How is uranium ore mined? Why is uranium and its compounds dangerous? Uranium enrichment methods
In search of a cheaper source of energy that would not harm the environment, the world scientific society paid attention to the field of nuclear energy. To date, the number of nuclear reactors that are being built to generate energy is in the hundreds. Uranium ore is used as a raw material for generating nuclear energy. It contains substances that belong to the actinide family. According to some estimates, the earth contains 1000 times more uranium ore than gold. To obtain fuel for nuclear power plants, it is processed.
Characteristics of uranium ores
Uranium ore in free form is represented by a gray-white metal, which can have a fairly large amount of various impurities. It should be borne in mind that the purified uranium itself is considered a chemically active substance. Considering the physical-mechanical and Chemical properties uranium, note the following points:
- The boiling point of this chemical element is 4,200 degrees Celsius, which greatly complicates the process of its processing.
- In air, uranium oxidizes, can dissolve in acids and react with water. However, this chemical element does not interact with alkalis, which can be called its feature.
- With a certain impact, the substance becomes a source of a fairly large amount of energy. In this case, a relatively small amount of mining is formed, with the disposal of which today there are quite a few problems.
It should be borne in mind that many consider uranium a rare chemical element, since its concentration in earth's crust is 0.002%. With such a relatively low concentration of this chemical element, an alternative substance has not yet been found. Of course, as long as there are enough reserves for continuous mining of uranium and powering nuclear power plants or engines.
Uranium deposits
It is not difficult to guess that with such relatively small reserves of the substance in question in the bowels of the earth and the constant growth in demand for the material, its cost rises. Per recent times A fairly large number of uranium deposits were discovered, Australia is considered to be the leader in its production. The conducted studies indicate that more than 30% of all reserves are concentrated in the territory of this country. The largest deposits are:
- Beaverley;
- Olympic Dam;
- Ranger.
An interesting point is that Kazakhstan is considered to be the main competitor of Australia in the field of uranium ore mining. More than 12% of world reserves are concentrated on the territory of this country. Despite enough large area, in Russia only 5% of world reserves.
According to some information, Russia's reserves amount to 400,000 tons of uranium. At the end of 2017, 16 deposits were discovered and developed. Interestingly, 15 of them are concentrated in Transbaikalia. Most of the uranium ore is concentrated in the Streltsovsky ore field.
As previously noted, uranium ore is used as a fuel, which determines the ongoing search for its deposits. Today, uranium is often used as fuel for rocket engines. In production nuclear weapons this element is used to increase its power. Some manufacturers use it to produce pigments that are used in painting.
Mining of uranium ores
The extraction of uranium ore has been established in many countries. It should be borne in mind that today three technologies can be used for ore mining:
- When uranium is close to the earth's surface, discovery technology is used. It is quite simple and does not require large expenses. Excavators and other similar special equipment are used to lift raw materials. After lifting and loading into dump trucks, it is delivered to processing plants. Note that this technology has a fairly large number of disadvantages, but due to the ease of production, it has become widespread. During the development of deposits, quarries are obtained, the area of \u200b\u200bwhich can reach several square kilometers. It should be borne in mind that this method of mining ore causes irreparable harm to the environment. A fairly large number of large mining companies are engaged in surface mining of uranium.
- With a deep location of the ore in the thickness of the earth, the creation of mines is carried out. The technology is quite complicated in execution, it also provides for mechanical extraction of the material. There is a fairly large number of mines in which uranium and other ore are mined. Such a method of rock extraction is associated with rather large risks, since pockets of gas or underwater rivers can be found in the thickness of the earth. The collapse of the vaults can lead to the mothballing of the mine, the death of workers and damage to expensive equipment. However, in the case of a deep occurrence of the rock in question, it is almost impossible to extract it in a different way.
- The third method is the formation of wells into which sulfuric acid is pumped. Near the previously done well, a second one is created, which is designed to raise the already obtained solution. After the completion of the sorption process, equipment is installed that can raise substances resembling resins to the surface. After raising the resulting resin to the surface, it is processed and uranium is isolated.
Underground leachingRecently, the third method of uranium mining has been increasingly used. This is due to the fact that it allows you to achieve a high concentration of the desired substance with a minimum content of polluting chemical elements. However, such a technology requires accurate geological surveys, since well drilling should be carried out over the field of the considered chemical. Otherwise, when acid is added, the sorption process at a low uranium concentration will take quite a long time.
