Document: NUREG-0800
Document ID: 97120913-d26f-4324-ab62-22f3f5b73925
Document Type: srp
Title: and 8.3.2.
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0636/ML063600410.pdf
Revision Date: 2023-06
Chapter: 8
Section ID: 8.3.1
CFR Part: 
CFR Title: 

Content:
relied on to maintain core cooling or containment integrity. Therefore, the passive reactor design supports an exemption to the requirements of GDC 17 for two physically independent offsite circuits, by providing safety-related passive safety systems for core cooling and containment integrity. As documented in SECY 94-084 & SECY-95-132, the staff addressed technical issues associated with the regulatory treatment of non-safety systems (RTNSS) process in passive plant designs. Risk-important, non-safety-related, active systems in passive light water reactors 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. For example, in the AP 1000 passive reactor design, ac power from an offsite system is required 8.2-15 Revision 4 - March 2007 to power the normal residual heat removal system (RNS) and also to provide a means of supplying power to post-accident monitoring and ac input power for Class 1E dc battery chargers. The RNS provides a non-safety-related means 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