URANIUM ORES (a. uranium ores; n. Uranerze; f. minerais uraniferes, minerais d"uranium; i. minerales de urania, minerales uraniсos) - natural mineral formations containing uranium in such concentrations, quantities and compounds at which its industrial production is economically feasible.
The main ore minerals: oxides - uraninite, uranium tar, uranium black; silicates - coffinit; titanates - brannerite; uranyl silicates - uranophane, betauranotyl; uranyl vanadates - carnotite, tyuyamunite; uranyl phosphates - otenite, torbernite. In addition, uranium in ores is often part of minerals containing P, Zr, Ti, Th and TR (fluorapatite, leucoxene, monazite, zircon, orthite, thorianite, davidite, etc.), or is in a sorbed state in carbonaceous matter.
Uranium ores are usually distinguished: super-rich (more than 0.3% U), rich (0.1-0.3%), ordinary (0.05-0.10%), poor (0.03-0.05%) and off-balance sheet (0.01-0.03%). Very large include uranium deposits with reserves (thousand tons) of more than 50, large - from 10 to 50, medium - from 1 to 10, small - 0.2-1.0 and very small - less than 0.2 .
Uranium ores are varied in terms of formation conditions, nature of occurrence, mineral composition, presence of associated components, and methods of development. Sedimentary uranium ores (exogenous syngenetic) include strata Paleogene deposits of the organogenic-phosphate type (deposits of fish bone detritus enriched in U and TR) and Early Proterozoic quartz-pebble uranium-bearing conglomerates of the Elliot Lake areas in Canada (with Th, Zr, Ti), Witwatersrand in South Africa (with Au) and Jacobina in Brazil (with Au). Ores, as a rule, are ordinary and poor. Among the infiltration deposits (exogenous epigenetic) there are soil-, reservoir- and fissure-infiltration deposits. The leading among them are coffinit-cherniye deposits of the bed-infiltration type, where uranium ores occur in permeable rocks of artesian basins and are controlled by the boundaries of zones of bed oxidation. Ore deposits have the shape of rolls (elongated crescent-shaped bodies) or lenses. The ores are predominantly ordinary and poor, sometimes complex with Se, Re, Mo, V, Sc (deposits of the arid regions of the CCCP, Wyoming, Niger).
Among the soil-infiltration deposits, of industrial interest are mainly uranium-coal deposits, where uranium and accompanying mineralization is localized in the roof of the layers, in contact with oxidized sands, as well as near-surface deposits of carnotite ores in “calcrete” and “hypcrete” (carbonate and gypsum soil formations of river paleovalleys) in Australia (Yilirri deposit) and Namibia. This group is adjacent to stratiform uranium-bitumen deposits in terrigenous and carbonate rocks, where the ore material is represented by pitchblende-containing kerites and anthraxolites (deposits of the Grante belt in the USA, Banata in Romania). These ore objects, together with infiltration ones, are sometimes combined into “sandstone” type deposits (ordinary and poor ores). Their possible metamorphosed analogs are the deposits of the Franceville ore district in Gabon, among them the unique Oklo deposit. Hydrothermal deposits (endogenous epigenetic medium-low temperature) are mainly veins and vein-stockworks, less often sheet-like. They are divided into uranium proper (including uranium carbonate veins), molybdenum-uranium (often with Pb, As, Zn and other chalcophiles), titanium-uranium, phosphorus-uranium (with Zr, Th). The main ore minerals: pitchblende, coffinitite, brannerite (in uranium-thorium ores), uranium-containing fluorapatite (in phosphorus-uranium ores). Secondary uranyl silicates, uranyl phosphates, and uranyl arsenates are developed in oxidation zones. Ores are ordinary and rich. This group includes deposits in volcano-tectonic structures and basement rocks of a number of areas of the CCCP, Ore Mountains, Massif Central, Beaverlodge and Great Bear Lake areas in Canada, the USA (Marysvale), Australia (Mount Isa and Westmoreland areas). Adjacent to this group are metasomatic deposits of the “unconformity” type, identified in Canada (Rabbit Lake, Key Lake, etc. ore districts) and Northern Australia (Alligator River region). They are characterized by control of mineralization by surfaces of stratigraphic unconformity, sheet-like or sheet-vein morphology, unusual high content uranium in ores (0, n - n%). The main ore minerals: pitchblende, uraninite, coffinitite, brannerite. A unique stratiform deposit of complex ores has been discovered in Australia. Uranium industry.
