Document: NUREG-0800
Document ID: dc63e8aa-2a74-4078-9e19-9a26ed1b4d8c
Document Type: srp
Title: Revision 6 – July 2012
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1105/ML110550791.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
CFR Part: 
CFR Title: 

Content:
may be used to meet the requirements of IEEE Std. 603-1991. If a D3 analysis indicates that the safety-related manual initiation would be subject to the same potential CCF affecting the automatically initiated protective action, then under Point 3 of the NRC position on D3, a diverse manual means of initiating protective action(s) would be needed (i.e., two manual initiation means would be needed). This diverse manual means may be safety or non-safety. If the system/division level manual initiation required by IEEE Std. 603-1991 is sufficiently diverse, the diverse (second) manual system level or division level actuation would not be necessary for the automated protective actions (see Figure 1). Revision 6 – July 2012 BTP 7-19-10 Figure 1. Two Manual Initiation Methods verses One Initiation Method 1.6 D3 Assessment To defend against potential CCF, the NRC staff considers D3 and the use of defensive measures to avoid or tolerate faults and to cope with unanticipated conditions to be key elements in high quality digital system designs. However, despite high quality in the development and use of defensive design measures, system errors could still defeat safety functions in redundant, safety-related channels. Therefore, as set forth in Points 1, 2, and 3 of the NRC position on D3, the applicant should perform a D3 assessment of the proposed DI&C system to demonstrate that vulnerabilities to CCF have been adequately addressed. In this assessment, the applicant may use realistic assumptions to analyze the plant response to DBEs (as identified in the SAR). If a postulated CCF could disable a safety function that is credited in Revision 6 – July 2012 BTP 7-19-11 the safety analysis to respond to the DBE being analyzed, a diverse means of effective response (with documented basis) is necessary. The D3 analysis methods used in ALWR DC applications and for operating plant upgrades are documented in NUREG/CR-6303, which describes an acceptable method for performing such