Tritium
A heavy form of hydrogen with one proton and two neutrons. It is weakly radioactive, almost absent in nature, and serves as fusion fuel.
The nucleus of ordinary hydrogen is a single proton; tritium carries two extra neutrons. It was first made in 1934 by Mark Oliphant, Paul Harteck and Ernest Rutherford, in experiments that fired deuterium at deuterium[1]. It gives off weak radiation (beta rays), and half of any sample turns into helium-3 in about 12 years.
Because it is so short-lived, almost none exists in nature, and a fusion reactor has to make its own supply. Neutrons striking lithium produce tritium, and that is the job of the blanket surrounding the reactor. Whether a reactor can make more than it burns is one of the conditions for fusion power to work at all[2].
Related terms
- D-T fusionThe fusion of deuterium (D) and tritium (T) into a helium-4 nucleus and a neutron. Almost every fusion reactor now under development is built around this reaction.
- DeuteriumA heavy form of hydrogen with one proton and one neutron. It is not radioactive and is found in seawater.
- Breeding blanketThe layer surrounding a fusion reactor's plasma. Neutrons striking lithium in it produce tritium fuel, and their energy is captured as heat.
- Tritium breeding ratioThe number of new tritium atoms a reactor's blanket makes for each tritium atom burned. Unless it exceeds one, the reactor cannot supply its own fuel.
On the timeline
Sources
- M. L. E. Oliphant, P. Harteck, E. Rutherford, “Transmutation effects observed with heavy hydrogen,” Proc. R. Soc. Lond. A 144, 692–703 (1934).
- M. Abdou, M. Riva, A. Ying, et al., “Physics and technology considerations for the deuterium–tritium fuel cycle and conditions for tritium fuel self sufficiency,” Nucl. Fusion 61, 013001 (2021).