Uranium: properties, application, extraction, compounds, enrichment. What is dangerous uranium and its compounds

Even in ancient times (I century BC), natural uranium oxide was used to make yellow glaze for ceramics. The first important date in the history of uranium is 1789, when the German natural philosopher and chemist Martin Heinrich Klaproth restored the golden-yellow "earth" extracted from the Saxon resin ore to a black metal-like substance. In honor of the most distant planet then known (discovered by Herschel eight years earlier), Klaproth, considering the new substance an element, called it uranium (by this he wanted to support the proposal of Johann Bode to name the new planet "Uranus" instead of "Georg's Star", as Herschel suggested). For fifty years, Klaproth's uranium was listed as a metal. Only in 1841 did the French chemist Eugene Melchior Peligot ( English) (1811-1890)) proved that, despite the characteristic metallic luster, Klaproth's uranium is not an element, but an oxide UO 2. In 1840, Peligo succeeded in obtaining real uranium - a heavy steel-gray metal - and determining its atomic weight. The next important step in the study of uranium was made in 1874 by D. I. Mendeleev. Based on the periodic system he developed, he placed uranium in the farthest cell of his table. Previously, the atomic weight of uranium was considered equal to 120. The great chemist doubled this value. After 12 years, Mendeleev's prediction was confirmed by the experiments of the German chemist Zimmermann.

In 1896, while studying uranium, the French chemist Antoine Henri Becquerel accidentally discovered Becquerel rays, which Marie Curie later renamed radioactivity. At the same time, the French chemist Henri Moissan managed to develop a method for obtaining pure metallic uranium. In 1899, Rutherford discovered that the radiation of uranium preparations is not uniform, that there are two types of radiation - alpha and beta rays. They carry a different electrical charge; far from the same range in the substance and ionizing ability. A little later, in May 1900, Paul Villard discovered a third type of radiation - gamma rays.

Ernest Rutherford conducted in 1907 the first experiments to determine the age of minerals in the study of radioactive uranium and thorium based on the theory of radioactivity he created together with Frederick Soddy (Soddy, Frederick, 1877-1956; Nobel Prize in Chemistry, 1921). In 1913, F. Soddy introduced the concept of isotopes (from other Greek. ἴσος - "equal", "same", and τόπος - "place"), and in 1920 predicted that isotopes could be used to determine the geological age of rocks. In 1928, Niggot realized, and in 1939 A. O. K. Nier (Nier, Alfred Otto Carl, 1911-1994) created the first equations for calculating age and applied a mass spectrometer for isotope separation.

Place of Birth

The content of uranium in the earth's crust is 0.0003%, it is found in the surface layer of the earth in the form of four types of deposits. Firstly, these are veins of uraninite, or uranium pitch (uranium dioxide UO 2), very rich in uranium, but rare. They are accompanied by deposits of radium, since radium is a direct product of the isotopic decay of uranium. Such veins are found in the Democratic Republic of the Congo, Canada (Great Bear Lake), the Czech Republic and France. The second source of uranium is conglomerates of thorium and uranium ore, together with ores of other important minerals. Conglomerates usually contain sufficient quantities of gold and silver to extract, and uranium and thorium become accompanying elements. Large deposits of these ores are found in Canada, South Africa, Russia and Australia. The third source of uranium is sedimentary rocks and sandstones, rich in the mineral carnotite (potassium uranyl vanadate), which contains, in addition to uranium, a significant amount of vanadium and other elements. Such ores are found in the western states of the United States. Iron-uranium shales and phosphate ores constitute the fourth source of deposits. Rich deposits are found in the shales of Sweden. Some phosphate ores in Morocco and the United States contain significant amounts of uranium, and phosphate deposits in Angola and the Central African Republic are even richer in uranium. Most lignites and some coals usually contain uranium impurities. Uranium-rich lignite deposits have been found in North and South Dakota (USA) and bituminous coals in Spain and the Czech Republic.

A layer of the lithosphere 20 km thick contains ~ 10 14 tons, in sea water 10 9 -10 10 tons. Russia in terms of uranium reserves, taking into account reserve deposits, ranks third in the world (after Australia and Kazakhstan). The deposits of Russia contain almost 550 thousand tons of uranium reserves, or a little less than 10% of its world reserves; about 63% of them are concentrated in the Republic of Sakha (Yakutia). The main uranium deposits in Russia are: Streltsovskoye, Oktyabrskoye, Antey, Malo-Tulukuevskoye, Argunskoye molybdenum-uranium in volcanics (Chita region), Dalmatovskoye uranium in sandstones (Kurgan region), Khiagda uranium in sandstones (Republic of Buryatia), Southern gold-uranium in metasomatites and Northern uranium in metasomatites (Republic of Yakutia). In addition, many smaller uranium deposits and ore occurrences have been identified and evaluated.

isotopes

Radioactive properties of some uranium isotopes (natural isotopes have been isolated):

Natural uranium consists of a mixture of three isotopes: 238 U (isotopic abundance 99.2745%, half-life T 1/2 \u003d 4.468 10 9 years), 235 U (0.7200%, T 1/2 = 7.04 10 8 years) and 234 U (0.0055%, T 1/2 = 2.455 10 5 years). The last isotope is not primary, but radiogenic; it is part of the radioactive series 238 U.

Under natural conditions, the isotopes 234 U, 235 U and 238 U are mainly distributed with a relative abundance 234 U: 235 U: 238 U = 0.0054: 0.711: 99.283. Almost half of the radioactivity of natural uranium is due to the isotope 234 U, which, as already noted, is formed during the decay of 238 U. The ratio of the contents of 235 U: 238 U, unlike other pairs of isotopes and regardless of the high migratory ability of uranium, is characterized by geographical constancy: 235 U / 238 U = 137.88. The value of this ratio in natural formations does not depend on their age. Numerous natural measurements showed its insignificant fluctuations. So in rolls, the value of this ratio relative to the standard varies within 0.9959-1.0042, in salts - 0.996-1.005. In uranium-containing minerals (nasturan, black uranium, cirtholite, rare-earth ores), the value of this ratio ranges from 137.30 to 138.51; moreover, the difference between the forms U IV and U VI has not been established; in sphene - 138.4. In some meteorites, a deficiency of the 235 U isotope was revealed. Its lowest concentration under terrestrial conditions was found in 1972 by the French researcher Buzhigues in the Oklo town in Africa (a deposit in Gabon). Thus, natural uranium contains 0.720% uranium 235 U, while in Oklo it decreases to 0.557%. This confirmed the hypothesis of the existence of a natural nuclear reactor, which caused the burn-up of the 235 U isotope. The hypothesis was put forward by George W. Wetherill from the University of California at Los Angeles, Mark G. Inghram from the University of Chicago and Paul Kuroda (Paul K. Kuroda), a chemist at the University of Arkansas, who described the process back in 1956. In addition, natural nuclear reactors have been found in the same districts: Okelobondo, Bangombe, and others. Currently, 17 natural nuclear reactors are known.

Receipt

The very first stage of uranium production is concentration. The rock is crushed and mixed with water. Heavy suspended matter components settle out faster. If the rock contains primary uranium minerals, they precipitate quickly: these are heavy minerals. Secondary uranium minerals are lighter, in which case heavy waste rock settles earlier. (However, it is far from always really empty; it can contain many useful elements, including uranium).

The next stage is the leaching of concentrates, the transfer of uranium into solution. Apply acid and alkaline leaching. The first is cheaper, since sulfuric acid is used to extract uranium. But if in the feedstock, as, for example, in uranium tar, uranium is in a tetravalent state, then this method is not applicable: tetravalent uranium in sulfuric acid practically does not dissolve. In this case, one must either resort to alkaline leaching, or pre-oxidize uranium to the hexavalent state.

Do not use acid leaching and in cases where the uranium concentrate contains dolomite or magnesite, reacting with sulfuric acid. In these cases, caustic soda (sodium hydroxide) is used.

The problem of uranium leaching from ores is solved by oxygen purge. A mixture of uranium ore and sulfide minerals heated to 150°C is fed with an oxygen stream. At the same time, sulfuric acid is formed from sulfur minerals, which washes out uranium.

At the next stage, uranium must be selectively isolated from the resulting solution. Modern methods - extraction and ion exchange - allow to solve this problem.

The solution contains not only uranium, but also other cations. Some of them under certain conditions behave in the same way as uranium: they are extracted with the same organic solvents, deposited on the same ion-exchange resins, and precipitate under the same conditions. Therefore, for the selective isolation of uranium, one has to use many redox reactions in order to get rid of one or another undesirable companion at each stage. On modern ion-exchange resins, uranium is released very selectively.

Methods ion exchange and extraction they are also good because they allow you to fully extract uranium from poor solutions (the uranium content is tenths of a gram per liter).

After these operations, uranium is transferred to a solid state - into one of the oxides or into UF 4 tetrafluoride. But this uranium still needs to be cleaned of impurities with a large thermal neutron capture cross section - boron, cadmium, hafnium. Their content in the final product should not exceed hundred thousandths and millionths of a percent. To remove these impurities, a commercially pure uranium compound is dissolved in nitric acid. In this case, uranyl nitrate UO 2 (NO 3) 2 is formed, which, upon extraction with tributyl phosphate and some other substances, is additionally purified to the desired conditions. Then this substance is crystallized (or precipitated peroxide UO 4 ·2H 2 O) and begin to carefully ignite. As a result of this operation, uranium trioxide UO 3 is formed, which is reduced with hydrogen to UO 2.

Uranium dioxide UO 2 at a temperature of 430 to 600 ° C is exposed to gaseous hydrogen fluoride to obtain tetrafluoride UF 4 . Metallic uranium is reduced from this compound with the help of calcium or magnesium.

