EVALUATION OF VULNERABILITIES TO UNSAFE DIGITAL COMMON CAUSE FAILURES IN SAFETY IC SYSTEMS

摘要

The use of digital equipment for safety applications in nuclear power plants raises technical and licensing issues, due in particular to the possibility that a single digital fault in software or in shared design elements could concurrently disable redundant channels or systems. This paper presents some aspects of the approach developed at EPRI to assess the potential of individual channels for digital failure, and of redundant I&C channels or systems for unsafe digital common cause failure (CCF). In particular, it presents how a detailed understanding of the structure and functioning of digital systems, and of the conditions that can influence their operation, can facilitate the identification of potential vulnerabilities to unsafe digital CCFs, and can therefore improve their design and their verification.