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
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lysis using the above acceptance criteria and the detailed guidance of NUREG/CR-6303, emphasis should be given to the following topics: 4.1 System Representation as Blocks The system being assessed is represented as a block diagram; the inner workings of the blocks are not necessarily shown. Diversity is determined at the block level. A block is a physical subset of equipment and software for which it can be credibly assumed that internal failures, including the effects of software and logic errors, will not propagate to other equipment or software. Examples of typical blocks are computers, local area networks, and programmable logic controllers. 4.2 Documentation of Assumptions Assumptions made to compensate for missing information in the design description materials or to explain particular interpretations of the analysis guidelines as applied to the system are documented by the applicant. 4.3 Exclusion of Components from D3 Analysis A software-based component 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. Revision 6 – July 2012 BTP 7-19-21 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