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'Uranium-233' is a fissile artificial isotope of uranium, which is proposed as a nuclear fuel. It has a half-life of 160,000 years.
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 only 22 minutes. Thorium-233 decays into protactinium-233 through beta decay. Protactinium-233 has a half life of 27 days and beta decays into uranium-233.
Breeding uranium-233 from thorium feedstock is the long-term strategy of the nuclear power program of India, which has substantial thorium reserves. This can in theory be accomplished using either fast or thermal reactors, unlike uranium-based fuel cycles which require the superior neutron economy of a fast reactor in order to ''breed'', that is to produce more fissile material than is consumed. Outside of India, interest in the thorium-based fuel cycle is not great, although the world's reserves of thorium are three times those of uranium.
It is possible to use uranium-233 as the fuel of a nuclear weapon, although none is known to have been tested. Fabrication of a bomb from U-233 presents difficulties beyond that of assembling one from uranium-235; production of U-233 invariably produces some U-232 as well, and the decay chain of U-232 yields many alpha and gamma emitters, making it a more difficult material to handle safely.
The radioisotope bismuth-213 is a decay product of uranium-233. Bismuth-213 has promise for the treatment of certain types of cancer, including acute myeloid leukemia and cancers of the pancreas, kidneys and other organs.