve to accept that safety and efficiency are not necessarily conflicting, and that a properly structured cost-benefit analysis allows radiological safety to remain critical while recognizing additional societal benefits of nuclear energy.

In addition, the NRC should refine its RIPB framework to eliminate internal contradictions and ensure alignment with efficiency principles. In parallel, academia and industry should expand curricula and training programs, so the next generation of regulators and engineers is equipped to apply cost-benefit analysis effectively to nuclear decision-making.

Notably, while this recommendation would require a substantial realignment for the NRC, it is also the safest route forward for ensuring that the commission does not waste more resources or generate greater uncertainty by having impermissible actions overturned by courts. Any stakeholder will be able to bring a challenge against NRC decisions, whether an affected member of the public, a small nuclear start-up, or a representative from competing energy industries.

Recommendation 2: Enhance quantitative risk assessment methods

Risk analysis remains the backbone of nuclear safety, but the current regulatory transition demands methods that can meet both technical challenges and the legal mandate of efficiency. PRA, already mature for LWRs, must be expanded and adapted to advanced reactors to overcome challenges of sparse operational data and new design features.

The NRC, in partnership with industry, academia, and national laboratories, must dedicate resources to advancing PRA methods. Current advancements encompass the integration of modeling and simulation of underlying phenomena and broader adoption of probabilistic physics‑of‑failure methods to generate simulation data and address limited experiential data, the use of AI techniques to accelerate simulation data analysis and improve computational efficiency, and enhanced methods for uncertainty quantification and validation. These advancements would also allow probabilistic methods to provide credible inputs to cost-benefit analyses, ensuring that efficiency requirements can be satisfied without compromising safety.

By contrast, deterministic safety assessments—such as the MHA—may serve as a useful starting point; however, additional work is required to ensure that these deterministic approaches are both theoretically sound and legally justifiable. These approaches must also be compatible with the RIPB requirements of the ADVANCE Act and avoid unnecessarily limiting the societal benefits of nuclear technologies.

The transition from strictly worst-case assumptions to probabilistic safety methods can be carried out gradually. Initially, strictly conservative worst-case assumptions may be used. If the design fails to meet cost-benefit criteria under these assumptions, more-refined probabilistic methods should be introduced. For components lacking sufficient data, some can be assessed using advanced modeling and simulation while others may still be conservatively treated as guaranteed failures. Given the limitations of worst-case-based methods—and the reality that not all designs can be benefit-justified under such deterministic approaches—there is an urgent need to invest in the advancement of PRA methods for new reactors. These should encompass a range of risks, including safety, nuclear waste, climate impacts, and even security-related threats. Failing to develop probabilistic methods for these domains may leave NRC decisions inefficient, incomplete, and vulnerable to legal reversal.

Recommendation 3: Understand regulatory independence in context

Nuclear safety relies on strong institutional and agency safeguards as well as other aspects of socio-technical systems. As such, stakeholders should approach nuclear safety holistically. Regulatory independence can be an important safeguard, but it is not the sole determinant of safety. Neglecting the multifaceted nature of nuclear safety has led to two extreme views within the nuclear community: one assumes that the loss of independence will inevitably lead to accidents; the other promotes next-generation nuclear power plants by highlighting the strong safety record of existing reactors and emphasizing the enhanced safety features in advanced reactor designs.

However, both views can be flawed. The safety of existing plants is the result of multiple factors, such as current technologies and regulatory frameworks, both of which are changing for advanced reactors. Regardless of the NRC’s independence, the regulation of advanced reactors differs significantly from that of existing plants due to developments in the ADVANCE Act and the Loper Bright decision. Past safety performance of existing plants does not guarantee the future safety of advanced reactors, particularly given that the “inherent passive safety” features in these new designs lack proven operational experience. By embracing shared ownership of safety, all stakeholders in the nuclear community can together engage and ensure that important aspects of safety are effectively maintained, regardless of how the courts ultimately define the NRC’s independence.

Conclusion

The ADVANCE Act and recent executive actions promoting nuclear energy were designed to accelerate deployment, but without clear answers on efficiency, safety, and independence, they could do the opposite. The path forward requires reflective cost-benefit analysis tools, advanced risk analysis methods, and a pragmatic understanding of independence. Acting now can transform today’s legal and technological uncertainties into opportunities for a safer, more efficient, and resilient nuclear future. These actions will not just help NRC navigate legal scrutiny; they will also reassure investors, policymakers, and the public. In this sense, the “new rule book” is not just about compliance—it is about securing nuclear power’s promise as a cornerstone of a clean energy future.

George Joslin is a graduate research assistant and Ph.D. student in the Nuclear, Plasma, and Radiological Engineering (NPRE) Department’s Socio-Technical Risk Analysis (SoTeRiA) Research Laboratory at the University of Illinois Urbana-Champaign (UIUC). Arden Rowell is a professor in UIUC’s College of Law and a faculty affiliate at the Beckman Institute for Advanced Science and Technology. Ha Bui is a research scientist in the NPRE Department at UIUC and the associate director of research and outreach at the SoTeRiA Research Laboratory. Justin Valentino is a research affiliate at the SoTeRiA Research Laboratory and the director of the Organizational Informatics consulting company. Ziwei Che is a Juris Doctor (J.D.) student at UIUC’s College of Law. Seyed Reihani is a senior research scientist in the NPRE Department at UIUC and the SoTeRiA Research Laboratory. Zahra Mohaghegh is a professor and Donald Biggar Willett faculty scholar in the NPRE Department at UIUC, where she leads the SoTeRiA Research Laboratory and is a faculty affiliate of the Beckman Institute for Advanced Science and Technology.