Document: NUREG-0800
Document ID: 06884384-e650-488f-bf96-f48afd211643
Document Type: srp
Title: Revision 5 - March 2007
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0705/ML070550075.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
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CFR Title: 

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modes of plant operation. • The positive aspects of self-test features are not compromised by the additional complexity that may be added to the safety system by the self-test features. • Hardware and software design support the required periodic testing. • Failure modes assumed to be detectable by the single-failure analysis are in fact detectable. Failures may be detectable by observing operational characteristics as well as other methods. BTP 7-17-4 Revision 5 - March 2007 B. BRANCH TECHNICAL POSITION 1. Introduction Surveillance testing taken together with automatic self-testing should provide a mechanism for detecting all detectable failures. Digital computer-based instrumentation and control (I&C) systems are more prone to different kinds of failures than traditional analog systems are. Self-testing and watchdog timers should reduce the time to detect and identify failures. Computer self-testing is most effective at detecting random hardware failures. The characteristics of digital systems should be considered in the review of technical specification surveillance features. Architectural differences between digital and analog systems warrant careful consideration during the review of surveillance test provisions. Furthermore, the concepts used to determine test intervals for hardware-based systems do not apply directly to the software used in digital computer-based I&C systems. Therefore, previous reliability analysis used to establish test intervals will address the effects of software usage. Similar reviews are performed as necessary to verify the self-test and periodic test provisions for non-safety systems. 2. Information to be Reviewed Applicant/licensee's technical description of surveillance and self-test features, single-failure analyses, failure modes and effects analyses, and plant technical specifications should be reviewed. 3. Acceptance Criteria Surveillance test and self-test features for digital computer-based protection systems should