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Of all the isotopic dating methods in use today, the uranium-lead method is the oldest and, when done carefully, the most reliable. Unlike any other method, uranium-lead has a natural cross-check built into it that shows when nature has tampered with the evidence. Uranium comes in two common isotopes with atomic weights of and we'll call them U and U. Both are unstable and radioactive, shedding nuclear particles in a cascade that doesn't stop until they become lead Pb. The two cascades are different-U becomes Pb and U becomes Pb. What makes this fact useful is that they occur at different rates, as expressed in their half-lives the time it takes for half the atoms to decay.

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The word in the example sentence does not match the entry word. The sentence contains offensive content. Cancel Submit. Your feedback will be reviewed. Chemical elements. Examples of uranium. This is no doubt related to the increased interest in gas centrifuges as a means of separating uranium isotopes. From Cambridge English Corpus. It has therefore been concluded that, it is necessary to develop an alternate target design for such high intensities of the uranium beam.

These examples are from the Cambridge English Corpus and from sources on the web. Any opinions in the examples do not represent the opinion of the Cambridge Dictionary editors or of Cambridge University Press or its licensors.

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And that conglomerate also owns nearly 70 percent of the Rossing uranium mine in Namibia. A six-month quasi-limit on uranium enrichment does not mean the government has changed. It completely stops enrichment of uranium to 20 percent-the level needed to make a bomb. Curie examined at the same time the salts of uranium and a number of uranium ores.

Los Alamos scientists devised two designs for an atomic bomb-one using the uranium and another using the plutonium. The number of free positive electrons in the nucleus varies from one in hydrogen to 92 in uranium. Platinotypes may be toned to a red-brown by uranium nitrate, or to a bluer colour with chloride of gold.

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Autunite, a hydrous phosphate of uranium and calcium, crystallizing in the rhombic system in yellow plates. A chemical element that is naturally radioactive. An isotope of uranium, uraniumis the main fuel for nuclear reactors and atomic bombs see also atomic bomb. Its symbol is U. Uranium dioxide is the form in which uranium is most commonly used as a nuclear reactor fuel.

Because of their stability, uranium oxides are generally considered the preferred chemical form for storage or disposal. Salts of many oxidation states of uranium are water- soluble and may be studied in aqueous solutions. Unlike the uranyl salts of uranium and polyatomic ion uranium-oxide cationic forms, the uranatessalts containing a polyatomic uranium-oxide anion, are generally not water-soluble.

The interactions of carbonate anions with uranium VI cause the Pourbaix diagram to change greatly when the medium is changed from water to a carbonate containing solution.

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While the vast majority of carbonates are insoluble in water students are often taught that all carbonates other than those of alkali metals are insoluble in wateruranium carbonates are often soluble in water.

This is because a U VI cation is able to bind two terminal oxides and three or more carbonates to form anionic complexes. The uranium fraction diagrams in the presence of carbonate illustrate this further: when the pH of a uranium VI solution increases, the uranium is converted to a hydrated uranium oxide hydroxide and at high pHs it becomes an anionic hydroxide complex.

When carbonate is added, uranium is converted to a series of carbonate complexes if the pH is increased. One effect of these reactions is increased solubility of uranium in the pH range 6 to 8, a fact that has a direct bearing on the long term stability of spent uranium dioxide nuclear fuels.

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Even higher temperatures will reversibly remove the hydrogen. This property makes uranium hydrides convenient starting materials to create reactive uranium powder along with various uranium carbidenitrideand halide compounds. Uranium carbides and uranium nitrides are both relatively inert semimetallic compounds that are minimally soluble in acidsreact with water, and can ignite in air to form U 3 O 8. Both UC and UC 2 are formed by adding carbon to molten uranium or by exposing the metal to carbon monoxide at high temperatures.

