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Tritium

physical science Maturity 11-13 Next article →

Tritium is a rare and radioactive isotope of hydrogen. An isotope is a version of an element that has a different number of neutrons in its nucleus. While most hydrogen on Earth is the light version called protium, tritium is the heaviest particle-bound isotope of hydrogen. Its nucleus, sometimes called a triton, contains one proton and two neutrons. Because it is unstable, it undergoes radioactive decay. This means it will eventually transform into a different element.

TritiationPyridine
TritiationPyridine

The process of decay is known as beta-minus decay. During this process, a tritium nucleus transforms into a helium-3 nucleus. This reaction releases 18.6 keV of energy. The energy is carried away by an electron and a nearly undetectable electron antineutrino. The electron's kinetic energy varies, with an average of 5.7 keV. These beta particles are very weak. They can only penetrate about 0.001 cm of air. They are also incapable of passing through the dead outermost layer of human skin.

Gaseous tritium light source
Gaseous tritium light source

Tritium has a half-life of 12.32 years. This is the time it takes for half of a sample to decay. Because of this relatively short timeframe, tritium is difficult to store for long periods. Scientists use the low energy of its decay for specific tasks. It is used in attempts to measure the absolute mass of the neutrino. However, these measurements have not yet succeeded. Because the radiation is so low-energy, scientists must use liquid scintillation counting to detect tritium-labeled compounds.

Humans first detected tritium in 1934. Scientists Ernest Rutherford, Mark Oliphant, and Paul Harteck found it by bombarding deuterium with deuterons. They could not isolate the substance at that time. In 1939, Luis Alvarez and Robert Cornog successfully isolated tritium. They were also the ones who realized it was radioactive. Later, in 1954, Willard Libby discovered that tritium could be used for radiometric dating. This allows scientists to determine the age of water and wine samples.

Naturally occurring tritium is extremely rare on Earth. It is formed in the atmosphere when cosmic rays interact with gases like nitrogen. The world maintains a balance between new production and decay. Natural sources produce about 4 megacuries of tritium per year. This creates a global equilibrium inventory of approximately 70 megacuries. Most tritium used today is produced artificially in nuclear reactors. One common method is the neutron activation of lithium-6. This is an exothermic reaction, meaning it releases 4.8 MeV of energy.

Tritium-watch
Tritium-watch

Tritium is used in many practical and scientific ways. It serves as the energy source in radioluminescent lights. These lights do not require electricity to glow. You can find them in watch faces, night sights for firearms, and self-illuminating key chains.

Tritium-watch
Tritium-watch

In medical and scientific settings, it acts as a radioactive tracer. It is also a critical fuel for nuclear fusion. In tokamak reactors and hydrogen bombs, tritium is used alongside the more abundant deuterium. This fusion process releases about 17.6 MeV of energy.

Managing tritium is a major task for nuclear power facilities. In Canada, the Darlington Tritium Recovery Facility recovers tritium from heavy water. Between 1989 and 2011, this facility produced a total of 25,000 Ci. In Japan, the Fukushima Daiichi plant has faced challenges with tritiated water. Experts decided that a controlled environmental release was the best way to treat low-concentration water. The water is diluted to less than 1500 Bq/L before release. This level is far below the limits recommended by the World Health Organization.

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File:Gaseous tritium light source.jpg
Gaseous tritium light source.jpg
File:TritiationPyridine.svg
TritiationPyridine.svg
File:Tritium-watch.jpg
Tritium-watch.jpg
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