Uranium preparation

The Uranium Series.—Ordinary uranium preparations emit a-, j8-, and y-rays. The a-rays alone come from the element uranium, the j8- and y-rays coming from products of its disintegration. By expulsion of one a-particle, the atom of uranium, of atomic -weight 238, produces an atom of a new element, kno vn as uranium X, of atomic w eight 234. This new atom is more unstable than the original uranium atom and emits a jS-partide, producing an atom of another new element, knowm as uranium Xg, of the same atomic weight as uranium X. ... 

US Environmental Protection Agency (EPA) (1999b) Understanding variation in partition coefficient, Kd, values Volume II. Review of geochemistry and available Kd values for cadmium, cesium, chromium, lead, plutonium, radon, strontium, thorium, tritium (3H) and uranium. Prepared for the EPA by Pacific Northwest National Laboratory. 

Hydrides, for example, CuH [16], ZnHg [15], CeHg [5], UHg [8] and so forth these are decomposed in high vacuum at relatively low temperatures. Active uranium prepared from UHg has the remarkable ability to absorb large quantities of Hg, Og, Ng, CO, COg and other base gases it can thus be used for the purification of inert gases, especially in closed systems [4],... 

Active uranium prepared by Na/K reduction in DME is also an extremely active polymerization catalyst and will polymerize 100 equiv of 1,3-butadiene at -4°C and atmospheric pressure in less than Ih. This is much more reactive than the active uranium powder prepared by Chang et al. (via thermal decomposition of U/Hg) which polymerized 80% of 1,3-butadiene (latm) in 4h at 70°C [62]. The resulting polybutadiene prepared by our method exhibited IR bands corresponding to cis (675cm ), vinyl (910cm ), and trans (970cm ) morphologies [63]. 

Unfortunately, the reactivity of active uranium prepared by this method 3 with acidic C—H bonds precludes its use with aliphatic ketones. Apparendy,... 

In addition to aromatic solvents, we have seen reactivity of active uranium prepared in 1-decene and TMEDA. The yields of TPE and TPA resulting from preparation and reaction of active uranium with benzophenone in 1-decene are only slightly lower than those in aromatic solvents, presumably due to solubility considerations. There was little difference in the proportion of TPA to TPE. It appears that decene does not serve as either a hydride source (allylic hydrogens) or a hydride sink (via hydrogenation of the double bond). The preparation and reaction of active uranium with benzophenone in TMEDA gave yields of TPE comparable to other aromatic solvents at that temperature ( 20%). Negligible amounts of TPA were seen, however. The presence of a large excess of a basic solvent could serve to reduce the amount of metal hydrides present. 

It has been previously reported by Rieke et al. that active uranium prepared in DME by a similar method reacts cleanly with allyl iodide and benzophenone [31]. This active uranium, however, was prepared at room temperature under conditions that were not as strictly anaerobic as those in the present report. 

OEHHA (2001) Public health goal for chemicals in drinking water uranium. Prepared by the Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, CA, USA, August 2001. 

The new elements neptunium and plutonium have been produced in quantity by neutron bombardment of uranium. Subsequently many isotopes have been obtained by transmutation and synthetic isotopes of elements such as Ac and Pa are more easily obtained than the naturally occurring species. Synthetic species of lighter elements, e.g. Tc and Pm are also prepared. 

Gr. aktis, aktinos, beam or ray). Discovered by Andre Debierne in 1899 and independently by F. Giesel in 1902. Occurs naturally in association with uranium minerals. Actinium-227, a decay product of uranium-235, is a beta emitter with a 21.6-year half-life. Its principal decay products are thorium-227 (18.5-day half-life), radium-223 (11.4-day half-life), and a number of short-lived products including radon, bismuth, polonium, and lead isotopes. In equilibrium with its decay products, it is a powerful source of alpha rays. Actinium metal has been prepared by the reduction of actinium fluoride with lithium vapor at about 1100 to 1300-degrees G. The chemical behavior of actinium is similar to that of the rare earths, particularly lanthanum. Purified actinium comes into equilibrium with its decay products at the end of 185 days, and then decays according to its 21.6-year half-life. It is about 150 times as active as radium, making it of value in the production of neutrons. 

Uranium can be prepared by reducing uranium halides with alkali or alkaline earth metals or by reducing uranium oxides by calcium, aluminum, or carbon at high temperatures. The metal can also be produced by electrolysis of KUF5 or UF4, dissolved in a molten mixture of CaCl2 and NaCl. High-purity uranium can be prepared by the thermal decomposition of uranium halides on a hot filament. 

