Uranium

This article is about the chemical element. For other articles with similar names, see Uranium (disambiguation).
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
Uranium
Atomic mass 238.02891(3) g/mol
Electron configuration [Rn] 5f3 6d1 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−1·K−1
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+ [1]
(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−1·K−1
Thermal expansion (25 °C) 13.9 µm·m−1·K−1
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

Uranium (IPA: /jəˈreɪniəm/) is a chemical element in the periodic table that has the symbol U and atomic number 92. Heavy, silvery metallic, and radioactive, uranium belongs to the actinide series. It occurs naturally and is commercially extracted from minerals such as Uraninite. Along with thorium and plutonium, it is one of the three fissile elements; its isotopes uranium-235 and to a lesser degree uranium-233 are used as the fuel for nuclear reactors and the explosive material for nuclear weapons. Depleted uranium (uranium-238) is used in kinetic energy penetrators and armor plating.[2]

Contents
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Notable characteristics

An induced nuclear fission event involving uranium-235
An induced nuclear fission event involving uranium-235

When refined, uranium is a silvery white, weakly radioactive metal, which is slightly softer than steel[3], strongly electropositive and a poor electrical conductor.[4] It is malleable, ductile, and slightly paramagnetic.[3] Uranium metal has very high density, 65% more dense than lead, but slightly less dense than gold.

Uranium metal reacts with nearly all nonmetallic elements and their compounds with reactivity increasing with temperature.[5]

Hydrochloric and nitric acids dissolve uranium but nonoxidizing acids attack the element very slowly.[4] When finely divided, it can react with cold water; in air, uranium metal becomes coated with a layer of uranium oxide.[3] Uranium in ores is extracted chemically and converted into uranium dioxide or other chemical forms usable in industry.

Uranium was the first element that was found to be fissile. Upon bombardment with slow neutrons, its uranium-235 isotope becomes the very short lived uranium-236 which immediately divides into two smaller nuclei, releasing nuclear binding energy and more neutrons. If these neutrons are absorbed by other uranium-235 nuclei, a nuclear chain reaction occurs and, if there is nothing to absorb some neutrons and slow the reaction, the reaction is explosive. As little as 15 lb (7 kg) of uranium-235 can be used to make an atomic bomb.[6] The first atomic bomb worked by this principle (nuclear fission). A more accurate name for both this and the hydrogen bomb (nuclear fusion) would be 'nuclear bomb' or 'nuclear weapon', because only the nuclei participate.

Uranium metal has three allotropic forms:

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Applications

Uranium glass glowing under UV light
Uranium glass glowing under UV light

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. uranium nitrate as a toner).[3] It was used in filaments for lamps and in the leather and wood industries for stains and dyes. Uranium salts are mordants of silk or wool. Uranium was also used to improve the appearance of dentures. After the discovery of uranium radiation, additional scientific and practical values of uranium were pursued.

After the discovery in 1939 that it could undergo nuclear fission, uranium gained importance with the development of practical uses of nuclear energy. The first atomic bomb used in warfare, "Little Boy", was a uranium bomb. This bomb contained enough of the uranium-235 isotope to start a runaway chain reaction which in a fraction of a second caused a large number of the uranium atoms to undergo fission, thereby releasing a fireball of energy.

The most visible civilian use of uranium is as the thermal power source used in nuclear power plants
The most visible civilian use of uranium is as the thermal power source used in nuclear power plants

The main use of uranium in the civilian sector is to fuel commercial nuclear power plants; by the time it is completely fissioned, one kilogram of uranium can theoretically produce about 20 trillion joules of energy (20 × 1012 joules); as much electricity as 1500 tonnes of coal.[2] Generally this is in the form of enriched uranium, which has been processed to have higher-than-natural levels of uranium-235 and can be used for a variety of purposes relating to nuclear fission. Commercial nuclear power plants use fuel typically enriched to around 3% uranium-235[2], though some reactor designs (such as the Candu reactors) can use unenriched uranium fuel. Fuel used for United States Navy submarine reactors is typically highly enriched in uranium-235 (the exact values are classified information). When uranium is enriched over 85% it is known as "weapons grade". In a breeder reactor, uranium-238 can also be converted into plutonium through the following reactions: 238U(n, gamma) -> 239U -(beta)-> 239Np -(beta)-> 239Pu.[3]

