Uranium ore. Minerals: Uranium ores Where is uranium mined?

Where did uranium come from? Most likely, it appears during supernova explosions. The fact is that for the nucleosynthesis of elements heavier than iron, there must be a powerful flow of neutrons, which occurs precisely during a supernova explosion. It would seem that then, during condensation from the cloud of new star systems formed by it, uranium, having collected in a protoplanetary cloud and being very heavy, should sink into the depths of the planets. But that's not true. Uranium is a radioactive element and when it decays it releases heat. Calculations show that if uranium were evenly distributed throughout the entire thickness of the planet, at least with the same concentration as on the surface, it would emit too much heat. Moreover, its flow should weaken as uranium is consumed. Since nothing like this has been observed, geologists believe that at least a third of uranium, and perhaps all of it, is concentrated in the earth’s crust, where its content is 2.5∙10 –4%. Why this happened is not discussed.

Where is uranium mined? There is not so little uranium on Earth - it is in 38th place in terms of abundance. And most of this element is found in sedimentary rocks - carbonaceous shales and phosphorites: up to 8∙10 –3 and 2.5∙10 –2%, respectively. In total, the earth's crust contains 10 14 tons of uranium, but the main problem is that it is very dispersed and does not form powerful deposits. Approximately 15 uranium minerals are of industrial importance. This is uranium tar - its basis is tetravalent uranium oxide, uranium mica - various silicates, phosphates and more complex compounds with vanadium or titanium based on hexavalent uranium.

What are Becquerel's rays? After the discovery of X-rays by Wolfgang Roentgen, French physicist Antoine-Henri Becquerel became interested in the glow of uranium salts, which occurs under the influence of sunlight. He wanted to understand if there were X-rays here too. Indeed, they were present - the salt illuminated the photographic plate through the black paper. In one of the experiments, however, the salt was not illuminated, but the photographic plate still darkened. When a metal object was placed between the salt and the photographic plate, the darkening underneath was less. Therefore, new rays did not arise due to the excitation of uranium by light and did not partially pass through the metal. They were initially called “Becquerel’s rays.” It was subsequently discovered that these are mainly alpha rays with a small addition of beta rays: the fact is that the main isotopes of uranium emit an alpha particle during decay, and the daughter products also experience beta decay.

How radioactive is uranium? Uranium has no stable isotopes; they are all radioactive. The longest-lived is uranium-238 with a half-life of 4.4 billion years. Next comes uranium-235 - 0.7 billion years. They both undergo alpha decay and become the corresponding isotopes of thorium. Uranium-238 makes up more than 99% of all natural uranium. Due to its huge half-life, the radioactivity of this element is low, and in addition, alpha particles are not able to penetrate the stratum corneum on the surface of the human body. They say that after working with uranium, I.V. Kurchatov simply wiped his hands with a handkerchief and did not suffer from any diseases associated with radioactivity.

Researchers have repeatedly turned to the statistics of diseases of workers in uranium mines and processing plants. Here, for example, is a recent article by Canadian and American specialists who analyzed health data of more than 17 thousand workers at the Eldorado mine in the Canadian province of Saskatchewan for the years 1950–1999 ( Environmental Research, 2014, 130, 43–50, DOI:10.1016/j.envres.2014.01.002). They proceeded from the fact that radiation has the strongest effect on rapidly multiplying blood cells, leading to the corresponding types of cancer. Statistics have shown that mine workers have a lower incidence of various types of blood cancer than the average Canadian population. In this case, the main source of radiation is not considered to be uranium itself, but the gaseous radon it generates and its decay products, which can enter the body through the lungs.

