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:
iod that should not exceed 72 hours if the electric grid system capability and reserves are such that a subsequent single failure (including a trip of the unit’s generator but excluding an unrelated failure of the remaining offsite circuit if the loss of an offsite source caused this degraded state) would not cause a total loss of offsite power. If these conditions for continued power operation are met and if the affected source is restored within 72 hours, unrestricted operation may resume. Conversely, if the actions required by the technical specifications for continued power operation are met, but the source is not restored within 72 hours, the licensee should shut down the unit in accordance with plant-specific technical specifications. 2. The available onsite ac power sources are one less than the LCO. If the available onsite ac power sources are one less than the LCO, power operation may continue for a period that should not exceed 72 hours, provided that the redundant diesel generator is assessed within 24 hours to be free from common-cause failure or is verified to be operable in accordance with plant-specific technical specifications. DG-1244, Page 10 If the affected source is restored within the time period specified in the plant-specific technical specifications, unrestricted operation may resume. Conversely, if the conditions for continued power operation are met, but the source is not restored within the time period specified in the plant-specific technical specifications, the unit should be shut down. 3. The available offsite ac power sources are two less than the LCO. If the available offsite ac power sources are two less than the LCO, power operation may continue for 24 hours or for the time period specified in the plant-specific technical specifications if it appears likely that at least one of the offsite sources can be restored within that time. If these conditions for continued power operation are met and if both offsite sources are restored