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:
guide contains information collection requirements covered by 10 CFR Part 50 that the Office of Management and Budget (OMB) approved under OMB control number 3150-0011. The NRC may neither conduct nor sponsor, and a person is not required to respond to, an information collection request or requirement unless the requesting document displays a currently valid OMB control number. B. DISCUSSION Background Pursuant to GDC 17, an electric power system is required to supply power to loads important to safety in an NPP. Nuclear plants with more power sources than the number of sources required by GDC 17 may be able to withstand the multiple failures and still satisfy the LCOs. However, during the normal course of operation, any NPP may lose power sources to the extent that the LCOs are not met. This regulatory guide provides specific guidance to address situations in which the electric power source(s) is less than the adequate number of power sources. Loss of Offsite Power For NPPs licensed in accordance with the GDC in Appendix A to 10 CFR Part 50, the design criteria for onsite and offsite electrical power systems are provided in GDC 17. For NPPs not licensed in accordance with the GDC in Appendix A, the applicable design criteria are provided in the updated final safety analysis report. These reports set forth criteria similar to GDC 17, which requires, among other things, that an offsite electric power system be provided to permit the functioning of certain structures, DG-1244, Page 3 systems, and components (SSCs) important to safety in the event of anticipated operational occurrences and postulated accidents. The technical specifications of operating NPPs include the operational restrictions resulting from the loss of power sources. In general, plant technical specifications require the operability of the offsite power system as a part of the LCOs and specify actions to be taken when the offsite power system is inoperable. Plant operators should be aware of (1) the