In the 80s Uranium ores with a mining cost of less than $80/kg of uranium were profitable for mining. The total reserves and resources of uranium, including potential, in industrialized capitalist and developing countries are estimated at 14 million tons (without associated uranium). The main reserves of uranium ores (thousands of tons) in these countries are concentrated in Australia (465), Canada (180), South Africa, Niger, Brazil, USA (133) and Namibia. Approximately 31% of the total reserves are deposits of the “unconformity” type, 25% are of the “sandstone” type, 16% are of uranium-bearing conglomerates, 14% are of the “porphyry” type, etc.
The world annual production of uranium concentrates in these countries in 1988 was 37.4 thousand tons of uranium with an average cost of 30 dollars per kg (beginning of 1989).
When the radioactive elements of the periodic table were discovered, man eventually came up with a use for them. This happened with uranium. It was used for both military and peaceful 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 the nature of uranium pure form does not exist - it is a component of ores and minerals. The main uranium ores are carnotite and pitchblende. Also, significant deposits of this strategic mineral were 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 earth's surface. All of them contain a huge number of tons of uranium. This amount can provide humanity with energy for many hundreds of years to come. The leading countries in which uranium ore is found in the largest volumes are Australia, Kazakhstan, Russia, Canada, South Africa, Ukraine, Uzbekistan, USA, Brazil, Namibia.
Types of uranium
Radioactivity determines the properties chemical element. Natural uranium is composed of three isotopes. Two of them are the founders of the radioactive series. Natural isotopes of uranium are used to create fuel for nuclear reactions and weapons. Uranium-238 also 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 U235 isotope is 21 times weaker, although it is successfully used for the above purposes - it has the ability to support without additional catalysts.
In addition to natural ones, there are also artificial isotopes of uranium. Today there are 23 known of them, the most important of them is U233. It is distinguished by its 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 strata in which it is found can vary in type. The extraction methods also depend on this. Uranium ore is classified according to the following parameters:
- Conditions of formation - endogenous, exogenous and metamorphogenic ores.
- The nature of uranium mineralization is primary, oxidized and mixed uranium ores.
- Aggregate and grain size of minerals - coarse-grained, medium-grained, fine-grained, fine-grained and dispersed fractions of ore.
- Usefulness of impurities - molybdenum, vanadium, etc.
- The composition of impurities is carbonate, silicate, sulfide, iron oxide, caustobiolite.
Depending on how the uranium ore is classified, there is a method for extracting the chemical element from it. Silicate is treated with various acids, carbonate - soda solutions, caustobiolite is enriched by combustion, and iron oxide is smelted 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 located in the lithosphere layer. Uranium ore is mined in three ways. It is economically feasible to isolate an element from rock when its content is 0.05-0.5%. There are mine, quarry and leaching methods 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 in shallow deposits. The risk of radiation exposure is minimal. There are no problems with equipment - bulldozers, loaders, and dump trucks are widely used.
Mine mining is more complex. This method is used when the element occurs at a depth of up to 2 kilometers and is economically profitable. The rock must contain a high concentration of uranium in order for it to be worth mining. The adit provides maximum safety, this is due to the way uranium ore is mined underground. Workers are provided with special clothing and work hours are strictly limited. The mines are equipped with elevators and enhanced ventilation.
Leaching - the third method - is the cleanest from an environmental point of view and the safety of mining company employees. A special chemical solution is pumped through a system of drilled wells. It dissolves in the formation and is saturated with uranium compounds. The solution is then pumped out and sent to processing plants. This method is more progressive, it allows you to reduce economic costs, although there are whole line restrictions.
Deposits in Ukraine
The country turned out to be the lucky owner of deposits of the element from which it is produced. According to forecasts, uranium ores of 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 developed. Some of the uranium was used domestically, and some was exported.
The main deposit is considered to be the Kirovograd uranium ore district. The uranium content 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 large deposit is Novokonstantinovskoye. The uranium content in the rock made it possible to reduce the cost by almost 2 times compared to Kirovograd. However, since the 90s, no development has been carried out; all the mines have been flooded. Due to the worsening political relations with Russia, Ukraine may be left without fuel for
Russian uranium ore
In terms of uranium production, 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. In the Chita region, 93% of all mined Russian uranium is mined (mainly by quarry and mine methods).
The situation is a little different with the deposits in Buryatia and Kurgan. Uranium ore in Russia in these regions is deposited in such a way that it allows the extraction of raw materials by leaching.