On the territory of Russia, in most cases, uranium mining is carried out by mechanical extraction. In addition, the extraction of raw materials for the production of nuclear fuel is carried out in China and Ukraine.
At present, nuclear energy is used in sufficient large scale. If in the last century radioactive materials were used mainly for the production of nuclear weapons, which have the greatest destructive power, then in our time the situation has changed. Nuclear energy at nuclear power plants is converted into electrical energy and used for completely peaceful purposes. Also created nuclear engines, which are used, for example, in submarines.
The main radioactive material used for the production of nuclear energy is Uranus. This chemical element belongs to the actinide family. Uranium was discovered in 1789 by the German chemist Martin Heinrich Klaproth while studying pitchblende, which is now also called "tar pitch". New chemical element named after newly discovered planet solar system. The radioactive properties of uranium were discovered only at the end of the 19th century.
Uranium is contained in the sedimentary shell and in the granite layer. This is a rather rare chemical element: its content in the earth's crust is 0.002%. In addition, uranium is found in insignificant amounts in sea water (10 −9 g/L). Due to its chemical activity, uranium is found only in compounds and does not occur in free form on Earth.
uranium ores called natural mineral formations containing uranium or its compounds in quantities in which it is possible and economically feasible to use it. Uranium ores also serve as raw materials for the production of other radioactive elements, such as radium and polonium.
Nowadays, about 100 different uranium minerals are known, 12 of which are actively used in industry to obtain radioactive materials. The most important minerals are uranium oxides (uranite and its varieties - pitchblende and uranium black), its silicates (coffinite), titanites (davidite and brannerite), as well as hydrous phosphates and uranium mica.
Uranium ores are classified according to various signs. In particular, they are distinguished by the conditions of education. One of the types is the so-called endogenous ores, which were deposited under the influence of high temperatures and from pegmatite melts and aqueous solutions. Endogenous ores are characteristic of folded areas and activated platforms. Exogenous ores are formed in near-surface conditions and even on the Earth's surface in the process of accumulation (syngenetic ores) or as a result (epigenetic ores). Occur mainly on the surface of young platforms. Metamorphogenic ores that arose during the redistribution of primary dispersed uranium in the process of metamorphism of sedimentary strata. Metamorphogenic ores are characteristic of ancient platforms.
In addition, uranium ores are divided into natural types and technological grades. By the nature of uranium mineralization, they distinguish: primary uranium ores - (U 4 + content is not less than 75% of the total), oxidized uranium ores (mainly contain U 6 +) and mixed uranium ores, in which U 4 + and U 6 + are in roughly equal proportions. The technology of their processing depends on the degree of oxidation of uranium. According to the degree of uneven content of U in the lumpy fraction of the mountain (“contrast”), very contrasting, contrasting, weakly contrasting and non-contrasting uranium ores are distinguished. This parameter determines the possibility and expediency of enrichment of uranium ores.
According to the size of aggregates and grains of uranium minerals, the following are distinguished: coarse-grained (over 25 mm in diameter), medium-grained (3–25 mm), fine-grained (0.1–3 mm), fine-grained (0.015–0.1 mm) and dispersed (less than 0.015 mm) uranium ores. The size of grains of uranium minerals also determines the possibility of enrichment of ores. According to the content of useful impurities, uranium ores are divided into: uranium, uranium-molybdenum, uranium-vanadium, uranium-cobalt-bismuth-silver and others.
According to the chemical composition of impurities, uranium ores are divided into: silicate (consist mainly of silicate minerals), carbonate (more than 10–15% of carbonate minerals), iron oxide (iron-uranium ores), sulfide (more than 8–10% of sulfide minerals) and caustobiolitic composed mainly of organic matter.
The chemical composition of ores often determines the way they are processed. From silicate ores, uranium is separated by acids, from carbonate ores by soda solutions. Iron oxide ores are subjected to blast-furnace smelting. Caustobiolitic uranium ores are sometimes enriched by incineration.
