Document: NUREG-0800
Document ID: 7a278d84-5310-4198-b914-fa3af5a0a0ef
Document Type: srp
Title: Appendix 7-A
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0525/ML052500553.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
CFR Part: 
CFR Title: 

Content:
ions," as an alternative to ANSI/IEEE Std 279. 3. Definitions Periodic tests are tests performed at scheduled intervals to detect failures and verify operability (IEEE Std 338). Periodic tests include surveillance tests. A self-test is a test or series of tests, performed by a device upon itself. Self-test includes on-line continuous self-diagnostics, equipment-initiated self-diagnostics, and operator-initiated self-diagnostics. Surveillance tests are tests conducted specifically to confirm compliance with technical specification surveillance requirements. A watchdog timer is a form of interval timer that is used to detect a possible malfunction (ANSI/IEEE Std C37.1, "Standard Definitions, Specification, and Analysis of Systems Used for Supervisory Control, Data Acquisition, and Automatic Control"). Appendix 7-A Rev. 4 — June 1997 BTP HICB-17-3 4. Purpose The purpose of this BTP is to provide guidance for NRC staff to verify that the previously cited regulatory basis and standards are met by an applicant/licensee's submittal. The objectives of this BTP are to confirm that: • The safety system (including self-test) is designed for in-service testability commensurate with the safety functions to be performed through all 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. B. Branch Technical Position 1. Introduction Digital computer-based instrumentation and control systems are prone to different kinds of failures than are traditional analog systems. Self-testing and watchdog timers may reduce the time to detect and identify failures, but are not a guarantee of hardware or