Integrated Risk Analysis of Function Safety and Cyber Security on I&C System of HTP-PM With STPA-SafeSec

Abstract

Cyber security risk analysis can identify and assess factors that may damage to the system such as digital instrumentation and control system of nuclear power plants. Performing cyber security risk analysis is important for instrumentation and control system of nuclear power plants because it could assess overall impacts of risks and help to identify vulnerabilities to determine next steps to address security risks. With the integration of information system and physical system, cyber security of information system and functional safety of physical system interact with each other, resulting in a type of new comprehensive security problem and introducing serious security risks. Most of the existing cyber security risk analysis methods pay more attention to cyberattacks like attack tree analysis method, Petri net method, and Bayesian network method. STPA-SafeSec is a top-down security risk analysis method focusing on the system itself based on system theory, which starts from unacceptable losses of the system and pays attention to the causal factors that produce unsafe control. In this paper, STPA-SafeSec is applied to the primary circuit pressure control system of high temperature gas-cold reactors in order to perform the hazard analysis of integrated risk assessment for both functional safety and cyber security. The application details are given and a part of the hazardous scenarios tree is obtained for the formulation of mitigation strategies.