Thorium-232

Thorium-232, 232Th
General
Symbol232Th
Namesthorium-232, 232Th, Th-232
Protons (Z)90
Neutrons (N)142
Nuclide data
Natural abundance99.98%[1]
Half-life (t1/2)1.4×1010 years[1]
Isotope mass232.0380536[2] Da
Spin0+
Parent isotopes236U (α)
232Ac (β−)
Decay products228Ra
Decay modes
Decay modeDecay energy (MeV)
alpha decay4.0816[3]
Isotopes of thorium
Complete table of nuclides

Thorium-232 (232
Th
) is the main naturally occurring isotope of thorium, with a relative abundance of 99.98%. It has a half life of 14 billion years, which makes it the longest-lived isotope of thorium. It decays by alpha decay to radium-228; its decay chain terminates at stable lead-208.

Thorium-232 is a fertile material; it can capture a neutron to form thorium-233, which subsequently undergoes two successive beta decays to uranium-233, which is fissile. As such, it has been used in the thorium fuel cycle in nuclear reactors; various prototype thorium-fueled reactors have been designed. However, as of 2024, thorium has not been used for commercial-scale nuclear power.

  1. ^ a b Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
  2. ^ Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3): 030003. doi:10.1088/1674-1137/abddaf.
  3. ^ National Nuclear Data Center. "NuDat 3.0 database". Brookhaven National Laboratory. Retrieved 19 Feb 2022.