Physical properties

Uranium is a very heavy, silvery-white, shiny metal. In its pure form, it is slightly softer than steel, malleable, flexible, and has little paramagnetic properties. Uranium has three allotropic forms: (prismatic, stable up to 667.7 °C), (quadrangular, stable from 667.7 °C to 774.8 °C), (body-centered cubic structure existing from 774.8 °C to the melting point).

Chemical properties

Characteristic oxidation states

Uranium can exhibit oxidation states from +3 to +6.

In addition, there is an oxide U 3 O 8 . The oxidation state in it is formally fractional, but in reality it is a mixed oxide of uranium (V) and (VI).

It is easy to see that, in terms of the set of oxidation states and characteristic compounds, uranium is close to the elements of subgroup VIB (chromium, molybdenum, tungsten). Because of this, for a long time it was attributed to this subgroup (“blurring of periodicity”).

Properties of a simple substance

Chemically, uranium is very active. It quickly oxidizes in air and is covered with an iridescent oxide film. Fine uranium powder spontaneously ignites in air; it ignites at a temperature of 150-175 °C, forming U 3 O 8 . Reactions of metallic uranium with other non-metals are given in the table.

Water is capable of corroding metal, slowly at low temperatures, and quickly at high temperatures, as well as with fine grinding of uranium powder:

In non-oxidizing acids, uranium dissolves, forming UO 2 or U 4+ salts (hydrogen is released). With oxidizing acids (nitric, concentrated sulfuric) uranium forms the corresponding salts of uranyl UO 2 2+
Uranium does not interact with alkali solutions.

With strong shaking, the metal particles of uranium begin to glow.

Uranium III compounds

Salts of uranium (+3) (mainly halides) are reducing agents. In air at room temperature, they are usually stable, but when heated, they oxidize to a mixture of products. Chlorine oxidizes them to UCl 4. They form unstable red solutions, in which they exhibit strong reducing properties:

Uranium III halides are formed by the reduction of uranium (IV) halides with hydrogen:

or hydrogen iodide:

and also under the action of hydrogen halide on uranium hydride UH 3 .

In addition, there is uranium (III) hydride UH 3 . It can be obtained by heating uranium powder in hydrogen at temperatures up to 225 ° C, and above 350 ° C it decomposes. Most of its reactions (for example, the reaction with water vapor and acids) can be formally considered as a decomposition reaction followed by the reaction of uranium metal:

Uranium IV compounds

Uranium (+4) forms green salts that are easily soluble in water. They easily oxidize to uranium (+6)

Uranium compounds V

Uranium(+5) compounds are unstable and easily disproportionate in aqueous solution:

Uranium chloride V, when standing, partially disproportionates:

and partially splits off chlorine:

Uranium VI compounds

The +6 oxidation state corresponds to UO 3 oxide. In acids, it dissolves to form compounds of the uranyl cation UO 2 2+:

With bases UO 3 (similar to CrO 3 , MoO 3 and WO 3) forms various uranate anions (primarily diuranate U 2 O 7 2-). The latter, however, are more often obtained by the action of bases on uranyl salts:

Of the compounds of uranium (+6) that do not contain oxygen, only UCl 6 hexachloride and UF 6 fluoride are known. The latter plays an important role in the separation of uranium isotopes.

Uranium compounds (+6) are the most stable in air and in aqueous solutions.

Uranyl salts such as uranyl chloride decompose in bright light or in the presence of organic compounds.

Application

Nuclear fuel

The uranium isotope 235 U has the greatest application, in which a self-sustaining nuclear chain reaction is possible. Therefore, this isotope is used as a fuel in nuclear reactors, as well as in nuclear weapons. Separation of the isotope U 235 from natural uranium is a complex technological problem (see isotope separation).

Here are some figures for a 1000 MW reactor operating at 80% load and producing 7000 GWh per year. The operation of one such reactor during the year requires 20 tons of uranium fuel with a content of 3.5% U-235, which is obtained after enrichment of approximately 153 tons of natural uranium.

The U 238 isotope is capable of fission under the influence of bombardment with high-energy neutrons, this feature is used to increase the power of thermonuclear weapons (neutrons generated by a thermonuclear reaction are used).

As a result of neutron capture followed by β-decay, 238 U can turn into 239 Pu, which is then used as nuclear fuel.

Heat generating capacity of uranium

1 ton of enriched uranium is equal to 1,350,000 tons of oil or natural gas in terms of heat release.

Geology

The main application of uranium in geology is the determination of the age of minerals and rocks in order to determine the sequence of geological processes. This is what geochronology does. The solution of the problem of mixing and sources of matter is also essential.

The solution of the problem is based on the equations of radioactive decay:

where 238 Uo, 235 Uo- modern concentrations of uranium isotopes; ; - decay constants atoms, respectively, of uranium 238 U and 235 U.

Their combination is very important:

Due to the fact that rocks contain different concentrations of uranium, they have different radioactivity. This property is used in the selection of rocks by geophysical methods. This method is most widely used in petroleum geology for well logging, this complex includes, in particular, γ-logging or neutron gamma logging, gamma-gamma logging, etc. . With their help, there is a selection of collectors and fluid seals.

Other applications

depleted uranium

After extraction of 235U and 234U from natural uranium, the remaining material (uranium-238) is called "depleted uranium" because it is depleted in the 235th isotope. According to some reports, about 560,000 tons of depleted uranium hexafluoride (UF 6) are stored in the United States.

Depleted uranium is half as radioactive as natural uranium, mainly due to the removal of 234 U from it. Due to the fact that the main use of uranium is energy production, depleted uranium is a low-use product with low economic value.

Basically, its use is associated with the high density of uranium and its relatively low cost. Depleted uranium is used for radiation shielding (ironically), extremely high capture cross-sections, and as ballast in aerospace applications such as aircraft control surfaces. Each Boeing 747 contains 1,500 kg of depleted uranium for these purposes. This material is also used in high-speed gyroscope rotors, large flywheels, as ballast in space descent vehicles and racing yachts, Formula 1 cars, and when drilling oil wells.

Armor-piercing projectile cores

The best-known use of depleted uranium is as cores for armor-piercing projectiles. Its high density (three times heavier than steel) makes the hardened uranium ingot an extremely effective armor penetration tool, similar in effectiveness to the more expensive and slightly heavier tungsten. The heavy uranium tip also changes the mass distribution in the projectile, improving its aerodynamic stability.

Similar alloys of the Stabilla type are used in arrow-shaped feathered shells of tank and anti-tank artillery pieces.

The process of destruction of the armor is accompanied by grinding the uranium ingot into dust and igniting it in air on the other side of the armor (see Pyrophoricity). About 300 tons of depleted uranium remained on the battlefield during Operation Desert Storm (for the most part, these are the remains of shells from the 30-mm GAU-8 cannon of A-10 attack aircraft, each shell contains 272 g of uranium alloy).

Such projectiles were used by NATO troops in combat operations on the territory of Yugoslavia. After their application, the ecological problem of radiation contamination of the country's territory was discussed.

For the first time, uranium was used as a core for shells in the Third Reich.

Depleted uranium is used in modern tank armor, such as the M-1 Abrams tank.

Physiological action

In microquantities (10 -5 -10 -8%) found in the tissues of plants, animals and humans. It accumulates to the greatest extent by some fungi and algae. Uranium compounds are absorbed in the gastrointestinal tract (about 1%), in the lungs - 50%. The main depots in the body: spleen, kidneys, skeleton, liver, lungs and broncho-pulmonary lymph nodes. The content in organs and tissues of humans and animals does not exceed 10 −7 g.

Uranium and its compounds toxic. Aerosols of uranium and its compounds are especially dangerous. For aerosols of water-soluble uranium compounds MPC in air is 0.015 mg/m³, for insoluble forms of uranium MPC is 0.075 mg/m³. When it enters the body, uranium acts on all organs, being a general cellular poison. Uranium almost irreversibly, like many other heavy metals, binds to proteins, primarily to the sulfide groups of amino acids, disrupting their function. The molecular mechanism of action of uranium is related to its ability to inhibit the activity of enzymes. First of all, the kidneys are affected (protein and sugar appear in the urine, oliguria). With chronic intoxication, hematopoietic and nervous system disorders are possible.

Explored reserves of uranium in the world

The amount of uranium in the earth's crust is about 1000 times greater than the amount of gold, 30 times - silver, while this figure is approximately equal to that of lead and zinc. A considerable part of uranium is dispersed in soils, rocks and sea water. Only a relatively small part is concentrated in deposits where the content of this element is hundreds of times higher than its average content in the earth's crust. The explored world reserves of uranium in deposits amount to 5.4 million tons.

Uranium mining in the world

10 countries providing 94% of the world's uranium production

According to the "Red Book of Uranium" issued by the OECD, 41,250 tons of uranium were mined in 2005 (in 2003 - 35,492 tons). According to the OECD data, there are 440 commercial and about 60 scientific reactors operating in the world, which consume 67,000 tons of uranium per year. This means that its extraction from deposits provided only 60% of its consumption (in 2009, this share increased to 79%). The rest of the uranium consumed by energy or 17.7% comes from secondary sources.

Uranium for "scientific and military" purposes

Most of the uranium for "scientific and military" purposes is recovered from old nuclear warheads:

• under the START-II agreement, 352 tons - out of the agreed 500 (despite the fact that the agreement did not enter into force, due to Russia's withdrawal from the agreement on June 14, 2002)
• under the START-I agreement (entered into force on December 5, 1994, expired on December 5, 2009) from the Russian side 500 tons,
• under the START III Treaty (START) - the agreement was signed on April 8, 2010 in Prague. The treaty replaced START I, which expired in December 2009.

