Editing Tritium (section)

== Properties ==
Tritium has an [[atomic mass]] of {{val|3.01604928|ul=Da}}. Diatomic tritium ({{chem2|T2}} or {{chem2|^{3}H2}}) is a gas at [[standard temperature and pressure]]. Combined with [[oxygen]], it forms [[tritiated water]] ({{chem2|^{3}H2O}}).

Compared to hydrogen in its natural composition on Earth, tritium has a higher [[melting point]] (20.62&nbsp;K vs. 13.99&nbsp;K), a higher [[boiling point]] (25.04&nbsp;K vs. 20.27&nbsp;K), a higher [[Critical point (thermodynamics)|critical temperature]] (40.59&nbsp;K vs. 32.94&nbsp;K) and a higher critical pressure (1.8317&nbsp;MPa vs. 1.2858&nbsp;MPa).<ref>{{Cite web |last=PubChem |title=Hazardous Substances Data Bank (HSDB): 6467 |url=https://pubchem.ncbi.nlm.nih.gov/source/hsdb/6467#section=Chemical-Physical-Properties&fullscreen=true |access-date=2023-02-27 |website=pubchem.ncbi.nlm.nih.gov |language=en}}</ref>

Tritium's [[specific activity]] is {{convert|9650|Ci/g|Bq/g|lk=on}}.<ref>
{{cite report
 |title=H-3
 |series=Radionuclide Safety Data Sheets 
 |department=OSEH
 |publisher=University of Michigan
 |url=http://www.oseh.umich.edu/radiation/h3.shtml
 |access-date=20 March 2013
}}
</ref>

Tritium figures prominently in studies of [[nuclear fusion]] due to its favorable reaction [[cross section (physics)|cross section]] and the large amount of energy (17.6&nbsp;MeV) produced through its reaction with deuterium:
: {{nuclide|hydrogen|3}} + {{nuclide|hydrogen|2}} → {{nuclide|helium|4}} + [[Neutron|n]]

All atomic nuclei contain protons as their only charged particles. They therefore repel one another because like charges repel ([[Coulomb's law]]). However, if the atoms have a high enough temperature and pressure (for example, in the core of the Sun), then their random motions can overcome such repulsion, and they can come close enough for the [[strong nuclear force]] to take effect, fusing them into heavier atoms.

A tritium nucleus (triton), containing one proton and two neutrons, has the same charge as any hydrogen nucleus, and it experiences the same electrostatic repulsion when close to another nucleus. However, the neutrons in the triton increase the attractive strong nuclear force when close enough to another nucleus. As a result, tritium can fuse more easily with other light atoms, than ordinary hydrogen can.

The same is true, albeit to a lesser extent, of deuterium. This is why [[brown dwarf]]s ("failed" [[Fusor (astronomy)|stars]]) cannot fuse normal hydrogen, but they do fuse a small minority of deuterium nuclei.

[[File:Gaseous tritium light source.jpg|thumb|right|[[Radioluminescent]] {{convert|1.8|Ci|GBq|lk=on}} {{convert|6|x|0.2|in|mm}} tritium vials are thin, tritium-gas-filled glass vials whose inner surfaces are coated with a [[phosphor]]. The vial shown here is brand-new.]]

Like the other isotopes of [[hydrogen]], tritium is difficult to confine. Rubber, plastic, and some kinds of steel are all somewhat permeable. This has raised concerns that if tritium were used in large quantities, in particular for [[fusion reactor]]s, it might contribute to [[radioactive contamination]], though its short half-life should prevent significant long-term accumulation in the atmosphere.

The high levels of atmospheric [[nuclear weapons testing]] that took place prior to the enactment of the [[Partial Nuclear Test Ban Treaty]] proved to be unexpectedly useful to oceanographers. The high levels of tritium oxide introduced into upper layers of the oceans have been used in the years since then to measure the rate of mixing of the upper layers of the oceans with their lower levels.