Thorium-232
General | |
---|---|
Decay mode | Decay energy (MeV) |
alpha decay | 4.0816[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.
Natural occurrence
The
Some minerals that contain thorium include
Decay
Thorium-232 has a half-life of 14 billion years and mainly decays by
The following table lists the intermediate decay products in the thorium-232 decay chain:
nuclide | decay mode | half-life (a=year) |
energy released, MeV | product of decay |
---|---|---|---|---|
232Th | α | 1.4×1010 a | 4.081 | 228Ra
|
228Ra | β− | 5.75 a | 0.046 | 228Ac
|
228Ac | β− | 6.15 h | 2.134 | 228Th
|
228Th | α | 1.9116 a | 5.520 | 224Ra
|
224Ra | α | 3.6319 d | 5.789 | 220Rn
|
220Rn | α | 55.6 s | 6.405 | 216Po
|
216Po | α | 0.145 s | 6.906 | 212Pb
|
212Pb | β− | 10.64 h | 0.569 | 212Bi
|
212Bi | β− 64.06% α 35.94% |
60.55 min | 2.252 6.207 |
208Tl
|
212Po | α | 294.4 ns[1] | 8.954 [3] | 208Pb
|
208Tl | β− | 3.053 min | 4.999 [3] | 208Pb |
208Pb | stable | . | . | . |
Rare decay modes
Although thorium-232 mainly decays by alpha decay, it also undergoes spontaneous fission 1.1×10−9% of the time.[3] In addition, it is capable of
Use in nuclear power
Thorium-232 is not fissile; it therefore cannot be used directly as fuel in nuclear reactors. However, 232
Th
is fertile: it can capture a neutron to form 233
Th
, which undergoes beta decay with a half-life of 21.8 minutes to 233
Pa
. This nuclide subsequently undergoes beta decay with a half-life of 27 days to form fissile 233
U
.[4]
One potential advantage of a thorium-based nuclear fuel cycle is that thorium is more abundant in nature than
References
- ^ .
- .
- ^ a b c d e National Nuclear Data Center. "NuDat 3.0 database". Brookhaven National Laboratory. Retrieved 19 Feb 2022.
- ^ a b c "Thorium - World Nuclear Association". World Nuclear Association. Retrieved 19 Feb 2022.
- ^ a b "Thorium". usgs.gov. Retrieved 19 Feb 2022.