Production in Russia

In the USSR, the main uranium ore regions were Ukraine (the Zheltorechenskoye, Pervomayskoye deposits, etc.), Kazakhstan (Northern - Balkashinskoe ore field, etc.; Southern - Kyzylsay ore field, etc.; Vostochny; all of them belong mainly to the volcanogenic-hydrothermal type); Transbaikalia (Antey, Streltsovskoye, etc.); Central Asia, mainly Uzbekistan with mineralization in black shales with a center in the city of Uchkuduk. There are many small ore occurrences and manifestations. In Russia, Transbaikalia remained the main uranium-ore region. About 93% of Russian uranium is mined at the deposit in the Chita region (near the city of Krasnokamensk). Mining is carried out by the Priargunsky Production Mining and Chemical Association (PIMCU), which is part of JSC Atomredmetzoloto (Uranium Holding), using the mine method.

The remaining 7% is obtained by in-situ leaching from ZAO Dalur (Kurgan Region) and OAO Khiagda (Buryatia).

The resulting ores and uranium concentrate are processed at the Chepetsk Mechanical Plant.

In terms of annual production of uranium (about 3.3 thousand tons), Russia ranks 4th after Kazakhstan. The annual consumption of uranium in Russia is now 16 thousand tons and consists of expenses for its own nuclear power plants in the amount of 5.2 thousand tons, as well as for the export of fuels (5.5 thousand tons) and low-enriched uranium (6 thousand tons ) .

Mining in Kazakhstan

In 2009, Kazakhstan came out on top in the world in terms of uranium mining (13,500 tons were mined).

Production in Ukraine

Price

Despite legends about tens of thousands of dollars for kilogram or even gram quantities of uranium, its real price on the market is not very high - unenriched uranium oxide U 3 O 8 costs less than 100 US dollars per kilogram.

The development of uranium ores is profitable at a price of uranium in the region of $80/kg. At present, the price of uranium does not allow for the effective development of its deposits, so there are forecasts that the price of uranium may rise to $75-90/kg by 2013-2014.

By 2030, large and accessible deposits with reserves of up to $80/kg will be fully developed, and hard-to-reach deposits with a production cost of more than $130/kg of uranium will begin to be involved in development.

This is due to the fact that to launch a nuclear reactor on unenriched uranium, tens or even hundreds of tons of fuel are needed, and for the manufacture of nuclear weapons, a large amount of uranium must be enriched to obtain concentrations suitable for creating a bomb.

see also

Links

• I. N. BEKMAN. "Uranus". Tutorial. Vienna, 2008, Moscow, 2009. (PDF)
• Russia sells large stocks of weapons-grade uranium to US

Notes

1. Editorial staff: Zefirov N. S. (editor-in-chief) Chemical Encyclopedia: in 5 volumes - Moscow: Great Russian Encyclopedia, 1999. - V. 5. - S. 41.
2. WebElements Periodic Table of the Elements | Uranium | crystal structures
3. Uranus in the Explanatory Dictionary of the Russian Language, ed. Ushakov
4. Encyclopedia "Round the World"
5. Uranus. Information and analytical center "Mineral"
6. Raw material base of uranium. S. S. Naumov, MINING JOURNAL, N12, 1999
7. G. Audi, O. Bersillon, J. Blachot and A. H. Wapstra (2003). "The NUBASE evaluation of nuclear and decay properties
8. G. Audi, O. Bersillon, J. Blachot and A. H. Wapstra (2003). "The NUBASE evaluation of nuclear and decay properties". Nuclear Physics A 729 : 3–128. DOI:10.1016/j.nuclphysa.2003.11.001 .
9. Uranium ores contain trace amounts of uranium-236, which is formed from uranium-235 during neutron capture; thorium ores contain traces of uranium-233, which arises from thorium-232 after neutron capture and two successive beta decays. However, the content of these uranium isotopes is so low that it can only be detected in special highly sensitive measurements.
10. Rosholt J.N., et al. Isotopic fractionatio of uranium related to role feature in Sandstone, Shirley Basin, Wyoming.//Economic Geology, 1964, 59, 4, 570-585
11. Rosholt J.N., et al. Evolution of the isotopic composition of uranium and thorium in Soil profiles.//Bull.Geol.Soc.Am./1966, 77, 9, 987-1004
12. Chalov PI Isotopic fractionation of natural uranium. - Frunze: Ilim, 1975.
13. Tilton G.R. et al. Isotopic composition and distribution of lead, uranium, and thorium in a precambrian granite.//Bull.Geol.Soc.Am., 1956, 66, 9, 1131-1148
14. Shukolyukov Yu. A. et al. Isotopic studies of a "natural nuclear reactor".//Geochemistry, 1977, 7. P. 976-991.
15. Meshik Alex. Ancient nuclear reactor.//In the world of science. Geophysics. 2006.2
16. Remy G. Inorganic chemistry. v.2. M., Mir, 1966. S. 206-223
17. Katz J, Rabinovich E. Chemistry of uranium. M., Publishing house of foreign literature, 1954.
18. Khmelevskoy VK Geophysical methods of studying the earth's crust. International University of Nature, Society and Man "Dubna", 1997.
19. Handbook of oil and gas geology / Ed. Eremenko N. A. - M .: Nedra, 1984
20. 1927 Technical Encyclopedia", Volume 24, Pillar. 596…597, article "Uranus"
21. http://www.pdhealth.mil/downloads/Characterisation_of_DU_projectiles.pdf
22. Uranium mining in the world
23. NEA, IAEA. - OECD Publishing, 2006. - ISBN 9789264024250
24. World Nuclear Association. Supply of Uranium. 2011.
25. Mineral resource base and uranium production in Eastern Siberia and the Far East. Mashkovtsev G. A., Miguta A. K., Shchetochkin V. N., Mineral Resources of Russia. Economics and Management, 1-2008
26. Uranium mining in Kazakhstan. Report by Mukhtar Dzhakishev
27. Konyrova, K. Kazakhstan came out on top in uranium mining in the world (rus.), News agency TREND(30.12.2009). Retrieved December 30, 2009.
28. Udo Rethberg; Translation by Alexander Polotsky(Russian). Translation(12.08.2009). Archived from the original on August 23, 2011. Retrieved May 12, 2010.
29. Experts on Uranium Price Forecast Russian Nuclear Community
30. http://2010.atomexpo.ru/mediafiles/u/files/Present/9.1_A.V.Boytsov.pdf
31. Nuclear weapon See the subsection on the uranium bomb.

Connections uranium

Ammonium diuranate ((NH 4) 2 U 2 O 7) Uranyl acetate (UO 2 (CH 3 COO) 2) Uranium borohydride (U(BH 4) 4) Uranium(III) bromide (UBr 3) Uranium(IV) bromide (UBr 4) Uranium(V) bromide (UBr 5) Uranium(III) hydride (UH 3) Uranium(III) hydroxide (U(OH) 3) Uranyl hydroxide (UO 2 (OH) 2) Diuronic acid (H 2 U 2 O 7) Uranium(III) iodide (UJ 3) Uranium(IV) iodide (UJ 4) Uranyl carbonate (UO 2 CO 3) Uranium monoxide (UO) US-UP Sodium diuranate (Na 2 U 2 O 7) Sodium uranate (Na 2 UO 4) Uranyl nitrate (UO 2 (NO 3) 2) Tetrauranium nonoxide (U 4 O 9) Uranium(IV) oxide (UO 2) Uranium(VI)-diuranium(V) oxide (U 3 O 8) Uranium peroxide (UO 4) Uranium(IV) sulfate (U(SO 4) 2) Uranyl sulfate (UO 2 SO 4) Pentauran tridecaoxide (U 5 O 13) Uranium trioxide (UO 3) Uranic acid (H 2 UO 4) Uranyl formate (UO 2 (CHO 2) 2) Uranium(III) phosphate (U 2 (PO 4) 3) Uranium(III) fluoride (UF 3) Uranium(IV) fluoride (UF 4) Uranium(V) fluoride (UF 5) Uranium(VI) fluoride (UF 6) Uranyl fluoride (UO 2 F 2) Uranium(III) chloride (UCl 3) Uranium(IV) chloride (UCl 4) Uranium(V) chloride (UCl 5) Uranium(VI) chloride (UCl 6) Uranyl chloride (UO 2 Cl 2)

In a message from the Ambassador of Iraq to the UN Mohammed Ali al-Hakim dated July 9, it says that at the disposal of extremists ISIS (Islamic State of Iraq and the Levant). The IAEA (International Atomic Energy Agency) hastened to declare that the nuclear substances used by Iraq earlier have low toxic properties, and therefore materials captured by the Islamists.

A U.S. government source familiar with the situation told Reuters that the uranium stolen by the militants is likely not enriched and therefore unlikely to be used to make nuclear weapons. The Iraqi authorities officially notified the United Nations about this incident and called for "preventing the threat of its use," RIA Novosti reports.

Uranium compounds are extremely dangerous. About what exactly, as well as about who and how can produce nuclear fuel, says AiF.ru.

What is uranium?

Uranium is a chemical element with atomic number 92, a silvery-white glossy metal, the periodic system is designated by the symbol U. In its pure form, it is slightly softer than steel, malleable, flexible, found in the earth's crust (lithosphere) and in sea water, and in its pure does not occur. Nuclear fuel is made from uranium isotopes.

Uranium is a heavy, silvery-white, shiny metal. Photo: Commons.wikimedia.org / Original uploader was Zxctypo at en.wikipedia.