All uranium fluorides are created using uranium tetrafluoride UF 4 ; UF 4 itself is prepared by hydrofluorination of uranium dioxide. Under the right conditions of temperature and pressure, the reaction of solid UF 4 with gaseous uranium hexafluoride UF 6 can form the intermediate fluorides of U 2 F 9U 4 F 17and UF 5.

At room temperatures, UF 6 has a high vapor pressuremaking it useful in the gaseous diffusion process to separate the rare uranium from the common uranium isotope. This compound can be prepared from uranium dioxide and uranium hydride by the following process: [98].

The resulting UF 6a white solid, is highly reactive by fluorinationeasily sublimes emitting a vapor that behaves as a nearly ideal gasand is the most volatile compound of uranium known to exist. One method of preparing uranium tetrachloride UCl 4 is to directly combine chlorine with either uranium metal or uranium hydride.

The reduction of UCl 4 by hydrogen produces uranium trichloride UCl 3 while the higher chlorides of uranium are prepared by reaction with additional chlorine. Bromides and iodides of uranium are formed by direct reaction of, respectively, bromine and iodine with uranium or by adding UH 3 to those element's acids. Stability of the oxyhalides decrease as the atomic weight of the component halide increases.

Natural uranium consists of three major isotopes : uranium All three are radioactiveemitting alpha particleswith the exception that all three of these isotopes have small probabilities of undergoing spontaneous fission.

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There are also five other trace isotopes: uranium, which is formed when U undergoes spontaneous fission, releasing neutrons that are captured by another U atom; uranium, which is formed when U captures a neutron but emits two more, which then decays to neptunium ; and finally, uranium, which is formed in the decay chain of that neptunium It is also expected that thorium should be able to undergo double beta decaywhich would produce uranium, but this has not yet been observed experimentally.

Uranium is the most stable isotope of uranium, with a half-life of about 4.

Uranium definition, a white, lustrous, radioactive, metallic element, occurring in pitchblende, and having compounds that are used in photography and in coloring glass. The isotope is used in atomic and hydrogen bombs and as a fuel in nuclear reactors. Symbol: U; atomic weight: ; atomic number: 92; specific gravity: See more. uranium definition: 1. a chemical element that is a heavy, radioactive metal, used in the production of nuclear power. Learn more. Of all the isotopic dating methods in use today, the uranium-lead method is the oldest and, when done carefully, the most reliable. Unlike any other method, uranium-lead has a natural cross-check built into it that shows when nature has tampered with the vizyonbarkod.com: Andrew Alden.

Uranium has a half-life of about 7. When the Earth was young, probably about one-fifth of its uranium was uranium, but the percentage of U was probably much lower than this.

The decay chain of U, which is called the actinium serieshas 15 members and eventually decays into lead Uranium, which is a member of the uranium series the decay chain of uraniumdecays to lead through a series of relatively short-lived isotopes. Uranium is made from thorium by neutron bombardment, usually in a nuclear reactor, and U is also fissile. Uranium is important for both nuclear reactors and nuclear weaponsbecause it is the only uranium isotope existing in nature on Earth in any significant amount that is fissile.

This means that it can be split into two or three fragments fission products by thermal neutrons. Uranium is not fissile, but is a fertile isotope, because after neutron activation it can be converted to plutoniumanother fissile isotope.

Indeed, the U nucleus can absorb one neutron to produce the radioactive isotope uranium Isotope separation concentrates enriches the fissionable uranium for nuclear weapons and most nuclear power plants, except for gas cooled reactors and pressurised heavy water reactors.

Most neutrons released by a fissioning atom of uranium must impact other uranium atoms to sustain the nuclear chain reaction. The concentration and amount of uranium needed to achieve this is called a ' critical mass '.

To be considered 'depleted', the uranium isotope concentration should be no more than 0. The gas centrifuge process, where gaseous uranium hexafluoride UF 6 is separated by the difference in molecular weight between UF 6 and UF 6 using high-speed centrifugesis the cheapest and leading enrichment process.

