Document: NUREG-0800
Document ID: 9a64419a-34ff-49d2-87dd-c6f10c12014f
Document Type: srp
Title: or 7.3 of the SAR.
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0525/ML052500501.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7.2
CFR Part: 
CFR Title: 

Content:
— ANSI/IEEE Std 279, Section 4.5 and GDC 21 require that all protection system channels maintain necessary functional capability under extremes of conditions relating to environment, energy supply, malfunctions, and accidents. Section 5.5 of IEEE Std 603 includes similar requirements for safety systems. Evaluation of digital systems with respect to these requirements includes assuring design for computer integrity and design for test and calibration. a. Design for computer integrity — As discussed in Section 5.5.1 of IEEE Std 7-4.3.2, digital systems must be designed to perform their safety function when subjected to all conditions that have significant potential for defeating their safety function. Evaluation with respect to the other topics discussed for computer-based systems addresses many aspects of design for integrity. In addition, design for computer integrity involves selecting system architectures and design standards to ensure that system real-time performance is predictable and within design requirements. BTP HICB-21 describes the review of digital computer real-time performance. Rev. 4 — June 1997 SRP 7.1-7 b. Design for test and calibration — Digital computer-based systems generally cannot be designed such that all failure modes are either "fail-safe" or revealed by indication of the failure. Therefore, automated self-test features may be necessary for failure detectability. Special features may also be needed to provide the capability to support surveillance testing. IEEE Std 603, Section 5.7 describes the fundamental guidance applicable to test and calibration features. BTP HICB-17 describes the automatic self-testing and surveillance testing features characteristic of an acceptable digital system. 5. Communications independence — Sections 4.6 and 4.7 of ANSI/IEEE Std 279 require independence between redundant channels of the protection system and between safety systems and non-safety systems. IEEE Std 603, Section 5.6 contains similar