Document: NUREG-0800
Document ID: 4cca74ec-66e0-4765-9c61-cf547e17c308
Document Type: srp
Title: of the plant safety analysis report (SAR).  Although the NRC did not endorse the annexes of
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1601/ML16019A114.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7.6
CFR Part: 
CFR Title: 

Content:
ing subsections address the criteria in the order they are listed in IEEE Std 7-4.3.2. For some criteria there are no additional criteria beyond what is stated in IEEE Std 603-1991 and the appropriate subsection of SRP Appendix 7.1-C is referenced. 5.1. Single-Failure Criterion (IEEE Std 7-4.3.2, Clause 5.1) The requirements are in IEEE Std 603-1991. Subsection 5.1 of SRP Appendix 7.1-C provides additional guidance. Clause 5.1 in IEEE Std 603-1991 defines the single- failure criterion. Guidance for the application of this criterion is in IEEE Std 379, “IEEE Standard Application of the Single-Failure Criterion to Nuclear Power Generating Station Safety Systems,” which is endorsed by RG 1.53, “Application of the Single-Failure Criterion to Safety.” The approach stated in Clause 5.5 of IEEE Std 379 is also appropriate for potential common-cause failures associated with computer hardware and software that have been developed under the criteria in IEEE Std 603-1991 and IEEE Std 7-4.3.2. SRP Appendix 7.1-C discusses certain concerns of digital computer-based systems; for example, a design using shared databases and process equipment has the potential to propagate a common-cause failure of redundant equipment and software programming errors can defeat the redundancy achieved by the hardware architectural structure. Because of these concerns, the NRC staff has placed significant emphasis on defense- in-depth against common-cause failures within and between functions. SRP BTP 7-19, “Guidance for Evaluation of Diversity and Defense-in-Depth in Digital Computer-Based Instrumentation and Control Systems,” provides guidance for evaluating diversity and defense-in-depth features. SRP BTP 7-19 has the following objectives: (1) to verify that adequate diversity has been provided in the design of the digital system to meet the criteria established by NRC requirements, (2) to verify that adequate defense-in-depth has been provided to meet NRC criteria, and (3) to verify