Tritium

Tritium, or hydrogen-3, is a radioactive isotope of hydrogen that contains one proton and two neutrons. It decays by beta emission to helium-3 with a half-life of about 12.32 years. The beta particles have low energy (maximum around 18.6 keV, with an average of ~5.7 keV), which means external exposure is limited, but internal exposure from inhalation or ingestion can be more significant. Chemically, tritium behaves like ordinary hydrogen and forms the same compounds, including tritiated water (HTO).

In nature, tritium is produced continuously by cosmic rays in the atmosphere and occurs in trace amounts in water and organic matter. Industrial production is mainly achieved in nuclear reactors by irradiating lithium-containing targets, such as lithium-6, which generates tritium. Tritium is then separated, sealed in containers, and supplied for various uses. It can also be produced as a byproduct in some fission and fusion-related facilities.

Applications of tritium include its use as a fuel or fusion reactor blanket source for research and development, particularly in deuterium-tritium fusion concepts. It is also employed as a radiolabel or tracer in biochemical, agricultural, and hydrological studies, where its low-energy beta emission provides sensitive tracing without penetrating external barriers. For consumer products, tritium has historically been used in self-luminous devices, such as certain watches and gun sights, where the gas is sealed in glass tubes with phosphor coatings.

Safety and regulation focus on controlling releases, monitoring environmental and occupational exposure, and proper disposal of tritium-containing materials due to its radioactivity and potential biological uptake.