Document: NUREG-0800
Document ID: 65f2433f-2c4a-4580-b173-0c6da7fa4d73
Document Type: srp
Title: Draft Revision 7 – August 2015
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1515/ML15159A996.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
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CFR Title: 

Content:
ip 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. BTP 7-19-15 Draft Revision 7 – August 2015 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 maintain plant conditions within recommended acceptance criteria for the particular AOO or postulated accident. The automated diverse means may be performed by a nonsafety system, if the system is of sufficient quality to perform the necessary function(s) under the associated event conditions. The automated diverse means should be similar in quality to systems required by the ATWS rule (10 CFR 50.62), as described in the enclosure to GL 85-06, “Quality Assurance Guidance for ATWS Equipment that is Not Safety-Related.” Other systems that are credited in the analysis that are in continuous use (e.g., the normal RCS inventory control system or normal steam generator level control system) are not required to be upgraded to the augmented quality discussed above. 3.5 Use of Manual Action as a Diverse Means of Accomplishing Safety Functions If manual operator actions are used as the diverse means or as part of the diverse means to accomplish a safety function, a suitable HFE analysis should be performed by the applicant to demonstrate