Document: NUREG-0800
Document ID: 9cfc38bf-7808-446e-a43d-4ca9ff55df2a
Document Type: srp
Title: AC POWER SYSTEMS (ONSITE)
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1007/ML100740289.pdf
Revision Date: 2023-06
Chapter: 8
Section ID: 8.3.1
CFR Part: 
CFR Title: 

Content:
capacity, capability, and reliability for operation of all systems necessary for coping with SBO and for the time necessary to bring and maintain the plant in safe shutdown that will be available on a sufficiently timely basis. Also pursuant to 10 CFR 50.63, through citation of the definition of AAC source in 10 CFR 50.2, there should be minimum potential for common mode failure (i.e., acceptable independence) between any AAC power source used for SBO and the offsite power system or onsite power sources. Electrical ties between these systems, as well as the physical arrangement of their interface equipment, should not prevent the use of any AAC power source during loss of the offsite power system and/or onsite power sources. It is also important that provisions for an AAC source not adversely affect performance of offsite or onsite power system functions. AAC power sources located at or near the plant should conform to guidance provided in RG 1.155 concerning their capacity, capability, and physical independence from onsite safety-related systems and the preferred power system. See SRP Section 8.4 for details of the review of AAC power sources for SBO. As specified in 10 CFR 50.63, the reliability and redundancy of emergency onsite ac power sources must be used as a factor in determining the duration for which the plant must be capable of coping with an SBO event. A reliability program should also be provided to attain and maintain the target reliability levels of emergency onsite ac sources with respect to SBO considerations. RGs 1.9 and 1.155, and SRP Section 8.4 describe guidance acceptable to the staff for meeting the requirements of 10 CFR 50.63 related to addressing emergency onsite ac source reliability for SBO. Determination of SBO coping time is reviewed in detail in SRP Section 8.4. As documented in SECY 94-084, the electrical distribution system for evolutionary LWR design plants should include: 1) an alternate offsite power source available for