ABSTRACT
This chapter summarizes the more important aspects of nuclear reactors in which heavy water is used as the moderator. In the 1950s and 1960s, heavy water reactor (HWR) technology was explored in most of the countries investigating the application of nuclear fission to energy production. The choice was influenced by the early development work in Canada within the Manhattan Project, which took advantage of the superior characteristics of heavy water moderation for the production of plutonium. Given the economic value of heavy water, the designers of HWRs pay great attention to preventing coolant leaks. The heat produced by controlled fission in the fuel is transferred to the pressurized heavy water coolant and circulated through the fuel channels and steam generators in a closed circuit. Radiolysis of the heavy water moderator in the calandria results in the production of deuterium and oxygen gases. Circulation of the cover gas to catalytic recombiners reforms heavy water and prevents accumulation of the gases.
