Applications using digital and software based technology have become as common in nuclear power plants as in conventional industry. The spread of digital technology in the nuclear sector is inexorable. With growing problems of obsolescence, difficulty in obtaining replacement parts, increased maintenance costs and stringent industry requirements, nuclear utilities need to upgrade their existing instrumentation and control (I&C) systems. Digital technologies also offer potential performance and reliability improvements. However, the implementation of modern and advanced technologies may throw up challenges when it comes to assessing reliability, vulnerability to common cause failure, radio-frequency interference or uncertainties around the licensing process.
The aim of this report is to summarize an analysis of NPP events related to digital I&C systems in various phases of the lifecycle, starting with design related issues and ending with implementation and operational aspects.