Uranium crushing

Uranyl Nitrate (Uranium Nitrate, UNH, Yellow Salt). U02(N03)2.6H20, mw 502.18, N 5.58% yellow rhomb crysts, greenish luster by reflected light mp 60.2°, bp 118°, d 2.807g/cc, RI 1.4967. Sol in 1.5p w, freely in ale and eth. Prepd by the action of nitric acid on U octoxide. When shaken, rubbed, or crushed, the crysts show remarkable triboluminescence with occasional detonations. It is highly toxic, and a severe fire and expln risk when shocked or heated,... 

Isotopes are also used to determine properties of the environment. Just as carbon-14 is used to date organic materials, geologists can determine the age of very old substances such as rocks by measuring the abundance in rocks of radioisotopes with longer half-lives. Uranium-238 (t1/2 = 4.5 Ga, 1 Ga = 10y years) and potassium-40 (t,/2 = 1.26 Ga) are used to date very old rocks. For example, potassium-40 decays by electron capture to form argon-40. The rock is placed under vacuum and crushed, and a mass spectrometer is used to measure the amount of argon gas that escapes. This technique was used to determine the age of rocks collected on the surface of the Moon they were found to be 3.5-4.0 billion years old, about the same age as the Earth. 

Uranium is best known as a fuel for nuclear power plants. To prepare this fuel, uranium ores are processed to extract and enrich the uranium. The process begins by mining uranium-rich ores and then crushing the rock. The ore is mixed with water and thickened to form a slurry. The slurry is treated with sulfuric acid and the product reacted with amines in a series of reactions to give ammonium diuranate, (NH4)2U20 . Ammonium diuranate is heated to yield an enriched uranium oxide solid known as yellow cake. Yellow cake contains from 70—90% U3Og in the form of a mixture of U02 and U03. The yellow cake is then shipped to a conversion plant where it can be enriched. 

Samarskite.—TYna tantaloniobate mineral has a widely varying composition, and was first discovered in the Urals. The presence of uranium in this mineral renders it radioactive. The presence of lead and helium has been detected. The ratio of lanthanides to yttrium is approximataly 1 6. In its crystal structure samarskite resembles yttrotantalite. Native crystals are brown, or velvet black, and become yellow orange when crushed showing pleochroism. 

Many uranium salts, like other fluorescent and phosphorescent substances, are tribolunoinescent— that is, they emit light when crushed (see p. 324). 

Szalay S. and Samsoni Z. (1969) Investigation of the leaching of the uranium from crushed magmatic rocks. Geochemistry 14, 613 -623. 

Uranium-containing ores are crushed, ground, leached, enriched and precipitated... 

The method formerly used by the Primos Chemical Company at Newmire, Colorado, depends on fusing the crushed roscoelite with sodium chloride. The sodium vanadate formed is dissolved out and ferrous sulfate added to precipitate ferrous vanadate. The uranium is not recovered by this process. Other similar processes fuse the ore with an alkali carbonate and carbon, 3 sodium nitrate, or potassium acid sulfate. 

Uranyl nitrate, U02(N0>)2 - 6 H20 is commonly called uranium nitrate and is the best known and most widely used uranyl salt. It may be prepared by dissolving any oxide of uranium in nitric acid. It forms lemon-yellow prisms which have a green fluorescence. They are readily soluble in water and are deliquescent. When shaken, rubbed, or crushed, the crystals show remarkable triboluminescence, with occasionally somewhat violent detonations. Numerous theories have been advanced to account... 

Triboluounescence and crystallolununescence are exhibited by many ordinary substances Sugar crystals, for example, when crushed in the dark, emit light The same is the case with crystals of uranium nitrate. The process of solidification of a melted substance is also in some cases (eg-, fused silver) accompanied by light emission. 

Uranium ore was mined in the USA in significant quantities by private companies to produce nuclear weaponry. After the 1950s, uranium was also needed as fuel for nuclear power plants to produce electricity. Ores are first crushed into centimeter to millimeter size. The ground ore is then disposed to the leach tanks to be dissolved and oxidized, respectively, by sulfuric acid (H2SO4) and sodium chlorate (NaC104). The dissolved uranium is extracted from the solutions. 

The residue of TRISO particles is crushed to expose the remaining uranium and fission products. These are then dissolved in nitric acid and separated by a simplified version of the Purex process (Chap. 10) into a decontaminated uranium fraction containing around 20 percent... 

A solid solution of uranium and zirconium hydrides is used as fuel in TRIGA reactors. Uraruum hydride is often pyrophoric and must be handled with care. It has been used to prepare finely divided uranium metal by reacting massive metal with hydrogen, then crushing the brittle hydride and heating it in vacuum to drive off hydrogen. 

Tailings from many South African gold mines contain sufficient uranium to permit its recovery at competitive costs, because the cost of mining and crushing the ore has been paid for by the gold previously extracted. Most South African uranium is produced in this way. 

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