Radioactivity of uranium

In 1938 the German physicists Otto Hahn and Fritz Strassmann irradiated the nucleus of uranium with neutrons and made a discovery: capturing a free neutron, the nucleus of the uranium isotope is divided and releases enormous energy due to the kinetic energy of the fragments and radiation. In 1939-1940 Julius Khariton and Yakov Zel'dovich for the first time theoretically explained that with a slight enrichment of natural uranium with uranium-235, it is possible to create conditions for the continuous fission of atomic nuclei, that is, to give the process a chain character.

What is enriched uranium?

Enriched uranium is uranium produced by technological process of increasing the proportion of the 235U isotope in uranium. As a result, natural uranium is divided into enriched uranium and depleted uranium. After extraction of 235U and 234U from natural uranium, the remaining material (uranium-238) is called "depleted uranium", since it is depleted in the 235th isotope. According to some reports, about 560,000 tons of depleted uranium hexafluoride (UF6) are stored in the United States. Depleted uranium is half as radioactive as natural uranium, mainly due to the removal of 234U from it. Due to the fact that the main use of uranium is energy production, depleted uranium is a low-value product with low economic value.

Nuclear power uses only enriched uranium. The uranium isotope 235U has the greatest application, in which a self-sustaining nuclear chain reaction is possible. Therefore, this isotope is used as fuel in nuclear reactors and in nuclear weapons. Separation of the isotope U235 from natural uranium is a complex technology that few countries can implement. Uranium enrichment makes it possible to produce atomic nuclear weapons - single-phase or single-stage explosive devices in which the main energy output comes from the nuclear fission reaction of heavy nuclei with the formation of lighter elements.

Uranium-233, artificially produced in reactors from thorium (thorium-232 captures a neutron and turns into thorium-233, which decays into protactinium-233 and then into uranium-233), may in the future become a common nuclear fuel for nuclear power plants (already now there are reactors using this nuclide as fuel, for example KAMINI in India) and the production of atomic bombs (critical mass of about 16 kg).

The core of a 30 mm caliber projectile (GAU-8 guns of the A-10 aircraft) with a diameter of about 20 mm from depleted uranium. Photo: Commons.wikimedia.org / Original uploader was Nrcprm2026 at en.wikipedia

Which countries produce enriched uranium?

• France
• Germany
• Holland
• England
• Japan
• Russia
• China
• Pakistan
• Brazil

10 countries providing 94% of the world's uranium production. Photo: Commons.wikimedia.org / KarteUrangewinnung

Why are uranium compounds dangerous?

Uranium and its compounds are toxic. Aerosols of uranium and its compounds are especially dangerous. For aerosols of water-soluble uranium compounds, the maximum allowable concentration (MPC) in the air is 0.015 mg / m³, for insoluble forms of uranium, the MAC is 0.075 mg / m³. When it enters the body, uranium acts on all organs, being a general cellular poison. Uranium almost irreversibly, like many other heavy metals, binds to proteins, primarily to the sulfide groups of amino acids, disrupting their function. The molecular mechanism of action of uranium is associated with its ability to inhibit the activity of enzymes. First of all, the kidneys are affected (protein and sugar appear in the urine, oliguria). With chronic intoxication, hematopoietic and nervous system disorders are possible.

The use of uranium for peaceful purposes

• A small addition of uranium gives a beautiful yellow-green color to the glass.
• Sodium uranium is used as a yellow pigment in painting.
• Uranium compounds were used as paints for painting on porcelain and for ceramic glazes and enamels (colored in colors: yellow, brown, green and black, depending on the degree of oxidation).
• At the beginning of the 20th century, uranyl nitrate was widely used to enhance negatives and stain (tint) positives (photographic prints) brown.
• Alloys of iron and depleted uranium (uranium-238) are used as powerful magnetostrictive materials.

Isotope - varieties of atoms of a chemical element that have the same atomic (ordinal) number, but different mass numbers.

Group III element of the periodic table, belonging to the actinides; heavy weakly radioactive metal. Thorium has a number of applications in which it sometimes plays an indispensable role. The position of this metal in the periodic system of elements and the structure of the nucleus predetermined its use in the field of peaceful use of atomic energy.

*** Oliguria (from the Greek oligos - small and ouron - urine) - a decrease in the amount of urine separated by the kidneys.

Nuclear technologies are largely based on the use of radiochemistry methods, which in turn are based on the nuclear-physical, physical, chemical and toxic properties of radioactive elements.

In this chapter, we restrict ourselves to a brief description of the properties of the main fissile isotopes - uranium and plutonium.

Uranus

Uranus ( uranium) U - an element of the actinide group, 7th-0th period of the periodic system, Z=92, atomic mass 238.029; the heaviest of those found in nature.

There are 25 known isotopes of uranium, all of which are radioactive. The easiest 217U (Tj/ 2 = 26 ms), the heaviest 2 4 2 U (7 T J / 2 = i6.8 min). There are 6 nuclear isomers. There are three radioactive isotopes in natural uranium: 2 s 8 and (99.2 739%, Ti/ 2 = 4.47109 l), 2 35U (0.7205%, G, / 2 = 7.04-109 years) and 2 34U ( 0.0056%, Ti/ 2=2.48-swl). The specific radioactivity of natural uranium is 2.48104 Bq, divided almost in half between 2 34U and 288 U; 235U makes a small contribution (the specific activity of the isotope 233 in natural uranium is 21 times less than the activity of 238U). The thermal neutron capture cross section is 46, 98, and 2.7 barn for 2 zz, 2 35U, and 2 3 8 U, respectively; fission cross section 527 and 584 barn for 2 zz and 2 s 8 and, respectively; natural mixture of isotopes (0.7% 235U) 4.2 barn.

Tab. 1. Nuclear-physical properties 2 h9 Ri and 2 35C.

Tab. 2. Neutron capture 2 35C and 2 h 8 C.

Six isotopes of uranium are capable of spontaneous fission: 282 U, 2 szy, 234U, 235U, 2 s 6 u and 2 s 8 u. The natural isotopes 233 and 235U fission under the action of both thermal and fast neutrons, while nuclei 238 and are capable of fission only when neutrons with an energy of more than 1.1 MeV are captured. When neutrons with lower energy are captured, the 288 U nuclei are first converted into 2 -i9U nuclei, which then undergo p-decay and go first into 2 - "*9Np, and then into 2 39Pu. Effective cross sections for the capture of thermal neutrons of 2 34U, 2 nuclei 35U and 2 3 8 and are equal to 98, 683 and 2.7-barns, respectively. Complete fission of 2 35U leads to a "thermal energy equivalent" of 2-107 kWh / kg. The isotopes 2 35U and 2 zzy are used as nuclear fuel, capable of supporting fission chain reaction.

Nuclear reactors produce n artificial isotopes of uranium with mass numbers 227-240, of which the longest-lived is 233U (7 V 2 \u003d i.62 *io 5 years); it is obtained by neutron irradiation of thorium. Uranium isotopes with mass numbers 239^257 are born in the superpowerful neutron fluxes of a thermonuclear explosion.

Uranium-232- technogenic nuclide, a-emitter, T x / 2=68.9 years, parent isotopes 2 3 6 Pu(a), 23 2 Np(p*) and 23 2 Pa(p), daughter nuclide 228 Th. The intensity of spontaneous fission is 0.47 divisions / s kg.

Uranium-232 is formed as a result of the following decays:

P + - decay of the nuclide * 3 a Np (Ti / 2 \u003d 14.7 min):

In the nuclear industry, 2 3 2 U is produced as a by-product in the synthesis of the fissile (weapon-grade) nuclide 2 33 in the thorium fuel cycle. When irradiated with 2 3 2 Th neutrons, the main reaction occurs:

and side two-step reaction:

The production of 232 U from thorium occurs only on fast neutrons (E„>6 MeV). If there is 2 s°Th in the initial substance, then the formation of 2 3 2 U is supplemented by the reaction: 2 s°Th + u-> 2 3'Th. This reaction takes place on thermal neutrons. Generation 2 3 2 U is undesirable for a number of reasons. It is suppressed by the use of thorium with a minimum concentration of 23°Th.

The decay of 2 from 2 occurs in the following directions:

A decay in 228 Th (probability 100%, decay energy 5.414 MeV):

the energy of emitted a-particles is 5.263 MeV (in 31.6% of cases) and 5.320 MeV (in 68.2% of cases).

• - spontaneous fission (probability less than ~ 12%);
• - cluster decay with the formation of the nuclide 28 Mg (the probability of decay is less than 5 * 10 "12%):

Cluster decay with the formation of nuclide 2

Uranium-232 is the ancestor of a long decay chain, which includes nuclides - emitters of hard y-quanta:

^U-(3.64 days, a, y)-> 220 Rn-> (55.6 s, a)-> 21b Po->(0.155 s, a)-> 212 Pb->(10.64 h , p, y) -> 212 Bi -> (60.6 m, p, y) -> 212 Po a, y) -> 208x1, 212 Po -> (3" 10' 7 s, a) -> 2o8 Pb (stub), 2o8 T1 -> (3.06 m, p, y -> 2o8 Pb.

The accumulation of 2 3 2 U is inevitable in the production of 2 zzy in the thorium energy cycle. Intense y-radiation arising from the decay of 2 3 2 U hinders the development of thorium energy. It is unusual that the even isotope 2 3 2 11 has a high fission cross section under the action of neutrons (75 barn for thermal neutrons), as well as a high neutron capture cross section - 73 barn. 2 3 2 U is used in the method of radioactive tracers in chemical research.

2 z 2 and is the ancestor of a long decay chain (according to the scheme 2 z 2 Th), which includes nuclides emitting hard y-quanta. The accumulation of 2 3 2 U is inevitable in the production of 2 zzy in the thorium energy cycle. Intense γ-radiation arising from the decay of 232 U hinders the development of thorium energy. It is unusual that the even isotope 2 3 2 U has a high fission cross section under the action of neutrons (75 barn for thermal neutrons), as well as a high neutron capture cross section - 73 barn. 2 3 2 U is often used in the method of radioactive tracers in chemical and physical research.