Depleted uranium is used by various militaries as high-density penetrators
Depleted uranium is used by various militaries as high-density penetrators

Currently the major application of uranium in the U.S. military sector is in high-density penetrators. This ammunition consists of depleted uranium alloyed with 1–2% other elements. The applications of these armor-piercing rounds range from the 20 mm Phalanx gun of the U.S. Navy for piercing attacking missiles, through the 30 mm gun in A-10 aircraft, to 105mm and larger tank barrels. At high impact speed, the density, hardness, and flammability of the projectile enable destruction of heavily armored targets. Tank armour and the removable armour on combat vehicles are also hardened with depleted uranium (DU) plates. The use of DU became a contentious political-environmental issue after US, UK and other countries' use of DU munitions in wars in the Persian Gulf and the Balkans raised questions of uranium compounds left in the soil.[6] Depleted uranium is also used as a shielding material in some containers used to store and transport radioactive materials.[4]

Uranyl acetate is used in analytical chemistry
Uranyl acetate is used in analytical chemistry

Other uses include:

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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.[3] Yellow glass with 1% uranium oxide was found in a Roman villa on Cape Posilipo in the Bay of Naples, Italy by R. T. Gunther of Oxford University in 1912.[2] Starting in the late Middle Ages, pitchblende was extracted from the Habsburg silver mines in Joachimsthal, Bohemia (now in the Czech Republic) and was secretly used as a coloring agent in the local glassmaking industry.[2] In the early 19th century, the world's only known source of uranium ores were these old mines.

Antoine Becquerel discovered the concept of radioactivity by exposing a photographic plate to uranium.
Antoine Becquerel discovered the concept of radioactivity by exposing a photographic plate to uranium.

The discovery of the element is credited to the German pharmacist Martin Heinrich Klaproth while he was working in his experimental laboratory in Berlin. In 1789 Klaproth was able to precipitate a yellow compound (likely sodium diuranate) by dissolving pitchblende in nitric acid and neutralizing the solution with sodium hydroxide.[2] Klaproth mistakingly assumed the yellow substance was the oxide of a yet-undiscovered element and heated it with charcoal to obtain a black powder, which he thought was the newly discovered metal itself (in fact, that powder was an oxide of uranium).[2] He named the newly discovered element after the planet Uranus, which had been discovered eight years earlier by William Herschel.[7]

In 1841, Eugene-Melchior Peligot, who was Professor of Analytical Chemistry at the Central School of Arts and Manufactures in Paris, isolated the first sample of uranium metal by heating uranium tetrachloride with potassium.[2] Uranium was not seen as being particularly dangerous during much of the 19th century, leading to the development of various uses for the element. One such use for the oxide was the before-mentioned but no longer secrete coloring of pottery and glass.

Antoine Becquerel found uranium to be radioactive in 1896 and in the process discovered the concept of radioactivity itself.[5] Becquerel made the discovery in Paris by leaving a sample of uranium on top of an unexposed photographic plate in a drawer and noting that the plate had become 'fogged' as if it were partially exposed to light.[2] He determined that a form of invisible light or rays emitted by uranium had exposed the plate.

The mushroom cloud over Hiroshima after the dropping of the uranium-based atomic bomb nicknamed 'Little Boy'.
The mushroom cloud over Hiroshima after the dropping of the uranium-based atomic bomb nicknamed 'Little Boy'.

Two types of atomic bomb were developed in the Manhattan Project during World War II; a plutonium-based device (see Trinity test and 'Fat Man') whose plutonium was derived from the uranium-238 isotope, and a uranium-based device (nicknamed 'Little Boy') whose fissile material was a blend of uranium isotopes that were highly enriched in uranium-235. The uranium-based Little Boy device became the first nuclear weapon used in anger when it was detonated over the Japanese city of Hiroshima on August 6th, 1945. Exploding with a yield equivalent to 12,500 tons of TNT, the blast and thermal wave of the bomb destroyed nearly 50,000 buildings and killed approximately 75,000 people (see Atomic bombings of Hiroshima and Nagasaki).[2]

