Helium-3

This article is about the isotope. For the record label, see Helium 3 (record label).
Helium-3, 3He
General
Symbol3He
Nameshelium-3, 3He, He-3,
tralphium (obsolete)
Protons (Z)2
Neutrons (N)1
Nuclide data
Natural abundance0.000137% (% He on Earth)
0.001% (% He in Solar System)
Half-life (t1/2)stable
Isotope mass3.0160293 Da
Spin1⁄2
Parent isotopes3H (beta decay of tritium)
Isotopes of helium
Complete table of nuclides

Helium-3 (3He[1][2] see also helion) is a light, stable isotope of helium with two protons and one neutron. (In contrast, the most common isotope, helium-4, has two protons and two neutrons.) Helium-3 and protium (ordinary hydrogen) are the only stable nuclides with more protons than neutrons. It was discovered in 1939.

Helium-3 occurs as a primordial nuclide, escaping from Earth's crust into its atmosphere and into outer space over millions of years. It is also thought to be a natural nucleogenic and cosmogenic nuclide, one produced when lithium is bombarded by natural neutrons, which can be released by spontaneous fission and by nuclear reactions with cosmic rays. Some found in the terrestrial atmosphere is a remnant of atmospheric and underwater nuclear weapons testing.

Nuclear fusion using helium-3 has long been viewed as a desirable future energy source. The fusion of two of its atoms would be aneutronic, not release the dangerous radiation of traditional fusion or require much higher temperatures.[3] The process may unavoidably create other reactions that themselves would cause the surrounding material to become radioactive.[4]

Helium-3 is thought to be more abundant on the Moon than on Earth, having been deposited in the upper layer of regolith by the solar wind over billions of years,[5] though still lower in abundance than in the Solar System's gas giants.[6][7]

  1. ^ Galli, D. (September 2004). "The cosmic saga of 3He". arXiv:astro-ph/0412380v1.
  2. ^ Ley, Willy (October 1966). "The Delayed Discovery". For Your Information. Galaxy Science Fiction. pp. 116–127.
  3. ^ Matson, John (12 Jun 2009). "Is MOON's Sci-Fi Vision of Lunar Helium 3 Mining Based in Reality?". Scientific American – News Blog. Archived from the original on 30 August 2017. Retrieved 29 Aug 2017.
  4. ^ Close, Frank (August 2007). "Fears Over Factoids" (PDF). CERN Document Server. Physicsworld.com. Archived (PDF) from the original on 22 October 2017. Retrieved 8 July 2018.
  5. ^ Fa WenZhe; Jin YaQiu (December 2010). "Global inventory of Helium-3 in lunar regoliths estimated by a multi-channel microwave radiometer on the Chang-E 1 lunar satellite". Archived from the original on 2017-10-11. Retrieved 2012-12-12.
  6. ^ Slyuta, E. N.; Abdrakhimov, A. M.; Galimov, E. M. (March 12–16, 2007). The Estimation of Helium-3 Probable Reserves in Lunar Regolith (PDF). 38th Lunar and Planetary Science Conference. p. 2175. Archived (PDF) from the original on 2008-07-05. Retrieved 2007-05-31.
  7. ^ Cocks, F. H. (2010). "3He in permanently shadowed lunar polar surfaces". Icarus. 206 (2): 778–779. Bibcode:2010Icar..206..778C. doi:10.1016/j.icarus.2009.12.032.