Document: NUREG-0800
Document ID: a2680f96-0e15-402d-89ab-688ff09806a8
Document Type: srp
Title: with respect to the specified station blackout event/duration.13
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070497.pdf
Revision Date: 2023-06
Chapter: 8
Section ID: 8.3.2
CFR Part: 
CFR Title: 

Content:
n 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 8.2-11 DRAFT Rev. 4 - April 1996 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 independent of ac power. For those designs that utilize a backfeed path through the main generator step-up transformer, the reviewer must first ascertain if this path is required to satisfy the GDC 17 requirement for an immediate or delayed access circuit. If the circuit is for delayed access only, then the same determination (as discussed in the previous paragraph) must be made, i.e., there is sufficient time to make this circuit available (assuming the availability of the grid itself but the unavailability of the immediate access circuit and the onsite power supplies) such that the reactor remains in a safe condition. If the circuit is required for immediate access or utilizes generator circuit breakers or generator load break switches, then the reviewer should use the guidelines contained in Appendix A to this SRP section. (e) Each of the circuits from the offsite system to the onsite distribution buses should have the capacity and capability to supply the loads assigned to the bus or buses it is connected to during normal or abnormal operating conditions, accident conditions, or plant shutdown conditions. Therefore, the loads to be supplied during these conditions should be determined from