Its importance depends on the nuclear property of being readily fissionable with neutrons and its availability in quantity. The world s nuclear-power reactors are now producing about 20,000 kg of plutonium/yr. By 1982 it was estimated that about 300,000 kg had accumulated. The various nuclear applications of plutonium are well known. 238Pu has been used in the Apollo lunar missions to power seismic and other equipment on the lunar surface. As with neptunium and uranium, plutonium metal can be prepared by reduction of the trifluoride with alkaline-earth metals. 

The preparation and structure determination of ferrocene marked the beginning of metallocene chemistry Metallocenes are organometallic compounds that bear cyclo pentadiemde ligands A large number are known even some m which uranium is the metal Metallocenes are not only stucturally interesting but many of them have useful applications as catalysts for industrial processes Zirconium based metallocenes for example are the most widely used catalysts for Ziegler-Natta polymerization of alkenes We 11 have more to say about them m Section 14 15... 

It is possible to prepare very heavy elements in thermonuclear explosions, owing to the very intense, although brief (order of a microsecond), neutron flux furnished by the explosion (3,13). Einsteinium and fermium were first produced in this way they were discovered in the fallout materials from the first thermonuclear explosion (the "Mike" shot) staged in the Pacific in November 1952. It is possible that elements having atomic numbers greater than 100 would have been found had the debris been examined very soon after the explosion. The preparative process involved is multiple neutron capture in the uranium in the device, which is followed by a sequence of beta decays. Eor example, the synthesis of EM in the Mike explosion was via the production of from followed by a long chain of short-Hved beta decays,... 

Fluorine was first produced commercially ca 50 years after its discovery. In the intervening period, fluorine chemistry was restricted to the development of various types of electrolytic cells on a laboratory scale. In World War 11, the demand for uranium hexafluoride [7783-81-5] UF, in the United States and United Kingdom, and chlorine trifluoride [7790-91 -2J, CIF, in Germany, led to the development of commercial fluorine-generating cells. The main use of fluorine in the 1990s is in the production of UF for the nuclear power industry (see Nuclearreactors). However, its use in the preparation of some specialty products and in the surface treatment of polymers is growing. 

Another impetus to expansion of this field was the advent of World War 11 and the development of the atomic bomb. The desired isotope of uranium, in the form of UF was prepared by a gaseous diffusion separation process of the mixed isotopes (see Fluorine). UF is extremely reactive and required contact with inert organic materials as process seals and greases. The wartime Manhattan Project successfully developed a family of stable materials for UF service. These early materials later evolved into the current fluorochemical and fluoropolymer materials industry. A detailed description of the fluorine research performed on the Manhattan Project has been pubUshed (2). 

Catalysts used for preparing amines from alcohols iaclude cobalt promoted with tirconium, lanthanum, cerium, or uranium (52) the metals and oxides of nickel, cobalt, and/or copper (53,54,56,60,61) metal oxides of antimony, tin, and manganese on alumina support (55) copper, nickel, and a metal belonging to the platinum group 8—10 (57) copper formate (58) nickel promoted with chromium and/or iron on alumina support (53,59) and cobalt, copper, and either iron, 2iac, or zirconium (62). 

Sihca is reduced to siUcon at 1300—1400°C by hydrogen, carbon, and a variety of metallic elements. Gaseous siUcon monoxide is also formed. At pressures of >40 MPa (400 atm), in the presence of aluminum and aluminum haUdes, siUca can be converted to silane in high yields by reaction with hydrogen (15). SiUcon itself is not hydrogenated under these conditions. The formation of siUcon by reduction of siUca with carbon is important in the technical preparation of the element and its alloys and in the preparation of siUcon carbide in the electric furnace. Reduction with lithium and sodium occurs at 200—250°C, with the formation of metal oxide and siUcate. At 800—900°C, siUca is reduced by calcium, magnesium, and aluminum. Other metals reported to reduce siUca to the element include manganese, iron, niobium, uranium, lanthanum, cerium, and neodymium (16). 

Preparation of Uranium Metal. Uranium is a highly electropositive element, and extremely difficult to reduce. As such, elemental uranium caimot be prepared by reduction with hydrogen. Instead, uranium metal must be prepared using a number of rather forcing conditions. Uranium metal can be prepared by reduction of uranium oxides (UO2 [1344-59-8] or UO [1344-58-7] with strongly electropositive elements (Ca, Mg, Na), reduction of uranium halides (UCl [10025-93-1], UCl [10026-10-5] UF [10049-14-6] with electropositive metals (Li, Na, Mg, Ca, Ba), electro deposition from molten... 

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