System theory safety analysis of network malfunction in nuclear power plant distributed control systems

A secure and highly reliable communication network is a crucial component of the distributed control system (DCS) in nuclear power plants (NPPs), particularly for the protection system. However, there have been numerous reported cases of cyber-attacks in the field of nuclear power, and the cybersecurity threats faced by a DCS are increasing. Given that the DCS is a complex integrated system combining computers, communication, and control with a large number of interactions between components and external interferences, traditional linear safety analysis methods fail to meet its requirements. To minimize cybersecurity accidents caused by potential vulnerabilities, it is necessary to conduct systematic safety analysis on DCS cybersecurity accidents in NPPs. Therefore, this paper selected a specific case of cybersecurity accidents in a NPP for abstract modeling and reproduction. The causal analysis based on system theory (CAST) method was applied to conduct an analysis of the accident causes. It can identify existing vulnerabilities and potential factors impacting the safe operation of NPPs, and countermeasures and recommendations can be proposed. The reference for assessing potential risks and devising solutions can be provided for other DCS communication networks.