Editing Tritium (section)

== Decay ==
The half life of tritium is listed by the [[National Institute of Standards and Technology]] as {{nowrap|4,500 ± 8 days}} ({{nowrap|12.33 ± 0.02 years}})<ref>
{{Cite journal
 |last1 = Lucas      |first1 = L.L.
 |last2 = Unterweger |first2 = M. P.
 |name-list-style = amp
 |year  = 2000
 |title = Comprehensive review and critical evaluation of the half-life of tritium
 |journal = [[Journal of Research of the National Institute of Standards and Technology]]
 |volume = 105  |issue = 4  |pages = 541–549
 |doi    = 10.6028/jres.105.043  |pmid = 27551621  |pmc= 4877155
 }}</ref> – an annualized rate of approximately 5.5% per year. Tritium decays into [[helium-3]] by [[beta-minus decay]] as shown in this nuclear equation:
: {| border="0"
|- style="height:2em;"
|{{nuclide|Hydrogen|3|}}&nbsp;||→&nbsp;||{{nuclide|link=yes|helium|3|}}&nbsp;||+&nbsp;||{{SubatomicParticle|link=yes|Electron}}&nbsp;||+&nbsp;||{{SubatomicParticle|link=yes|Electron Antineutrino}}
|}
<!-- simpler
:<chem>^3_1H \to ^3_2{He^+} + {e^-} + \bar{\nu}_e</chem>
-->
releasing 18.6&nbsp;[[Electronvolt|keV]] of energy in the process. The [[electron]]'s kinetic energy varies, with an average of 5.7&nbsp;keV, while the remaining energy is carried off by the nearly undetectable [[Electron neutrino#Electron antineutrino|electron antineutrino]]. [[Beta particle]]s from tritium can penetrate only about {{convert|6.0|mm}} of air, and they are incapable of passing through the dead outermost layer of human skin.<ref>
{{cite report
 |title=Hydrogen-3
 |series=Nuclide safety data sheet
 |website=ehso.emory.edu
 |url=http://www.ehso.emory.edu/content-forms/3anuclidedatasafetysheets.pdf
 |archive-url=https://web.archive.org/web/20130520184942/http://www.ehso.emory.edu/content-forms/3anuclidedatasafetysheets.pdf
 |archive-date=2013-05-20
}}</ref> Because of their low energy compared to other beta particles, the amount of [[bremsstrahlung]] generated is also lower. The unusually low energy released in the tritium beta decay makes the decay (along with that of [[Isotopes of rhenium|rhenium-187]]) useful for absolute neutrino mass measurements in the laboratory.

The low energy of tritium's radiation makes it difficult to detect tritium-labeled compounds except by using [[liquid scintillation counting]].