In total, deposits of 830 tons of uranium are predicted in Russia; 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 be inaccurate, since much of the data is classified and only a certain category of people has access to it.
In a message from the Iraqi Ambassador to the UN Mohammed Ali al-Hakim dated July 9, it is said that ISIS extremists (Islamic State of Iraq and the Levant) are at their disposal. The IAEA (International Atomic Energy Agency) hastened to declare that the nuclear substances previously used by Iraq have low toxic properties, and therefore the materials seized by the Islamists.
A US government source familiar with the situation told Reuters that the uranium stolen by the militants was most 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 on them to “prevent the threat of its use,” RIA Novosti reports.
Uranium compounds are extremely dangerous. AiF.ru talks about what exactly, as well as who and how can produce nuclear fuel.
What is uranium?
Uranium is a chemical element with atomic number 92, a silvery-white shiny metal, designated in the periodic table by the symbol U. In its pure form, it is slightly softer than steel, malleable, flexible, found in earth's crust(lithosphere) and in sea water and is practically never found in its pure form. 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 uranium nucleus with neutrons and made a discovery: capturing a free neutron, the uranium isotope nucleus divides and releases enormous energy due to the kinetic energy of fragments and radiation. In 1939-1940 Yuliy Khariton And Yakov Zeldovich for the first time theoretically explained that with a small enrichment of natural uranium with uranium-235, it is possible to create conditions for the continuous fission of atomic nuclei, that is, give the process a chain character.
What is enriched uranium?
Enriched uranium is uranium that is produced using technological process of increasing the share of the 235U isotope in uranium. As a result, natural uranium is divided into enriched uranium and depleted uranium. After 235U and 234U are extracted from natural uranium, the remaining material (uranium-238) is called "depleted uranium" because it is depleted in the 235 isotope. According to some estimates, the United States stores about 560,000 tons of depleted uranium hexafluoride (UF6). Depleted uranium is half as radioactive as natural uranium, mainly due to the removal of 234U from it. Because the primary use of uranium is energy production, depleted uranium is a low-use product with low economic value.
In nuclear energy, only enriched uranium is used. The most widely used isotope of uranium is 235U, in which a self-sustaining nuclear chain reaction is possible. Therefore, this isotope is used as fuel in nuclear reactors and nuclear weapons. Isolation of the U235 isotope from natural uranium is a complex technology that not many countries can implement. Uranium enrichment allows nuclear production nuclear weapon- single-phase or single-stage explosive devices in which the main energy output comes from the nuclear reaction of fission 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 that use 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 cannon of an A-10 aircraft) with a diameter of about 20 mm is made of 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 producing 94% of world 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 permissible concentration (MPC) in the air is 0.015 mg/m³, for insoluble forms of uranium the MAC is 0.075 mg/m³. When uranium enters the body, it affects all organs, being a general cellular poison. Uranium, like many other heavy metals, almost irreversibly binds to proteins, primarily to sulfide groups of amino acids, disrupting their function. The molecular mechanism of action of uranium is associated with its ability to suppress enzyme activity. The kidneys are primarily affected (protein and sugar appear in the urine, oliguria). With chronic intoxication, disorders of hematopoiesis and the nervous system are possible.
Use of uranium for peaceful purposes
- A small addition of uranium gives the glass a beautiful yellow-green color.
- 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 (painted 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 color (tint) positives (photographic prints) brown.
- Alloys of iron and depleted uranium (uranium-238) are used as powerful magnetostrictive materials.
An isotope is a variety of atoms of a chemical element that have the same atomic (ordinal) number, but different mass numbers.
An element of group III of the periodic table, belonging to the actinides; heavy, slightly radioactive metal. Thorium has a number of applications in which it sometimes plays an irreplaceable role. The position of this metal in the periodic table of elements and the structure of the nucleus predetermined its use in the field of peaceful uses of atomic energy.
*** Oliguria (from the Greek oligos - small and ouron - urine) - a decrease in the amount of urine excreted by the kidneys.
A feature of the development of uranium deposits is the possibility of using both conventional mining methods (open-pit and underground) and underground (borehole, block) and heap leaching methods. Prevalence in the world in various ways uranium mining: underground 37%, open pit 24%, associated mining 18%, borehole underground leaching 12%, undetermined 7%.
When mining and producing uranium, various precautions are taken to protect the health of personnel:
- - The dust level is carefully controlled to minimize the entry of y- or a-emitting substances into the body. Dust is the main source of radioactive exposure. It typically contributes 4 mSv/year to the annual dose received by personnel.
