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Related to heavy water: light water
Either of two isotopic forms of water, especially deuterium oxide, consisting chiefly of molecules that contain deuterium instead of protium. Heavy water is used as a moderator in certain nuclear reactors.
(Elements & Compounds) water that has been electrolytically decomposed to enrich it in the deuterium isotope in the form HDO or D2O
water in which hydrogen atoms have been replaced by deuterium, used as a nuclear reactor coolant.
Water formed of oxygen and deuterium. Heavy water is much like ordinary water but has higher freezing and boiling points. It is used in certain nuclear reactors for cooling.
Did You Know? How can one drop of water be heavier than another? The answer lies at the atomic level. Normal hydrogen has a nucleus consisting entirely of one proton, around which whirls one electron. However, in a variety of hydrogen called heavy hydrogen or deuterium, a neutron accompanies the proton in the nucleus. Deuterium thus weighs about twice as much as standard hydrogen. The substance we call heavy water is H2O in which many of the hydrogen atoms are replaced by deuterium. Heavy water played a part in the development of the atomic bomb during World War II. It is an excellent absorber of the neutrons that are produced in large quantities in a nuclear chain reaction. It therefore provided a means of regulating the reactions so that they could be studied safely. Once it was shown that a controlled chain reaction was possible, making a device that could create a powerful uncontrolled chain reaction—an atomic bomb—seemed within reach. Heavy water is still found today in nuclear power plants that use natural uranium fuel.