Who discovered the element uranium. What is dangerous uranium and its compounds

Discovery on a planetary scale. So you can call the discovery by scientists of Uranus. The planet was discovered in 1781.

Her discovery was the reason for naming one of elements of the periodic table. Uranus metal was isolated from resin blende in 1789.

The hype around the new planet has not yet subsided, therefore, the idea of ​​​​naming a new substance lay on the surface.

At the end of the 18th century there was still no concept of radioactivity. Meanwhile, this is the main property of terrestrial uranium.

Scientists who worked with him were irradiated without knowing it. Who was the pioneer, and what are the other properties of the element, we will tell further.

Properties of uranium

Uranium is an element discovered by Martin Klaproth. He fused the resin with the caustic. The fusion product was not completely soluble.

Klaproth realized that there were no supposed, and in the composition of the mineral. Then, the scientist dissolved the snag in.

Green hexagons fell out of the solution. The chemist exposed them to yellow blood, that is, potassium hexacyanoferrate.

A brown precipitate fell out of the solution. Klaproth reduced this oxide with linseed oil and calcined it. Got a powder.

I had to ignite it already, mixing it with brown. Grains of a new metal were found in the sintered mass.

Later it turned out that it was not pure uranium, and its dioxide. Separately, the element was received only 60 years later, in 1841. And after another 55, Antoine Becquerel discovered the phenomenon of radioactivity.

Radioactivity of uranium due to the ability of the nucleus of an element to capture neutrons and break up. At the same time, impressive energy is released.

It is due to the kinetic data of radiation and fragments. It is possible to ensure the continuous fission of nuclei.

The chain reaction starts when natural uranium is enriched with its 235th isotope. It is not something that is added to the metal.

On the contrary, the low-radioactive and inefficient 238th nuclide, as well as the 234th, are removed from the ore.

Their mixture is called depleted, and the remaining uranium is called enriched. This is exactly what industrialists need. But, we will talk about this in a separate chapter.

Uranus radiates, both alpha and beta with gamma rays. They were discovered by seeing the effect of the metal on a photographic plate wrapped in black.

It became clear that the new element was emitting something. While the Curies were investigating what it was, Marie received a dose of radiation that caused the chemist to develop blood cancer, from which the woman died in 1934.

Beta radiation can destroy not only the human body, but also the metal itself. What element is formed from uranium? Answer: Brevi.

Otherwise, it is called protactinium. Discovered in 1913, just when studying uranium.

The latter turns into brevia without external influences and reagents, only from beta decay.

Externally uranium is a chemical element- colors with a metallic sheen.

This is how all actinides look, to which the 92nd substance belongs. The group starts with the 90th number, and ends with the 103rd.

Standing at the top of the list radioactive element uranium, acts as an oxidizing agent. The oxidation states can be 2nd, 3rd, 4th, 5th, 6th.

That is, chemically the 92nd metal is active. If you grind uranium into a powder, it will ignite spontaneously in air.

In its usual form, the substance will oxidize upon contact with oxygen, becoming covered with an iridescent film.

If the temperature is raised to 1000 degrees Celsius, chem. element uranium connect with . Metal nitride is formed. This substance is yellow.

Throw it into water and dissolve like pure uranium. Corrode it and all acids. The element displaces hydrogen from organic matter.

Uranium pushes it out, in the same way, from salt solutions,,,,,. If such a solution is shaken, the particles of the 92nd metal will begin to glow.

uranium salts unstable, decompose in the light, or in the presence of organics.

The element is indifferent, perhaps, only to alkalis. The metal does not react with them.

Discovery of uranium is the discovery of a superheavy element. Its mass makes it possible to isolate the metal, more precisely, the minerals with it, from the ore.

It is enough to crush it and fall asleep in water. The uranium particles will settle first. This is where mining starts. Details in the next chapter.

Uranium mining

Having received a heavy sediment, industrialists leach the concentrate. The goal is to bring the uranium into solution. Sulfuric acid is used.

An exception is made for tar. This mineral is insoluble in acid, therefore, alkalis are used. The secret of difficulties in the 4-valence state of uranium.

Acid leaching does not pass with , . In these minerals, the 92nd metal is also 4-valent.

This is treated with hydroxide, known as sodium hydroxide. In other cases, oxygen purge is good. No need to separately stock up on sulfuric acid.