Why is uranium harmful?? It, like other heavy metals, is highly toxic and can cause kidney and liver failure. On the other hand, uranium, being a dispersed element, is inevitably present in water, soil and, concentrating in the food chain, enters the human body. It is reasonable to assume that in the process of evolution, living beings have learned to neutralize uranium in natural concentrations. Uranium is the most dangerous in water, so the WHO set a limit: initially it was 15 µg/l, but in 2011 the standard was increased to 30 µg/g. As a rule, there is much less uranium in water: in the USA on average 6.7 µg/l, in China and France - 2.2 µg/l. But there are also strong deviations. So in some areas of California it is a hundred times more than the standard - 2.5 mg/l, and in Southern Finland it reaches 7.8 mg/l. Researchers are trying to understand whether the WHO standard is too strict by studying the effect of uranium on animals. Here is a typical job ( BioMed Research International, 2014, ID 181989; DOI:10.1155/2014/181989). French scientists fed rats water for nine months with additives of depleted uranium, and in relatively high concentrations - from 0.2 to 120 mg/l. The lower value is water near the mine, while the upper value is not found anywhere - the maximum concentration of uranium, measured in Finland, is 20 mg/l. To the surprise of the authors - the article is called: “The unexpected absence of a noticeable effect of uranium on physiological systems ...” - uranium had practically no effect on the health of rats. The animals ate well, gained weight properly, did not complain of illness and did not die from cancer. Uranium, as it should be, was deposited primarily in the kidneys and bones and in a hundred times smaller quantities in the liver, and its accumulation expectedly depended on the content in the water. However, this did not lead to renal failure or even the noticeable appearance of any molecular markers of inflammation. The authors suggested that a review of the WHO's strict guidelines should begin. However, there is one caveat: the effect on the brain. There was less uranium in the rats' brains than in the liver, but its content did not depend on the amount in the water. But uranium affected the functioning of the brain’s antioxidant system: the activity of catalase increased by 20%, glutathione peroxidase by 68–90%, and the activity of superoxide dismutase decreased by 50%, regardless of the dose. This means that the uranium clearly caused oxidative stress in the brain and the body responded to it. This effect - the strong effect of uranium on the brain in the absence of its accumulation in it, by the way, as well as in the genitals - was noticed before. Moreover, water with uranium in a concentration of 75–150 mg/l, which researchers from the University of Nebraska fed rats for six months ( Neurotoxicology and Teratology, 2005, 27, 1, 135–144; DOI:10.1016/j.ntt.2004.09.001), affected the behavior of animals, mainly males, released into the field: they crossed lines, stood up on their hind legs and preened their fur differently than the control ones. There is evidence that uranium also leads to memory impairment in animals. Behavioral changes were correlated with levels of lipid oxidation in the brain. It turns out that the uranium water made the rats healthy, but rather stupid. These data will be useful to us in the analysis of the so-called Gulf War Syndrome.

Does uranium contaminate shale gas development sites? It depends on how much uranium is in the gas-containing rocks and how it is associated with them. For example, Associate Professor Tracy Bank of the University at Buffalo studied the Marcellus Shale, which stretches from western New York through Pennsylvania and Ohio to West Virginia. It turned out that uranium is chemically related precisely to the source of hydrocarbons (remember that related carbonaceous shales have the highest uranium content). Experiments have shown that the solution used during fracturing perfectly dissolves uranium. “When the uranium in these waters reaches the surface, it can cause contamination of the surrounding area. This does not pose a radiation risk, but uranium is a poisonous element,” notes Tracy Bank in a university press release dated October 25, 2010. No detailed articles have yet been prepared on the risk of environmental contamination with uranium or thorium during shale gas production.

Why is uranium needed? Previously, it was used as a pigment for making ceramics and colored glass. Now uranium is the basis of nuclear energy and atomic weapons. In this case, its unique property is used - the ability of the nucleus to divide.