In this process, uranium hexafluoride is repeatedly diffused through a silver - zinc membrane, and the different isotopes of uranium are separated by diffusion rate since uranium is heavier it diffuses slightly slower than uranium This leaves uranium bonded to fluorine and allows uranium metal to precipitate from the solution.

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A person can be exposed to uranium or its radioactive daughterssuch as radon by inhaling dust in air or by ingesting contaminated water and food.

The amount of uranium in air is usually very small; however, people who work in factories that process phosphate fertilizerslive near government facilities that made or tested nuclear weapons, live or work near a modern battlefield where depleted uranium weapons have been used, or live or work near a coal -fired power plant, facilities that mine or process uranium ore, or enrich uranium for reactor fuel, may have increased exposure to uranium.

Most ingested uranium is excreted during digestion.

Only 0. After entering the bloodstream, the absorbed uranium tends to bioaccumulate and stay for many years in bone tissue because of uranium's affinity for phosphates. Incorporated uranium becomes uranyl ions, which accumulate in bone, liver, kidney, and reproductive tissues. Uranium can be decontaminated from steel surfaces and aquifers. Normal functioning of the kidneybrainliverheartand other systems can be affected by uranium exposure, because, besides being weakly radioactive, uranium is a toxic metal.

Alpha radiation from inhaled uranium has been demonstrated to cause lung cancer in exposed nuclear workers. Uranium metal is commonly handled with gloves as a sufficient precaution.

From Wikipedia, the free encyclopedia.

This article is about the chemical element. For other uses, see Uranium disambiguation. Chemical element with atomic number Main article: Natural nuclear fission reactor. Main article: Uranium in the environment. Main article: Uranium mining. This section needs to be ated. Please ate this article to reflect recent events or newly available information. September Main article: Uranium market. Triuranium octoxide left and uranium dioxide right are the two most common uranium oxides.

Main article: Isotopes of uranium.

Uranium dating meaning

Main article: Enriched uranium. K residues List of countries by uranium production List of countries by uranium reserves List of uranium projects Lists of nuclear disasters and radioactive incidents Nuclear and radiation accidents and incidents Nuclear engineering Nuclear fuel cycle Nuclear physics Thorium fuel cycle Uranium bubble of Uranium nitride Uranium tile World Uranium Hearing.

Pure and Applied Chemistry. The Chemistry of the Actinide and Transactinide Elements 3rd ed. Netherlands: Springer. Encyclopaedia Britannica. Retrieved 22 April Archived from the original on 27 April CRC press. Royal Society of Chemistry. Columbia Electronic Encyclopedia 6th ed. Columbia University Press. Encyclopedia of Espionage, Intelligence, and Security.

The Gale Group, Inc. Applications of Texture Analysis.

Uranium dating definition, a method of dating archaeological or geological specimens by determining the decay activity of the uranium in a given sample. See more.

John Wiley and Sons. In Morss, Lester R. Dordrecht, the Netherlands: Springer. Archived from the original on 7 March Depleted Uranium in the Gulf II. Federation of American Scientists.

uranium dating

Archived from the original on 26 December Retrieved 19 February Retrieved 12 September Environmental Protection Agency. Retrieved 20 September Oak Ridge Associated Universities. Retrieved 10 October Chemische Annalen. Houghton Mifflin Company. Annales de chimie et de physique. Westinghouse Club.

The Bureau - via Google Books. Royal Swedish Academy of Sciences.

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Archived from the original on 9 August Retrieved 14 June Nuovo Saggiatore. Bibcode : physics Retrieved 5 May Bibcode : Natur.

Retrieved 4 December Bibcode : Sci Retrieved 23 March Department of Energy, Argonne National Laboratory. Retrieved 25 July Archived from the original on 26 September Retrieved 28 January BBC News. Retrieved 28 June Office of Civilian Radioactive Waste Management. Archived from the original on 3 June Earth and Planetary Science Letters.



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