Uranium-233- technogenic radionuclide, a-emitter (energies 4.824 (82.7%) and 4.783 MeV (14.9%),), Tvi= 1.585105 years, parent nuclides 2 37Pu(a)-? 2 33Np(p +) -> 2 33Pa(p), daughter nuclide 22 9Th. 2 zzi is obtained in nuclear reactors from thorium: 2 s 2 Th captures a neutron and turns into 2 zz Th, which decays into 2 zz Pa, and then into 2 zz. Nuclei 2 zzi (odd isotope) are capable of both spontaneous fission and fission under the action of neutrons of any energy, which makes it suitable for the production of both atomic weapons and reactor fuel. The effective fission cross section is 533 barn, the capture cross section is 52 barn, the neutron yield is 2.54 per fission event, and 2.31 per absorbed neutron. The critical mass of 2 zz is three times less than the critical mass of 2 35U (-16 kg). The intensity of spontaneous fission is 720 cases / s kg.

Uranium-233 is formed as a result of the following decays:

- (3 + -decay of nuclide 2 33Np (7^=36.2 min):

On an industrial scale, 2 zzi is obtained from 2 32Th by neutron irradiation:

When a neutron is absorbed, the 234 nucleus usually fissions, but occasionally captures a neutron, turning into 234U. Although 2 zzy, having absorbed a neutron, usually fissions, nevertheless it sometimes saves a neutron, turning into 2 34U. The operating time of 2 zz is carried out both in fast and in thermal reactors.

From a weapon point of view, 2 zzi is comparable to 2 39 Pu: its radioactivity is 1/7 of the activity of 2 39 Pu (Ti/ 2 \u003d 159200 l versus 24100 l for Pu), the critical mass of 2 szi is 6o% higher than that of IgPu (16 kg versus 10 kg), and the rate of spontaneous fission is 20 times higher (b-u - ' versus 310 10). The neutron flux from 239Pu is 3 times higher than that from 239Pu. The creation of a nuclear charge on the basis of 2 sz requires more effort than on ^Pu. The main obstacle is the presence of the 232U impurity in 232U, the y-radiation of the decay projects of which makes it difficult to work with 2zzi and makes it easy to detect ready-made weapons. In addition, the short half-life of 2 3 2 U makes it an active source of a-particles. 2 zzi with 1% 232 and has 3 times stronger a-activity than weapons-grade plutonium and, accordingly, greater radiotoxicity. This a-activity causes the birth of neutrons in the light elements of the weapon charge. To minimize this problem, the presence of such elements as Be, B, F, Li should be minimal. The presence of a neutron background does not affect the operation of implosion systems, but a high level of purity for light elements is required for gun schemes. zgi is not harmful, and even desirable, because it reduces the possibility of using uranium for weapons purposes.After processing the spent nuclear fuel and reusing the fuel, the content of 232U reaches 0.1 + 0.2%.

The decay of 2 zzy occurs in the following directions:

A-decay in 22 9Th (probability 100%, decay energy 4.909 MeV):

the energy of the emitted n-particles is 4.729 MeV (in 1.61% of cases), 4.784 MeV (in 13.2% of cases) and 4.824 MeV (in 84.4% of cases).

• - spontaneous fission (probability
• - cluster decay with the formation of the nuclide 28 Mg (the probability of decay is less than 1.3*10 -13%):

Cluster decay with the formation of the nuclide 24 Ne (decay probability 7.3-10-“%):

The 2 zz decay chain belongs to the Neptunium series.

The specific radioactivity is 2 zzi 3.57-8 Bq/g, which corresponds to an a-activity (and radiotoxicity) of -15% of plutonium. Only 1% 2 3 2 U increases the radioactivity to 212 mCi/g.

Uranium-234(Uranus II, UII) is a part of natural uranium (0.0055%), 2.445105 years, a-emitter (energy of a-particles 4.777 (72%) and

4.723 (28%) MeV), parent radionuclides: 2 s 8 Pu(a), 234 Pa(P), 234 Np(p +),

daughter isotope in 2 s"t.

Usually 234 U is in equilibrium with 2 3 8 u, decaying and forming at the same rate. Approximately half of the radioactivity of natural uranium is the contribution of 234U. Usually 234U is obtained by ion-exchange chromatography of old preparations of pure 238 Pu. In a-decay, *34U lends itself to 234U, so the old preparations of 238Pu are good sources of 234U. 100 g 2s8Pu contain 776 mg 234U after a year, after 3 years

2.2 g 2 34U. The concentration of 2 34U in highly enriched uranium is quite high due to the preferential enrichment in light isotopes. Because 234u is a strong y-emitter, there are restrictions on its concentration in uranium intended for processing into fuel. The increased level of 234i is acceptable for reactors, but reprocessed SNF contains already unacceptable levels of this isotope.

The decay of 234u occurs along the following lines:

A-decay in 23°T (probability 100%, decay energy 4.857 MeV):

the energy of emitted a-particles is 4.722 MeV (in 28.4% of cases) and 4.775 MeV (in 71.4% of cases).

• - spontaneous fission (probability 1.73-10-9%).
• - cluster decay with the formation of the nuclide 28 Mg (the probability of decay is 1.4-10 "n%, according to other sources 3.9-10-"%):

• - cluster decay with the formation of nuclides 2 4Ne and 26 Ne (the probability of decay is 9-10 ", 2%, according to other data 2.3-10 - 11%):

The only isomer 2 34ti is known (Tx/ 2 = 33.5 μs).

The absorption cross section of 2 34U thermal neutrons is 10 barn, and for the resonance integral averaged over various intermediate neutrons, 700 barn. Therefore, in thermal neutron reactors, it is converted to fissile 235U at a faster rate than a much larger amount of 238U (with a cross section of 2.7 barn) is converted into 239Pu. As a result, SNF contains less 234U than fresh fuel.

Uranium-235 belongs to the 4P + 3 family, is capable of producing a fission chain reaction. This is the first isotope on which the reaction of forced fission of nuclei under the action of neutrons was discovered. Absorbing a neutron, 235U goes into 2 zbi, which is divided into two parts, releasing energy and emitting several neutrons. Fissile by neutrons of any energy, capable of spontaneous fission, the 2 35U isotope is part of natural uthanum (0.72%), a-emitter (energies 4.397 (57%) and 4.367 (18%) MeV), Ti/j=7.038-th 8 years, parent nuclides 2 35Pa, 2 35Np and 2 39Pu, daughter - 23"Th. The intensity of spontaneous fission 2 3su 0.16 divisions/s kg. The fission of one 2 35U nucleus releases 200 MeV of energy = 3.2 Yu p J, i.e. 18 TJ/mol=77 TJ/kg. The cross section of fission by thermal neutrons is 545 barns, and by fast neutrons - 1.22 barns, neutron yield: per fission event - 2.5, per absorbed neutron - 2.08.

Comment. The capture cross section of slow neutrons to form the isotope 2 si (10 barn), so that the total absorption cross section of slow neutrons is 645 barn.

• - spontaneous fission (probability 7*10~9%);
• - cluster decay with the formation of nuclides 2 °Ne, 2 5Ne and 28 Mg (the probabilities are respectively 8-io - 10%, 8-kg 10%, 8 * 10 ".0%):

Rice. one.

The only isomer known is 2 35n»u (7/ 2 = 26 min).

Specific activity 2 35C 7.77-u 4 Bq/g. The critical mass of weapons-grade uranium (93.5% 2 35U) for a ball with a reflector is 15-7-23 kg.

Fission 2 » 5U is used in atomic weapons, for energy production, and for the synthesis of important actinides. The chain reaction is maintained due to the excess of neutrons produced during the fission of 2 35C.

Uranium-236 occurs on Earth in nature in trace amounts (on the Moon it is more), a-emitter (?

Rice. 2. Radioactive family 4/7+2 (including -3 8 and).

In an atomic reactor, 233 absorbs a thermal neutron, after which it fissions with a probability of 82%, and emits a y-quantum with a probability of 18% and turns into 236 and . In small quantities it is part of fresh fuel; accumulates when uranium is irradiated with neutrons in the reactor, and therefore is used as a SNF “signaling device”. 2 h b and is formed as a by-product during the separation of isotopes by gaseous diffusion during the regeneration of spent nuclear fuel. The 236 U produced in a power reactor is a neutron poison; its presence in nuclear fuel is compensated by a high level of 2 35U enrichment.

2b and is used as a mixing tracer for oceanic waters.

Uranium-237,T&= 6.75 days, beta and gamma emitter, can be obtained by nuclear reactions:

Detection 287 and carried out along lines with eu= o.v MeV (36%), 0.114 MeV (0.06%), 0.165 MeV (2.0%), 0.208 MeV (23%)

237U is used in the method of radioactive tracers in chemical research. Measurement of the concentration (2 4°Am) in the fallout from an atomic weapon test provides valuable information about the type of charge and the equipment used.

Uranium-238- belongs to the 4P + 2 family, fissile with high-energy neutrons (more than 1.1 MeV), capable of spontaneous fission, forms the basis of natural uranium (99.27%), a-emitter, 7'; /2=4>468-109 years, directly decomposes into 2 34Th, forms a number of genetically related radionuclides, and after 18 products turns into 206 Pb. Pure 2 3 8 U has a specific radioactivity of 1.22-104 Bq. The half-life is very long - about 10 16 years, so that the probability of fission in relation to the main process - the emission of an a-particle - is only 10 "7. One kilogram of uranium gives only 10 spontaneous fissions per second, and during the same time an a-particle emit 20 million nuclei Parent nuclides: 2 4 2 Pu(a), *spa(p-) 234Th, daughter T,/ 2 = 2 :i 4 th.