What is nuclear fission? The decay of a nucleus into two unequal large pieces. It is because of this property that during nucleosynthesis due to neutron irradiation, nuclei heavier than uranium are formed with great difficulty. The essence of the phenomenon is as follows. If the ratio of the number of neutrons and protons in the nucleus is not optimal, it becomes unstable. Typically, such a nucleus emits either an alpha particle - two protons and two neutrons, or a beta particle - a positron, which is accompanied by the transformation of one of the neutrons into a proton. In the first case, an element of the periodic table is obtained, spaced two cells back, in the second - one cell forward. However, in addition to emitting alpha and beta particles, the uranium nucleus is capable of fission - decaying into the nuclei of two elements in the middle of the periodic table, for example barium and krypton, which it does, having received a new neutron. This phenomenon was discovered shortly after the discovery of radioactivity, when physicists exposed the newly discovered radiation to everything they could. Here is how Otto Frisch, a participant in the events, writes about this (“Advances in Physical Sciences,” 1968, 96, 4). After the discovery of beryllium rays - neutrons - Enrico Fermi irradiated uranium with them, in particular, to cause beta decay - he hoped to use it to obtain the next, 93rd element, now called neptunium. It was he who discovered a new type of radioactivity in irradiated uranium, which he associated with the appearance of transuranium elements. At the same time, slowing down the neutrons, for which the beryllium source was covered with a layer of paraffin, increased this induced radioactivity. American radiochemist Aristide von Grosse suggested that one of these elements was protactinium, but he was wrong. But Otto Hahn, who was then working at the University of Vienna and considered protactinium discovered in 1917 to be his brainchild, decided that he was obliged to find out what elements were obtained. Together with Lise Meitner, at the beginning of 1938, Hahn suggested, based on experimental results, that entire chains of radioactive elements are formed due to multiple beta decays of neutron-absorbing nuclei of uranium-238 and its daughter elements. Soon Lise Meitner was forced to flee to Sweden, fearing possible reprisals from the Nazis after the Anschluss of Austria. Hahn, having continued his experiments with Fritz Strassmann, discovered that among the products there was also barium, element number 56, which in no way could be obtained from uranium: all chains of alpha decays of uranium end with much heavier lead. The researchers were so surprised by the result that they did not publish it; they only wrote letters to friends, in particular to Lise Meitner in Gothenburg. There, at Christmas 1938, her nephew, Otto Frisch, visited her, and, walking in the vicinity of the winter city - he on skis, the aunt on foot - they discussed the possibility of the appearance of barium during the irradiation of uranium as a result of nuclear fission (for more information about Lise Meitner, see “Chemistry and Life ", 2013, No. 4). Returning to Copenhagen, Frisch literally caught Niels Bohr on the gangway of a ship departing for the United States and told him about the idea of ​​fission. Bohr, slapping himself on the forehead, said: “Oh, what fools we were! We should have noticed this earlier." In January 1939, Frisch and Meitner published an article on the fission of uranium nuclei under the influence of neutrons. By that time, Otto Frisch had already carried out a control experiment, as well as many American groups who received the message from Bohr. They say that physicists began to disperse to their laboratories right during his report on January 26, 1939 in Washington at the annual conference on theoretical physics, when they grasped the essence of the idea. After the discovery of fission, Hahn and Strassmann revised their experiments and found, just like their colleagues, that the radioactivity of irradiated uranium is associated not with transuraniums, but with the decay of radioactive elements formed during fission from the middle of the periodic table.

How does a chain reaction occur in uranium? Soon after the possibility of fission of uranium and thorium nuclei was experimentally proven (and there are no other fissile elements on Earth in any significant quantity), Niels Bohr and John Wheeler, who worked at Princeton, as well as, independently of them, the Soviet theoretical physicist Ya. I. Frenkel and the Germans Siegfried Flügge and Gottfried von Droste created the theory of nuclear fission. Two mechanisms followed from it. One is associated with the threshold absorption of fast neutrons. According to it, to initiate fission, a neutron must have a fairly high energy, more than 1 MeV for the nuclei of the main isotopes - uranium-238 and thorium-232. At lower energies, neutron absorption by uranium-238 has a resonant character. Thus, a neutron with an energy of 25 eV has a capture cross-sectional area that is thousands of times larger than with other energies. In this case, there will be no fission: uranium-238 will become uranium-239, which with a half-life of 23.54 minutes will turn into neptunium-239, which with a half-life of 2.33 days will turn into long-lived plutonium-239. Thorium-232 will become uranium-233.

