Document: NRC Regulatory Guide
Document ID: 9a8db182-3194-4663-aeb3-64f2e4edd6aa
Document Type: regulatory_guide
Title: Availability of Electric Power Sources (Rev. 1)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1008/ML100840581.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.93
CFR Part: 
CFR Title: 

Content:
nd periodically during the performance of any grid-risk-sensitive activities. The communication between the NPP operator and grid TSO should enable the NPP operator to obtain up-to-date information on existing and projected grid conditions for use in maintaining a current and valid risk assessment and in managing possibly changing risk. The communication with the TSO should include whether a loss of NPP electrical output could DG-1244, Page 4 impact the local grid, as well as, activities that increase the likelihood of a plant trip or a loss of offsite power. Passive plant designs may not require multiple power sources if those passive plant designs rely on passive safety-related systems for core cooling and containment integrity. These passive safety-related systems do not require offsite electric power for valves and the related instrumentation. If offsite power is not available, the nonsafety-related onsite diesel generators should be available for important plant functions. These nonsafety-related diesel generators do not require any technical specification requirements because they are treated under the regulatory treatment of nonsafety systems. The basis for the regulatory treatment of nonsafety systems applies to those nonsafety systems that perform risk- significant functions and that, therefore, are candidates for regulatory oversight. However, if an offsite power system or a diesel generator is found to be inoperable at these plants, the licensees should make a concerted effort to restore the inoperable offsite ac source or the diesel generator to operable status within a reasonable time period. For evolutionary plant designs that have three or four safety trains and have excess redundancy in their onsite power systems, the restrictions imposed on such plants on the loss of required onsite power sources may differ from those recommended in this guide and should be evaluated on a case-by-case basis. Operational Restrictions The operational restrictions