There are numerous safety systems in a reactor that contribute to the defence-in-depth philosophy, but which also have a role in plant operation. In CANDU reactors, the normal computerized systems that control the plant are designed to immediately and safely shut down the reactor in the event of equipment failure or other abnormal reactor conditions.

Also, the CANDU 6 reactor has two elements unique to its design, both of which can remove decay heat from the fuel, and are part of its configuration. These are a cool, low-temperature heavy water moderator and a cool shield tank of water. The moderator surrounds the fuel channels, while the shield tank surrounds the moderator. The shield tank during normal operations provides a radioactive shielding function, so that staff can work near the reactor when it is shut down.