Uranium-238 is formed as a result of the following decays:

2 (V0 4) 2] 8Н 2 0. Of the secondary minerals, hydrated calcium uranyl phosphate Ca (U0 2) 2 (P0 4) 2 -8H 2 0 is common. Often uranium in minerals is accompanied by other useful elements - titanium, tantalum, rare earths. Therefore, it is natural to strive for the complex processing of uranium-containing ores.

Basic physical properties of uranium: atomic mass 238.0289 a.m.u. (g/mol); atomic radius 138 pm (1 pm = 12 m); ionization energy (first electron 7.11 eV; electronic configuration -5f36d‘7s 2; oxidation states 6, 5, 4, 3; G P l \u003d 113 2, 2 °; T t,1=3818°; density 19.05; specific heat capacity 0.115 JDKmol); tensile strength 450 MPa, heat of fusion 12.6 kJ/mol, heat of vaporization 417 kJ/mol, specific heat capacity 0.115 J/(mol-K); molar volume 12.5 cm3/mol; the characteristic Debye temperature © D = 200K, the transition temperature to the superconducting state is 0.68K.

Uranium is a heavy, silvery-white, glossy metal. It is slightly softer than steel, malleable, flexible, has slight paramagnetic properties, and is pyrophoric in the powdered state. Uranium has three allotropic forms: alpha (rhombic, a-U, lattice parameters 0=285, b= 587, c=49b pm, stable up to 667.7°), beta (tetragonal, p-U, stable from 667.7 to 774.8°), gamma (with a cubic body-centered lattice, y-U, existing from 774.8° to melting points, frm=ii34 0), at which uranium is most malleable and convenient for processing.

At room temperature, the rhombic a-phase is stable, the prismatic structure consists of wavy atomic layers parallel to the plane abc, in an extremely asymmetric prismatic lattice. Within the layers, the atoms are closely bonded, while the strength of the bonds between the atoms of adjacent layers is much weaker (Fig. 4). This anisotropic structure makes it difficult to fuse uranium with other metals. Only molybdenum and niobium create solid-state alloys with uranium. Yet metallic uranium can interact with many alloys, forming intermetallic compounds.

In the interval 668 ^ 775 ° there is a (3-uranium. Tetragonal type lattice has a layered structure with layers parallel to the plane ab in positions 1/4С, 1/2 with and 3/4C unit cell. At temperatures above 775°, y-uranium is formed with a body-centered cubic lattice. The addition of molybdenum makes it possible to have the y-phase at room temperature. Molybdenum forms a wide range of solid solutions with y-uranium and stabilizes the y-phase at room temperature. y-Uranium is much softer and more malleable than the brittle a- and (3-phases.

Neutron irradiation has a significant effect on the physical and mechanical properties of uranium, causing an increase in the size of the sample, a change in shape, as well as a sharp deterioration in the mechanical properties (creep, embrittlement) of uranium blocks during the operation of a nuclear reactor. The increase in volume is due to the accumulation in uranium during fission of impurities of elements with a lower density (translation 1% uranium into fragmentation elements increases the volume by 3.4%).

Rice. 4. Some crystal structures of uranium: a - a-uranium, b - p-uranium.

The most common methods for obtaining uranium in the metallic state are the reduction of their fluorides with alkali or alkaline earth metals or the electrolysis of their salt melts. Uranium can also be obtained by metallothermic reduction from carbides with tungsten or tantalum.

The ability to easily donate electrons determines the reducing properties of uranium and its high chemical activity. Uranium can interact with almost all elements, except noble gases, while acquiring oxidation states +2, +3, +4, +5, +6. In solution, the main valency is 6+.

Rapidly oxidizing in air, metallic uranium is covered with an iridescent film of oxide. Fine powder of uranium ignites spontaneously in air (at temperatures of 1504-175°), forming and;) Ov. At 1000°, uranium combines with nitrogen to form yellow uranium nitride. Water is able to react with metal slowly at low temperatures and rapidly at high temperatures. Uranium reacts violently with boiling water and steam to release hydrogen, which forms a hydride with uranium.

This reaction is more vigorous than the combustion of uranium in oxygen. Such chemical activity of uranium makes it necessary to protect uranium in nuclear reactors from contact with water.

Uranium dissolves in hydrochloric, nitric and other acids, forming U(IV) salts, but does not interact with alkalis. Uranium displaces hydrogen from inorganic acids and salt solutions of metals such as mercury, silver, copper, tin, platinum and gold. With strong shaking, the metal particles of uranium begin to glow.

Features of the structure of the electron shells of the uranium atom (the presence of ^/-electrons) and some of its physico-chemical properties serve as the basis for classifying uranium as an actinide. However, there is a chemical analogy between uranium and Cr, Mo, and W. Uranium is highly reactive and reacts with all elements except the noble gases. In the solid phase, examples of U(VI) are uranyl trioxide U0 3 and uranyl chloride U0 2 C1 2 . Uranium tetrachloride UC1 4 and uranium dioxide U0 2

U(IV) examples. Substances containing U(IV) are usually unstable and become hexavalent upon prolonged exposure to air.

Six oxides are installed in the uranium-oxygen system: UO, U0 2 , U 4 0 9 , and 3 Ov, U0 3 . They are characterized by a wide area of ​​homogeneity. U0 2 is a basic oxide, while U0 3 is amphoteric. U0 3 - interacts with water to form a number of hydrates, the most important of which are diuronic acid H 2 U 2 0 7 and uranic acid H 2 1U 4. With alkalis, U0 3 forms salts of these acids - uranates. When U0 3 is dissolved in acids, salts of the doubly charged uranyl cation U0 2 a+ are formed.

Uranium dioxide, U0 2 , is brown in stoichiometric composition. As the oxygen content in the oxide increases, the color changes from dark brown to black. Crystal structure of CaF 2 type, a = 0.547 nm; density 10.96 g / cm "* (the highest density among uranium oxides). T , pl \u003d 2875 0, T kn „ \u003d 3450 °, D # ° 298 \u003d -1084.5 kJ / mol. Uranium dioxide is a semiconductor with hole conductivity, a strong paramagnet. MAC = 0.015 mg/m3. Let's not dissolve in water. At a temperature of -200° it adds oxygen, reaching the composition U0 2>25.

Uranium (IV) oxide can be obtained by reactions:

Uranium dioxide exhibits only basic properties, it corresponds to the basic hydroxide U (OH) 4, which then turns into hydrated hydroxide U0 2 H 2 0. Uranium dioxide slowly dissolves in strong non-oxidizing acids in the absence of atmospheric oxygen to form W + ions:

U0 2 + 2H 2 S0 4 ->U(S0 4) 2 + 2Н 2 0. (38)

It is soluble in concentrated acids, and the dissolution rate can be greatly increased by the addition of fluorine ion.

When dissolved in nitric acid, the uranyl ion 1U 2 2+ is formed:

Triuran octoxide U 3 0s (uranium oxide) - powder, the color of which varies from black to dark green; at strong crushing - olive-green color. Large black crystals leave green strokes on porcelain. There are three known crystalline modifications of U 3 0 h: a-U 3 C>8 - rhombic crystal structure (sp. gr. C222; 0=0.671 nm; 6=1.197 nm; c=0.83 nm; d =0.839 nm); p-U 3 0e - rhombic crystal structure (space group Stst; 0=0.705 nm; 6=1.172 nm; 0=0.829 nm. The beginning of decomposition is 100° (goes to 110 2), MPC = 0.075 mg / m3.

U 3 C>8 can be obtained by the reaction:

By calcining U0 2, U0 2 (N0 3) 2, U0 2 C 2 0 4 3H 2 0, U0 4 -2H 2 0 or (NH 4) 2 U 2 0 7 at 750 0 in air or in an oxygen atmosphere (p = 150 + 750 mm Hg) receive stoichiometrically pure U 3 08.

When U 3 0s is calcined at T > 100°, it is reduced to 110 2, however, when cooled in air, it returns to U 3 0s. U 3 0e dissolves only in concentrated strong acids. In hydrochloric and sulfuric acids, a mixture of U(IV) and U(VI) is formed, and in nitric acid, uranyl nitrate is formed. Diluted sulfuric and hydrochloric acids react very weakly with U 3 Os even when heated, the addition of oxidizing agents (nitric acid, pyrolusite) sharply increases the dissolution rate. Concentrated H 2 S0 4 dissolves U 3 Os with the formation of U(S0 4) 2 and U0 2 S0 4 . Nitric acid dissolves U 3 Oe with the formation of uranyl nitrate.

Uranium trioxide, U0 3 - crystalline or amorphous substance of bright yellow color. Reacts with water. MPC \u003d 0.075 mg / m 3.

It is obtained by calcining ammonium polyuranates, uranium peroxide, uranyl oxalate at 300-500 ° and hexahydrate uranyl nitrate. In this case, an orange powder of an amorphous structure is formed with a density

6.8 g/cm. The crystalline form IO 3 can be obtained by the oxidation of U 3 0 8 at temperatures of 450°-750° in an oxygen stream. There are six crystalline modifications of U0 3 (a, (3, y> §> ?, n) - U0 3 is hygroscopic and turns into uranyl hydroxide in moist air. further heating to 6oo° makes it possible to obtain U 3 Os.

Hydrogen, ammonia, carbon, alkali and alkaline earth metals reduce U0 3 to U0 2 . By passing a mixture of HF and NH 3 gases, UF 4 is formed. In the highest valency, uranium exhibits amphoteric properties. Under the action of U0 3 acids or its hydrates, uranyl salts (U0 2 2+) are formed, colored yellow-green:

Most uranyl salts are highly soluble in water.