The second mechanism is the non-threshold absorption of a neutron, it is followed by the third more or less common fissile isotope - uranium-235 (as well as plutonium-239 and uranium-233, which are not found in nature): by absorbing any neutron, even slow, so-called thermal, with energy as for molecules participating in thermal motion - 0.025 eV, such a nucleus will split. And this is very good: thermal neutrons have a capture cross-sectional area four times higher than fast, megaelectronvolt neutrons. This is the significance of uranium-235 for the entire subsequent history of nuclear energy: it is it that ensures the multiplication of neutrons in natural uranium. After being hit by a neutron, the uranium-235 nucleus becomes unstable and quickly splits into two unequal parts. Along the way, several (on average 2.75) new neutrons are emitted. If they hit the nuclei of the same uranium, they will cause neutrons to multiply exponentially - a chain reaction will occur, which will lead to an explosion due to the rapid release of a huge amount of heat. Neither uranium-238 nor thorium-232 can work like that: after all, during fission, neutrons are emitted with an average energy of 1–3 MeV, that is, if there is an energy threshold of 1 MeV, a significant part of the neutrons will certainly not be able to cause a reaction, and there will be no reproduction. This means that these isotopes should be forgotten and the neutrons will have to be slowed down to thermal energy so that they interact as efficiently as possible with the nuclei of uranium-235. At the same time, their resonant absorption by uranium-238 cannot be allowed: after all, in natural uranium this isotope is slightly less than 99.3% and neutrons more often collide with it, and not with the target uranium-235. And by acting as a moderator, it is possible to maintain the multiplication of neutrons at a constant level and prevent an explosion - control the chain reaction.

A calculation carried out by Ya. B. Zeldovich and Yu. B. Khariton in the same fateful year of 1939 showed that for this it is necessary to use a neutron moderator in the form of heavy water or graphite and enrich natural uranium with uranium-235 at least 1.83 times. Then this idea seemed to them pure fantasy: “It should be noted that approximately double the enrichment of those rather significant quantities of uranium that are necessary to carry out a chain explosion,<...>is an extremely cumbersome task, close to practical impossibility.” Now this problem has been solved, and the nuclear industry is mass-producing uranium enriched with uranium-235 to 3.5% for power plants.

What is spontaneous nuclear fission? In 1940, G. N. Flerov and K. A. Petrzhak discovered that fission of uranium can occur spontaneously, without any external influence, although the half-life is much longer than with ordinary alpha decay. Since such fission also produces neutrons, if they are not allowed to escape from the reaction zone, they will serve as the initiators of the chain reaction. It is this phenomenon that is used in the creation of nuclear reactors.

Why is nuclear energy needed? Zeldovich and Khariton were among the first to calculate the economic effect of nuclear energy (Uspekhi Fizicheskikh Nauk, 1940, 23, 4). “...At the moment, it is still impossible to make final conclusions about the possibility or impossibility of carrying out a nuclear fission reaction with infinitely branching chains in uranium. If such a reaction is feasible, then the reaction rate is automatically adjusted to ensure its smooth progress, despite the enormous amount of energy at the experimenter’s disposal. This circumstance is extremely favorable for the energy use of the reaction. Let us therefore present - although this is a division of the skin of an unkilled bear - some numbers characterizing the possibilities of the energy use of uranium. If the fission process proceeds with fast neutrons, therefore, the reaction captures the main isotope of uranium (U238), then<исходя из соотношения теплотворных способностей и цен на уголь и уран>the cost of a calorie from the main isotope of uranium turns out to be approximately 4000 times cheaper than from coal (unless, of course, the processes of “combustion” and heat removal turn out to be much more expensive in the case of uranium than in the case of coal). In the case of slow neutrons, the cost of a “uranium” calorie (based on the above figures) will be, taking into account that the abundance of the U235 isotope is 0.007, already only 30 times cheaper than a “coal” calorie, all other things being equal.”

The first controlled chain reaction was carried out in 1942 by Enrico Fermi at the University of Chicago, and the reactor was controlled manually - pushing graphite rods in and out as the neutron flux changed. The first power plant was built in Obninsk in 1954. In addition to generating energy, the first reactors also worked to produce weapons-grade plutonium.

