Document: NUREG-0800
Document ID: f1629507-6318-4e71-94a6-9d6664ba96a3
Document Type: srp
Title: of the plant safety analysis report (SAR).  Although NRC did not endorse the annexes of
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0706/ML070660327.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7.6
CFR Part: 
CFR Title: 

Content:
n communications independence is provided in SRP Appendix 7.0-A, SRP Appendix 7.1-C, and SRP Section 7.9. 5.7 Capability for Test and Calibration (IEEE Std 7-4.3.2-2003 Clause 5.7) Sub-Clause 5.5.2 of IEEE Std 7-4.3.2-2003 recommends that test and calibration functions should not adversely affect the ability of the computer to perform its safety function. The reviewer should check to ensure this has been accomplished. Sub-Clause 5.5.3 of IEEE Std 7-4.3.2-2003 recommends that fault detection and self-diagnostics are one means that can be used to assist in detecting partial system failures that could degrade the capabilities of the computer system, but may not be immediately detectable by the system. Appendix 7.1-D-18 March 2007 The reviewer should carefully examine the capability of the software to test itself. From experience with a number of digital failures, the failures, were not in the operational code but in the diagnostic code. One of the reasons for this may be that the diagnostic code may be much more complex than the operational code. The reviewer should examine the portion of the analysis in the Factory Mutual Engineering Associates (FMEA) on diagnostic code failure. Assertions that failure of the operation code is not credible because the system and software diagnostics will find every failure should be carefully examined. The total amount of software code should be compared to the amount of operational code. Large amounts of test and diagnostic software increase the complexity of the total software, and this increase in complexity should be balanced against the potential gain in confidence in the system provided by that test and diagnostic software. This may also be balanced by the extensive previous use of these diagnostic routines. The test and diagnostic software may have been well tested and extensively used in the past, while the operational code is likely new for this application. The reviewer’s judgement should be used. A non-software watchdog