Document: NUREG-0800
Document ID: 97120913-d26f-4324-ab62-22f3f5b73925
Document Type: srp
Title: and 8.3.2.
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0636/ML063600410.pdf
Revision Date: 2023-06
Chapter: 8
Section ID: 8.3.1
CFR Part: 
CFR Title: 

Content:
eans of complying with 10 CFR 50.63 requirements involves the provision of an alternate ac (AAC) source (as defined in 10 CFR 50.2) of sufficient capacity, capability, and reliability for operation of all systems required for coping with station blackout and for the time required to bring and maintain the plant in safe shutdown that will be available on a sufficiently timely basis. 10 CFR 50.63 also requires (through citation of the definition of AAC source in 10 CFR 50.2) minimum potential for common mode failure (i.e., acceptable independence) between any AAC power source used for station blackout and the offsite power system or onsite power sources. Electrical ties between these systems, as well as the physical arrangement of their interface equipment, must 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 will 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 Regulatory Guide 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 station blackout. For passive reactor design applications, such as the AP 1000, the potential risk contribution of a station blackout is minimized by not requiring ac power sources for design-basis events. The safety-related passive systems in these plants do not need non-safety-related ac power sources to perform safety-related functions. They are designed to automatically establish and maintain safe shutdown conditions after design basis events for 72 hours, without operator action, following a loss of both onsite and offsite ac power sources. Consequently, passive reactor designs meet the requirements of 10 CFR 50.63 for 72 hours. Meeting the requirements