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:
5.5) In addition to the system integrity criteria provided by IEEE Std 603-1991, and the guidance in Subsection 5.5 of SRP Appendix 7.1-C, IEEE Std 7-4.3.2-2003 includes criteria in Sub- Clauses 5.5.1 through 5.5.3 for designs for computer integrity, test and calibration, and fault detection and self-diagnostics activities. The following are necessary to achieve system integrity in digital equipment for use in safety systems: • Design for computer integrity • Design for test and calibration • Fault detection and self-diagnostics. 5.6 Independence (IEEE Std 7-4.3.2-2003 Clause 5.6) Consistent with the requirements of IEEE Std 603-1991, data communication between safety channels or between safety and non-safety systems should not inhibit the performance of the safety function. Additional guidance on physical, electrical, and communication independence is provided in SRP Appendix 7.1-C Subsection 5.6. IEEE Std 603-1991 requires that safety functions be separated from non-safety functions such that the non-safety functions cannot prevent the safety system from performing its intended functions. In digital systems, software performing both safety and non-safety functions may reside on the same computer and use the same computer resources. However, IEEE Std 603-1991, Sub-Clause 5.6.3.1 also requires that equipment that is used for both safety and non-safety functions shall be classified as part of the safety system. The term "equipment" includes both software and hardware of the digital systems. For this reason, any software providing non-safety functions that resides on a computer providing a safety function must be classified as a part of the safety system. If an applicant/licensee desires that a non-safety function be performed by a safety computer, the software to perform that function must be classified as safety-related, with all the attendant regulatory requirements for safety software, including communications isolation from other non-safety software. In