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: 

Content:
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 conform to the guidance of Regulatory Guide 1.22 and Regulatory Guide 1.118. Bypasses necessary to enable testing should conform with the guidance of Regulatory Guide 1.47. Failure Detection Failures detected by hardware, software, and surveillance testing should be consistent with the failure detectability assumptions of the single-failure analysis and the failure modes and effects analysis. Self-Test Features Digital computer-based I&C systems should include self-test features to confirm computer system operation on system initialization. Digital computer-based I&C systems should generally include continuous self-testing. Some small, stand-alone, embedded digital computers may not need self-testing. Typical self-tests include monitoring memory and memory reference integrity, using watch-dog timers or processors, monitoring communication channels, monitoring central processing unit status, and checking data integrity. BTP 7-17-5 Revision 5 - March 2007 Other self-testing features that are candidates for incorporation into digital computer-based I&C systems include plausibility checks for intermediate results, evaluation using different methods, ranges of variables, array bound checking, well-defined outputs for detected failures, reporting of errors for which error recovery techniques are used, use of counters and reasonableness traps, and correctness verification of transferred parameters. SRP BTP 7-14 discusses a number of functional characteristics for software design, such as robustness and timing, which could give rise to self-testing features. Self-tests may also include automatic calibration tests such as the use of fundamental physical principles in Johnson noise thermometry to calibrate resistance temperature detectors (RTDs). The design of automatic