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:
eaking can simultaneously affect both circuits in such a way that neither can be returned to service in time to prevent fuel design limits or design conditions of the reactor coolant pressure boundary from being exceeded. In addition, the reviewer should verify that no single-point vulnerability exists whereby a weather-related event could disable any portion of the preferred power sources and simultaneously cause failure to supply AAC power. C. As the switchyard may be common to both offsite circuits, the electrical schematics of the switchyard breaker control system, its power supply and the breaker arrangement itself should be examined for the possibility of simultaneous failure of both circuits from single events such as a breaker not operating during fault conditions, spurious relay trip, loss of a control circuit power supply, or a fault in a switchyard bus or transformer. An example of a single-failure susceptibility of a transmission line protection scheme that was the primary cause of a cascading blackout and LOOP event is described in Reference 27. In addition, the reviewer should examine the failure modes and effects analysis (FMEA) of the switchyard by the applicant to verify that no single event would simultaneously fail both offsite power circuits and would fail one offsite circuit for passive design. D. The design is examined to determine that at least one of the two required circuits can, within a few seconds, provide power to safety-related equipment following a loss-of-coolant accident. GDC 17 does not require these circuits in themselves to be single-failure-proof for this accident. However, it is required that each circuit have the capability to be available in sufficient time to prevent fuel design limits and design conditions of the reactor coolant pressure boundary from being exceeded. Therefore, the design is examined to determine that the period of time that the station can remain in a safe condition assuming no ac power is available is