It is enough to heat the ore with sulfide minerals up to 150 degrees and send an oxygen jet to it. This leads to the formation of an acid that leaches Uranus.

Chemical element and its application associated with pure forms of metal. Sorption is used to remove impurities.

It is carried out on ion exchange resins. Also suitable for extraction with organic solvents.

It remains to add alkali to the solution in order to precipitate ammonium uranates, dissolve them in nitric acid and subject them to.

The result will be the oxides of the 92nd element. They are heated to 800 degrees and reduced with hydrogen.

The resulting oxide is converted to uranium fluoride, from which the pure metal is obtained by calcium thermal reduction. , as you can see, is not simple. Why try so hard?

Application of uranium

The 92nd metal is the main fuel for nuclear reactors. A lean mixture is suitable for stationary, and an enriched element is used for power plants.

The 235th isotope is also the basis of nuclear weapons. Secondary nuclear fuel can also be obtained from the 92nd metal.

Here it is worth asking the question, what element turns uranium. From its 238th isotope, one more radioactive, superheavy substance is obtained.

At the very 238th uranium great half life, lasts 4.5 billion years. Such a long destruction leads to low energy consumption.

If we consider the use of uranium compounds, its oxides come in handy. They are used in the glass industry.

Oxides act as dyes. Can be obtained from pale yellow to dark green. In ultraviolet rays, the material fluoresces.

This property is used not only in glasses, but also in uranium glazes for. Uranium oxides in them are from 0.3 to 6%.

As a result, the background is safe, does not exceed 30 microns per hour. Photo of uranium elements, more precisely, products with his participation, are very colorful. The glow of glasses and dishes attracts the eye.

Uranium price

For a kilogram of unenriched uranium oxide, they give about 150 dollars. Peak values ​​were observed in 2007.

Then the cost reached 300 dollars per kilo. The development of uranium ores will remain profitable even at a price of 90-100 conventional units.

Who discovered the element uranium, did not know what its reserves were in the earth's crust. Now, they've been counted.

Large fields with a profitable production price will be depleted by 2030.

If new deposits are not discovered, or alternatives to the metal are not found, its value will creep up.

Uranus(lat. uranium), u, a radioactive chemical element of group III of the periodic system of Mendeleev, belongs to the family actinides, atomic number 92, atomic mass 238.029; metal. Natural U. consists of a mixture of three isotopes: 238 u - 99.2739% with a half-life t 1 / 2 = 4.51 10 9 years, 235 u - 0.7024% (t 1 / 2 = 7.13 10 8 years) and 234 u - 0.0057% (t 1 / 2 \u003d 2.48 10 5 years). Of the 11 artificial radioactive isotopes with mass numbers from 227 to 240, long-lived is 233 u (t 1 / 2 \u003d 1.62 10 5 years); it is obtained by neutron irradiation of thorium. 238 u and 235 u are the progenitors of two radioactive series.

Historical reference. U. opened in 1789. chemist M. G. Klaproth and named by him in honor of the planet Uranus, discovered by V. Herschel in 1781. In the metallic state, U. was obtained in 1841 by the French. chemist E. Peligo during the reduction of ucl 4 with metallic potassium. Initially, U. was assigned an atomic mass of 120, and only in 1871 D.I. Mendeleev came to the conclusion that this value should be doubled.

For a long time, uranium was of interest only to a narrow circle of chemists and found limited use for the production of paints and glass. With the discovery of the phenomenon radioactivity W. in 1896 and radium In 1898, industrial processing of uranium ores began with the aim of extracting and using radium in scientific research and medicine. Since 1942, after the discovery in 1939 of the phenomenon of nuclear fission , U. became the main nuclear fuel.

distribution in nature. U. is a characteristic element for the granite layer and sedimentary shell of the earth's crust. The average content of U. in the earth's crust (clarke) is 2.5 10 -4% by weight, in acidic igneous rocks 3.5 10 -4%, in clays and shales 3.2 10 -4%, in basic rocks 5 10 -5%, in ultramafic rocks of the mantle 3 10 -7%. U. migrates vigorously in cold and hot, neutral and alkaline waters in the form of simple and complex ions, especially in the form of carbonate complexes. Redox reactions play an important role in the geochemistry of water, since compounds of water, as a rule, are highly soluble in waters with an oxidizing environment and poorly soluble in waters with a reducing environment (for example, hydrogen sulfide).

