1. Presentation of the CANDU reactor

Figure  1 presents a cut-away picture of the containment building and balance-of-plant buildings of a CANDU-6, a single-unit CANDU of nominal net capacity of 600MW(e). The figure  1 shows the reactor as a horizontal cylindrical vessel (the calandria) that contains the low-temperature, heavy-water moderator. The vessel is surrounded by a shield tank of light water and the faces are shielded by tanks of light water filled with steel balls. Passing through the calandria and the end shields are the 380 pressure tubes containing the fuel bundles and the high-temperature, heavy-water primary coolant. They are accessed at both ends by fuelling machines that unload spent bundles and replace them with...