INDEPENDENCE AS A CONTRIBUTION TO DEMONSTRATE SOFTWARE-BASED IC DEPENDABILITY

摘要

Independence is one of the most important and well established principles to demonstrate nuclear safety. Software-based Instrumentation and Control (I&C) are implemented in nuclear power plants as distributed computer networks with information transfer via busses and communication links to Human Machine Interfaces (HMI). Such networks provide various opportunities for sequential or parallel signal and command processing. The experience gained from related safety demonstration procedures is, that there is a growing concern about the credit which can be taken for independence claims and the methods of how to demonstrate independence for new I&C and HMI technologies. Software-based dependability aspects such as equipment safety and security are directly influenced by the demonstration of certain kinds of independence. This paper gives an overview over independence requirements within the nuclear regulatory framework for I&C and HMI and thus remembers on the outstanding importance of independence to demonstrate safety for the application of software-based I&C and new HMI. Furthermore certain arguments on independence - on I&C system level but also on I&C equipment level - are addressed as contribution to cope with CCF and malware.