The CANDU pressurized heavy-water reactor (PHWR) is based on more than 50 years of nuclear technology development. An ongoing comprehensive product development program is advancing all aspects of CANDU technology, with a focus on improving economics, enhancing safety, and ensuring fuel-cycle flexibility to secure fuel supply for the foreseeable future. The development program retains the essential features of CANDU reactors: high neutron economy, utilization of natural rather than enriched uranium, modular core components for easy upgrading and plant life extension, simple fuel bundle designs for on-power fueling, and emphasis on passive safety.