About 100 U. minerals are known; 12 of them are of industrial importance . In the course of geological history, the content of U. in the earth's crust has decreased due to radioactive decay; this process is associated with the accumulation of Pb and He atoms in the earth's crust. The radioactive decay of U. plays an important role in the energy of the earth's crust, being a significant source of deep heat.

physical properties. U. is similar in color to steel and can be easily processed. It has three allotropic modifications - a, b and g with phase transformation temperatures: a ®b 668.8 ± 0.4 ° C, b® g 772.2 ± 0.4 ° С; a -shape has a rhombic lattice a= 2.8538 å, b= 5.8662 å, With\u003d 4.9557 å), b-form - tetragonal lattice (at 720 ° С A = 10,759 , b= 5.656 å), g-form - body-centered cubic lattice (at 850°c a = 3.538 å). U. density in a-form (25°c) 19.05 ± 0.2 g/cm 3 , t pl 1132 ± 1°С; t kip 3818 °C; thermal conductivity (100–200°c), 28.05 Tue/(m· TO) , (200–400 °c) 29.72 Tue/(m· TO) ; specific heat (25°c) 27.67 kJ/(kg· TO) ; electrical resistivity at room temperature approx. 3 10 -7 ohm· cm, at 600°c 5.5 10 -7 ohm· cm; has superconductivity at 0.68 ± 0.02K; weak paramagnet, specific magnetic susceptibility at room temperature 1.72 10 -6 .

The mechanical properties of U. depend on its purity, on the modes of mechanical and heat treatment. The average value of the modulus of elasticity for cast U. 20.5 10 -2 Mn/m 2 ultimate tensile strength at room temperature 372–470 Mn/m 2 , strength increases after hardening from b - and g -phases; average hardness according to Brinell 19.6–21.6 10 2 Mn/m 2 .

Irradiation with a neutron flux (which takes place in nuclear reactor) changes the physico-mechanical properties of uranium: creep develops and brittleness increases, deformation of products is observed, which forces the use of uranium in nuclear reactors in the form of various uranium alloys.

U. - radioactive element. The 235 u and 233 u nuclei fission spontaneously, as well as during the capture of both slow (thermal) and fast neutrons with an effective fission cross section of 508 10 -24 cm 2 (508 barn) and 533 10 -24 cm 2 (533 barn) respectively. Nuclei 238 u are fissioned by capturing only fast neutrons with an energy of at least 1 Mev; when slow neutrons are captured, 238 u turns into 239 pu , whose nuclear properties are close to 235 u. Critical mass U. (93.5% 235 u) in aqueous solutions is less than 1 kg, for an open ball - about 50 kg, for a ball with a reflector - 15 - 23 kg; the critical mass of 233 u is approximately 1/3 of the critical mass of 235 u.

Chemical properties. The configuration of the outer electron shell of the atom U. 7 s 2 6 d 1 5 f 3 . U. refers to reactive metals, in compounds it exhibits oxidation states + 3, + 4, + 5, + 6, sometimes + 2; the most stable compounds are u (iv) and u (vi). In air, it slowly oxidizes with the formation of a film of dioxide on the surface, which does not protect the metal from further oxidation. In the powdered state, U. is pyrophoric and burns with a bright flame. With oxygen, it forms uo 2 dioxide, uo 3 trioxide, and a large number of intermediate oxides, the most important of which is u 3 o 8 . These intermediate oxides are similar in properties to uo 2 and uo 3 . At high temperatures, uo 2 has a wide range of homogeneity from uo 1.60 to uo 2.27. With fluorine at 500–600°c it forms tetrafluoride (green needle-like crystals, sparingly soluble in water and acids) and uf 6 hexafluoride (a white crystalline substance sublimes without melting at 56.4°c); with sulfur - a number of compounds, of which the most important is us (nuclear fuel). When U. interacts with hydrogen at 220 ° C, a hydride uh 3 is obtained; with nitrogen at a temperature from 450 to 700 ° C and atmospheric pressure - u 4 n 7 nitride, at a higher nitrogen pressure and the same temperature, un, u 2 n 3 and un 2 can be obtained; with carbon at 750–800°c, monocarbide uc, dicarbide uc 2 , and also u 2 c 3 ; forms alloys of various types with metals . U. slowly reacts with boiling water to form uo 2 and h 2 , with water vapor in the temperature range of 150–250 °C; soluble in hydrochloric and nitric acids, slightly - in concentrated hydrofluoric acid. For u (vi) the formation of the uranyl ion uo 2 2 + is characteristic; uranyl salts are yellow and highly soluble in water and mineral acids; salts u (iv) are green and less soluble; the uranyl ion is extremely capable of complex formation in aqueous solutions with both inorganic and organic substances; the most important for the technology are carbonate, sulfate, fluoride, phosphate, and other complexes. A large number of uranates (salts of uranic acid not isolated in pure form) are known, the composition of which varies depending on the conditions of preparation; all uranates have low solubility in water.

