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: 

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y safety function, have lower priority and may be overridden by other commands. The reasoning behind the proposed priority ranking should be explained in detail. The reviewer should refer the proposed priority ranking and the explanation to appropriate systems experts for review. The priority module itself should be shown to apply the commands correctly in order of their priority rankings, and should meet all other applicable guidance. It should be shown that the unavailability or spurious operation of the actuated device is accounted for in, or bounded by, the plant safety analysis. This recommendation does not prohibit the use of manual controls for operating individual safety system components after the corresponding safety system functions have been actuated. 3.6 Applicability to Current or New Plants This guidance applies to both the currently operating NPPs licensed under 10 CFR Part 50 and new NPPs licensed under 10 CFR Part 52. The potential for CCF in digital safety systems should be considered whether the systems are to be used in new plants or for upgrades in existing plants. The main difference is that new NPPs predominantly will use digital technology, whereas currently operating plants may introduce digital upgrades in a phased approach. Revision 6 – July 2012 BTP 7-19-18 Therefore, Point 4 applies to new plants and to existing plants installing digital equipment in the RTS or ESF. 3.7 Effects of Spurious Actuation Caused by CCF In cases in which a credible postulated spurious actuation(s) caused by a software CCF is not evaluated in design basis accident analyses, an analysis should be performed to determine whether such a postulated spurious actuation results in a plant response that falls outside the values or ranges of values chosen for controlling parameters as reference bounds for design. Further, the analysis should identify whether coping strategies exist for these postulated spurious actuations and consider the adequacy of such strategies.