Lessons Learned from Safety-Critical Software-Based Automation Architectures of Nuclear Power Plants

Engineering large software-based systems in safety-critical domains is a challenging task despite extensive research on the topic. The software technologies and development processes are established, and basic safety principles are well known. However, demonstrating the safety of a software-based automation system remains a key challenge, particularly in the nuclear domain. In this paper, we describe our experiences from current nuclear projects featuring software-based automation. We observed a number of assumptions in regulation and standards related to safety principles, such as separation and diversity, which do not apply to software systems. The assumptions result in unrealistic expectations for software-based systems, making both design and safety demonstration challenging.