SUPPLEMENTARY INFORMATION:

I. Discussion

The NRC is issuing a new guide in the NRC's “Regulatory Guide” series. This series was developed to describe methods that are acceptable to the NRC staff for implementing specific parts of the agency's regulations, to explain techniques that the staff uses in evaluating specific issues or postulated events, and to describe information that the staff needs in its review of applications for permits and licenses.

The proposed RG 1.261 was issued with a temporary identification of Draft Regulatory Guide (DG)-1439 (ADAMS Accession No. ML24295A187). The NRC is issuing RG 1.261 to describe an approach that the NRC staff finds acceptable for using a technology-inclusive risk-informed change evaluation process for changes to a facility described in final safety analysis reports (as updated). Subject to the clarifications in Section C of the RG, this RG endorses the methodology described in NEI 22-05, Revision 0 (ADAMS Accession No. ML24032A237) as an acceptable alternative to using the criteria in section 50.59 of title 10 of the Code of Federal Regulations (10 CFR), “Changes, tests, and experiments.” Plants licensed using the methodology in NEI 18-04, Revision 1, “Risk-Informed Performance-Based Technology Inclusive Guidance for Non-Light Water Reactor Licensing Basis Development” (ADAMS Accession No. ML19241A472), and NEI 21-07, Revision 1, “Technology Inclusive Guidance for Non-Light Water Reactors, Safety Analysis Report Content for Applicants Using the NEI 18-04 Methodology” (ADAMS Accession No. ML22060A190), will have a licensing basis that is derived from a probabilistic risk assessment to a greater extent than if those plants were licensed under the existing regulatory frameworks in 10 CFR part 50, “Domestic Licensing of Production and Utilization Facilities,” and 10 CFR part 52, “Licenses, Certifications, and Approvals for Nuclear Power Plants.” Therefore, the criteria in 10 CFR 50.59, which were developed to reflect a licensing basis developed under the 10 CFR parts 50 and 52 frameworks, may not readily apply to those plants. Consequently, RG 1.261 addresses an area of regulation where special circumstances may warrant departure from some, or parts of some, regulations, such as 10 CFR 50.59. Ultimately, the licensee is responsible for preparing requests for such exemptions and related proposed license conditions to support this alternative.

II. Additional Information

The NRC published a notice of the availability of DG-1439 in the Federal Register on August 8, 2025 (90 FR 38516) for a 30-day public comment period. The public comment period closed on September 8, 2025. Public comments on DG-1439 and the NRC staff responses to the public comments are available in ADAMS under Accession No. ML26051A105.

III. Congressional Review Act

This RG is a rule as defined in the Congressional Review Act (5 U.S.C. 801-808). However, the Office of Management and Budget has not found it to be a major rule as defined in the Congressional Review Act.

IV. Backfitting, Forward Fitting, and Issue Finality

Licensees generally are not required to comply with the guidance in RG 1.261. If the NRC proposes to use this RG in an action that would constitute backfitting, as that term is defined in 10 CFR 50.109, “Backfitting,” and as described in NRC Management Directive 8.4, “Management of Backfitting, Forward Fitting, Issue Finality, and Information Requests”; affect the issue finality of an approval issued under 10 CFR part 52; or constitute forward fitting, as that term is defined in Management Directive (MD) 8.4, then the NRC staff will apply the applicable policy in MD 8.4 to justify the action. If a licensee believes that the NRC is using this RG in a manner inconsistent with the discussion in its Implementation section, then the licensee may inform the NRC staff in accordance with MD 8.4.

V. Submitting Suggestions for Improvement of Regulatory Guides

A member of the public may, at any time, submit suggestions to the NRC for improvement of existing RGs or for the development of new RGs. Suggestions can be submitted on the NRC's public website at https://www.nrc.gov/​reading-rm/​doc-collections/​reg-guides/​contactus.html. Suggestions will be considered in future updates and enhancements to the “Regulatory Guide” series.

VI. Executive Order (E.O.) 12866

The Office of Information and Regulatory Affairs determined that RG 1.261 is not a significant regulatory action under E.O. 12866.

Authority:42 U.S.C. 2011 et seq.