Digital Computers in Candu Safety Systems Part I History and Concepts

For many years, digital computers have been used in CANDU (CANada Deuterium Uranium) reactors for direct digital control as well as control room functions such as alarm annunciation, data logging and the display of operating data on the control panels. However, until recently computers were not used in the special safety systems. This paper examines the increasing role computers are playing in CANDU safety systems, especially the two shutdown systems. The reasons for this strong trend toward increased use of computers are outlined and recent designs are described, with special emphasis on system concepts. A companion paper (Part II) describes implementation details for the safety system computer applications and summarizes the experience gained so far during development and operation of these systems.