U. and its compounds are radiation and chemically toxic. Maximum allowable dose (SDA) for occupational exposure 5 rem in year.

Receipt. U. is obtained from uranium ores containing 0.05–0.5% u. Ores are practically not enriched, with the exception of a limited method of radiometric sorting, based on radiation of radium, which is always associated with uranium. Basically, ores are leached with solutions of sulfuric, sometimes nitric acids, or soda solutions, with the conversion of U. into an acid solution in the form of uo 2 so 4 or complex anions 4-, and into a soda solution in the form of 4-. Sorption on ion-exchange resins and extraction with organic solvents (tributyl phosphate, alkyl phosphoric acids, and amines) are used to extract and concentrate uric acid from solutions and pulps, as well as to remove impurities. Further, ammonium or sodium uranates or hydroxide u (oh) 4 are precipitated from the solutions by adding alkali. To obtain high purity compounds, technical products are dissolved in nitric acid and subjected to refining purification operations, the end products of which are uo 3 or u 3 o 8 ; these oxides are reduced at 650–800°c with hydrogen or dissociated ammonia to uo 2 followed by its conversion to uf 4 by treatment with gaseous hydrogen fluoride at 500–600°c. uf 4 can also be obtained by precipitation of the uf 4 · nh 2 o crystalline hydrate from solutions with hydrofluoric acid, followed by dehydration of the product at 450°C in a stream of hydrogen. In industry, the main method of obtaining U. from uf 4 is its calcium-thermal or magnesium-thermal reduction, with the output of U. in the form of ingots weighing up to 1.5 tons. The ingots are refined in vacuum furnaces.

A very important process in U. technology is its enrichment with the 235 u isotope above the natural content in ores or the isolation of this isotope in its pure form. , since it is 235 u that is the main nuclear fuel; this is carried out by gas thermal diffusion, centrifugal, and other methods based on the difference in masses 235 u and 238 u; U. is used in separation processes in the form of volatile uf 6 hexafluoride. Upon receipt of highly enriched U. or isotopes, their critical masses are taken into account; the most convenient method in this case is the reduction of U. oxides with calcium; the cao slag formed in this process is easily separated from U. by dissolution in acids.

Powder metallurgy methods are used to produce powdered carbon dioxide, carbides, nitrides, and other refractory compounds.

Application. Metallic U. or its compounds are mainly used as nuclear fuel in nuclear reactors. A natural or low-enriched mixture of U isotopes is used in stationary reactors of nuclear power plants; the product of a high degree of enrichment is used in nuclear power plants or in reactors operating on fast neutrons. 235 u is the source of nuclear energy in nuclear weapons. 238 u serves as a source of secondary nuclear fuel - plutonium.

