Document: NUREG-0800
Document ID: 757b676a-0f71-4094-8677-ca3a50743281
Document Type: srp
Title: Revision 7 – August 2016
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1601/ML16019A344.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
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nent may be sufficiently simple and deterministic in performance such that the component is not a source of a CCF. Such components need not be considered in a D3 analysis. When a basis is given that a component is not susceptible to CCF, the NRC staff should examine the justification carefully. 4.4 Effect of Other Blocks When considering the effects of a postulated CCF, diverse blocks are assumed to function correctly. This includes the functions of blocks that act to prevent or mitigate consequences of the CCF under consideration. 4.5 Identification of Alternate Trip or Initiation Sequences Thermal-hydraulic analyses using realistic assumptions 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.) 4.6 Identification of Alternative Mitigation Capability For each DBE, alternate mitigation actuation functions that will prevent or mitigate core damage and unacceptable release of radioactivity should be identified. When a CCF is compensated by BTP 7-19-21 Revision 7 – August 2016 a different automatic function, a basis should be 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 should demonstrate that adequate information (indication), appropriate operator training, and sufficient time for operator action are available in accordance with Appendix 18-A of SRP Chapter 18. Note: As the difference between Time Available and Time Required for operator action is a measure of the safety margin and as it decreases, uncertainty in the estimate of the difference between these times should be appropriately considered. This uncertainty could reduce the level of assurance and potentially invalidate a conclusion