As mentioned above, the content of uranium in the earth's crust is quite small. There are several uranium ore deposits in Russia:
Zherlovoye and Argunskoye deposits. They are located in the Krasnokamensky district of the Chita region. The reserves of the Zherlovoye deposit are 4,137 thousand tons of ore, which contain only 3,485 tons of uranium (average content 0.082%), as well as 4,137 tons of molybdenum (content 0.227%). The reserves of uranium at the Argunskoye deposit in category C1 are 13,025 thousand tons of ore, 27,957 tons of uranium (average grade 0.215%) and 3,598 tons of molybdenum (average grade 0.048%). C2 category reserves are: 7990 thousand tons of ore, 9481 tons of uranium (with an average grade of 0.12%) and 3191 tons of molybdenum (average grade of 0.0489%). Approximately 93% of all Russian uranium is mined here.
5 uranium deposits ( Istochnoe, Kolichkanskoe, Dybrynskoe, Namarusskoe, Koretkondinskoe) are located on the territory of the Republic of Buryatia. The total explored reserves of the deposits amount to 17.7 thousand tons of uranium, the predicted resources are estimated at another 12.2 thousand tons.
Khiagdinsky uranium deposit. Extraction is carried out by the method of borehole underground leaching. The explored reserves of this field in category C1 + C2 are estimated at 11.3 thousand tons. The deposit is located on the territory of the Republic of Buryatia.
Radioactive materials are used not only to create nuclear weapons and fuel. For example, uranium is added in small amounts to glass to give it color. Uranium is a constituent of various metal alloys and is used in photography and other fields.
Uranium is a chemical element of the actinide family with atomic number 92. It is the most important nuclear fuel. Its concentration in the earth's crust is about 2 parts per million. Important uranium minerals include uranium oxide (U 3 O 8), uraninite (UO 2), carnotite (potassium uranyl vanadate), otenite (potassium uranyl phosphate), and torbernite (hydrous copper and uranyl phosphate). These and other uranium ores are sources of nuclear fuel and contain many times more energy than all known recoverable fossil fuel deposits. 1 kg of uranium 92 U gives as much energy as 3 million kg of coal.
Discovery history
The chemical element uranium is a dense, solid silver-white metal. It is ductile, malleable and can be polished. Metal oxidizes in air and ignites when crushed. Relatively poor conductor of electricity. Electronic formula uranium - 7s2 6d1 5f3.
Although the element was discovered in 1789 by the German chemist Martin Heinrich Klaproth, who named it after the newly discovered planet Uranus, the metal itself was isolated in 1841 by the French chemist Eugène-Melchior Peligot by reduction from uranium tetrachloride (UCl 4 ) with potassium.
Radioactivity
Creation periodic system Russian chemist Dmitri Mendeleev in 1869 focused on uranium as the heaviest known element, which it remained until the discovery of neptunium in 1940. In 1896, the French physicist Henri Becquerel discovered the phenomenon of radioactivity in it. This property was later found in many other substances. It is now known that radioactive uranium in all its isotopes consists of a mixture of 238 U (99.27%, half-life - 4,510,000,000 years), 235 U (0.72%, half-life - 713,000,000 years) and 234 U (0.006%, half-life - 247,000 years). This makes it possible, for example, to determine the age of rocks and minerals for studying geological processes and the age of the earth. To do this, they measure the amount of lead, which is the final product radioactive decay uranium. In this case, 238 U is the initial element, and 234 U is one of the products. 235 U gives rise to actinium decay series.
Opening a chain reaction
The chemical element uranium became the subject of wide interest and intensive study after the German chemists Otto Hahn and Fritz Strassmann discovered nuclear fission in it at the end of 1938 when bombarding it with slow neutrons. In early 1939, the American physicist of Italian origin Enrico Fermi suggested that among the products of the fission of the atom there could be elementary particles capable of starting a chain reaction. In 1939, the American physicists Leo Szilard and Herbert Anderson, as well as the French chemist Frederic Joliot-Curie and their colleagues, confirmed this prediction. Subsequent studies have shown that, on average, 2.5 neutrons are released during the fission of an atom. These discoveries led to the first self-sustaining nuclear chain reaction (12/02/1942), the first atomic bomb(07/16/1945), its first use during military operations (08/06/1945), the first nuclear submarine (1955) and the first full-scale nuclear power plant (1957).