- - External radioactive exposure of personnel in mines, factories and waste disposal sites is limited. In practice, the level of external exposure from ore and waste is usually so low that it has little effect on increasing the permissible annual dose.
- - Natural ventilation of open deposits reduces the level of exposure to radon and its daughter isotopes. The level of exposure from radon does not exceed 1% of the level permissible for continuous exposure of personnel. Underground mines are equipped with ventilation systems to achieve the same level. In Australian and Canadian underground mines, the average radiation dose is ~3 mSv/year.
- - There are strict hygiene standards for personnel working with uranium oxide concentrate, since it is chemically toxic, like lead oxide. In practice, precautions are taken to protect the respiratory system from ingestion of toxins, similar to those used when working in lead smelters.
Let us dwell on the main methods of mining uranium raw materials in a little more detail.
Mine method of uranium mining- one of the main methods of uranium production. The organization of work is similar to the methods of mining of other metals, but there are also differences. Uranium ores most often occur in the form of narrow layers, which leads to the formation of a mine in the form of branched drifts. Since the development of uranium ore is carried out on one horizon with the formation of drifts and mining blocks located close to the main haulage, the formation of dust is largely localized. The lack of air circulation from one block to another does not cause their mutual contamination, and the formation of dust in uranium mines is not great.
When operating underground uranium mines, the mine water is constantly pumped out and sent to the hydrometallurgical plant into a closed technological water circulation system. Powerful ventilation prevents radon from concentrating in the air. If the ventilation is turned off after the end of the work shift, then the atmospheric concentrations of radon and its daughter products increase sharply, and therefore, before the start of the next shift, it is necessary to reduce these concentrations to the maximum permissible
The main danger for uranium miners comes from inhaling air containing radon released from the ore. Uranium ores, in addition to uranium, contain all other members of the radioactive series, in which it is the parent nuclide. The greatest danger to the health of miners are the following elements of this family: 222 Rn, 21t *Pb, 211 Bi and 21 "Po. The content of radon in the mine atmosphere is determined by the rate of emanation, the rate of ventilation and the half-life of radon. The immediate daughter products of radon decay have a short half-life and quickly accumulate in the atmosphere, even if radon enters the mine without daughter products.
Due to the fact that the relative harmfulness of radon daughter products is greater than the harmfulness of radon itself, control of radioactive air pollution in uranium mines can be carried out based on its decay products. As an acceptable working level for the content of daughter products of radon decay in a mine atmosphere, a “latent energy” value equal to 1.3*15 MeV/l of air is proposed.
A popular method of mining uranium is open pits (some of them are up to 500 m deep). It is believed that the radiation danger of such quarries for miners is much less than that of underground mines. However, for environment Open-pit mining of uranium can pose a serious danger due to dust entrainment. Landscape changes, disturbance of vegetation cover, adverse effects on local fauna are inevitable consequences open-pit mining. The difficult task is to backfill the quarry with waste rock and reclaim it after the completion of mining operations.
There are rules and laws that define environmental protection measures, stipulate requirements such as preliminary
environmental impact assessments; gradual implementation of a restoration program, including restoration of landscapes and forests, planting of endogenous flora, restoration of endogenous wildlife; as well as checking the compliance of the environment with existing standards.
Rice. 4. Uranium mining using underground leaching method.
Extraction by solution
(in situ leaching) involves injecting an alkaline or acidic liquid (such as sulfuric acid) through boreholes into uranium ore deposits and pumping them back out. This method does not require the removal of ore from the mining site, but can only be used where uranium deposits are located in an aquifer in permeable rock and are not too deep (-200 m).
The advantages of this technology are a reduced risk of accidents and radiation exposure for personnel, low cost, and does not require much space for waste storage. The main disadvantages are the risk of leaching liquids diverting from the uranium deposit and subsequent contamination of groundwater, and the inability to restore natural conditions in the leaching zone after the end of operations. The resulting contaminated mixture is either transported to reservoirs or sent to deep disposal wells.
Leaching - extraction of one or more components from ores, concentrates, production waste with an aqueous solution containing an alkali, acid or other reagent, as well as using certain types bacteria; a special case of extraction from the solid phase. Leaching is usually accompanied by chemical reaction, as a result of which the extracted component passes from a form insoluble in water to soluble.
In-situ leaching - in-situ leaching of uranium ores. It involves injecting sulfuric acid into the ore mass and eliminates the problem of tailings storage, but under unfavorable conditions it can cause groundwater contamination.
