Views on safety demonstration and systems engineering for digital I&C

Designing and licensing a nuclear power plant and qualification of its subsystems and components is a challenging task involving several stakeholders and integrating information from various disciplines. Several recent discussions and workshops have shown that the current practice of justifying safety of nuclear power plant's systems can be improved. There still seems to be considerable confusion concerning the key terminology and the flow of the qualification and licensing processes. Existing standards and regulations provide limited guidance on how the licensee should formulate and communicate a convincing story on the safety of the facility. All this can be made more systematic and transparent by utilising the principles of Systems Engineering and model-based computer tools as the general framework for both engineering and safety assessment. There are several analysis methods for collecting the required evidences for a safety demonstration. These methods range from plant-level safety architectures to detailed I&C functions and from technical solutions to human-machine interactions and safety culture. A standards-based, structured safety demonstration can be seen as a knowledge repository that integrates different disciplines and assessment results into a consistent overall picture of systems and their safety properties.