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:
ibed 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 power operation, the licensee should shut down the plant in accordance with plant-specific technical specifications. 5. The available onsite ac power sources are two less than the LCO. If the available onsite ac electric power sources are two less than the LCO, power operation may continue for a period that should not exceed 2 hours. If both onsite ac electric power sources are restored within these 2 hours, unrestricted operation may resume. If only one onsite ac power source is restored within these 2 hours, power operation may continue for a total time that should not exceed 72 hours in accordance with the conditions described in Regulatory Position 2 for the loss of one onsite ac source. Conversely, if no onsite ac source can be restored within the first 2 hours of continued power operation, the licensee should shut down the plant in accordance with plant-specific technical specifications. 6. The available onsite dc power sources are one less than the LCO. If the available onsite dc power sources are one less than the LCO, power operation may continue for a period that should not exceed 2 hours. If the affected dc source is restored within DG-1244, Page 11 these 2 hours, unrestricted operation may resume. If not, the licensee should shut down the plant in accordance with plant-specific technical specifications. The licensee should closely monitor the required functions of the dc system during the shutdown process and take necessary actions (such as cross-connecting a supply or shedding optional loads) to ensure safe shutdown. 7. The available inverters are one less than the LCO. If the available inverters are one less than the LCO, power operation may continue for a period that should not exceed the 24 hour time period specified in the standard technical