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 Cold War between the Soviet Union and the United States, huge stockpiles of uranium were amassed and tens of thousands of nuclear weapons were created using enriched uranium. Since the break-up of the Soviet Union in 1991, an estimated 600 tons of highly-enriched weapons grade uranium (enough to make 40,000 nuclear warheads) have been stored in poorly guarded facilities in the Russian Federation and several other former Soviet states.[6] Police in Asia, Europe, and South America on at least 16 occasions from 1993 to 2005 have intercepted shipments of smuggled bomb-grade uranium or plutonium, most of which was from ex-Soviet sources.[6] Since 1993, the Material Protection, Control, and Accounting Program, operated by the United States government, has spent approximately $550 million to help safeguard uranium and plutonium stockpiles in Russia.[6]

Above-ground nuclear tests by the Soviet Union and the United States in the 1950s and early 1960s and by France and Israel into the 1970s and 1980s, spread a significant amount of fallout from uranium daughter isotopes around the world.[2] Additional fallout and pollution occurred from several nuclear accidents; the Windscale fire at the Sellafield nuclear plant in 1957 spread iodine-131 over much of Northern England, the Three Mile Island accident in 1979 released radon gas and some iodine-131, the Chernobyl disaster in 1986 released radon, iodine-131 and strontium-90 that spread over much of Europe.[2]

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Occurrence

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Biotic and abiotic

Uranium ore
Uranium ore

Uranium is a naturally occurring element found in low levels and always combined with other elements within all rock, soil, and water. This is the highest-numbered element to be found naturally in significant quantities on earth.[3] It's average concentration in the Earth's crust is (depending on the reference) 2 to 4 parts per million,[4][2] or about 40 times as abundant as silver.[5] The Earth's crust from the surface to 25 km (15 miles) down is calculated to contain 1017 kg (2 x 1017 lb) of uranium while the oceans may contain 1013 kg (2 x 1013 lb).[4] The concentration of uranium in soil ranges from 0.7 to 11 parts per million (up to 15 parts per million in farmland soil due to use of phosphate fertilizers) and 3 parts per billion of sea water is composed of the element.[2]

It is more plentiful than antimony, tin, cadmium, mercury, or silver and is about as abundant as arsenic or molybdenum.[3][2] It is found in hundreds of minerals including uraninite (the most common uranium ore), autunite, uranophane, torbernite, and coffinite.[3] Significant concentrations of uranium occur in some substances such as phosphate rock deposits, and minerals such as lignite, and monazite sands in uranium-rich ores[3] (it is recovered commercially from these sources with as little as 0.1% uranium[5]).

Four parts per million of the Earth's crust is composed of uranium and the decay of this element in the mantle contributes to the heat needed to drive plate tectonics.
Four parts per million of the Earth's crust is composed of uranium and the decay of this element in the mantle contributes to the heat needed to drive plate tectonics.

The decay of uranium, thorium and potassium-40 in the Earth's mantle is thought to be the main source of heat[8][9] that keeps the outer core liquid and drives mantle convection, which in turn drives plate tectonics.

Some micro-organisms, such as the lichen Trapelia involuta or the bacterium Citrobacter, can absorb concentrations of uranium that are up to 300 times higher than its environment.[2] Citrobactor species absorb uranyl ions when given glycerol phosphate (or other similar organic phosphates). After one day, one gram of bacteria will encrust themselves with nine grams of uranyl phosphate crystals; creating the possibility that these organisms could be used to decontaminate uranium-polluted water.[2]

Plants absorb some uranium from the soil they are rooted in. Dry weight concentrations of uranium in plats range from 5 to 60 parts per billion and ash from burnt wood can have concentrations up to 4 parts per million.[2] Dry weight concentrations of uranium in food plants are typically lower with one to two micrograms per day ingested through the food people eat.[2]

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Mining and reserves

Uraninite, also known as Pichblende, is the most common ore mined to extract uranium
Uraninite, also known as Pichblende, is the most common ore mined to extract uranium

Uranium is distributed worldwide and 21 countries export uranium ore, with Canada, Australia and Niger being the three largest exporters[6] and the United States, Congo, South Africa, Gabon, Russia and China also having significant deposits.[2] Three million tonnes of uranium ore reserves are known to exist and an additional five billion tonnes of uranium are estimated to be in sea water (Japanese scientists in the 1980s proved that extraction of uranium from sea water using ion exchangeers was feasible).[2]