V. M. Kulifeev.

Uranium in the body In microquantities (10 -5 -10 -5%) it is found in the tissues of plants, animals and humans. In the ashes of plants (with a content of U. in the soil of about 10 -4), its concentration is 1.5 10 -5%. U. is accumulated to the greatest extent by some fungi and algae (the latter are actively involved in the biogenic migration of U. along the chain water - aquatic plants - fish - man). U. enters the body of animals and humans with food and water into the gastrointestinal tract, with air into the respiratory tract, and also through the skin and mucous membranes. U. compounds are absorbed in the gastrointestinal tract - about 1% of the incoming amount of soluble compounds and no more than 0.1% of sparingly soluble ones; in the lungs, 50% and 20% are absorbed, respectively. U. is distributed unevenly in the body. The main depots (places of deposition and accumulation) are the spleen, kidneys, skeleton, liver, and, when sparingly soluble compounds are inhaled, the lungs and broncho-pulmonary lymph nodes. U.'s blood (in the form of carbonates and complexes with proteins) does not circulate for a long time. The content of U. in the organs and tissues of animals and humans does not exceed 10 -7 y/y. So, the blood of cattle contains 1 10 -8 g/ml liver 8 10 -8 y/y, muscles 4 10 -8 y/y, spleen 9 10 -8 y/y. U.'s content in human organs is: in the liver 6 10 -9 y/y, in the lungs 6 10 -9 -9 10 -9 g / g, in the spleen 4.7 10 -9 y/y, in blood 4 10 -9 g/ml in the kidneys 5.3 10 -9 (cortical layer) and 1.3 10 -9 y/y(medulla), in bones 1 10 -9 y/y, in the bone marrow 1 10 -9 y/y, in hair 1.3 10 -7 y/y. U., contained in the bone tissue, causes its constant irradiation (the half-life of U. from the skeleton is about 300 day) . The lowest concentrations of U. are in the brain and heart (10 -10 y/y). Daily intake of U. with food and liquids - 1.9 10 -6 g, s air - 7 10 -9 G. The daily excretion of U. from the human body is: with urine 0.5 10 -7 -5 10 -7, with feces - 1.4 10 -6 -1.8 10 -6 g, s hair - 2 10 -8 g.

According to the International Commission on Radiation Protection, the average content of U. in the human body is 9 10 -8 g. This value may vary for different regions. It is believed that U. is necessary for the normal life of animals and plants, but its physiological functions have not been elucidated.

G. P. Galibin.

Toxic action U. is due to its chemical properties and depends on solubility: uranyl and other soluble compounds of U are more toxic. U. and its compounds can be poisoned at enterprises for the extraction and processing of uranium raw materials and other industrial facilities where it is used in the technological process. When ingested, U. acts on all organs and tissues, being a general cellular poison. Signs of poisoning due preim. kidney damage (the appearance of protein and sugar in the urine, subsequent oliguria) , the liver and gastrointestinal tract are also affected. There are acute and chronic poisoning; the latter are characterized by gradual development and lesser severity of symptoms. With chronic intoxication, disturbances in hematopoiesis, the nervous system, etc. are possible. It is believed that the molecular mechanism of U.'s action is associated with its ability to suppress the activity of enzymes.

Prevention of poisoning: continuity of technological processes, the use of sealed equipment, prevention of air pollution, wastewater treatment before they are discharged into water bodies, honey. control over the state of health of workers, over compliance with hygienic standards for the permissible content of U. and its compounds in the environment.

V. F. Kirillov.

Lit.: The doctrine of radioactivity. History and Modernity, ed. B. M. Kedrova. Moscow, 1973. Petrosyants A. M., From scientific search to the nuclear industry, M., 1970; Emelyanov V. S., Evstyukhin A. I., Metallurgy of nuclear fuel, M., 1964; Sokursky Yu. N., Sterlin Ya. M., Fedorchenko V. A., Uranus and its alloys, M., 1971; Evseeva L. S., Perelman A. I., Ivanov K. E., Geochemistry of uranium in the zone of hydrogenation, 2nd ed., M., 1974; Pharmacology and toxicology of uranium compounds, [transl. from English], vol. 2, M., 1951; Guskova V. N., Uranus. Radiation-hygienic characteristic, M., 1972; Andreeva O. S., Occupational health when working with uranium and its compounds, M., 1960; Novikov Yu.V., Hygienic issues of studying the content of uranium in the environment and its effect on the body, M., 1974.

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.

; atomic number 92, atomic mass 238.029; metal. Natural Uranium consists of a mixture of three isotopes: 238 U - 99.2739% with a half-life T ½ = 4.51 10 9 years, 235 U - 0.7024% (T ½ = 7.13 10 8 years) and 234 U - 0.0057% (T ½ \u003d 2.48 10 5 years).

Of the 11 artificial radioactive isotopes with mass numbers from 227 to 240, long-lived is 233 U (T ½ = 1.62 10 5 years); it is obtained by neutron irradiation of thorium. 238 U and 235 U are the progenitors of two radioactive series.

