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Availability of Electric Power Sources

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Regulatory guide; issuance.


The U.S. Nuclear Regulatory Commission (NRC or Commission) is issuing Revision 1 of Regulatory Guide (RG) 1.93, “Availability of Electric Power Sources.” This guide describes actions the NRC staff considers acceptable when available electric power sources are less than the number of sources required by the limiting conditions for operations (LCOs) for the facility.


Please refer to Docket ID NRC-2010-0305 when contacting the NRC about the availability of information regarding this document. You may access information related to this document, which the NRC possesses and is publicly available using the following methods:

  • Federal Rulemaking Web site: Go to and search for Docket ID NRC-2010-0305. Address questions about NRC dockets to Carol Gallagher; telephone 301-492-3668; email:
  • NRC's Agencywide Documents Access and Management System (ADAMS): Publicly available documents created or received at the NRC are available online in the NRC Library at To begin the search, select “ADAMS Public Document” and then select “Begin Web-based ADAMS Search.” For problems with ADAMS, please contact the NRC's Public Document Room (PDR) reference staff at 1-800-397-4209 or 301-415-4737, or by email to The ADAMS accession number for each document referenced in this notice (if that document is available in ADAMS) is provided the first time that document is referenced. Revision 1 of Regulatory Guide 1.93 is available electronically under ADAMS Accession Number ML090550661. The regulatory analysis may be found in ADAMS under Accession Number ML101870610. Public Comments and the NRC staff response to them are summarized in a table that may be found in ADAMS under Accession Number ML090550693.

Regulatory guides are not copyrighted, and NRC approval is not required to reproduce them.

  • NRC's Public Document Room (PDR): The public may examine and have copied, for a fee, publicly available documents at the NRC's PDR, O1-F21, One White Flint North, 11555 Rockville Pike, Rockville, Maryland 20852.


Sheila Ray, Division of Engineering, Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, telephone: 301-251-7644; email:


I. Introduction

The NRC is issuing a revision to an existing guide in the NRC's “Regulatory Guide” series. This series was developed to describe and make available to the public information such as methods that are acceptable to the NRC staff for implementing specific parts of the agency's regulations, techniques that the staff uses in evaluating specific problems or postulated accidents, and data that the staff needs in its review of applications for permits and licenses.

The recommendations in this guide describe actions that the staff of the NRC considers acceptable when the number of available electric power sources are less than the number of sources required by the limiting conditions for operation (LCOs) for a facility. This regulatory guide applies to single- and multiple-unit plants and is consistent with the improved standard technical specifications (iSTS) (NUREG-1430 through NUREG-1434). The LCO-required actions and specified completion times referred to in this guide are based on the completion times presented in Regulatory Guide 1.93, Revision 0, “Availability of Electric Power Sources,” issued December 1974, which have been incorporated into the required actions in the iSTS.

The recommendations described in this guide are an approach that the NRC staff finds acceptable for satisfying some of the requirements of General design criterion (GDC) 17, “Electric Power Systems,” of Appendix A, “General Design Criteria for Nuclear Power Plants,” to 10 CFR part 50, “Domestic Licensing of Production and Utilization Facilities.”

II. Further Information

Revision 1 of RG 1.93 was issued with a temporary identification as Draft Regulatory Guide, DG-1244. DG-1244, was published in the Federal Register on September 24, 2010 (75 FR 5844) for a 60 day public comment period. The public comment period closed on November 26, 2010. The NRC staff's responses to the public comments on DG-1244 are available under ADAMS Accession Number ML090550693.

Dated at Rockville, Maryland, this 19th day of March, 2012.

For the Nuclear Regulatory Commission.

Richard Jervey,

Acting Chief, Regulatory Guide Development Branch, Division of Engineering, Office of Nuclear Regulatory Research.

[FR Doc. 2012-7437 Filed 3-27-12; 8:45 am]