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(trĭt`ēəm), radioactive isotope of hydrogenhydrogen
[Gr.,=water forming], gaseous chemical element; symbol H; at. no. 1; interval in which at. wt. ranges 1.00784–1.00811; m.p. −259.14°C;; b.p. −252.87°C;; density 0.08988 grams per liter at STP; valence usually +1.
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 with mass number 3. The tritium nucleus, called a triton, contains one proton and two neutrons. It has a half-life of 12.5 years and decays by beta-particle emission. The symbol is T or 3H. It is one form of heavy hydrogen, the other being deuterium. It is usually produced in nuclear reactors as a byproduct of the irradiation of lithium. Its current major use is to increase the yield of thermonuclear devices. The U.S. Department of Energy has a production reactor in Savannah, Georgia for this purpose. In the future, vast amounts of tritium will fuel experiments in fusion research. Canada, Europe and Japan have extensive programs underway to develop physics-based, as opposed to mechanical based, production procedures to generate the volumes necessary to proceed with these experiments.
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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



(T, or 3H), a radioactive isotope of hydrogen with mass number 3 (hence its name, from the Greek tritos, “third”).

Tritium was discovered in 1934 by the British scientists E. Rutherford, M. L. Oliphant, and P. Harteck. The tritium nucleus consists of one proton and two neutrons. Tritium is β-active, with a half-life of 12.26 yr. In nature, it is formed in in-significant quantities by the action of the neutrons of cosmic rays on nitrogen atoms (147N + n = 31T + 126C) and in nuclear transformations induced by high-energy cosmic particles. The mean content of tritium in natural waters is one atom per 1018 atoms of !H.

Tritium is obtained in nuclear reactors by irradiation of 63Li with neutrons (63Li + n = 31T + 42He). It is used as the most important component in thermonuclear synthesis reactions, as a fuel in thermonuclear bombs, and in chemical, biological, and hydrological studies.


Evans, E. A. Tritii i ego soedineniia. Moscow, 1970. (Translated from English.)
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


(nuclear physics)
The hydrogen isotope having mass number 3; it is one form of heavy hydrogen, the other being deuterium. Symbolized 3H; T.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


a radioactive isotope of hydrogen, occurring in trace amounts in natural hydrogen and produced in a nuclear reactor. Tritiated compounds are used as tracers. Symbol: T or 3H; half-life: 12.5 years
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005