Historical reference. Uranium was discovered in 1789 by the German chemist M. G. Klaproth and named by him in honor of the planet Uranus, discovered by W. Herschel in 1781. In the metallic state, Uranium was obtained in 1841 by the French chemist E. Peligot by reducing UCl 4 with potassium metal. Initially, Uranus was assigned an atomic mass of 120, and only in 1871 D. I. Mendeleev came to the conclusion that this value should be doubled.

For a long time, uranium was of interest only to a narrow circle of chemists and found limited use for the production of paints and glass. With the discovery of the radioactivity of uranium in 1896 and radium in 1898, the industrial processing of uranium ores began in order to extract and use radium in scientific research and medicine. Since 1942, after the discovery in 1939 of the phenomenon of nuclear fission, uranium has become the main nuclear fuel.

Distribution of Uranus in nature. Uranium is a characteristic element for the granite layer and sedimentary shell of the earth's crust. The average content of Uranium in the earth's crust (clarke) is 2.5 10 -4% by mass, in acidic igneous rocks 3.5 10 -4%, in clays and shales 3.2 10 -4%, in basic rocks 5 10 -5%, in ultrabasic rocks of the mantle 3 10 -7%. Uranium migrates vigorously in cold and hot, neutral and alkaline waters in the form of simple and complex ions, especially in the form of carbonate complexes. An important role in the geochemistry of Uranus is played by redox reactions, since Uranium compounds, as a rule, are highly soluble in waters with an oxidizing environment and poorly soluble in waters with a reducing environment (for example, hydrogen sulfide).

About 100 minerals of Uranus are known; 12 of them are of industrial importance. In the course of geological history, the content of Uranus in the earth's crust has decreased due to radioactive decay; this process is associated with the accumulation of Pb and He atoms in the earth's crust. The radioactive decay of Uranus plays an important role in the energy of the earth's crust, being a significant source of deep heat.

Physical properties of Uranus. Uranium is similar in color to steel and can be easily processed. It has three allotropic modifications - α, β and γ with phase transformation temperatures: α → β 668.8 °С, β → γ 772.2 °С; the α-form has a rhombic lattice (a = 2.8538Å, b = 5.8662Å, c = 4.9557Å), the β-form has a tetragonal lattice (at 720 °C a = 10.759Å, b = 5.656Å), the γ-form - body-centered cubic lattice (at 850 °C a = 3.538Å). The density of Uranus in the α-form (25 ° C) is 19.05 g / cm 3; t pl 1132 °C; bp t 3818 °С; thermal conductivity (100-200 ° C), 28.05 W / (m K) , (200-400 ° C) 29.72 W / (m K) ; specific heat capacity (25 °C) 27.67 kJ/(kg K); electrical resistivity at room temperature is about 3 10 -7 ohm cm, at 600 °C 5.5 10 -7 ohm cm; possesses superconductivity at 0.68 K; weak paramagnet, specific magnetic susceptibility at room temperature 1.72·10 -6 .

The mechanical properties of uranium depend on its purity, on the modes of mechanical and thermal processing. The average value of the modulus of elasticity for cast uranium is 20.5·10 -2 MN/m 2 ; ultimate tensile strength at room temperature 372-470 MN/m 2 ; strength increases after hardening from β- and γ-phases; average hardness according to Brinell 19.6-21.6·10 2 MN/m 2 .

Irradiation with a neutron flux (which takes place in a nuclear reactor) changes the physical and mechanical properties of Uranium: creep develops and brittleness increases, deformation of products is observed, which forces the use of Uranium in nuclear reactors in the form of various uranium alloys.

Uranium is a radioactive element. Nuclei 235 U and 233 U fission spontaneously, as well as during the capture of both slow (thermal) and fast neutrons with an effective fission cross section of 508 10 -24 cm 2 (508 barn) and 533 10 -24 cm 2 (533 barn) respectively. 238 U nuclei are fissioned by capturing only fast neutrons with an energy of at least 1 MeV; when slow neutrons are captured, 238 U turns into 239 Pu, whose nuclear properties are close to 235 U. The critical mass of Uranium (93.5% 235 U) in aqueous solutions is less than 1 kg, for an open ball - about 50 kg, for a ball with a reflector - 15-23 kg; the critical mass of 233 U is approximately 1/3 of the critical mass of 235 U.

