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:
and controls shall be independent and diverse from the safety computer system identified in Items 1 and 3 above.” Concerning Point 2: The term “best-estimate methods” is more accurately referred to as “realistic assumptions,” which are defined as normal plant conditions corresponding to the event. For example: • power levels, • temperatures, • pressures, • flows, and • alignments of equipment. Thus, in performing the assessment, the vendor or applicant should analyze each postulated CCF for each event that is evaluated in the SAR section analyzing power operation accidents at the plant conditions corresponding to the event. This analysis may use realistic assumptions to analyze the plant response to DBEs, or the conservative assumptions on which the Chapter 15 SAR analysis is based. Concerning Point 3: If the D3 analysis indicates a postulated CCF could disable a safety function, then Point 3 directs that an applicant should identify an existing diverse means or add a diverse means that may be non-safety (see Section 1.6, “D3 Assessment”). Point 3 also addresses manual initiation methods of RTS and ESFAS, if subject to a postulated CCF. The independence requirements of a diverse protection system from the safety protection system (i.e., physical, electrical, and communication separation) are defined in IEEE Std. 603-1991. The diverse means could be safety-related and part of a safety division, and would then be subject to meeting divisional independence requirements. The diverse means could also be non-safety-related in which case the IEEE Std. 603-1991 requirement to separate safety-related equipment from that which is not safety-related would still apply and would require independence of the two systems. In either case, the diverse means should be independent of the safety system such that a CCF of the safety system would not affect the diverse system. Revision 6 – July 2012 BTP 7-19-8 Concerning Point 4: Point 4 directs the inclusion of