With alkalis, when fused, U0 3 forms salts of uranic acid - uranates MDKH,:

With alkaline solutions, uranium trioxide forms salts of polyuranic acids - polyuranates dgM 2 0y110 3 pH^O.

Salts of uranium acid are practically insoluble in water.

The acidic properties of U(VI) are less pronounced than the basic ones.

Uranium reacts with fluorine at room temperature. The stability of higher halides decreases from fluorides to iodides. Fluorides UF 3 , U4F17, U2F9 and UF 4 are non-volatile, and UFe is volatile. The most important of the fluorides are UF 4 and UFe.

Ftpppippyanir okgilya t "yanya ppptrkart in practice:

The reaction in a fluidized bed is carried out according to the equation:

It is possible to use fluorinating agents: BrF 3, CC1 3 F (freon-11) or CC1 2 F 2 (freon-12):

Uranium (1U) fluoride UF 4 ("green salt") - powder from bluish-green to emerald color. G 11L \u003d SW6 °; G to, ",. \u003d -1730 °. DYa ° 29 8 = 1856 kJ / mol. The crystal structure is monoclinic (sp. gp C2/c; 0=1.273 nm; 5=1.075 nm; 0=0.843 nm; d= 6.7 nm; p \u003d 12b ° 20 "; density 6.72 g / cm3. UF 4 is a stable, inactive, non-volatile compound, poorly soluble in water. The best solvent for UF 4 is fuming perchloric acid HC10 4. It dissolves in oxidizing acids to form a uranyl salt quickly dissolves in a hot solution of Al(N0 3) 3 or A1C1 3 , as well as in a solution of boric acid acidified with H 2 S0 4 , HC10 4 or HC1. or boric acid, also contribute to the dissolution of UF 4. Forms a number of sparingly soluble double salts with fluorides of other metals (MeUFe, Me 2 UF6, Me 3 UF 7, etc.) NH 4 UF 5 is of industrial importance.

U(IV) fluoride is an intermediate product in the preparation

both UF6 and uranium metal.

UF 4 can be obtained by reactions:

or by electrolytic reduction of uranyl fluoride.

Uranium hexafluoride UFe - at room temperature, ivory crystals with a high refractive index. Density

5.09 g/cm3, density of liquid UFe is 3.63 g/cm3. Flying connection. Tvoag = 5^>5°> Gil=64.5° (under pressure). Saturated vapor pressure reaches the atmosphere at 560°. Enthalpy of formation of AR° 29 8 = -2116 kJ/mol. The crystal structure is rhombic (sp. gr. Rpta; 0=0.999 nm; fe= 0.8962 nm; c=0.5207 nm; d 5.060 nm (250). MPC - 0.015 mg / m3. From the solid state, UF6 can sublime from the solid phase (sublimate) into a gas, bypassing the liquid phase over a wide range of pressures. Heat of sublimation at 50 0 50 kJ/mg. The molecule does not have a dipole moment, so UF6 does not associate. Vapors UFr, - an ideal gas.

It is obtained by the action of fluorine on U of its compounds:

In addition to gas-phase reactions, there are also liquid-phase reactions.

obtaining UF6 using halofluorides, for example

There is a way to obtain UF6 without the use of fluorine - by oxidizing UF 4:

UFe does not react with dry air, oxygen, nitrogen and CO 2, but upon contact with water, even with traces of it, it undergoes hydrolysis:

It interacts with most metals, forming their fluorides, which complicates the methods of its storage. Suitable vessel materials for working with UF6 are: Ni, Monel and Pt when heated, Teflon, absolutely dry quartz and glass, copper and aluminum when cold. At temperatures of 25 yuo 0 it forms complex compounds with fluorides of alkali metals and silver of the type 3NaFUFr>, 3KF2UF6.

It dissolves well in various organic liquids, inorganic acids and in all halogen fluorides. Inert to dry 0 2 , N 2 , CO 2 , C1 2 , Br 2 . UFr is characterized by reduction reactions with most pure metals. UF6 reacts vigorously with hydrocarbons and other organic substances, so closed containers of UFe can explode. UF6 in the range 25 - 100° forms complex salts with fluorides of alkali and other metals. This property is used in technology for the selective extraction of UF

Uranium hydrides UH 2 and UH 3 occupy an intermediate position between salt-like hydrides and hydrides such as solid solutions of hydrogen in metal.

When uranium reacts with nitrogen, nitrides are formed. Four phases are known in the U-N system: UN (uranium nitride), a-U 2 N 3 (sesquinitride), p-U 2 N 3 and UN If90. It is not possible to reach the composition of UN 2 (dinitride). Reliable and well controlled are the syntheses of uranium mononitride UN, which are best done directly from the elements. Uranium nitrides are powdery substances, the color of which varies from dark gray to gray; look like metal. UN has a cubic face-centered crystal structure, such as NaCl (0=4.8892 A); (/ = 14.324, 7 ^ = 2855 °, stable in vacuum up to 1700 0. It is obtained by reacting U or U hydride with N 2 or NH 3 , decomposition of higher nitrides U at 1300 ° or their reduction with metallic uranium. U 2 N 3 is known in two polymorphic modifications: cubic a and hexagonal p (0=0.3688 nm, 6=0.5839 nm), releases N 2 in vacuum above 8oo°. It is obtained by reduction of UN 2 with hydrogen. Dinitride UN 2 is synthesized by the reaction of U with N 2 at high pressure N 2 . Uranium nitrides are readily soluble in acids and alkali solutions, but decompose with molten alkalis.

Uranium nitride is obtained by two-stage carbothermal reduction of uranium oxide:

Heating in argon at 7M450 0 for 10 * 20 hours

It is possible to obtain uranium nitride with a composition close to dinitride, UN 2 , by the action of ammonia on UF 4 at high temperature and pressure.

Uranium dinitride decomposes when heated:

Uranium nitride, enriched in 2 35U, has a higher fission density, thermal conductivity and melting point than uranium oxides, the traditional fuel of modern power reactors. It also has good mechanical and stability, exceeding traditional fuel. Therefore, this compound is considered as a promising basis for nuclear fuel fast neutron reactors (generation IV nuclear reactors).

Comment. UN is very useful to enrich on ‘5N, because ,4 N tends to capture neutrons, generating the radioactive isotope 14 C by the (n, p) reaction.

Uranium carbide UC 2 (?-phase) is a light gray crystalline substance with a metallic sheen. In the U-C system (uranium carbides) there are UC 2 (?-phase), UC 2 (b 2-phase), U 2 C 3 (e-phase), UC (b 2-phase) - uranium carbides. Uranium dicarbide UC 2 can be obtained by the reactions:

U + 2C ^ UC 2 (54v)

Uranium carbides are used as fuel for nuclear reactors, they are promising as fuel for space rocket engines.

Uranyl nitrate, uranyl nitrate, U0 2 (N0 3) 2 -6H 2 0. The role of the metal in this salt is played by the uranyl cation 2+. Yellow crystals with a greenish sheen, easily soluble in water. The aqueous solution is acidic. Soluble in ethanol, acetone and ether, insoluble in benzene, toluene and chloroform. When heated, the crystals melt and release HN0 3 and H 2 0. The crystalline hydrate easily erodes in air. A characteristic reaction is that under the action of NH 3 a yellow precipitate of ammonium urate is formed.

Uranium is able to form metal organic compounds. Examples are cyclopentadienyl derivatives of the composition U(C 5 H 5) 4 and their halogenated u(C 5 H 5) 3 G or u(C 5 H 5) 2 G 2 .

In aqueous solutions, uranium is most stable in the oxidation state U(VI) in the form of the uranyl ion U0 2 2+ . To a lesser extent, it is characterized by the U(IV) state, but it can even exist in the U(III) form. The U(V) oxidation state can exist as the IO 2 + ion, but this state is rarely observed due to the tendency to disproportionation and hydrolysis.

In neutral and acidic solutions, U(VI) exists as U0 2 2+ - a yellow uranyl ion. Well-soluble uranyl salts include nitrate U0 2 (N0 3) 2, sulfate U0 2 S0 4, chloride U0 2 C1 2, fluoride U0 2 F 2, acetate U0 2 (CH 3 C00) 2. These salts are isolated from solutions in the form of crystalline hydrates with different numbers of water molecules. Slightly soluble salts of uranyl are: oxalate U0 2 C 2 0 4, phosphates U0 2 HP0., and UO2P2O4, ammonium uranyl phosphate UO2NH4PO4, sodium uranyl vanadate NaU0 2 V0 4, ferrocyanide (U0 2) 2. The uranyl ion is characterized by a tendency to form complex compounds. So complexes with fluorine ions of the type -, 4- are known; nitrate complexes ‘ and 2 *; sulfate complexes 2 "and 4-; carbonate complexes 4" and 2 ", etc. Under the action of alkalis on solutions of uranyl salts, sparingly soluble precipitates of diuranates of the Me 2 U 2 0 7 type are released (Me 2 U0 4 monouranates are not isolated from solutions, they are obtained by fusion uranium oxides with alkalis) Me 2 U n 0 3 n+i polyuranates are known (for example, Na 2 U60i 9).

U(VI) is reduced in acidic solutions to U(IV) by iron, zinc, aluminum, sodium hydrosulfite, and sodium amalgam. The solutions are colored green. Alkalis precipitate hydroxide and 0 2 (0H) 2 from them, hydrofluoric acid - fluoride UF 4 -2.5H 2 0, oxalic acid - oxalate U (C 2 0 4) 2 -6H 2 0. The tendency to complex formation in the U 4+ ion less than that of uranyl ions.

Uranium (IV) in solution is in the form of U 4+ ions, which are highly hydrolyzed and hydrated:

Hydrolysis is suppressed in acidic solutions.

