Uranium-233
| General | |
|---|---|
| Symbol | 233U |
| Names | uranium-233 |
| Protons (Z) | 92 |
| Neutrons (N) | 141 |
| Nuclide data | |
| Half-life (t1/2) | 159,200 years |
| Isotope mass | 233.03963 Da |
| Parent isotopes | 237Pu (α) 233Np (β+) 233Pa (β−) |
| Decay products | 229Th |
| Decay modes | |
| Decay mode | Decay energy (MeV) |
| Alpha | 4.909 |
| Isotopes of uranium Complete table of nuclides | |
Uranium-233 (233
U or U-233) is a fissile isotope of uranium that is bred from thorium-232 as part of the thorium fuel cycle. Uranium-233 was investigated for use in nuclear weapons and as a reactor fuel. It has been used successfully in experimental nuclear reactors and has been proposed for much wider use as a nuclear fuel. It has a half-life of 159,200 years to alpha decay and is a part of the neptunium decay chain.
Uranium-233 is produced by the neutron irradiation of thorium-232. When thorium-232 absorbs a neutron, it becomes thorium-233, which has a half-life of about 22 minutes. Thorium-233 decays into protactinium-233 through beta decay. Protactinium-233 has a longer half-life of about 27 days to further decay into uranium-233; some proposed molten salt reactor designs attempt to physically isolate the protactinium from further neutron capture before beta decay can occur, to maintain the neutron economy (if it misses the 233U window, the next fissile target is 235U, meaning a total of 4 neutrons needed to trigger fission).
233U usually fissions on neutron absorption, but sometimes retains the neutron, becoming uranium-234. For both thermal neutrons and fast neutrons, the capture-to-fission ratio of uranium-233 is smaller than those of the other two major fissile fuels, uranium-235 and plutonium-239.