Improved Containment Isolation for CANDU Plants

Abstract

The publication of Regulatory Policy Statement R-7 in February 1991 by the Atomic Energy Control Board imposes new requirements for the isolation of fluid piping penetrating the containment boundary. The Appendix of R-7 describes the detailed requirements for metal extensions of the containment envelope, including the code classification of the pressure retaining portions and isolation requirements for fluid piping and tubing. The application of these new requirements to the existing CANDU 6 design resulted in a number of design changes, including the addition of manual and automatic isolation valves, changes in code classification, and leakage monitoring considerations.