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:
em or in any way jeopardize plant safety. If an immediate shutdown is determined to be the safer course of action, the plant should commence an orderly shutdown in parallel with efforts to restore the inoperable power source(s) to operable status. If continued power operation is determined to be the safer course, the plant operator or the TSO should use the period of continued operation to restore the inoperable or degraded power system elements and DG-1244, Page 5 prepare for an orderly shutdown of the plant within the plant-specific completion time allowed by the technical specifications. 3. Orderly Shutdown If compliance with the technical specification LCO has not been restored within the required completion time limits, the nuclear plant operator shall promptly initiate an orderly shutdown in accordance with technical specifications. If resources are available, the plant operator should take all actions to improve the inoperable or degraded condition during the plant shutdown. During the plant shutdown, the TSO may take systemwide actions, such as increasing power generation or dropping selected loads, to ensure that the plant shutdown does not cause power grid instability or inadequate offsite power voltage. If the technical specification LCO is restored during the shutdown, the plant operator may terminate the shutdown and, assuming that there are no other restrictions, return the plant to rated power in accordance with the plant- specific technical specifications. However, the plant operator should also consider that the initiating condition may worsen and that a manual or automatic trip of the plant may be required or may occur. Levels of Power System Degradation To develop bases for specific guidance, this guide describes the following seven levels of power system degradation in order of increasing severity: 1. The available offsite ac power sources are one less than the LCO. This degradation level means that one of the required offsite ac sources is not