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:
tions 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 within 24 hours or within the time period specified in the plant-specific technical specifications, unrestricted operation may resume. If only one offsite source is restored within 24 hours, power operation may continue for a total time that should not exceed 72 hours in accordance with the conditions described in Regulatory Position 1. Conversely, if no offsite source is restored within the first 24-hour period of continued power operation, within 6 hours, the licensee should promptly bring the unit to a hot shutdown condition for boiling-water reactors (BWRs) (Mode 3) and to a hot standby condition for pressurized-water reactors (Mode 3) or as specified in plant- specific technical specifications. 4. The available offsite and onsite ac power sources are each one less than the LCO. If the available offsite and onsite ac power sources are each one less than the LCO, power operation may continue for 12 hours (1) if the capacity and voltage 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) would not cause a total loss of offsite power and (2) if it appears highly likely that at least one of the affected sources can be restored within 12 hours. If these conditions for continued power operation are met and if both sources are restored within 12 hours, unrestricted operation may resume. If either an offsite or an onsite ac source is restored within 12 hours, power operation may continue for a total time that should not exceed 72 hours in accordance with the condition described in Regulatory Position 1 (or Regulatory Position 2) for the loss of one ac source. Conversely, if neither an offsite source nor an onsite source is restored within the first 12 hours of continued