Oxidation states
The chemical element uranium, being a strong electropositive metal, reacts with water. It dissolves in acids, but not in alkalis. Important oxidation states are +4 (as in UO 2 oxide, tetrahalides such as UCl 4 , and the green water ion U 4+) and +6 (as in UO 3 oxide, UF 6 hexafluoride, and UO 2 2+ uranyl ion). In an aqueous solution, uranium is most stable in the composition of the uranyl ion, which has a linear structure [O = U = O] 2+ . The element also has +3 and +5 states, but they are unstable. Red U 3+ oxidizes slowly in water that does not contain oxygen. The color of the UO 2 + ion is unknown because it undergoes disproportionation (UO 2 + is simultaneously reduced to U 4+ and oxidized to UO 2 2+ ) even in very dilute solutions.
Nuclear fuel
When exposed to slow neutrons, the fission of the uranium atom occurs in the relatively rare isotope 235 U. This is the only natural fissile material, and it must be separated from the isotope 238 U. However, after absorption and negative beta decay, uranium-238 turns into a synthetic element plutonium, which is split by the action of slow neutrons. Therefore, natural uranium can be used in converter and breeder reactors, in which fission is supported by rare 235 U and plutonium is produced simultaneously with the transmutation of 238 U. Fissile 233 U can be synthesized from the thorium-232 isotope, which is widespread in nature, for use as nuclear fuel. Uranium is also important as the primary material from which synthetic transuranium elements are obtained.
Other uses of uranium
Compounds of the chemical element were previously used as dyes for ceramics. Hexafluoride (UF 6) is a solid with an unusual high pressure vapor (0.15 atm = 15,300 Pa) at 25 °C. UF 6 is chemically very reactive, but despite its corrosive nature in the vapor state, UF 6 is widely used in gas diffusion and gas centrifuge methods to obtain enriched uranium.
Organometallic compounds are an interesting and important group of compounds in which metal-carbon bonds connect a metal to organic groups. Uranocene is an organouranium compound U(C 8 H 8) 2 in which the uranium atom is sandwiched between two layers of organic rings bonded to C 8 H 8 cyclooctatetraene. Its discovery in 1968 opened up a new field of organometallic chemistry.
Depleted natural uranium is used as a means of radiation protection, ballast, in armor-piercing projectiles and tank armor.
Recycling
The chemical element, although very dense (19.1 g / cm 3), is a relatively weak, non-flammable substance. Indeed, the metallic properties of uranium seem to place it somewhere between silver and other true metals and non-metals, so it is not used as a structural material. The main value of uranium lies in the radioactive properties of its isotopes and their ability to fission. In nature, almost all (99.27%) of the metal consists of 238 U. The rest is 235 U (0.72%) and 234 U (0.006%). Of these natural isotopes, only 235 U is directly fissioned by neutron irradiation. However, upon absorption, 238 U forms 239 U, which eventually decays into 239 Pu, a fissile material having great importance for nuclear energy and nuclear weapons. Another fissile isotope, 233 U, can be produced by neutron irradiation with 232 Th.
crystalline forms
The characteristics of uranium cause it to react with oxygen and nitrogen even under normal conditions. At higher temperatures, it reacts with a wide range of alloying metals to form intermetallic compounds. The formation of solid solutions with other metals is rare due to the special crystal structures, formed by atoms element. Between room temperature and a melting point of 1132 °C, uranium metal exists in 3 crystalline forms known as alpha (α), beta (β) and gamma (γ). The transformation from α- to β-state occurs at 668 °C and from β to γ - at 775 °C. γ-uranium has a body-centered cubic crystal structure, and β - tetragonal. The α phase consists of layers of atoms in a highly symmetrical orthorhombic structure. This anisotropic distorted structure prevents the alloying metal atoms from replacing the uranium atoms or occupying the space between them in the crystal lattice. It was found that only molybdenum and niobium form solid solutions.
Ores
The Earth's crust contains about 2 parts per million of uranium, which indicates its wide distribution in nature. The oceans are estimated to contain 4.5 x 109 tons of this chemical element. Uranium is an important constituent of over 150 different minerals and a minor constituent of another 50. Primary minerals found in igneous hydrothermal veins and in pegmatites include uraninite and its variety pitchblende. In these ores, the element occurs in the form of dioxide, which, due to oxidation, can vary from UO 2 to UO 2.67. Other economically significant products from uranium mines are autunite (hydrated calcium uranyl phosphate), tobernite (hydrated copper uranyl phosphate), coffinite (black hydrated uranium silicate) and carnotite (hydrated potassium uranyl vanadate).
