Aheavy water reactor (HWR) is a type ofnuclear reactor which usesheavy water (D2O,deuterium oxide) as aneutron moderator. It may also use this as the coolant, in the case ofpressurized heavy water reactors. Due to heavy water's low neutron absorption cross section, HWRs can operate withnatural uranium fuel.[1]
"Atomic pile" experiments were carried out across Europe and North America following the 1938discovery of nuclear fission. The sole supply was from theVemork hydroelectric power plant in Norway. The world's entire supply had been sent to Paris for experiments, but smuggled to England during theFall of France. In November 1940,Hans von Halban andLew Kowarski at theUniversity of Cambridge carried out one of the first heavy water-moderated pile experiments, measuring net neutron production. In 1958,Patrick Blackett wrote aboutFrédéric Joliot-Curie: "There is little doubt that, had the war not intervened, the world’s first self-sustaining chain reaction would have been achieved in France."[2] From late 1940, theNazi German nuclear weapons program focused on heavy water piles as their path to a reactor, discounting graphite on erroneous measurements ofWalther Bothe. This culminated in theB-VIII experiment.[3]
TheManhattan Project pursued both graphite and heavy water-moderated reactors as paths to plutonium weapons. TheP-9 Project sourced the heavy water. AtSite A, alongside CP-2,Chicago Pile-3 was constructed as the world's first heavy water reactor, achieving criticality in May 1944. In September 1945, theZEEP reactor achieved criticality in Canada, following development by a team of European scientists excluded from the central work of the Manhattan Project.[4] Canada further developed HWRs with theNRX research reactor and ultimatelyCANDU design of commercial reactors. In the United States, HWRs were ultimately employed from the 1950s in for plutonium and tritium production at theSavannah River Site.
HWRs were also chosen as early research reactors in many countries, including the firstEL-1 in France, the thirdTVR in the USSR, and the firstHWRR in China.
HWRs can be categorized by whether they use a pressure-shell or pressure-tube design. They can also be categorized by the coolant. Coolant options include:[1]