Chemical properties of uranium. The configuration of the outer electron shell of the Uranus atom is 7s 2 6d l 5f 3 . Uranium belongs to reactive metals, in compounds it exhibits oxidation states +3, +4, + 5, +6, sometimes +2; the most stable compounds are U(IV) and U(VI). In air, it slowly oxidizes with the formation of an oxide (IV) film on the surface, which does not protect the metal from further oxidation. In its powdered state, uranium is pyrophoric and burns with a bright flame. With oxygen, it forms oxide (IV) UO 2, oxide (VI) UO 3 and a large number of intermediate oxides, the most important of which is U 3 O 8. These intermediate oxides are similar in properties to UO 2 and UO 3 . At high temperatures, UO 2 has a wide homogeneity range from UO 1.60 to UO 2.27. With fluorine at 500-600 ° C, it forms tetrafluoride UF 4 (green needle-like crystals, slightly soluble in water and acids) and hexafluoride UF 6 (white crystalline substance sublimes without melting at 56.4 ° C); with sulfur - a number of compounds, of which the most important is US (nuclear fuel). When Uranium interacts with hydrogen at 220 ° C, a hydride UH 3 is obtained; with nitrogen at a temperature from 450 to 700 ° C and atmospheric pressure - U 4 N 7 nitride, at a higher nitrogen pressure and the same temperature, UN, U 2 N 3 and UN 2 can be obtained; with carbon at 750-800 ° C - UC monocarbide, UC 2 dicarbide, and also U 2 C 3; with metals forms alloys of various types. Uranium slowly reacts with boiling water to form UO 2 n H 2 , with water vapor - in the temperature range of 150-250 ° C; soluble in hydrochloric and nitric acids, slightly - in concentrated hydrofluoric acid. For U (VI), the formation of the uranyl ion UO 2 2+ is characteristic; uranyl salts are yellow and highly soluble in water and mineral acids; U(IV) salts are green and less soluble; the uranyl ion is extremely capable of complex formation in aqueous solutions with both inorganic and organic substances; the most important for the technology are carbonate, sulfate, fluoride, phosphate and other complexes. A large number of uranates (salts of uranic acid not isolated in pure form) are known, the composition of which varies depending on the conditions of preparation; all uranates have low solubility in water.

Uranium and its compounds are radiation and chemically toxic. The maximum allowable dose (SDA) for occupational exposure is 5 rem per year.

Getting Uranus. Uranium is obtained from uranium ores containing 0.05-0.5% U. Ores are practically not enriched, with the exception of a limited method of radiometric sorting, based on the γ-radiation of radium, which always accompanies uranium. Basically, ores are leached with solutions of sulfuric, sometimes nitric acids or soda solutions with the transfer of Uranium into an acidic solution in the form of UO 2 SO 4 or complex anions 4-, and into a soda solution - in the form of 4-. To extract and concentrate uranium from solutions and pulps, as well as to remove impurities, sorption on ion-exchange resins and extraction with organic solvents (tributyl phosphate, alkyl phosphoric acids, amines) are used. Further, ammonium or sodium uranates or hydroxide U(OH) 4 are precipitated from the solutions by adding alkali. To obtain high purity compounds, technical products are dissolved in nitric acid and subjected to refining purification operations, the end products of which are UO 3 or U 3 O 8 ; these oxides are reduced at 650–800°C with hydrogen or dissociated ammonia to UO 2 followed by its conversion to UF 4 by treatment with gaseous hydrogen fluoride at 500–600°C. UF 4 can also be obtained by precipitation of UF 4 nH 2 O crystalline hydrate from solutions with hydrofluoric acid, followed by dehydration of the product at 450 °C in a stream of hydrogen. In industry, the main method for obtaining uranium from UF 4 is its calcium-thermal or magnesium-thermal reduction with the release of uranium in the form of ingots weighing up to 1.5 tons. The ingots are refined in vacuum furnaces.

