Filmed at the Pickering, Ontario, nuclear power plant, showing also the earlier Douglas Point station and Québec's new Gentilly plant, this film offers audiences a clear illustration of how an atomic reactor produces electricity. Special features of the Canadian (CANDU) (Canada Deuterium Uranium) system are explained: on-power refueling; the use of natural uranium; the use of heavy water as moderator. CANDU is recognized internationally as a leader in man's search for new sources of energy. Produced for the NFB by Crawley Films Ltd. for Atomic Energy of Canada Limited.