NRC Calibrates Performance Deficiency Screening Under the Reactor Oversight Process

The US Nuclear Regulatory Commission (NRC) recently updated the Inspection Manual Chapters (IMCs) that guide how inspectors screen and characterize “Performance Deficiencies” at operating nuclear power reactors. The revised IMCs add quantitative thresholds and qualitative questions early in the issue-screening process, with the stated goal of making more-than-minor determinations more objective and consistent.

For licensees, the updates may affect when an issue is identified as part of an inspection finding, when additional significance review is required, and how quickly lower-risk issues can exit the Significance Determination Process (SDP). These updates clarify that not all Performance Deficiencies will be reported as inspection findings, limit NRC staff review of low-risk Performance Deficiencies, or reduce subjective decision-making in the SDP. The updated IMCs and related guidance became effective on May 18, 2026.

BACKGROUND

Each operating nuclear power reactor is subject to the NRC’s Reactor Oversight Process (ROP), through which the NRC staff inspects nuclear power plant performance and operations. The ROP is structured around safety-focused cornerstones, including initiating events, mitigating systems, barrier integrity, emergency preparedness, public radiation safety, occupational radiation safety, and security.

As part of the ROP, NRC inspectors collect and document observations about plant performance and operations. An observation may be identified as an “issue-of-concern” if it has a potential impact on safety or security that warrants additional inspection, screening, evaluation or regulatory action.

A Performance Deficiency occurs when two conditions are met:

• The issue-of-concern resulted from the licensee’s failure to meet a regulatory requirement or standard.
• The cause for the issue-of-concern was reasonably within the licensee’s ability to foresee and correct.

Performance Deficiencies are inputs to the NRC’s overall assessment of plant performance. The NRC will evaluate the safety significance of a Performance Deficiency through the SDP. IMC 0308, Attachment 3, “Technical Basis for Significance Determination Process,” provides the fundamental structure and background for the SDP framework.

As an early step in the SDP, the NRC must determine whether the Performance Deficiency is more-than-minor, in which case the deficiency is reflected as an inspection finding. Generally, the SDP involves the screening of Performance Deficiencies and a series of analyses to determine the significance of any resulting inspection findings in relation to the associated risk of a nuclear plant accident, either as a cause of the accident or the ability of plant safety systems or personnel to respond to the accident. The NRC may adjust its regulatory oversight of a facility depending on the significance of the inspection findings, categorized by colors: green, white, yellow, and red (in increasing level of significance).

The guidance in IMC 0609, “Significance Determination Process,” IMC 0609, Attachment 4, “Initial Characterization of Performance Deficiencies,” and IMC 0612, Appendix B, “Issue Screening Directions,” outlines the NRC’s process for the initial screening and characterization of Performance Deficiencies. 

DRIVERS FOR THESE CHANGES

The NRC aims to focus the ROP on issues of the highest safety and security significance while reducing unnecessary regulatory burden. These recent and coordinated IMC updates are part of the NRC’s ROP revision efforts in response to the Accelerating Deployment of Versatile, Advanced Nuclear for Clean Energy Act of 2024 (ADVANCE Act)[1] and Executive Order (EO) 14300, “Ordering the Reform of the Nuclear Regulatory Commission.”[2]

In Section 507 of the ADVANCE Act, Congress directed the NRC to identify improvements to its oversight and inspection processes and measures to increase the use of risk-informed procedures that balance resource levels commensurate with safety significance. Subsequently, EO 14300 directed the NRC to revise the ROP to reduce unnecessary burdens while remaining responsive to credible risks.

The NRC staff presented their initial recommendations in SECY-25-0045, followed by recommendations on revisions to the ROP baseline inspection program in SECY-26-0014. The Commission approved the staff’s proposal in SECY-26-0014 on March 25, 2026 and provided direction for the staff to revise the more-than-minor issue screening criteria for greater efficiency and effectiveness.

