(symbol '''T''' or '''
3H''') is a radioactive
Isotope of
Hydrogen . The
Nucleus of tritium (sometimes called '''triton''') contains one
Proton and two
Neutron s, whereas the nucleus of
Protium (the most abundant hydrogen isotope) contains no neutrons. Its
Atomic Weight is 3.0160492. It is a gas (T
2 or
3H
2) at
Standard Temperature And Pressure . Tritium combines with
Oxygen to form a liquid called
Tritiated Water T
2O or partially tritiated THO.
Tritium is radioactive with a
Half-life of 12.32 years. It decays into
Helium-3 by the reaction
:
releasing 18.6 keV of energy. The
Electron has an average kinetic energy of 6.5 keV, while the remaining energy is carried off undetectably by the
Electron Antineutrino . The low-energy
Beta Radiation from tritium cannot penetrate human skin, so tritium is only dangerous if inhaled or ingested. Its low energy also makes it difficult to detect tritium labelled compounds except by using
Liquid Scintillation Counting .
Tritium occurs naturally due to
Cosmic Ray s interacting with atmospheric gases. In the most important reaction for natural tritium production, a fast neutron interacts with atmospheric
Nitrogen :
:
Because of tritium's relatively short half-life, however, tritium produced in this manner does not accumulate over geological timescales, and its natural abundance is negligible. Industrially, tritium is produced in
Nuclear Reactors by
Neutron Activation of
Lithium-6 .
:
Tritium is also produced in
Heavy Water -moderated reactors when
Deuterium captures a neutron; however, this reaction has a much smaller
Cross Section and is only a useful tritium source for a reactor with a very high neutron flux. It can also be produced from
Boron-10 through
Neutron Capture .
Tritium figures prominently in studies of
Nuclear Fusion due to its favorable reaction
Cross Section and the high energy yield of 17.6 MeV for its reaction with deuterium:
:
All atomic nuclei, being composed of protons and neutrons, repel one another because of their positive charge. However, if the atoms have a high enough temperature and pressure (as is the case in the core of the Sun, for example), then their random motions can overcome such electrical repulsion, and they can come close enough for the
Strong Nuclear Force to take effect, fusing them into heavier atoms. Since tritium has the same charge as ordinary hydrogen, it experiences the same electrical repulsive force. However, due to its higher mass, it is less responsive to such forces, and thus can more easily fuse with other atoms. The same is also true, albeit to a lesser extent, of deuterium, and that is why
Brown Dwarf s (so called failed
Star s) can not burn hydrogen, but do indeed burn deuterium.
Before the onset of atmospheric nuclear weapons tests, the global equilibrium tritium inventory was estimated at about 80 megacuries (MCi).
Tritium is used in
Nuclear Weapon s to obtain higher yields through nuclear fusion. However, as it decays and is difficult to contain, many nuclear weapons contain lithium instead, since the high neutron fluxes will produce tritium from the lithium when the bomb detonates; see
Nuclear Weapon Design .
Like
Hydrogen , it is difficult to confine tritium;
Rubber ,
Plastic , and some kinds of
Steel are all somewhat permeable. This has raised concerns that if tritium is used in quantity, in particular for
Fusion Reactor s, it may contribute to
Radioactive Contamination .
Atmospheric nuclear testing (prior to the
Partial Test Ban Treaty ) proved unexpectedly useful to oceanographers, as the sharp spike in surface tritium levels could be used over the years to measure the rate at which the lower and upper ocean levels mixed.
The emitted electrons from small amounts of tritium cause
Phosphor s to glow so as to make self-illuminating devices called
Traser s which are now used in watches and
Exit Signs . It is also used in certain countries to make
Glowing Keychains , and compasses. In recent years, the same process has been used to make self-illuminating
Gun Sights for firearms. These take the place of
Radium , which causes
Bone Cancer , and so has been banned for decades.
Tritiated
Thymidine is used in
Cell Proliferation assays. The molecule, a
Nucleoside , is incorporated into the
DNA of cells as they are replicated during
Cell Division . The extent of cell proliferation may then be determined by
Liquid Scintillation Counting .
Tritium was first predicted in the late twenties by
Walter Russell , using his "spiral"
Periodic Table , then produced in
1934 from
Deuterium , another isotope of hydrogen, by
Ernest Rutherford , working with
Mark Oliphant and
Paul Harteck . Rutherford was unable to isolate the tritium, a job that was left to
Luis Alvarez , who correctly deduced that the substance was radioactive.
Willard F. Libby discovered that tritium could be used for
Dating water, and therefore
Wine .
