Document: NUREG-0800
Document ID: 853719df-a6ea-408b-8d43-5956155abc38
Document Type: srp
Title: and 8.3.2.
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1007/ML100740246.pdf
Revision Date: 2023-06
Chapter: 8
Section ID: 8.3.1
CFR Part: 
CFR Title: 

Content:
ansmission 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 LOCA. 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 greater than the time required to reestablish ac power from the offsite grid to the onsite Class 1E distribution buses for each single failure event. The switchyard circuit breaker control scheme should be such that any incoming transmission line, switchyard bus, or any path to the onsite safety-related distribution buses can be isolated so that ac power can be reestablished to the onsite Class 1E buses through its redundant counterpart. This should be achieved with separate and redundant breaker tripping and closing devices that are actuated by redundant dc battery supplies. Air stored under pressure in accumulators or spring energy should be used to open and/or close breakers 8.2-17 Revision 5 - May 2010 independent of ac power. Further information for the reviewer on the importance of redundancy in transmission grid protective schemes is provided by operating experience events (Reference 27). For those designs that utilize a backfeed path through the