Groundwater dating and residence time measurements
Tritium is also produced in heavy water-moderated reactors whenever a deuterium nucleus captures a neutron.This reaction has a quite small absorption cross section, making heavy water a good neutron moderator, and relatively little tritium is produced.Tritium is used as a radioactive tracer, in radioluminescent light sources for watches and instruments, and, along with deuterium, as a fuel for nuclear fusion reactions with applications in energy generation and weapons.The name of this isotope is derived from Greek τρίτος (trítos), meaning "third".Naturally occurring tritium is extremely rare on Earth, where trace amounts are formed by the interaction of the atmosphere with cosmic rays.It can be produced by irradiating lithium metal or lithium-bearing ceramic pebbles in a nuclear reactor.
The production of tritium was resumed with irradiation of rods containing lithium (replacing the usual control rods containing boron, cadmium, or hafnium), at the reactors of the commercial Watts Bar Nuclear Generating Station in 2003–2005 followed by extraction of tritium from the rods at the new Tritium Extraction Facility All atomic nuclei, being composed of protons and neutrons, repel one another because of their positive charge.
This has raised concerns that if tritium were used in large quantities, in particular for fusion reactors, it may contribute to radioactive contamination, although 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 Test Ban Treaty proved to be unexpectedly useful to oceanographers.
Since it continually decays into helium-3, the total amount remaining was about 75 kg (165 lb) at the time of the report.
Tritium for American nuclear weapons was produced in special heavy water reactors at the Savannah River Site until their closures in 1988.