It is estimated that more than 90% of known low-cost uranium reserves are found in Australia, Kazakhstan, Canada, Russia, South Africa, Niger, Namibia, Brazil, China, Mongolia and Uzbekistan. Large deposits are found in the conglomerate rock formations of Elliot Lake, located north of Lake Huron in Ontario, Canada, and in the South African Witwatersrand gold mine. Sand formations in the Colorado Plateau and in the Wyoming Basin of the western United States also contain significant uranium reserves.
Mining
Uranium ores are found both in near-surface and deep (300-1200 m) deposits. Underground, the seam thickness reaches 30 m. As in the case of ores of other metals, uranium mining at the surface is carried out by large earth-moving equipment, and the development of deep deposits is carried out by traditional methods of vertical and inclined mines. The world production of uranium concentrate in 2013 amounted to 70 thousand tons. The most productive uranium mines are located in Kazakhstan (32% of the total production), Canada, Australia, Niger, Namibia, Uzbekistan and Russia.
Uranium ores usually contain only a small amount of uranium-bearing minerals, and they cannot be smelted by direct pyrometallurgical methods. Instead, hydrometallurgical procedures should be used to extract and purify uranium. Increasing the concentration greatly reduces the load on the processing circuits, but none of the conventional beneficiation methods commonly used for mineral processing, such as gravity, flotation, electrostatic and even hand sorting, are applicable. With few exceptions, these methods result in a significant loss of uranium.
Burning
The hydrometallurgical processing of uranium ores is often preceded by a high-temperature calcination step. Firing dehydrates the clay, removes carbonaceous materials, oxidizes sulfur compounds to harmless sulfates, and oxidizes any other reducing agents that may interfere with subsequent processing.
Leaching
Uranium is extracted from roasted ores with both acidic and alkaline aqueous solutions. For all leaching systems to function successfully, the chemical element must either initially be present in the more stable 6-valent form or be oxidized to this state during processing.
Acid leaching is usually carried out by stirring a mixture of ore and lixiviant for 4-48 hours at a temperature environment. Except in special circumstances, sulfuric acid is used. It is served in quantities sufficient to obtain the final liquor at pH 1.5. Sulfuric acid leaching schemes typically use either manganese dioxide or chlorate to oxidize tetravalent U 4+ to 6-valent uranyl (UO 2 2+). As a rule, about 5 kg of manganese dioxide or 1.5 kg of sodium chlorate per ton is sufficient for the oxidation of U 4+. In any case, oxidized uranium reacts with sulfuric acid to form the 4- uranyl sulfate complex anion.
Ore containing a significant amount of basic minerals such as calcite or dolomite is leached with a 0.5-1 molar sodium carbonate solution. Although various reagents have been studied and tested, the main oxidizing agent for uranium is oxygen. Ores are usually leached in air at atmospheric pressure and at a temperature of 75-80 °C for a period of time that depends on the specific chemical composition. Alkali reacts with uranium to form a readily soluble complex ion 4-.
Before further processing, solutions resulting from acid or carbonate leaching must be clarified. Large-scale separation of clays and other ore slurries is accomplished through the use of effective flocculating agents, including polyacrylamides, guar gum, and animal glue.
Extraction
Complex ions 4- and 4- can be sorbed from their respective leaching solutions of ion exchange resins. These special resins, characterized by their sorption and elution kinetics, particle size, stability and hydraulic properties, can be used in various processing technologies, such as fixed and moving bed, basket type and continuous slurry ion exchange resin method. Usually, solutions of sodium chloride and ammonia or nitrates are used to elute adsorbed uranium.
Uranium can be isolated from acid ore liquors by solvent extraction. In industry, alkyl phosphoric acids, as well as secondary and tertiary alkylamines, are used. As a general rule, solvent extraction is preferred over ion exchange methods for acidic filtrates containing more than 1 g/l uranium. However, this method is not applicable to carbonate leaching.
The uranium is then purified by dissolving in nitric acid to form uranyl nitrate, extracted, crystallized and calcined to form UO 3 trioxide. The reduced UO2 dioxide reacts with hydrogen fluoride to form tetrafluoride UF4, from which metallic uranium is reduced by magnesium or calcium at a temperature of 1300 °C.
Tetrafluoride can be fluorinated at 350 °C to form UF 6 hexafluoride, which is used to separate enriched uranium-235 by gas diffusion, gas centrifugation, or liquid thermal diffusion.
