Document: NUREG-0800
Document ID: 9cfc38bf-7808-446e-a43d-4ca9ff55df2a
Document Type: srp
Title: AC POWER SYSTEMS (ONSITE)
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1007/ML100740289.pdf
Revision Date: 2023-06
Chapter: 8
Section ID: 8.3.1
CFR Part: 
CFR Title: 

Content:
e power source for non-safety loads, unless it has been demonstrated that the design margins will result in transients for loss-of non-safety-power events that are no more severe than those associated with the turbine-trip-only event in existing plant designs. As documented in SECY-91-078, evolutionary LWR design applications should satisfy the requirements of GDC 17 with an electrical distribution system design that includes at least one offsite circuit to each redundant safety division supplied directly from one of the offsite power sources with no intervening non-safety buses in such a manner that the offsite source can power the safety buses upon the failure of any non-safety bus. Aside from this configuration variation, the review to ascertain the independence of the onsite with respect to the offsite power systems is similar to that for existing plant designs. Passive LWR design applications provide passive safety systems that do not need Class 1E ac electric power, other than that provided by the Class 1E dc batteries and their inverters, to accomplish the plant's safety-related functions for 72 hours. However, as documented in SECY 94-084, SECY-95-132, and RG 1.206 Section C.IV.10, the staff addressed technical issues associated with the RTNSS process in passive plant designs for risk-important, non-safety-related, active systems, such as the ac power system. These systems may have a significant role in accident and consequence mitigation by providing defense-in-depth functions to supplement the capability of the safety-related passive systems. Passive reactor plant designs should, therefore, include one offsite power source with sufficient capacity and capability from the transmission network to power the safety-related systems and all other auxiliary systems under normal, abnormal, and accident conditions. The offsite power source should be designed to minimize to the extent practical the likelihood of its failure under normal, abnormal, and accident