uranium - Applications, History, Production and distribution, Compounds

U, element 92, density 19 g/cm³, melting point 1132°C. The heaviest of the naturally occurring elements, it has no stable isotopes, but the commonest (²³⁸U) has a half-life of more than 10⁹ years. Once used as a yellow glass pigment, uranium compounds are now used almost exclusively for conversion to plutonium in nuclear fuel applications.

92 protactinium ← uranium → neptunium Nd ↑ U ↓ (Uqb) Periodic Table - Extended Periodic Table
General
Name, Symbol, Number	uranium, U, 92
Chemical series	actinides
Group, Period, Block	n/a, 7, f
Appearance	silvery gray metallic; corrodes to a spalling black oxide coat in air
Atomic mass	238.02891(3) g/mol
Electron configuration	[Rn] 5f 7s2
Electrons per shell	2, 8, 18, 32, 21, 9, 2
Physical properties
Phase	solid
Density (near r.t.)	19.1 g·cm−3
Liquid density at m.p.	17.3 g·cm−3
Melting point	1405.3 K (1132.2 °C, 2070 °F)
Boiling point	4404 K (4131 °C, 7468 °F)
Heat of fusion	9.14 kJ·mol−1
Heat of vaporization	417.1 kJ·mol−1
Heat capacity	(25 °C) 27.665 J·mol
Vapor pressure P/Pa 1 10 100 1 k 10 k 100 k at T/K 2325 2564 2859 3234 3727 4402
Atomic properties
Crystal structure	orthorhombic
Oxidation states	3+,4+,5+,6+ (weakly basic oxide)
Electronegativity	1.38 (Pauling scale)
Ionization energies	1st: 597.6 kJ/mol
	2nd: 1420 kJ/mol
Atomic radius	175 pm
Van der Waals radius	186 pm
Miscellaneous
Magnetic ordering	paramagnetic
Electrical resistivity	(0 °C) 0.280 µΩ·m
Thermal conductivity	(300 K) 27.5 W·m
Thermal expansion	(25 °C) 13.9 µm·m
Speed of sound (thin rod)	(20 °C) 3155 m/s
Young's modulus	208 GPa
Shear modulus	111 GPa
Bulk modulus	100 GPa
Poisson ratio	0.23
CAS registry number	7440-61-1
Selected isotopes
Main article: Isotopes of uranium iso NA half-life DM DE (MeV) DP 232U syn 68.9 y α & SF 5.414 228Th 233U syn 159,200 y SF & α 4.909 229Th 234U 0.0058% 245,500 y SF & α 4.859 230Th 235U 0.72% 7.038×108 y SF & α 4.679 231Th 236U syn 2.342×107 y SF & α 4.572 232Th 238U 99.275% 4.468×109 y SF & α 4.270 234Th
References

This article is about the chemical element. in air, uranium metal becomes coated with a layer of uranium oxide. Because natural uranium begins with such a low percentage of U-235, the enrichment process produces large quantities of depleted uranium. For example, producing 1 kg of 5% enriched uranium requires 11.8 kg of natural uranium, and leaves about 10.8 kg of depleted uranium with only 0.3% U-235 remaining.

Applications

Before radiation was discovered, uranium was primarily used in small amounts for yellow glass and pottery dyes (such as uranium glass and in Fiestaware.) There was also some use in photographic chemicals (esp. Generally this is in the form of enriched uranium, which has been processed to have higher-than-natural levels of U, though some reactor designs (such as the Candu reactors) can use natural uranium (unenriched, less than 1% U (the exact values are classified information). Depleted uranium (uranium with the percentage of 235U lowered to 0.2%) has found use as counterweights for aircraft control surfaces, as ballast for missile re-entry vehicles and as a shielding material.

History

The use of uranium, in its natural oxide form, dates back to at least CE 79, when it was used to add a yellow color to ceramic glazes (yellow glass with 1% uranium oxide was found near Naples, Italy). Uranium was found to be radioactive by French physicist Henri Becquerel in 1896, who first discovered the process of radioactivity with uranium minerals. Initially it was believed that uranium was relatively rare, and that nuclear proliferation could be avoided by simply buying up all known uranium stocks, though within a decade large deposits of it were discovered in many places around the world.

During the Manhattan Project, the names tuballoy and oralloy were used to refer to natural uranium and enriched uranium respectively, originally for purposes of secrecy.

Uranium ore is rock containing uranium mineralisation in concentrations that can be mined economically, typically 1 to 4 pounds of uranium oxide per ton or 0.05 to 0.20 percent uranium oxide.

Production and distribution

Commercial-grade uranium can be produced through the reduction of uranium halides with alkali or alkaline earth metals.

Uranium exploration and mining

Uranium is distributed worldwide. Almost all the uranium is exported, but under strict International Atomic Energy Agency safeguards to satisfy the Australian people and government that none of the uranium is used in nuclear weapons. Cameco, the world’s largest, low-cost uranium producer accounting for 18% of the world’s uranium production, operates three mines in the area.

Compounds

Uranium tetrafluoride (UF4) is known as "green salt" and is an intermediate product in the production of uranium hexafluoride.

Uranium carbonate (UO2(CO3)) is found in both the mineral and organic fractions of coal and its fly ash and is the main component of uranium in mine tailing seepage water. The process produces huge quantities of uranium that is depleted of U, called depleted uranium or "DU". From Pressurised water reactors (PWRs) of typical design (most USA reactors are PWR) we note the fuel goes in with about 4% U and comes out with about 1% Pu and 95% Pu were removed (fuel reprocessing is not allowed in the USA) and this were added to the depleted uranium then we would have 1.2% fissile material in the reprocessed depleted uranium and at the same time have 1% fissile material in the left over spent fuel. Although accidental inhalation exposure to a high concentration of uranium hexafluoride has resulted in human fatalities, those deaths were not associated with uranium . On the basis of the available data, exposure to environmental uranium or to uranium at levels found at hazardous waste sites will not be lethal to humans. Uranyl (UO2+) ions, such as from uranium trioxide or uranyl nitrate and other hexavalent uranium compounds have been shown to cause birth defects and immune system damage in laboratory animals.

Finely-divided uranium metal presents a fire hazard because uranium is pyrophoric, so small grains will ignite spontaneously in air at room temperature. however, people who live near government facilities that made or tested nuclear weapons, or facilities that mine or process uranium ore or enrich uranium for reactor fuel, may have increased exposure to uranium. Uranium does not absorb through the skin, and alpha particles released by uranium cannot penetrate the skin, so uranium that is outside the body is much less harmful than it would be if it were inhaled or swallowed.