![]() Ģ34U nuclei usually last for hundreds of thousands of years, but then they decay by alpha emission to thorium-230, except for the small percentage of nuclei that undergo spontaneous fission.Įxtraction of rather small amounts of 234U from natural uranium would be feasible using isotope separation, similar to that used for regular uranium-enrichment. Finally, 234Pa nuclei each emit another beta particle to become 234U nuclei. Next, with a short half-life, a 234Th nucleus emits a beta particle to become protactinium-234. The path of production of 234U via nuclear decay is as follows: 238U nuclei emit an alpha particle to become thorium-234. In natural uranium and in uranium ore, 234U occurs as an indirect decay product of uranium-238, but it makes up only 0.0055% (55 parts per million) of the raw uranium because its half-life of just 245,500 years is only about 1/18,000 as long as that of 238U. The capture-to-fission ratio is smaller than the other two major fissile fuels uranium-235 and plutonium-239 it is also lower than that of short-lived plutonium-241, but bested by very difficult-to-produce neptunium-236. Uranium-233 usually fissions on neutron absorption but sometimes retains the neutron, becoming uranium-234. Protactinium-233 has a half-life of 27 days and beta decays into uranium-233 some proposed molten salt reactor designs attempt to physically isolate the protactinium from further neutron capture before beta decay can occur. Thorium-233 decays into protactinium-233 through beta decay. ![]() When thorium-232 absorbs a neutron, it becomes thorium-233, which has a half-life of only 22 minutes. ![]() ![]() Uranium-233 is produced by the neutron irradiation of thorium-232. It has a half-life of around 160,000 years. It has been used successfully in experimental nuclear reactors and has been proposed for much wider use as a nuclear fuel. It was occasionally tested but never deployed in nuclear weapons and has not been used commercially as a nuclear fuel. Uranium-233 was investigated for use in nuclear weapons and as a reactor fuel. Uranium-233 is a fissile isotope of uranium that is bred from thorium-232 as part of the thorium fuel cycle. ^ Neutron capture product, parent of trace quantities of 237Np.^ Intermediate decay product of 244Pu, also produced by neutron capture of 235U.^ a b # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).^ ( ) spin value – Indicates spin with weak assignment arguments.^ Bold symbol as daughter – Daughter product is stable.^ Bold italics symbol as daughter – Daughter product is nearly stable.^ # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).^ ( ) – Uncertainty (1 σ) is given in concise form in parentheses after the corresponding last digits.Uranium-238 is also important because it is fertile: it absorbs neutrons to produce a radioactive isotope that subsequently decays to the isotope plutonium-239, which also is fissile. A chain reaction can be sustained with a sufficiently large ( critical) mass of uranium-235. Uranium-235 is important for both nuclear reactors (energy production) and nuclear weapons because it is the only isotope existing in nature to any appreciable extent that is fissile in response to thermal neutrons, i.e., thermal neutron capture has a high probability of inducing fission. Uranium-233 is made from thorium-232 by neutron bombardment. The constant rates of decay in these series makes comparison of the ratios of parent-to-daughter elements useful in radiometric dating. The decay series of uranium-235 (historically called actino-uranium) has 15 members and ends in lead-207. Uranium-238 is an alpha emitter, decaying through the 18-member uranium series into lead-206. All three isotopes are radioactive (i.e., they are radioisotopes), and the most abundant and stable is uranium-238, with a half-life of 4.4683 ×10 9 years (close to the age of the Earth). The standard atomic weight of natural uranium is 238.028 91(3). In addition to isotopes found in nature or nuclear reactors, many isotopes with far shorter half-lives have been produced, ranging from 214U to 242U (with the exception of 220U). Other isotopes such as uranium-233 have been produced in breeder reactors. The decay product uranium-234 is also found. It has two primordial isotopes, uranium-238 and uranium-235, that have long half-lives and are found in appreciable quantity in the Earth's crust. Uranium ( 92U) is a naturally occurring radioactive element that has no stable isotope.
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