Leaching is based on the ability of the extracted substance to dissolve better than others. Solvents - a solution of ammonia, acids, alkalis, metal or chlorine chlorides, sulfates, etc. Leaching may be accompanied by oxidation of the extracted material in order to convert sparingly soluble compounds into readily soluble ones (oxidative leaching). Gases (air, oxygen), liquid and solid inorganic substances (HN0 3, Mn0 2, KMn0 4, etc.), bacteria (bacterial leaching) are used as oxidizers.
Borehole in-situ leaching is used in the development of reservoir deposits. The conditions for its applicability are high permeability and water content of the ore-bearing environment. When using this method, the field is divided into polygons, sequentially drilled by systems of injection and extraction wells, with two or three or more extraction wells per injection well. The time of leaching of uranium from rocks at each site is 1^-3 years. Depending on the composition of the working solutions used, an acid scheme for uranium leaching (solutions of sulfuric acid) and a carbonate scheme (solutions of sodium and ammonium carbonates-bicarbonates) are distinguished.
In-situ leaching involves pumping a leach solution underground directly into an ore body or into a layer of specially prepared ore and pumping the solution that has percolated through the ore layer to the surface. There are two main options for underground leaching - borehole (shaftless) and mine (block). In underground mines, old or specially created mines, prepared underground chambers with tumbled ore are used, and adits or drifts are used to collect the product solution.
In-ground leaching, usually used when the depth of the ore body is no more than 100 m, makes it possible to involve low-grade uranium ores into the mining industry, sharply reduce the volume of capital investments and the construction time of enterprises, increase labor productivity several times, significantly reduce the harmful impact on nature (do not disturb landscape, sharply reduce the amount of solid waste and harmful substances carried to the surface of the earth, and it is relatively simple to restore waste areas).
In-ground borehole leaching is a method of developing ore deposits without raising ore to the surface by selectively transferring natural uranium ions into a productive solution directly in the subsurface. This method is carried out by drilling wells through uranium ore bodies, supplying a solution to the uranium ore bodies, lifting uranium-containing solutions to the surface and extracting uranium from them using sorption ion-exchange units, adding acid to the mother liquors and pumping them back into the subsurface. During borehole leaching, there is no change in the geological state of the subsoil, since the mining mass is not excavated.
During the process of borehole leaching, less than 5% of radioactivity is transferred to a mobile state in the subsurface and brought to the surface, compared to 100% with traditional methods of uranium mining. There is no need to build tailings dumps to store waste from high level radiation. The natural hydrogeochemical environment at uranium deposits is usually capable of self-healing from anthropogenic impact. Due to the gradual restoration of natural redox conditions, a slow but irreversible process of reclamation of groundwater in ore-bearing aquifers occurs. There are methods for significantly intensifying this process, accelerating reclamation tens of times.
However, the borehole leaching method is a rather dangerous mining method from an environmental point of view. The leaching uranium-bearing solution may leak from the zone's orebody through fractures in the rock or breaks in the waterproofing layers and then spread through the aquifer. This can lead to contamination of groundwater at large distances from the mine. In addition to uranium, leaching solutions also dissolve other minerals, as a result of which not only uranium, but also elements become mobile: radium, arsenic, vanadium, molybdenum, cadmium, nickel, lead, etc., and they are concentrated a thousand times. Minerals are precipitated from solution by underground leaching to form calcite, gypsum and other minerals. The resulting precipitation can reduce or even completely block the flow of solution through uranium-bearing areas, leading to unpredictable results or premature closure of the mine.
Borehole leaching produces large quantities Wastewater and solutions that must be disposed of in an environmentally acceptable manner. These include wash water and liquid waste from the uranium enrichment plant. These fluids are mixed and reinjected into the same groundwater that was involved in uranium mining, or injected into a deep aquifer far from other groundwater users. These liquid wastes contain high concentrations of radionuclides and heavy metals, and the area where they are distributed needs to be restored after the mine is closed.
Heap leaching is the process of obtaining useful components by dissolving prepared (crushed low-grade ores or tailings of a processing plant) and placed in a special stack of mineral raw materials, followed by their separation (precipitation) from circulating solutions.
Heap leaching is used for processing ores containing readily soluble useful components; such ores must be relatively porous and inexpensive. Heap leaching is sometimes used to reprocess waste dumps resulting from upstream mining processes. To load ore, a slightly inclined surface is prepared that is impenetrable to leaching solutions. Catchment depressions are created along and across this surface for drainage. After loading, the ore is filled with a quantity of leaching solution sufficient to saturate its entire thickness. The solution penetrates between the ore particles and dissolves useful components. After a certain period of time, the material is dried and the crust formed by dissolved valuable components is removed, and the processed loose rock is washed into the drainage system.
