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- alpha hindrance factor
- In radioactivity: Alpha decay
The existence of uranium-235 in nature rests on the fact that alpha decay to the ground and low excited states exhibits hindrance factors of over 1,000. Thus the uranium-235 half-life is lengthened to 7 × 108 years, a time barely long enough compared to the age of the…
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- In radioactivity: Alpha decay
- fissile material
- In fissile material
The principal fissile materials are uranium-235 (0.7 percent of naturally occurring uranium), plutonium-239, and uranium-233, the last two being artificially produced from the fertile materials uranium-238 and thorium-232, respectively. A fertile material, not itself capable of undergoing fission with low-energy neutrons, is one that decays into fissile
Read More - In uranium processing
…uranium-238; the remainder consists of uranium-235 (0.72 percent) and uranium-234 (0.006 percent). Of these naturally occurring isotopes, only uranium-235 is directly fissionable by neutron irradiation. However, uranium-238, upon absorbing a neutron, forms uranium-239, and this latter isotope eventually decays into plutonium-239—a fissile material of great importance in nuclear power and…
Read More - In uranium processing: Conversion and isotopic enrichment
…separate and concentrate the fissile uranium-235 isotope into several grades, from low-enrichment (2 to 3 percent uranium-235) to fully enriched (97 to 99 percent uranium-235). Low-enrichment uranium is typically used as fuel for light-water nuclear reactors.
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- In fissile material
- fission research
- In nuclear fission: History of fission research and technology
…established that the rare isotope uranium-235 was responsible for this phenomenon. The more abundant isotope uranium-238 could be made to undergo fission only by fast neutrons with energy exceeding 1 MeV. The nuclei of other heavy elements, such as thorium and protactinium, also were shown to be fissionable with fast…
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- In nuclear fission: History of fission research and technology
- fission-track dating
- In fission-track dating
…to produce thermal fission of uranium-235, which produces another population of tracks, these related to the uranium concentration of the mineral. Thus, the ratio of naturally produced, spontaneous fission tracks to neutron-induced fission tracks is a measure of the age of the sample.
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- In fission-track dating
- gaseous diffusion and isotope separation
- In isotope: Gaseous diffusion
…uranium enriched in the readily fissionable isotope 235U, which is needed for nuclear reactors and nuclear weapons. (Natural uranium contains only about 0.7 percent 235U, with the remainder of the isotopic mixture consisting almost entirely of 238U.) In the separation process, natural uranium in the form of uranium hexafluoride (UF6)…
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- In isotope: Gaseous diffusion
- helium dating
- In helium dating
…decay of the radioactive isotopes uranium-235, uranium-238, and thorium-232. Because of this decay, the helium content of any mineral or rock capable of retaining helium will increase during the lifetime of that mineral or rock, and the ratio of helium to its radioactive progenitors then becomes a measure of geologic…
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- In helium dating
- isotopic fractionation
- In isotopic fractionation
The fissile isotope uranium-235 has been separated from the more abundant, nonfissile isotope uranium-238 by exploiting the slight difference in the rates at which the gaseous hexafluorides of the two isotopes pass through a porous barrier.
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- In isotopic fractionation
- Manhattan Project research
- In Manhattan Project
Uranium-235, the essential fissionable component of the postulated bomb, cannot be separated from its natural companion, the much more abundant uranium-238, by chemical means; the atoms of these respective isotopes must rather be separated from each other by physical means. Several physical methods to do…
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- In Manhattan Project
- neutron absorption
- In fission product
…many known fission reactions of uranium-235 induced by absorbing a neutron results, for example, in two extremely unstable fission fragments, a barium and a krypton nucleus. These fragments almost instantaneously release three neutrons between themselves, becoming barium-144 and krypton-89. By repeated beta decay, the barium-144 in turn is converted step…
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- In fission product
- structure
- In uranium
27 percent, 4,510,000,000-year half-life), uranium-235 (0.72 percent, 713,000,000-year half-life), and uranium-234 (0.006 percent, 247,000-year half-life). These long half-lives make determinations of the age of Earth possible by measuring the amounts of lead, uranium’s ultimate decay product, in certain uranium-containing rocks. Uranium-238 is the parent and uranium-234 one of the…
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- In uranium
- uranium-thorium-lead dating
- In uranium-thorium-lead dating
, the uranium isotopes uranium-235 and uranium-238 and the thorium isotope thorium-232.
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- In uranium-thorium-lead dating
applications
Uranium glass contains a very small amount of radioactive uranium, so they are, technically, radioactive, and the student, who wishes to remain anonymous, made the further mistake of taking with him the certificate provided by the original source (my favorite mad scientist supplier, United Nuclear) certifying that they definitely are genuinely. Uranium (U): a naturally occurring radioactive element whose principal isotopes are uranium-238 (U-238) and uranium-235 (U-235). Natural uranium is a hard, silvery-white, shiny metallic ore that contains a minute amount of uranium-234 (U-234).
- Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table.A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons.
- Uranium, radioactive chemical element of the actinoid series of the periodic table, atomic number 92. It is an important nuclear fuel. It is a dense, hard metallic element that is silvery white in color. It is ductile, malleable, and capable of taking a high polish. Learn more about uranium in this article.
