Document: NUREG-0800
Document ID: 106978f1-fb10-4fa9-ad95-601f3c16bd36
Document Type: srp
Title: Revision 5 - March 2007
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0705/ML070550072.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
CFR Part: 
CFR Title: 

Content:
cause failure of such components need not be considered in the course of a D3 analysis. When a basis is given that a block is not susceptible to software common-cause failure, the Staff should examine the justification carefully. The safety evaluation of Westinghouse WCAP-15413, “Westinghouse 7300a ASIC-Based Replacement Module Licensing Summary Report," provides an example of the basis for such a determination. Effect of Other Blocks When considering the effects of a postulated common-cause failure, diverse blocks are assumed to function correctly. This includes functions of blocks that act to prevent or mitigate consequences of the common-cause failure under consideration. Identification of Alternate Trip or Initiation Sequences Thermal-hydraulic analyses, using best-estimate (realistic assumptions) methods, of the sequence of events that would occur if the primary trip channel failed to trip the reactor or actuate ESF are included in the assessment. (Coordination with the organization responsible for the review of reactor systems is necessary in reviewing these analyses.) Identification of Alternative Mitigation Capability For each design basis event, alternate mitigation actuation functions that will prevent or mitigate core damage and unacceptable release of radioactivity are identified. When a common-cause failure is compensated by a different automatic function, a basis is provided that demonstrates that the different function constitutes adequate mitigation for the conditions of the event. When operator action is cited as the diverse means for response to an event, the applicant/licensee should demonstrate that adequate information (indication), appropriate operator training, and sufficient time for operator action are available. BTP 7-19-9 Revision 5 - March 2007 Justification for Not Correcting Specific Vulnerabilities If any identified vulnerabilities are not addressed by design modification, refined analyses, or provision of alternate trip, initiation,