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Thorium: Radionuclides

  1. Zal Uyun Wan Mahmood,
  2. Che Abd Rahim Mohamed

Published Online: 15 JUN 2010

DOI: 10.1002/0470862106.ia737

Encyclopedia of Inorganic Chemistry

Encyclopedia of Inorganic Chemistry

How to Cite

Wan Mahmood, Z. U. and Rahim Mohamed, C. A. 2010. Thorium: Radionuclides. Encyclopedia of Inorganic Chemistry. .

Author Information

  1. Universiti Kebangsaan Malaysia, Bangi, Malaysia

Publication History

  1. Published Online: 15 JUN 2010


Thorium is composed of 25 different isotopes with the common ones being 224Th, 226Th, 227Th, 228Th, 229Th, 230Th, 231Th, 232Th, 233Th, and 234Th. These decay with considerably different half-lives and nuclear properties. Although thorium is considered one of the more highly radiotoxic elements, its toxicity is low because of its stability at ambient temperature. The intake of thorium isotopes by human being occurs mainly through animal products, cereals, vegetables, and waters. Thorium is widely distributed in small amounts, with an average lithospheric concentration of 8–12 mg g−1 in the earth's crust (at an average concentration of 6 mg g−1 in soil). Furthermore, thorium is quite useful, especially in industries, and it is also recognized as a potential fuel for fast breeder reactors, where it is converted to fissile 233U. This article presents details on the occurrence, chemistry, speciation, separation, and analytical characterization techniques of the more common isotopes of thorium.


  • thorium isotopes;
  • mobility;
  • toxicity;
  • detection;
  • neutron activation analysis (NAA);
  • inductively coupled plasma-mass spectroscopy