Encyclopedia of Chemistry

Thorium-232 is the primary abundant nuclide of thorium. It is a slightly unstable radionuclide that is found in the earth's crust. It is a fertile material able to absorb a neutron and undergo transmutation into a nuclide that is able to support fission (uranium-233).

In the form of Thorotrast, a thorium oxide suspension, it was used as contrast medium in early X-ray diagnostics. Thorium-232 is now classified as carcinogenic. The half-life of thorium-232 is 1.405×10¹⁰ years.