heavy-water reactor

A heavy-water reactor is a type of nuclear reactor that uses heavy water as a moderator and coolant. Heavy water, or deuterium oxide (D₂O), is water composed of deuterium (an isotope of hydrogen with a mass double that of ordinary hydrogen) and oxygen.1

Physics and Operation

Nuclear reactors operate on the principle of nuclear fission, where a heavy atomic nucleus splits, releasing neutrons and energy. These neutrons can trigger further fissions, creating a self-sustaining chain reaction. In a heavy-water reactor, the heavy water moderator slows down these neutrons, making them more likely to cause further fission. This controlled chain reaction generates heat, which is then used to produce electricity.21

CANDU Reactors

A prominent example of a heavy-water reactor is the Canada Deuterium Uranium (CANDU) reactor. These reactors use natural uranium as fuel and heavy water for both moderation and cooling. A key feature of CANDU reactors is their ability to refuel while in operation, which contributes to high capacity factors.3