Uranium (VI) in solution forms uranyl oxocation - U0 2 2+ Numerous uranyl compounds are known, examples of which are: U0 3, U0 2 (C 2 H 3 0 2) 2, U0 2 C0 3 -2 (NH 4) 2 C0 3 U0 2 C0 3 , U0 2 C1 2 , U0 2 (0H) 2 , U0 2 (N0 3) 2 , UO0SO4, ZnU0 2 (CH 3 C00) 4 etc.

During the hydrolysis of the uranyl ion, a number of multinuclear complexes are formed:

With further hydrolysis, U 3 0s (0H) 2 appears and then U 3 0 8 (0H) 4 2 -.

For the qualitative detection of uranium, methods of chemical, luminescent, radiometric and spectral analyzes are used. Chemical methods are mainly based on the formation of colored compounds (for example, red-brown color of the compound with ferrocyanide, yellow with hydrogen peroxide, blue with arsenazo reagent). The luminescent method is based on the ability of many uranium compounds to give a yellowish-greenish glow under the action of UV rays.

Quantitative determination of uranium is carried out by various methods. The most important of them are: volumetric methods, consisting in the reduction of U(VI) to U(IV) followed by titration with solutions of oxidizing agents; weight methods - precipitation of uranates, peroxide, U(IV) kupferranates, oxyquinolate, oxalate, etc. followed by their calcination at 100° and weighing U 3 0s; polarographic methods in a nitrate solution make it possible to determine 10 x 7 x 10-9 g of uranium; numerous colorimetric methods (for example, with H 2 0 2 in an alkaline medium, with the arsenazo reagent in the presence of EDTA, with dibenzoylmethane, in the form of a thiocyanate complex, etc.); luminescent method, which makes it possible to determine when fused with NaF to yu 11 g uranium.

235U belongs to group A of radiation hazard, the minimum significant activity MZA=3.7-10 4 Bq, 2 s 8 and - to group D, MZA=3.7-10 6 Bq (300 g).

When the radioactive elements of the periodic table were discovered, a person eventually came up with an application for them. This is what happened with uranium. It was used for both military and civilian purposes. Uranium ore was processed, the resulting element was used in the paint and varnish and glass industries. After its radioactivity was discovered, it began to be used in How clean and environmentally friendly is this fuel? This is still being debated.

natural uranium

In nature, uranium does not exist in its pure form - it is a component of ore and minerals. The main uranium ore is carnotite and pitchblende. Also, significant deposits of this strategic are found in rare earth and peat minerals - orthite, titanite, zircon, monazite, xenotime. Uranium deposits can be found in rocks with an acidic environment and high concentrations of silicon. Its companions are calcite, galena, molybdenite, etc.

World deposits and reserves

To date, many deposits have been explored in a 20-kilometer layer of the earth's surface. All of them contain a huge number of tons of uranium. This amount is capable of providing humanity with energy for many hundreds of years to come. The leading countries in which uranium ore is located in the largest volume are Australia, Kazakhstan, Russia, Canada, South Africa, Ukraine, Uzbekistan, USA, Brazil, Namibia.

Types of uranium

Radioactivity determines the properties of a chemical element. Natural uranium is made up of three of its isotopes. Two of them are the ancestors of the radioactive series. Natural isotopes of uranium are used to create fuel for nuclear reactions and weapons. Also, uranium-238 serves as a raw material for the production of plutonium-239.

Uranium isotopes U234 are daughter nuclides of U238. They are recognized as the most active and provide strong radiation. The isotope U235 is 21 times weaker, although it has been successfully used for the above purposes - it has the ability to maintain without additional catalysts.

In addition to natural, there are also artificial isotopes of uranium. Today there are 23 such known, the most important of them - U233. It is distinguished by the ability to be activated under the influence of slow neutrons, while the rest require fast particles.

Ore classification

Although uranium can be found almost everywhere - even in living organisms - the layers in which it is contained can be of different types. This also depends on the methods of extraction. Uranium ore is classified according to the following parameters:

1. Formation conditions - endogenous, exogenous and metamorphogenic ores.
2. The nature of uranium mineralization is primary, oxidized and mixed ores of uranium.
3. The size of aggregates and grains of minerals - coarse-grained, medium-grained, fine-grained, fine-grained and dispersed ore fractions.
4. The usefulness of impurities - molybdenum, vanadium, etc.
5. The composition of impurities - carbonate, silicate, sulfide, iron oxide, caustobiolitic.

Depending on how uranium ore is classified, there is a way to extract a chemical element from it. Silicate is treated with various acids, carbonate - with soda solutions, caustobiolite is enriched by burning, and iron oxide is melted in a blast furnace.

How is uranium ore mined?

As in any mining business, there is a certain technology and methods for extracting uranium from rock. Everything also depends on which isotope is in the lithosphere layer. Uranium ore is mined in three ways. Economically justified isolating the element from the rock is when its content is in the amount of 0.05-0.5%. There is a mine, quarry and leaching method of extraction. The use of each of them depends on the composition of the isotopes and the depth of the rock. Quarry mining of uranium ore is possible with a shallow occurrence. The risk of exposure is minimal. There are no problems with equipment - bulldozers, loaders, dump trucks are widely used.

Mining is more complex. This method is used when the element occurs at a depth of up to 2 kilometers and is economically viable. The rock must contain a high concentration of uranium in order to be expediently mined. The adit provides maximum security, this is due to the way uranium ore is mined underground. Workers are provided with overalls, the working hours are strictly limited. The mines are equipped with elevators, enhanced ventilation.

Leaching is the third method - the cleanest from an environmental point of view and the safety of the employees of the mining enterprise. A special chemical solution is pumped through a system of drilled wells. It dissolves in the reservoir and becomes saturated with uranium compounds. The solution is then pumped out and sent to processing plants. This method is more progressive, it allows to reduce economic costs, although there are a number of limitations for its application.

Deposits in Ukraine

The country turned out to be a happy owner of deposits of the element from which it is produced. According to forecasts, uranium ores in Ukraine contain up to 235 tons of raw materials. Currently, only deposits containing about 65 tons have been confirmed. A certain amount has already been worked out. Part of the uranium was used domestically, and part was exported.

The main deposit is the Kirovograd uranium ore region. The content of uranium is low - from 0.05 to 0.1% per ton of rock, so the cost of the material is high. As a result, the resulting raw materials are exchanged in Russia for finished fuel rods for power plants.

The second major deposit is Novokonstantinovskoye. The content of uranium in the rock made it possible to reduce the cost compared to the Kirovogradskoye by almost 2 times. However, development has not been carried out since the 90s, all mines are flooded. In connection with the aggravation of political relations with Russia, Ukraine may be left without fuel for

Russian uranium ore

In terms of uranium mining, the Russian Federation is in fifth place among other countries in the world. The most famous and powerful are Khiagdinskoye, Kolichkanskoye, Istochnoye, Koretkondinskoye, Namarusskoye, Dobrynskoye (Republic of Buryatia), Argunskoye, Zherlovoye. 93% of all Russian uranium is mined in the Chita region (mainly by open pit and mine methods).

The situation is somewhat different with deposits in Buryatia and Kurgan. Uranium ore in Russia in these regions lies in such a way that it makes it possible to extract raw materials by leaching.

In total, deposits of 830 tons of uranium are predicted in Russia, and there are about 615 tons of confirmed reserves. These are also deposits in Yakutia, Karelia and other regions. Since uranium is a strategic global raw material, the numbers may not be accurate, since many of the data are classified, only a certain category of people have access to them.

Uranium is a radioactive metal. In nature, uranium consists of three isotopes: uranium-238, uranium-235 and uranium-234. The highest level of stability is recorded for uranium-238.

radioactive decay of uranium

Radioactive decay is the process of a sudden change in the composition or internal structure of atomic nuclei, which are characterized by instability. In this case, elementary particles, gamma quanta and/or nuclear fragments are emitted. Radioactive substances contain a radioactive nucleus. The daughter nucleus resulting from radioactive decay can also become radioactive and, after a certain time, undergoes decay. This process continues until a stable nucleus devoid of radioactivity is formed. E. Rutherford experimentally proved in 1899 that uranium salts emit three types of rays:

• α-rays - a stream of positively charged particles
• β-rays - a stream of negatively charged particles
• γ-rays - do not create deviations in the magnetic field.

Radioactivity of uranium

Natural radioactivity is what distinguishes radioactive uranium from other elements. Uranium atoms, regardless of any factors and conditions, gradually change. In this case, invisible rays are emitted. After the transformations that occur with uranium atoms, a different radioactive element is obtained and the process is repeated. He will repeat as many times as necessary to get a non-radioactive element. For example, some chains of transformations have up to 14 stages. In this case, the intermediate element is radium, and the last stage is the formation of lead. This metal is not a radioactive element, so a number of transformations are interrupted. However, it takes several billion years for the complete transformation of uranium into lead.
Radioactive uranium ore often causes poisoning at enterprises involved in the extraction and processing of uranium raw materials. In the human body, uranium is a general cellular poison. It mainly affects the kidneys, but liver and gastrointestinal lesions also occur.
Uranium does not have completely stable isotopes. The longest lifetime is noted for uranium-238. The semi-decay of uranium-238 occurs over 4.4 billion years. A little less than one billion years is the half-decay of uranium-235 - 0.7 billion years. Uranium-238 occupies over 99% of the total volume of natural uranium. Due to its colossal half-life, the radioactivity of this metal is not high, for example, alpha particles cannot penetrate the stratum corneum of human skin. After a series of studies, scientists found that the main source of radiation is not uranium itself, but the radon gas formed by it, as well as its decay products that enter the human body during breathing.