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Tritium
Tritium, symbol T or 3H, is a radioactive isotope of hydrogen. The nucleus contains one proton and two neutrons. Naturally occurring tritium is extremely rare on Earth, but trace amounts are formed when the atmosphere interacts with cosmic rays. It has a half-life of 12.32 years an decays into helium-3. Tritium can not pass through skin, but can be dangerous if inhaled or ingested. It can be absorbed through the skin if mixed with oxygen to form tritiated water. It has an atomic mass of 3.0160492 and is a gas at standard temperature and pressure.
Tritium is mainly produced in nuclear reactions by neutron activation of lithium-6. This is possible with neutrons of any energy, and is an exothermic reaction yielding 4.8 MeV. There are other methods that will produce the isotope, but in negligible and unreliable amounts. One other common method of production is in heavy water moderated reactors. This happens when a deuterium nucleus captures a neutron. In this reaction heavy water a good neutron moderator, so only a little tritium is produced.
Tritium is important to the study of nuclear fusion because of its favorable reaction cross section and the large amount of energy produced during its reaction with deuterium. All atomic nuclei repel one another because of their positive charge. If the atoms have a high enough temperature and pressure their random motions can overcome this repulsion and they can come close enough for the strong nuclear force to take effect, which fuses them into heavier atoms. The tritium nucleus has the same charge as that of ordinary hydrogen and experiences the same repulsive force; however, the neutrons in the tritium nucleus increase the attractive strong nuclear force when brought close enough to another atomic nucleus. So, tritium can more easily fuse with other light atoms. In one sense, tritium is the main hope for safe, reliable nuclear power.
We have written many articles about Tritium for Universe Today. Here’s an article about who discovered Hydrogen, and here’s an article about beta particles.
If you’d like more info on Tritium, check out ISU’s Tritium Information page, and here’s a link to more information about Tritium by Wise Geek.
We’ve also recorded an entire episode of Astronomy Cast all about Fusion. Listen here, Episode 205: Fusion.
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