Percolation leaching is used in the processing of ores that are poorly crushed and do not contain natural slurry or clay. This is a rather slow process. Infiltration leaching is carried out in tanks well suited for loading and unloading. The bottom of the tank must be an effective filter, allowing the solution to be pumped in and out. The tanks are loaded with crushed ore of a certain size fraction. Then the leaching solution is pumped into the tank and absorbed into the ore After the required holding time, the solution with the leached components is pumped out, and the ore is washed to remove any remaining leaching solution.
The leaching process may release dust, radon, and leach liquid. Once the leaching process is complete, especially if the ore contains iron sulfide, once exposed to water and air, continuous bacterial production of acid in the dumps may begin, leading to spontaneous leaching of uranium over many centuries, contaminating groundwater.
How is uranium mined in Kazakhstan? aslan wrote in March 27th, 2017
The uranium industry of Kazakhstan in terms of revenues to the country's budget is perhaps second only to oil production. More than 25 thousand people work in this industry, however, due to the regime of the facilities, guests at uranium mines are extremely a rare event.
Today we will see how the Ortalyk mining enterprise, located in the Suzak district of the South Kazakhstan region, works
The work shift of employees of Ortalyk Mining Enterprise LLP begins with a mandatory medical examination
Workers at a uranium mining enterprise have their blood pressure and temperature measured and are also tested with a breathalyzer. Although, according to the doctor, alcohol is strictly prohibited at the facility, and there was not a single case where the last test was “failed”
After the medical examination - breakfast in the mine canteen
The specifics of production create additional safety requirements - employees put on work clothes in a separate locker room; going out into the shift camp and the clean area of the mine is prohibited.
The shift foreman issues an order - a task that defines the content, place of work, start and end times, conditions for safe execution, necessary safety measures
One of the safety measures is to wear respirators in workshops. This is due to the fact that in the production of uranium, reagents such as sulfuric acid and ammonium nitrate are used
Uranium mining is fully automated. In the control room you can track all the processes that occur at the facility
Uranium mining at Ortalyk, as at all other enterprises in Kazakhstan, is carried out by underground borehole leaching. This method was chosen because it is the most environmentally friendly. The radiation background in the fields does not differ from the radiation background in large cities
The principle of the underground leaching method is as follows: a 2% solution of sulfuric acid is pumped underground into uranium-bearing layers, which, interacting with rocks, dissolves uranium, then this uranium-enriched solution is pumped to the surface. Above each well there is a pump control panel
In this room on the territory of the landfill with wells there is a solution distribution unit
Employees are given glasses and hats to protect them from the incredible heat.
A solution of sulfuric acid is pumped into the wells through these pipes. Pumping wells that pump uranium out of the ground look similar.
Then the solution with uranium is sent through pipes to the shop for processing productive solutions (sorption-regeneration cycle).
This extraction method uses about 15 tons of sulfuric acid per hour at Ortalyk.
In uranium production, all processes are automated, but manual control is also possible
This workshop receives a uranium solution - commercial uranium desorbate
The solution reacts with ammonium carbonate salt to obtain a concentrate of natural uranium - “yellow cake”
Checking the pressure filter readings
Yellowcake or natural uranium concentrate is the final product of the enterprise, which is packaged in special containers. Actually, uranium in this compound is about 45-50%. This year it is planned to extract 2,000 tons of uranium. The field itself is designed for 25 years of operation.
Submersible pumps require virtually no repairs; they last about 30 thousand operating hours. However, it is necessary to constantly inspect and, if necessary, change the impellers.
In parallel with the direct extraction of uranium, the laboratory conducts research that allows for the most efficient development of the deposit.
According to accepted standards, no more than 3 milligrams of uranium per liter should remain in the solution sent back to the subsurface after processing, but according to sample results, losses did not exceed 1.2 milligrams.
After finishing their work shift, employees are required to have their radiation dose checked.
When we went to the enterprise, we expected that the uranium workers' camp would look like in the old days good times- trailers in which workers live. However, the rotational camp at Ortalyk looks completely different - it is a modern complex of buildings that have everything a person needs to relax after work.
After dinner, many workers spend time playing table tennis.
The rotational camp also has its own mini-football field