Uranium ore is a natural mineral formation that contains uranium in such quantity, concentration and combination that its extraction becomes economically profitable and expedient. There is a lot of uranium in the bowels of the earth. For example in nature:
- uranium is 1000 times more than gold;
- 50 times more than silver;
- uranium reserves are almost equal to those of zinc and lead.
Particles of uranium are found in soil, rock, sea water. A very small part of it is concentrated in the deposits. Known, explored uranium deposits are estimated at 5.4 million tons.
Characteristics and types
The main types of uranium-bearing ores: oxides (uranites, uranium resins, uranium blacks), silicates (coffinites), titanates (brannerites), uranyl silicates (uranophanes, betauranotyls), uranyl-vanadates (carnotites), tyuyamunites, uranyl phosphates (otenites, torbenites). Containing Zr, TR, Th, Ti, P minerals (fluorapatites, monazites, zircons, orthites…) often also include uranium. There is also adsorbed uranium in carbonaceous rock.
Field and production
The three leading countries in terms of uranium ore reserves are Australia, Kazakhstan, and Russia. Almost 10% of the world's uranium reserves are concentrated in Russia, and in our country, two-thirds of the reserves are localized in Yakutia (Republic of Sakha). The largest Russian deposits of uranium are in such deposits: Streltsovskoye, Oktyabrskoye, Anteyskoye, Malo-Tulukuevsky, Argunskoye, Dalmatovsky, Khiagdinskoye ... There are still a great number of smaller deposits and deposits.
Application of uranium ores
- The most important application is nuclear fuel. The most used isotope is U235, which can be the basis for a self-sustaining nuclear chain reaction. It is used in nuclear reactors, weapons. The isotope U238 fission increases the power of thermonuclear weapons. U233 is the most promising fuel for a gas-phase nuclear rocket engine.
- Uranium is able to actively release heat. Its heat generating capacity is a thousand times more powerful than oil or natural gas.
- Geologists use uranium to determine the age of rocks and minerals. There is even such a science - geochronology.
- It is sometimes used in the construction of aircraft, photography, painting (it has a beautiful yellow-green tint).
- Iron + U238 = magnetostrictive material.
- Depleted uranium is used to manufacture radiation protection equipment.
- There are many more functions that uranium performs.
Uranium (U) mining is of great importance for modern society. This is the heaviest metal used in the nuclear industry as a fuel, it is used to make nuclear weapons. For peaceful purposes, they are used for the production of glass and paints and varnishes. Pure uranium in natural conditions does not occur, it is part of minerals and ore.
world reserves
Currently, uranium mining is carried out in the territory a large number deposits. AT earth layer at a depth of twenty kilometers is an impressive number of tons of uranium ore, capable of supplying mankind with fuel for many centuries to come. Uranium is mined in 28 countries of the world. But the main world reserves belong to 10 states that share 90% of the market.
Australia. There are 19 large deposits in this country. U reserves in them amount to 661,000 tons (the share is 31.18% of all world deposits).
Kazakhstan. It has 16 large U production points. The volume of deposits is 629,000 tons, which is 11.81% of the total share of reserves in the world.
Russia. The share of the Russian Federation in the world uranium industry is 9.15%. U reserves are 487,000 tons. U production is forecast to increase to 830,000 tons.
Canada. Ore reserves are at around 468,000 tons, which occupies 8.80% of the world market. Uranium mining is 9 thousand tons per year.
Niger. Uranium deposits in the country amount to 421,000 tons, which is 7.9% of the total share of world reserves. 4 deposits produce 4.5 thousand tons of U per year.
SOUTH AFRICA. U reserves in the country amount to 297,000 tons; which occupies about 6% of the share of world reserves. In South Africa, 540 tons of uranium are mined per year.
Brazil. The country's indicator is 276,700 tons of uranium ore. U production per year is 198 tons per year.
Namibia. The country's uranium reserves are 261,000 tons. There are four large U deposits in Namibia.
USA. The total U reserves in the USA are 207,000 tons.
China. The country's indicator is 166,000 tons. About 1.5 thousand tons of uranium ore are mined in the DPRK per year.
