The physics design of the advanced CANDU reactor

AECL has for many years successfully developed, built and serviced a fleet of CANDU® reactors, which distinguish themselves from more common reactor types through the use of natural uranium in a heavy-water moderated core. Refuelling of CANDU reactors is on-power, with fuel bundles being shifted through horizontal pressure tubes mat also contain the high-pressure coolant. This traditional CANDU reactor forms the basis for AECL's design of its GEN III+ reactor, the Advanced CANDU Reactor, ACR-1000®. The ACR-1000 maintains key CANDU features such as heavy-water moderation in a low-pressure calandria vessel and on-power replacement of fuel bundles in the horizontal pressure tubes. Significant differences with the traditional CANDU reactors include the use of low-enriched fuel, light water coolant, and a reduced lattice pitch. These features allow for a shift in emphasis from engineered safety to inherent safety features, such as a negative power coefficient, and a slightly negative full-core void reactivity under nominal operating conditions. This paper illustrates the design process of the ACR-1000 core; it describes the physics analysis methods used to arrive at the key parameters of the design, and a number of results of the analyses.