CANDU Development: The Next 25 Years

Abstract

CANDU Pressurized Heavy Water Reactors have three main characteristics that ensure viability for the very long term. First, great care has been taken in designing the CANDU reactor core so that relatively few neutrons produced in the fission process are absorbed by the structural or moderator materials. The result is a reactor with high neutron economy that can burn natural uranium and a core that operates with 2-3 times less fissile content rather than other, similarly-sized reactors. In addition to neutron economy, the use of a simple bundle design and on-power fuelling augment the ability of CANDU reactors to burn a variety of fuels with relatively low fissile content with high efficiency. This ensures that fuel supply will not limit the applicability of the technology over the long term. Second, the presence of large water reservoirs ensures that even the severest postulated accidents are mitigated by passive means. For example, the presence of the heavy water moderator, which operates at low pressure and temperature, acts as a passive heat sink for many postulated accidents. Third, the modular nature of the core (e.g., fuel channels) means that components can be relatively easily replaced for plant life extension and upgrading. Since these factors all influence the long-term sustainability of CANDU nuclear technology, it is logical to build on this base and to add improvements to CANDU reactors using an evolutionary approach. This paper reviews AECL's product development directions and shows how the above characteristics are being exploited to improve economics, enhance safety, and ensure fuel cycle flexibility for sustainable development.