KEY CHANGES

The NRC’s updates to guidance for the initial screening and assessment of Performance Deficiencies span several IMCs. Below, we have identified some of the most significant guidance updates, including underlying appendices and attachments. This list is not exhaustive but represents the type and scope of the updates.

IMC 0612, Appendix B, Issue Screening Directions

• Routes screening of issues-of-concern under the Emergency Preparedness cornerstone through IMC 0609, Appendix B, and issues-of-concern under all other cornerstones through IMC 0612, Appendix B. This change effectively removes the more-than-minor determination for most Performance Deficiencies from the more subjective screening approach under IMC 0609.
• Clarifies that IMC 0609, Attachment 4, provides the initial screening for applicable cornerstone, and that the more-than-minor screening for Performance Deficiencies is done through the IMC 0609 appendix for the applicable cornerstone.
• Adds examples of violations that contributed to actual safety consequences, including instances where a licensee’s recommendation during a general emergency resulted in inappropriate protective actions by offsite response organizations.

IMC 0609, Significance Determination Process

• Establishes that minor Performance Deficiencies are not considered inspection findings and are not further evaluated for significance.
• Clarifies that the IMC updates aim to improve objectivity and consistency in the screening of Performance Deficiencies and are limited to the decision-making criteria in the determination of whether a Performance Deficiency is more-than-minor. The updates do not address the screening of finding with a risk significance higher than a green level.
• Provides that NRC staff must hold an Inspection Finding Review Board (IFRB) to gain alignment on the proposed screening path for a Performance Deficiency when the NRC staff disagrees on the screening result, subject to approval by the director of the Division of Reactor Oversight (DRO) in the Office of Nuclear Reactor Regulation.
• Assigns to the DRO director the responsibility and authority to approve proposed deviations from Performance Deficiency screening guidance.

IMC 0609, Attachment 1, Significance and Enforcement Review Panel (SERP) Process

• Adds an option for the NRC staff leading the issue determination to hold a “choice call” with the license before issuing a preliminary determination on an enforcement action. Through the “choice call,” the NRC would provide the licensee the option to (1) receive a preliminary determination letter and provide additional information through a written response or regulatory conference, or (2) receive a final significance determination if the licensee does not wish to provide additional information through a written response or regulatory conference.

IMC 0609, Attachment 4, Initial Characterization of Performance Deficiencies

• Confirms that minor Performance Deficiencies are not findings, and that more-than-minor Performance Deficiencies are findings, which may screen to green or be subject to further evaluation.
• Updates the term “finding” to “Performance Deficiency” throughout the attachment. Through this change, the NRC more accurately focuses on the screening of Performance Deficiencies and removes emphasis on the screening of findings, which have higher risk significance and may result in increased NRC oversight under the ROP.
• Adds (1) maintenance rule scoping and performance monitoring and (2) risk-significant operator actions to the list of degraded conditions or programmatic weaknesses under the scope of the mitigating systems cornerstone.

IMC 0308, Attachment 3, Technical Basis for Significance Determination Process

• Confirms that the determination of whether inspection results amount to a Performance Deficiency is done through IMC 0612, Appendix B.
• Adds to the IFRB scope an option to define resources, sponsor, coordination, and communications regarding the issue under review; thus, creating a main NRC staff point of contact for licensee interactions.

IMC 0308, Appendices

The NRC’s revised SDP guidance encompassed both IMC 0609 and IMC 0308 Appendices. IMC 0609 Appendices provide more detailed guidance for the screening of Performance Deficiencies based on the nature of the underlying issue and applicable ROP cornerstone. The IMC 0308 Appendices provide the technical bases, including background information and risk insights, for the corresponding IMC 0609 Appendix screening process. This section focuses on updates to the IMC 0308 Appendices, which provide context on the corresponding IMC 0609 Appendix revisions.

The discussion below provides examples of the qualitative screening questions and quantitative thresholds that the NRC added to the early steps of Performance Deficiency screening with the goal of increasing efficiency and consistency in the implementation of the SDP, as captured in the IMC 0308 Appendices.

