Safety implications of control systems

The Safety Implications of Control Systems (SIOC) Program has three interrelated objectives: (1) to investigate failure modes and effects in non-safety control systems, including single failures and common cause, common mode, cascade, and other credible multiple failures, (2) to assess the impact upon safety of control system designs and their dynamic behavior, using methods that include computer modeling and analysis of system dynamics under stress, and (3) to develop criteria for determining the relative importance of control system influences upon safety, and with these as a basis to recommend design and operational standards for the systems involved. In support of these goals, the SIOC Program consists of three principal activities: (1) an augmented failure mode and effects analysis (FMEA) of the overall plant; (2) specific analysis of the plant electrical system; and (3) a hybrid computer model to augment the FMEA. This paper will discuss the status of each of these activities