SUPPLEMENTARY INFORMATION:

I. Obtaining Information and Submitting Comments

A. Obtaining Information

Please refer to Docket ID NRC-2026-0826 when contacting the NRC about the availability of information for this action. You may obtain publicly available information related to this action by any of the following methods:

• Federal Rulemaking website: Go to https://www.regulations.gov and search for Docket ID NRC-2026-0826.
• NRC's Agencywide Documents Access and Management System (ADAMS): You may obtain publicly available documents online in the ADAMS Public Documents collection at https://www.nrc.gov/​reading-rm/​adams.html. To begin the search, select “Begin ADAMS Public Search.” For problems with ADAMS, please contact the NRC's Public Document Room (PDR) reference staff at 1-800-397-4209, at 301-415-4737, or by email to PDR.Resource@nrc.gov. The ADAMS accession number for each document referenced (if it is available in ADAMS) is provided the first time that it is mentioned in this document.
• NRC's PDR: The PDR, where you may examine and order copies of publicly available documents, is open by appointment. To make an appointment to visit the PDR, please send an email to PDR.Resource@nrc.gov or call 1-800-397-4209 or 301-415-4737, between 8 a.m. and 4 p.m. eastern time (ET), Monday through Friday, except Federal holidays.

B. Submitting Comments

The NRC encourages electronic comment submission through the Federal rulemaking website ( https://www.regulations.gov). Please include Docket ID NRC-2026-0826 in your comment submission.

The NRC cautions you not to include identifying or contact information that you do not want to be publicly disclosed in your comment submission. The NRC will post all comment submissions at https://www.regulations.gov as well as enter the comment submissions into ADAMS. The NRC does not routinely edit comment submissions to remove identifying or contact information.

If you are requesting or aggregating comments from other persons for submission to the NRC, then you should inform those persons not to include identifying or contact information that they do not want to be publicly disclosed in their comment submission. Your request should state that the NRC does not routinely edit comment submissions to remove such information before making the comment submissions available to the public or entering the comment into ADAMS.

II. Additional Information

The NRC is issuing for public comment a DG 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 DG, entitled “Application and Testing of Onsite Emergency Alternating Current Power Sources in Production and Utilization Facilities,” is temporarily identified by its task number, DG-1477 (ADAMS Accession No. ML26007A205).

The staff is also issuing for public comment a draft regulatory analysis (ADAMS Accession No. ML26007A215). The staff developed a regulatory analysis to assess the value of issuing or revising a regulatory guide as well as alternative courses of action.

The NRC previously published a DG to update RG 1.9, Revision 4. On January 19, 2021, the NRC issued DG-1303 for public comment by Federal Register notice (86 FR 5267). Public comments were received from members of the public, the Nuclear Energy Institute, and Institute of Electrical and Electronics Engineers (IEEE) (ADAMS Accession Nos. ML21050A427, ML21050A428, and ML21050A429), and the Advisory Committee on Reactor Safeguards (ACRS) provided feedback in a letter dated July 26, 2021 (ADAMS Accession No. ML21202A149). The staff responded to the ACRS letter on October 13, 2021 (ADAMS Accession No. ML21277A254). The staff considered the public comments and ACRS feedback, to the extent possible, in the development of DG-1477. The staff issued DG-1477 to supersede DG-1303 because International Electrotechnical Commission (IEC) and IEEE have released new standards regarding emergency AC standby power ( printed page 33004) supplies that supersede the existing standards endorsed in RG 1.9, Revision 4. This revision of the guide (Revision 5) is updated to endorse and provide guidance for these new standards. Revision 5 applies to production and utilization facilities licensed under part 50 of title 10 of the Code of Federal Regulations (10 CFR) and 10 CFR part 52 within the scope of this RG. Revision 5 is the result of lessons learned from license amendment review activities and inspections, industry operating experience, design certification reviews, combined license application reviews, and NRC staff analysis. Furthermore, Revision 5 includes specific guidance on CTGs and onsite emergency AC power sources other than EDGs and CTGs. If finalized, the NRC will issue Revision 5 of this RG to provide current guidance, based on the generally accepted methods and procedures for EDGs, CTGs, and any other onsite power sources.

This proposed Revision 5 of RG 1.9 endorses, with supplements and clarifications, IEC/IEEE Std 63332 387:2024, “Nuclear facilities-Electrical power systems-Diesel generator units applied as standby power sources,” and IEEE Std 2420-2019, “IEEE Standard Criteria for Combustion Turbine-Generator Units Applied as Standby Power Supplies for Nuclear Power Generating Stations.” These standards delineate principal design criteria and qualification and testing guidelines to help ensure that EDGs and CTGs meet performance requirements.

III. Backfitting, Forward Fitting, and Issue Finality

The issuance of DG-1477, proposed Revision 5 to RG 1.9, provides guidance that the staff of the NRC considers acceptable to comply with the NRC regulations for onsite emergency AC power sources in production and utilization facilities. Revision 5 to RG 1.9 would not constitute backfitting as defined in 10 CFR 50.109, “Backfitting,” and as described in NRC Management Directive (MD) 8.4, “Management of Backfitting, Forward Fitting, Issue Finality, and Information Requests”; affect issue finality of any approval issued under 10 CFR part 52, “Licenses, Certificates, and Approvals for Nuclear Power Plants”; or constitute forward fitting as defined in MD 8.4. As explained in DG-1477, applicants or licensees generally would not be required to comply with the positions in DG-1477.

IV. 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.

V. Executive Order (E.O.) 12866

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

Authority:

42 U.S.C. 2011 et seq.

91 FR 33003