A very important process in the technology of uranium is its enrichment with the 235 U isotope above the natural content in ores or the isolation of this isotope in its pure form, since it is 235 U that is the main nuclear fuel; this is carried out by the methods of gas thermal diffusion, centrifugal and other methods based on the difference in the masses of 238 U and 235 U; in separation processes, uranium is used in the form of volatile UF 6 hexafluoride. When obtaining highly enriched Uranium or isotopes, their critical masses are taken into account; the most convenient method in this case is the reduction of uranium oxides with calcium; the resulting CaO slag is easily separated from uranium by dissolution in acids. To obtain powdered uranium, oxide (IV), carbides, nitrides and other refractory compounds, powder metallurgy methods are used.

Application of Uranus. Metallic uranium or its compounds are mainly used as nuclear fuel in nuclear reactors. A natural or low-enriched mixture of uranium isotopes is used in stationary reactors of nuclear power plants, a highly enriched product - in nuclear power plants or in reactors operating on fast neutrons. 235 U is the source of nuclear energy in nuclear weapons. 238 U serves as a source of secondary nuclear fuel - plutonium.

Uranium in the body In microquantities (10 -5 -10 -8%) it is found in the tissues of plants, animals and humans. In the ashes of plants (with the content of Uranium in the soil of about 10 -4%), its concentration is 1.5·10 -5%. To the greatest extent, Uranium is accumulated by some fungi and algae (the latter are actively involved in the biogenic migration of Uranus along the chain water - aquatic plants - fish - man). Uranium enters the body of animals and humans with food and water into the gastrointestinal tract, with air into the respiratory tract, as well as through the skin and mucous membranes. Uranium compounds are absorbed in the gastrointestinal tract - about 1% of the incoming amount of soluble compounds and no more than 0.1% of sparingly soluble ones; in the lungs, 50% and 20% are absorbed, respectively. Uranium is distributed unevenly in the body. The main depot (places of deposition and accumulation) is the spleen, kidneys, skeleton, liver, and, when sparingly soluble compounds are inhaled, the lungs and bronchopulmonary lymph nodes. In the blood, Uranium (in the form of carbonates and complexes with proteins) does not circulate for a long time. The content of uranium in the organs and tissues of animals and humans does not exceed 10 -7 g/g. Thus, the blood of cattle contains 1 10 -8 g/ml, liver 8 10 -8 g/g, muscles 4 10 -11 g/g, spleen 9 10 8-8 g/g. The content of Uranium in human organs is: in the liver 6 10 -9 g/g, in the lungs 6 10 -9 -9 10 -9 g/g, in the spleen 4.7 10 -7 g/g, in the blood 4-10 -10 g / ml, in the kidneys 5.3 10 -9 (cortical layer) and 1.3 10 -8 g / g (medulla), in the bones 1 10 -9 g / g, in in the bone marrow 1-10 -8 g/g, in the hair 1.3 10 -7 g/g. The uranium contained in the bone tissue causes its constant irradiation (the half-life of Uranus from the skeleton is about 300 days). The lowest concentrations of Uranium are in the brain and heart (10 -10 g/g). The daily intake of Uranium with food and liquids is 1.9 10 -6 g, with air - 7 10 -9 g. The daily excretion of Uranium from the human body is: with urine 0.5 10 -7 - 5 10 -7 g, with feces - 1.4 10 -6 -1.8 10 -6 g, with hair - 2 10 -8 g.

According to the International Commission on Radiation Protection, the average content of Uranium in the human body is 9·10 -5 g. This value may vary for different regions. It is believed that Uranium is necessary for the normal functioning of animals and plants.

The toxic effect of uranium is due to its chemical properties and depends on solubility: uranyl and other soluble compounds of uranium are more toxic. Poisoning by uranium and its compounds is possible at enterprises for the extraction and processing of uranium raw materials and other industrial facilities where it is used in the technological process. When it enters the body, Uranium acts on all organs and tissues, being a general cellular poison. Signs of poisoning are due to the predominant damage to the kidneys (the appearance of protein and sugar in the urine, subsequent oliguria); the liver and gastrointestinal tract are also affected. There are acute and chronic poisoning; the latter are characterized by gradual development and lesser severity of symptoms. In case of chronic intoxication, disorders of hematopoiesis, the nervous system, etc. are possible. It is believed that the molecular mechanism of action of Uranium is associated with its ability to suppress the activity of enzymes.

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 employees of a 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.