Uranium ore is is mined in several ways; by open pit, underground or by leaching uranium from low-grade ores.[2]

Australia has the world's largest uranium ore reserves — 40 percent of the planet's known supply. In fact, the world's largest single uranium deposit is located at the Olympic Dam Mine in South Australia.[10] 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. Australian uranium is used strictly for electricity production. The Australian government is currently advocating an expansion of uranium mining, although issues with state governments and indigenous interests complicate the issue.[11]

In spite of Australia's huge reserves, Canada remains the largest exporter of uranium ore, with mines located in the Athabasca Basin in northern Saskatchewan. Cameco, the world’s largest, low-cost uranium producer accounting for 18% of the world's uranium production, operates three mines in the area.

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Production and enrichment

Cascades of gas centrifuges are used to enrich uranium ore to concentrate its fissionable isotopes.
Cascades of gas centrifuges are used to enrich uranium ore to concentrate its fissionable isotopes.

Commercial-grade uranium can be produced through the reduction of uranium halides with alkali or alkaline earth metals.[3] Uranium metal can also be made through electrolysis of KUF5 or UF4, dissolved in a molten calcium chloride (CaCl2) and sodium chloride (NaCl).[3] Very pure uranium can be produced through the thermal decomposition of uranium halides on a hot filament.[3]

Owners and operators of U.S. civilian nuclear power reactors purchased from U.S. and foreign suppliers a total of 21,300 tons of uranium deliveries during 2001. The average price paid was $26.39 per kilogram of uranium, a decrease of 16 percent compared with the 1998 price. In 2001, the U.S. produced 1,018 tons of uranium from seven mining operations, all of which are west of the Mississippi River.

Enrichment of uranium ore to concentrate the fissionable uranium-235 is needed for use in power plants and nuclear weapons. A majority of neutrons released by a fissioning atom of uranium-235 must impact other uranium-235 atoms to sustain the nuclear chain reaction needed for these applications. The concentration and amount of uranium-235 needed to achieve this is called a 'critical mass.' The gas centrifuge process, where gaseous uranium hexafluoride (UF6) is separated by weight using high-speed centrifuges has become the cheapest and leading enrichment process (lighter UF6 concentrates in the center of the centrifuge).[2] The gaseous diffusion process was the previous leading method for enrichment and the one used in the Manhattan Project. In this process, uranium hexafluoride is repeatedly diffused through a silver-zinc membrane and the different isotopes of uranium are separated by diffusion rate (uranium 238 is heavier and thus diffuses slightly slower than uranium-235).[2] The laser excitation method employs a laser beam of precise energy to sever the bond between uranium-235 and fluorine. This leaves uranium-238 bonded to fluorine and allows uranium-235 metal to precipitate from the solution.[2] Another method is called liquid thermal diffusion.[4]

The ultimate supply of uranium is very large. It is estimated that for a ten times increase in price, the supply of uranium that can be economically mined is increased 300 times.[12]

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Compounds

Uranium dioxide is used to create fuel rods in nuclear power plants
Uranium dioxide is used to create fuel rods in nuclear power plants

Uranium dioxide a dark brown, crystalline powder, once used in the late 1800s to mid-1900s in ceramic glazes is now used mainly as nuclear fuel, specifically in the form of fuel rods.

Uranium tetrafluoride (UF4) is known as "green salt" and is an intermediate product in the production of uranium hexafluoride. It has the appearance of an emerald-green solid.

Uranium hexafluoride (UF6) is a colorless crystalline solid which forms a vapor at temperatures above 56.4 °C. UF6 is the compound of uranium used for the two most common enrichment processes, gaseous diffusion enrichment, and gas centrifuge enrichment.[4] It is simply called "hex" in the industry. It is corrosive to many metals and reacts violently with water and oils.

