heavy water



water in which hydrogen atoms have been replaced by deuterium, used chiefly as a coolant in nuclear reactors.

Origin of heavy water

First recorded in 1930–35
Also called deuterium oxide.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for heavy water

Historical Examples of heavy water

  • I managed to locate the house which was headquarters for the heavy-water dealers, again with the aid of an informant.

  • We've already informed the British, through channels, that the heavy-water menace no longer exists.

  • Now a complete list of your uranium-refining plants, your military reactors, heavy-water and heavy-hydrogen plants, and so on.

    The Galaxy Primes

    Edward Elmer Smith

British Dictionary definitions for heavy water

heavy water


water that has been electrolytically decomposed to enrich it in the deuterium isotope in the form HDO or D 2 O
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Science definitions for heavy water

heavy water

Water in which deuterium, a heavy isotope of hydrogen, takes the place of hydrogen. Heavy water has physical and chemical properties that are like those of ordinary water, but heavy water is 10 percent heavier and has higher freezing and boiling points. Also called deuterium oxide. Chemical formula: D2O. Semiheavy water is similar to heavy water, but only one of the two hydrogen atoms in each molecule is replaced with deuterium. Chemical formula: DHO.
A Closer Look: The nucleus of most hydrogen atoms consists of a single proton, but in one isotope of hydrogen, called deuterium or heavy hydrogen, the nucleus also contains a neutron and thus weighs nearly twice as much as standard hydrogen. The substance called heavy water is chemically identical to ordinary water (H2O), except that the hydrogen atoms in the molecule are the deuterium isotopes (D2O). Heavy water makes up a small percentage (0.02%) of water naturally occurring on Earth. It is an excellent moderator for nuclear reactions, slowing down the fast neutrons produced in a nuclear fission reaction, increasing the likelihood that the neutrons will successfully collide with heavy nuclei to cause further fission. Although heavy water is chemically nearly identical with ordinary water, it is about ten percent heavier and interferes with cell mitosis if consumed in place of normal water. Ice cubes made of heavy water are denser than ordinary liquid water and will sink to the bottom of a glass of cola.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Culture definitions for heavy water

heavy water

Water with a higher average molecular weight than ordinary water. In a molecule of heavy water, the hydrogen atoms are isotopes in which the nuclei each contain a proton and a neutron, and hence are twice as heavy as a normal hydrogen atom.

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.