The world's largest deposits of uranium
№ | Country | Quantity | Name of fields | Uranium mining volume per year |
1 | Australia | 19 | Olympic Dam | 3 thousand tons 1 thousand tons |
2 | Kazakhstan | 16 | Korsan Budenovskoye Western Mynkuduk Southern Yingkai | |
3 | Russia | 7 | Chita region: Argun, Zherlovoe, Istochnoe, Namarusskoe Koretkondinskoe, Kolichkanskoe, Dybrynskoe | 27957 thousand tons 17.7 thousand tons in total |
4 | Canada | 18 | MacArthur River waterbury | |
5 | Niger | 4 | Imuraren, Madauela, Azelit, Arlit | |
6 | South Africa | 5 | Dominion, Western Aries, Palabora, Randfontein and Vaal River | |
7 | Brazil | 3 | Santa Quiteria, Pocos de Caldas, Lagoa Real |
In Russia, Rosatom Corporation controls the main uranium mining assets. It unites the International mining division of Uranium One and has a portfolio of shares in the USA, Kazakhstan and Tanzania.
Characteristics of uranium ores
Types of uranium
Natural uranium consists of the interaction of 3 isotopes: U238, U235, U234. The radioactive properties of the metal are affected by isotopes 238 and its daughter nucleotide 234. Due to the presence of these atoms in U, uranium is used in the production of fuel for nuclear power plants and nuclear weapons. Although the activity of the U235 isotope is 21 times weaker, it is able to maintain a nuclear chain reaction without third-party active elements.
In addition to natural isotopes, there are also artificial U atoms.
At least 23 species are known. The U233 isotope deserves special attention; it is formed when thorium-232 is irradiated with neutrons and fissions under the influence of thermal neutrons. This ability makes U233 an optimal energy source for nuclear reactors.
Ore classification
The concept of natural uranium ore refers to a mineral formation with a high concentration of uranium. During the development of uranium deposits, as a rule, other radioactive metals - radium and polonium - are adjacently obtained. Rocks containing uranium can vary in composition. The structure of the layers affects the way the valuable metal is mined.
According to the formation conditions, ore can be divided into:
- endogenous;
- exogenous;
- metamorphogenic.
According to the type of mineralization, uranium ores are distinguished:
- primary;
- oxidized;
- mixed.
Grain size classification:
- dispersed (<0,015 мм);
- fine-grained (0.015–0.1 mm);
- fine-grained (0.1–3 mm);
- medium-grained (3 to 25 mm);
- coarse-grained (> 25 mm).
- molybdenum;
- anadium;
- uranium-cobalt-nickel-bismuth;
- monoore.
Classification by chemical composition:
- carbonate;
- iron oxide;
- silicate;
- sulfide;
- caustobiol.
The ore is divided according to the processing method:
- soda solution, used if carbonate is present in the chemical composition of the ore;
- acid is used for silicate rocks;
- the blast furnace method is used if iron oxide in its composition.
- poor (< 0,1%);
- ordinary (0.25–0.1%);
- medium (0.5–0.25%);
- rich (1–0.5%);
- very rich (>1% U).
It makes sense to mine uranium if its content in the earth layer is at least 0.5%. If there is less than 0.015% uranium in the rock layer, it is mined as a by-product.
Methods for mining uranium ore
There are three main ways to mine uranium:
- open (or career);
- mine (underground);
- leaching.
All these methods depend on many factors. For example, from the depth of rock deposits, the composition of isotopes, etc.
It is applicable in the case when the rock is not deep and in order to extract it, it is enough to arm yourself with special equipment:
- dump trucks;
- bulldozers;
- loaders.
The quarry method of uranium mining has been used for quite a long time. One of the advantages of this method is the minimal risk of radiation exposure for miners. But a significant disadvantage of the open method is the irreparable environmental damage to the land that is under development.
Mining method of extraction is more costly, with material point vision. To extract uranium, mines are drilled, up to two kilometers deep, if mining is carried out deeper than this mark, the fuel will turn out to be very expensive. In any case, mining companies are required to equip miners with all related equipment, radiation protection. AND Install the necessary ventilation systems to remove radon and supply the mine with fresh air. At the mine, metal is extracted from the rock mass by drilling and blasting.
The leaching method of uranium mining is considered optimal. Wells are drilled in the rock, through which a solution is pumped - a leaching agent with a special chemical composition. It dissolves in the depths of ore deposits and is saturated with valuable metal compounds.
conclusions
Uranium mining using underground leaching does significantly less harm to the environment than the methods described above. Over time, reclamation processes take place on the developed land plot. The application of this method can reduce economic costs. But he has his limitations. It is not used only in sandstone and below the water table.