- Uranium 235 is a fissile isotope and its fission cross-section for thermal neutrons is about 585 barns (for 0.0253 eV neutron). For fast neutrons its fission cross-section is on the order of barns. Most of absorption reactions result in fission reaction, but a minority results in radiative capture forming 236 U.
- nuclear reactors
- In nuclear reactor: Fissile and fertile materials
…nuclear industry are uranium-233 (233U), uranium-235 (235U), plutonium-239 (239Pu), and plutonium-241 (241Pu). Of these, only uranium-235 occurs in a usable amount in nature—though its presence in natural uranium is only some 0.7204 percent by weight, necessitating a lengthy and expensive enrichment process to generate a usable reactor fuel (see below…
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- In nuclear reactor: Fissile and fertile materials
- nuclear weapons
- In atomic bomb: The properties and effects of atomic bombs
…an atom of the isotopes uranium-235 or plutonium-239, it causes that nucleus to split into two fragments, each of which is a nucleus with about half the protons and neutrons of the original nucleus. In the process of splitting, a great amount of thermal energy, as well as gamma rays…
Read More - In nuclear weapon: Discovery of nuclear fission
…postulated that the uranium isotope uranium-235 was the one undergoing fission; the other isotope, uranium-238, merely absorbed the neutrons. It was discovered that neutrons were also produced during the fission process; on average, each fissioning atom produced more than two neutrons. If the proper amount of material were assembled, these…
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- In atomic bomb: The properties and effects of atomic bombs
work of
- Dempster
- In Arthur Jeffrey Dempster
Dempster discovered the isotope uranium-235, which is used in atomic bombs.
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- In Arthur Jeffrey Dempster
- Dunning
- In John R. Dunning
…that it was mostly the uranium-235 isotope that was involved in the fission of the uranium nucleus. Dunning went on to direct the research team at Columbia that developed the gaseous-diffusion method of separating uranium-235 from the more abundant uranium-238 isotope. Gaseous diffusion is still the principal method for obtaining…
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- In John R. Dunning
Researchers just produced the lightest-yet version of a uranium atom — with just 122 neutrons compared to the 146 neutrons present in more than 99% of uranium that forms naturally, called uranium-238, according to a recent study published in the journal Physical Review Letters.
Uranium Atomic Number
New uranium isotope experiences powerful internal interaction
An isotope of an element always carries the same number of protons — uranium possessing 92, but with varying numbers of neutrons. Scientists identify isotopes labeled by the total number of neutrons and protons in their nuclei — and the new isotope has the lowest number of these particles ever discovered — 214, which is why it's called uranium-214.
The new uranium isotope was produced by Zhiyuan Zhang and his colleagues of the Chinese Academy of Sciences — using a long-term process of blasting tungsten samples with calcium and argon beams until the atoms fused. After this happened, the scientists pulled the uranium-214 atoms out of the sample via a magnetic tool called a separator. 'The production of these atoms is very difficult, because not every collision can produce what we want,' said Zhang, in a report from New Scientist. 'About 10^18 beam particles were delivered to collide with the target, but only two nuclei of uranium-214 were produced successfully and separated.'
The researchers observed the nuclei decay and found that uranium-214's half-life — which is the timespan until half of a given sample of particles has undergone radioactive decay — is roughly 0.52 milliseconds. They then executed similar experiments on two previously-discovered isotopes — uranium-216 and uranium-218 — and discovered that their half-lives were roughly 2.25 milliseconds and 0.65 milliseconds, respectively.
The team of scientists also found that uranium-214 and uranium-216 isotopes experience alpha decay, when an atom loses two neutrons and protons — which means interactions between neutrons and protons in these atoms are more potent than those in others. 'Our finding might be the first experimental evidence that the strong proton-neutron interaction can play an important role in alpha decay in [heavy nuclei],' said Zhang in the New Scientist report.
And its half-life is very impressive.
More efficient, sustainable nuclear power
This is significant for several reasons, but amid a global transition toward renewable energy sources, an ultra-light version of uranium might provide more efficient sources of fuel for nuclear power generators. And efficiency is key amid a possible reclassification of nuclear power as 'sustainable' by the European Commission of the European Union. Of course, this is only speculation, but the rising status of nuclear power is indisputable.
The European Commission's sustainable finance taxonomy is deciding which economic activities are sustainable investments in the region based on firm environmental criteria. Popular misconceptions of nuclear power consider it highly dangerous for the environment, but the reality shows the mode of energy generation produces low levels of CO2 emissions. One subject of debate revolves around the environmental impact of radioactive waste disposal.
Uranium Atom Gif
'The analyses did not reveal any science-based evidence that nuclear energy does more harm to human health or to the environment than other electricity production technologies,' read a report from the European Commission. Nuclear waste can be stored in deep geologic formations in ways that are 'appropriate and safe,' continued the report, citing cases like France and Finland, where such sites are already in advanced development stages. And, if uranium-214 can offer a substantially shorter period of radioactive decay, it might open new avenues for radioactive waste disposal that minimizes harm to the environment more than ever before.