IEEE 379-2000 pdf free.IEEE Standard Application of the Single-Failure Criterion to Nuclear Power Generating Station Safety Systems.
IEEE 379 The principle of independence is basic to the effective utilization of the single-failure criterion.The designof a safety system shall be such that no single failure of a component will interfere with the proper operationof an independent redundant component or system.
The detectability of failures is implicit in the application of the single failure criterion. Detectability is afunction of the system design and the specified tests. A failure that cannot be detected through periodic test-ing, or revealed by alarm or anomalous indication, is nondetectable.An objective in an analysis of safetysystems is to identify nondetectable failures. When nondetectable failures are identified, one of the follow-ing courses of action shall be taken:
Preferred course:The system or the test scheme shall be redesigned to make the failure detectable.— Alternative course: When analyzing the effect of each single failure, all identified nondetectable fail-
ures shall be assumed to have occurred.
Whenever the design is such that additional failures could be expected from the occurrence of a single fail-ure from any source (e.g., mechanical, electrical, and environmental), these cascaded failures, collectively,shall be considered to be a single failure.
A design basis event that results in the need for safety functions may cause failure of system components,modules, or channels. In order to provide protection from these failures, the equipment should be designed,qualified, and installed so as to be immune to such anticipated challenges. When analysis indicates that failures in a safety system result from design basis events, these failures shall be considered a consequence ofthe event.
Certain common-cause failures shall be treated as single failures when conducting the single-failure analy-sis.Such failures can be in dissimilar components and can have dissimilar failure modes.Failures resultingfrom cascaded failure (see 5.3) and design basis events(see 5.4) have already been discussed, and are thosethat shall be included in the analysis.
Common-cause failures not subject to single-failure analysis include those that can result from externalenvironmental effects (e.g.， voltage,frequency，radiation，temperature,humidity, pressure,vibration， andelectromagnetic interference), design deficiencies,manufacturing errors, maintenance errors, and operatorerrors. Design qualification and quality assurance programs are intended to afford protection from externalenvironmental effects,design deficiencies， and manufacturing errors. Personnel training; proper controlroom design; and operating，maintenance,and surveillance procedures are intended to afford protectionfrom maintenance and operator errors.
Additionally, provisions should be made to address common-cause failures. Examples of techniques aredetailed defense-in-depth studies, failure mode and effects analysis, and analyses of abnormal conditions orevents. Design techniques,such as diversity and defense-in-depth, can be used to address common-causefailures.IEEE 379 pdf download.