Appendix A, Technical Basis for the At-Power SDP

• Screens as green finding a Performance Deficiency for steam generator tube operational leakage exceeding technical specification or administrative limits or requiring plant shut down, when the steam generator leakage does not exceed the accidental leakage criterion and meets the structural integrity performance criterion.
• Screens as a minor a Performance Deficiency that increases the likelihood of a plant trip or transients greater than 10% reactor power when it does not (1) result in an actual complete or partial loss of a support system and (2) increase the likelihood of the loss of a support system that would cause a plant trip or a transient greater than 10 percent reactor power.
• Screens as a green finding a Performance Deficiency where a mitigating system maintained its operability and probabilistic risk assessment (PRA) functionality after repairs, compensatory measures, procedure revisions, or reanalysis.
• Screens as minor a Performance Deficiency where a mitigating system maintained its operability and PRA functionality without reliance on repairs, compensatory measures, procedure revisions, or reanalysis.
• Screens as green finding a Performance Deficiency for the degradation of equipment or function specifically designed to mitigate a seismic, flooding, or severe weather initiating event for more than 24 hours but less than 14 days.
• Screens as a green finding a Performance Deficiency for a containment isolation valve or airlock door not functioning when there is another door or valve in series that is functional, and there is no degradation to isolation pathways.

Appendix C, Technical Basis for Fire Protection SDP

• Revises qualitative screening questions to identify conditions under which Performance Deficiencies associated with certain fire protection actions, including fire prevention and administrative controls, fixed fire protection systems, fire confinement, and manual firefighting actions may result in a minor Performance Deficiency or a green finding.

Appendix K, Technical Basis for “Maintenance Risk Assessment and Risk Management SDP”

• Adds qualitative screening questions to identify minor Performance Deficiencies prior to performing SDP calculations, including consideration of whether (1) the licensee’s decision was based on incorrect PRA assumptions; (2) there was an actual risk impact when failing to implement a risk management action; (3) the Performance Deficiency resulted in actual plant risk beyond licensee-calculated risk; and (4) the Performance Deficiency would have caused the licensee to enter a higher risk category or perform additional risk management actions.
• Adopts quantitative thresholds to separate minor Performance Deficiencies from green findings based on risk assessment results.

WHAT THE IMC UPDATES MEAN FOR LICENSEES

Individually and collectively, the IMC updates are designed to make the NRC’s assessment of Performance Deficiencies more efficient, particularly for issues with low-risk significance. They clarify the process to be used by the staff and clarify the applicable standards. For licensees, these efficiency gains in issue screening and significance determination may reduce the resources necessary for the review of Performance Deficiencies. Implementation of the IMC updates presents the following regulatory themes and opportunities:

• Clear distinction between Performance Deficiencies and inspection findings: The IMC sharpens the NRC’s focus on the screening of Performance Deficiencies. Not all Performance Deficiencies are inspection findings, but a Performance Deficiency may rise to an inspection finding if the Performance Deficiency is of more-than-minor risk significance.
• Additional screening paths defined for low-risk significance Performance Deficiencies: The IMC updates add qualitative screening questions and quantitative criteria to identify minor Performance Deficiencies and green inspection findings earlier in the SDP.
• Efficient use of resources: The IMC updates support early identification of low-risk Performance Deficiencies and instruct NRC staff to stop further assessment of Performance Deficiencies when additional review is not commensurate with risk significance.
• Consistent screening of Performance Deficiencies among NRC regional offices: The qualitative and quantitative thresholds should help limit inconsistent or subjective screening decisions in the early steps of the SDP. When staff disagree on Performance Deficiency screening, the IFRB process and DRO director approval provide a headquarters-level mechanism for alignment, thus reinforcing the governance of NRC headquarters offices over regional operations.

HOW WE CAN HELP

Our team stands ready to assist clients as they navigate fast-moving changes at the NRC. We are closely monitoring the evolution of the NRC’s licensing and oversight frameworks, and our nuclear team will continue to provide analysis and guidance as changes are implemented.