Yellowcake is purified U-238. It takes its name from the color and texture of the concentrates produced by early mining operations, despite the fact that modern mills using higher calcining temperatures produce "yellowcake" that is dull yellow to almost black. Initially, the compounds formed in yellowcakes were not identified; in 1970, the U.S. Bureau of Mines still referred to yellowcakes as the final precipitate formed in the milling process and considered it to be ammonium diuranate or sodium diuranate. The compositions were variable and depended upon precipitating conditions. Among the compounds identified in yellowcakes include: uranyl hydroxide, uranyl sulfate, sodium para-uranate, and uranyl peroxide, along with various uranium oxides. Modern yellowcake typically contains 70 to 90 percent uranium oxide (U3O8) by weight. (Other uranium oxides, such as UO2 and UO3, exist; the most stable oxide, U3O8, is actually considered to be a 1:2 molar mixture of these.)

Uranyl nitrate (UO2(NO3)2) is an extraordinarily toxic, soluble uranium salt. It appears as a yellow crystalline solid.

Uranium rhodium germanium (URhGe) is the first discovered alloy that becomes superconducting in the presence of an extremely strong electromagnetic field.

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.

Uranium trihydride (UH3) appears as a black powder, is highly reactive, and pyrophoric.

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Isotopes

Its two principal isotopes are uranium-235 and uranium-238. Naturally-occurring uranium also contains a small amount of the uranium-234 isotope, which is a decay product of uranium-238. The isotope uranium-235 or enriched uranium is important for both nuclear reactors and nuclear weapons because it is the only isotope existing in nature to any appreciable extent that is fissile, that is, fissionable by thermal neutrons. The isotope uranium-238 is also important because it absorbs neutrons to produce a radioactive isotope that subsequently decays to the isotope plutonium-239 (plutonium), which also is fissile.

Naturally occurring uranium is composed of three major isotopes, uranium-238 (99.28% natural abundance), uranium-235 (0.71%), and uranium-234 (0.0054%. All three isotopes are radioactive, creating radioisotopes, with the most abundant and stable being uranium-238 with a half-life of 4.5 × 109 years (close to the age of the Earth), uranium-235 with a half-life of 7 × 108 years, and uranium-234 with a half-life of 2.5 × 105 years. uranium-238 is an α emitter, decaying through the 18-member uranium natural decay series into lead#Isotopes-206.[5] The decay series of uranium-235 (also called actinouranium) has 15 members that ends in lead-207, protactinium-231 and actinium-227.[5] The constant rates of decay in these series makes comparison of the ratios of parent to daughter elements useful in radiometric dating.

Uranium isotope separation is used to increase the concentration of one isotope relative to another. This process is called uranium enrichment. To be considered 'enriched' the uranium-235 fraction has to be increased to significantly greater than 0.711% (by weight) (typically to levels from 3% to 7%). uranium-235 is typically the main fissile material for nuclear power reactors. Either uranium-235 or plutonium-239 are used for making nuclear weapons. The process produces huge quantities of uranium that is depleted of uranium-235 and with a correspondingly increased fraction of uranium-238, called depleted uranium or "DU". To be considered 'depleted', the uranium-235 isotope concentration has to have been decreased to significantly less than 0.711% (by weight). Typically the amount of uranium-235 left in depleted uranium is 0.2% to 0.3%. This represents anywhere from 28% to 42% of the original fraction of uranium-235.

Another way to look at this is as follows: Pressurised Heavy Water Reactors (PHWR) use natural uranium (0.71% fissile material). From Pressurised water reactors (PWRs) of typical design (most USA reactors are PWR) we note the fuel goes in with about 4% uranium-235 and 96% uranium-238 and comes out with about 1% uranium-235, 1% plutonium-239 and 95% uranium-238. If the plutonium-239 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. Both of these would be considered enriched fuels for a PHWR style reactor.

uranium-233, an artificial isotope, is used as a reactor fuel in India. It has also been tested in nuclear weapons, but the results were unpromising. It is made from thorium-232 by neutron bombardment.[3]

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Hazards

All isotopes and compounds of uranium are chemically poisonous, teratogenic, and radioactive.[3]

Uranium salts could cause irreversible renal damage because they accumulate in kidney tubules, but no conclusive evidence has yet been produced.[13][2]

No deaths have been associated with prolonged occupational exposure to inhaled uranium compounds.[14] Although accidental inhalation exposure to a high concentration of uranium hexafluoride has resulted in human fatalities, those deaths were not associated with uranium itself.[15]

Exposure to environmental uranium or to uranium at levels found at hazardous waste sites will not be lethal to humans[16] but exposure to some of its decay products, especially radon, strontium-90, and iodine-131 does pose a significant health threat.[2] Radon can collect in confined spaces, such as basements, and when inhaled over long periods, can lead to the wasting of lung tissue and lung cancer. Strontium-90, a component of nuclear fallout, is a highly radioactive isotope that is chemically similar to calcium and is therefore readily absorbed by bones and bone marrow. Its presence in these tissues can cause bone cancer, cancer of nearby tissues, and leukemia. Iodine-131, also a component of radioactive fallout, it is absorbed by the body and can cause damage to the thyroid and even cause thyroid cancer.

