Document: NUREG-0800
Document ID: 81256f55-72dd-4777-9472-f373c71c4554
Document Type: srp
Title: AC POWER SYSTEMS (ONSITE)
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0705/ML070550065.pdf
Revision Date: 2023-06
Chapter: 8
Section ID: 8.3.1
CFR Part: 
CFR Title: 

Content:
ater or resulting from pre-existing manufacturing defects could result in multiple equipment failures. The reviewer should verify that underground or inaccessible power and control cable runs that are susceptible to protracted exposure to wetted environments or submergence as a result of tidal, seasonal, or weather event water intrusion are adequately identified, that they are monitored, or that corrective actions are implemented. Underground or inaccessible power cables connecting offsite power to safety 8.3.1-23 Revision 3 - March 2007 buses or power cables to equipment with accident mitigating functions should be considered in the review. Examples of submerged and wetted underground cable failures from the operating experience are provided in Information Notice (IN) 2002-12 and GL 2007-01. 3. Onsite and Offsite Power System Independence In ascertaining the independence of the onsite power system with respect to the offsite power system, the electrical ties between these two systems as well as the physical arrangement of the interface equipment are reviewed to ensure that no single failure will prevent the separation of the redundant portions of the onsite power system from the offsite power system when necessary. The scope of the review for independence extends from the supply breakers connected to the low side of the unit auxiliary transformers and startup transformers (referred to as the offsite or preferred power supplies) to the station safety-related distribution system. The number and capability of electrical circuits from the offsite power system to the safety buses should be consistent with satisfying the requirements of GDC 17. Then, downstream of the offsite power breakers at the safety buses, the design must satisfy the requirements for redundancy and independence of GDCs 34, 35, 38, 41, and 44; that is, for onsite power system operation (assuming offsite power is not available), the system safety function can be accomplished assuming a single failure.