The Enhanced CANDU 6 (EC6) plant design includes complementary design features that assist the goals of preventing severe accident scenarios and mitigating their consequences if they do occur. These features include design or procedural considerations (or both), and are based on a combination of phenomenological models, engineering judgments, and probabilistic methods. This paper provides an overview of the EC6 instrumentation and control (I&C) and electrical design specifically related to prevention of severe accidents during station blackouts (SBOs).
The I&C and electrical components and devices may include those used in normal operation, those of the safety systems used during design basis accidents, and those added solely for preventing or mitigating severe accidents. They are evaluated by an equipment survivability assessment to demonstrate a reasonable level of assurance for their operability, and a seismic fragility evaluation in consideration of a seismic initiating event.
The requirements for the I&C and electrical design for SBOs are developed by reviewing EC6 event sequences leading to SBOs, identifying the available systems, and identifying the actions needed and whether they are manual or automatic, passive or active. Monitoring plays a critical role in the prevention of severe accidents. The correct operation of instrumentation and associated display devices for key parameters is essential in diagnosing the plant state and safety challenges.