Uranium trioxide has been shown to cause birth defects
Uranium trioxide has been shown to cause birth defects

Radiological effects are generally local because this is the nature of alpha radiation, the primary form from U-238 decay. Uranium compounds in general are poorly absorbed by the lining in the lungs and may remain a radiological hazard indefinitely. 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.[3]

A person can be exposed to uranium (or its radioactive daughters such as radon) by inhaling dust in air or from smoking tobacco which have been grown using certain phosphate fertilizers, or ingesting water and food.

Almost all uranium that is ingested is excreted during digestion, but up to 5% is absorbed by the body when the soluble uranyl ion is ingested while only 0.5% is absorbed when insoluble forms of uranium, such as its oxide, are ingested.[2] However, soluble uranium compounds tend to quickly pass through the body whereas insoluble uranium compounds, especially when ingested via dust into the lungs, pose a more serious exposure hazard. 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. Uranium does not absorb through the skin, and alpha particles released by uranium cannot penetrate the skin.

The amount of uranium in air is usually very small; 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. Houses or structures which are over uranium deposits (either natural or man-made slag deposits) may have an increased incidence of exposure to radon gas.

Uranium mining carries the danger of airborne radioactive dust and the release of radioactive radon gas and its daughter products (an added danger to the already dangerous activity of all hard rock mining). As a result, without proper ventilation, uranium miners have a dramatically increased risk of later development of lung cancer and other pulmonary diseases. There is also the possible danger of groundwater contamination with the toxic chemicals used in the separation of the uranium ore.

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See also

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References

  1. ↑ The Chemistry of the Actinide and Transactinide Elements: Third Edition by L.R. Morss, N.M. Edelstein, J. Fuger, eds. (Netherlands: Springer, 2006.)
  2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 2.15 2.16 2.17 2.18 2.19 2.20 2.21 2.22 2.23 2.24 2.25 2.26 2.27 2.28
  3. ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6
  5. ↑ 5.0 5.1 5.2 5.3 5.4 5.5 "uranium". Columbia Electronic Encyclopedia (6th Edition). Columbia University Press.
  6. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 "uranium". Encyclopedia of Espionage, Intelligence, and Security. The Gale Group, Inc..
  7. ↑ "Uranium". The American Heritage Dictionary of the English Language (4th edition). Houghton Mifflin Company.
  8. ↑ Biever, Celeste (27 July 2005). "First measurements of Earth's core radioactivity".
  9. ↑ Potassium-40 heats up Earth's core. physicsweb (7 May 2003). Retrieved on 2007-01-14.
  10. ↑ Uranium Mining and Processing in South Australia. South Australian Chamber of Mines and Energy (2002). Retrieved on 2007-01-14.
  11. ↑ "Nuclear Balance of Power", BRW, 26 Oct. 2006, pp. 41–44
  12. ↑ "World Uranium Resources", by Kenneth S. Deffeyes and Ian D. MacGregor, Scientific American, January, 1980, page 66, argues that the supply of uranium is very large.
  13. ↑ Toxicological Profile for Uranium. Agency for Toxic Substances and Disease Registry (ATSDR).
  14. ↑ Archer et al. 1973a, 1973b; Brown and Bloom 1987; Checkoway et al. 1988; Cragle et al. 1988; Gottlieb and Husen 1982; Hadjimichael et al. 1983; Lundin et al. 1969; Polednak and Frome 1981; Samet et al. 1984, 1986; Scott et al. 1972; Waxweiler et al. 1983
  15. ↑ Kathren and Moore 1986; Moore and Kathren 1985; USNRC 1986
  16. ↑ http://www.atsdr.cdc.gov/toxprofiles/tp150-c2.pdf
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