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:
ost-accident monitoring and ac input power for Class 1E dc battery chargers. The RNS provides a non-safety-related means 8.2-16 Revision 5 - May 2010 available to inject water into the reactor coolant system (RCS) for reactor coolant makeup and decay heat removal. The design review should therefore cover the offsite power requirements to support those risk-important, non-safety-related, active systems identified through the RTNSS process. B. The routing of transmission lines should be examined on the station layout drawings and verified during the site visit to ensure that at least two circuits from the offsite grid to the onsite distribution buses are physically separate and independent. No other lines should cross above these two circuits. Attention should be directed toward ensuring that no single event such as a tower falling or a line breaking 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