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:
dicates: 1. the protective function is needed, 2. the safety-related automated system did not perform the protective function, and Revision 6 – July 2012 BTP 7-19-16 3. whether the automated diverse means or manual action is successful in performing the safety function. (9) If the D3 assessment reveals a potential for a CCF, then, in accordance with the augmented quality guidance for the diverse means used to cope with a CCF, the design of a diverse automated or diverse manual actuation system should address how to minimize the potential for a spurious actuation of the protective system caused by the diverse means. Use of design techniques (for example, redundancy, conservative setpoint selection, coincidence logic, and use of quality components) to mitigate these concerns is recommended. The adequacy of the diversity provided with respect to the above criteria should be justified by the applicant and explicitly addressed in the staff’s safety evaluation. 3.2 RTS and ESFAS Interconnection Interconnections between the RTS and ESFAS (for interlocks providing for reactor trip if certain ESFs are initiated, ESF initiation when a reactor trip occurs, or operating bypass functions) are permitted if it can be demonstrated that the functions required by the ATWS rule (10 CFR 50.62) are not impaired. Further, RTS and ESFAS could be combined into a single controller or central processing unit (CPU) provided D3 is adequately addressed to protect against CCF. 3.3 Single Failure and CCF Since CCF is not classified as a single failure (as defined in RG 1.53), a postulated CCF need not be assumed to be a single failure in design basis evaluations. Consequently, realistic assumptions can be employed in performing analyses to evaluate the effect of CCF coincident with DBEs. 3.4 Use of Automation in Diverse Means If automation is used in the diverse means, then the functions should be provided by equipment that is not affected by the postulated CCF and should be sufficient to