How does a nuclear power plant operate? Nowadays, most reactors operate on slow neutrons. Enriched uranium in the form of a metal, an alloy such as aluminum, or an oxide is placed in long cylinders called fuel elements. They are installed in a certain way in the reactor, and moderator rods are inserted between them, which control the chain reaction. Over time, reactor poisons accumulate in the fuel element - uranium fission products, which are also capable of absorbing neutrons. When the concentration of uranium-235 falls below a critical level, the element is taken out of service. However, it contains many fission fragments with strong radioactivity, which decreases over the years, causing the elements to emit a significant amount of heat for a long time. They are kept in cooling pools, and then either buried or tried to be processed - to extract unburned uranium-235, produced plutonium (it was used to make atomic bombs) and other isotopes that can be used. The unused part is sent to burial grounds.

In so-called fast reactors, or breeder reactors, reflectors made of uranium-238 or thorium-232 are installed around the elements. They slow down and send back into the reaction zone neutrons that are too fast. Neutrons slowed down to resonant speeds absorb these isotopes, turning into plutonium-239 or uranium-233, respectively, which can serve as fuel for a nuclear power plant. Since fast neutrons react poorly with uranium-235, its concentration must be significantly increased, but this pays off with a stronger neutron flux. Despite the fact that breeder reactors are considered the future of nuclear energy, since they produce more nuclear fuel than they consume, experiments have shown that they are difficult to manage. Now there is only one such reactor left in the world - at the fourth power unit of the Beloyarsk NPP.

How is nuclear energy criticized? If we do not talk about accidents, then the main point in the arguments of opponents of nuclear energy today is the proposal to add to the calculation of its efficiency the costs of protecting the environment after decommissioning the station and when working with fuel. In both cases, the challenges of reliable disposal of radioactive waste arise, and these are costs borne by the state. There is an opinion that if you transfer them to the cost of energy, then its economic attractiveness will disappear.

There is also opposition among supporters of nuclear energy. Its representatives point to the uniqueness of uranium-235, which has no replacement, because alternative isotopes fissile by thermal neutrons - plutonium-239 and uranium-233 - due to their half-lives of thousands of years, are not found in nature. And they are obtained precisely as a result of the fission of uranium-235. If it runs out, a wonderful natural source of neutrons for a nuclear chain reaction will disappear. As a result of such wastefulness, humanity will lose the opportunity in the future to involve thorium-232, the reserves of which are several times greater than uranium, into the energy cycle.

Theoretically, particle accelerators can be used to produce a flux of fast neutrons with megaelectronvolt energies. However, if we are talking, for example, about interplanetary flights on a nuclear engine, then implementing a scheme with a bulky accelerator will be very difficult. The depletion of uranium-235 puts an end to such projects.

What is weapons-grade uranium? This is highly enriched uranium-235. Its critical mass - it corresponds to the size of a piece of substance in which a chain reaction occurs spontaneously - is small enough to produce ammunition. Such uranium can be used to make an atomic bomb, and also as a fuse for a thermonuclear bomb.

What disasters are associated with the use of uranium? The energy stored in the nuclei of fissile elements is enormous. If it gets out of control due to oversight or intentionally, this energy can cause a lot of trouble. The two worst nuclear disasters occurred on August 6 and 8, 1945, when the US Air Force dropped atomic bombs on Hiroshima and Nagasaki, killing and injuring hundreds of thousands of civilians. Smaller scale disasters are associated with accidents at nuclear power plants and nuclear cycle enterprises. The first major accident occurred in 1949 in the USSR at the Mayak plant near Chelyabinsk, where plutonium was produced; Liquid radioactive waste ended up in the Techa River. In September 1957, an explosion occurred on it, releasing a large amount of radioactive material. Eleven days later, the British plutonium production reactor at Windscale burned down, and the cloud with the explosion products dispersed over Western Europe. In 1979, a reactor at the Three Mail Island Nuclear Power Plant in Pennsylvania burned down. The most widespread consequences were caused by the accidents at the Chernobyl nuclear power plant (1986) and the Fukushima nuclear power plant (2011), when millions of people were exposed to radiation. The first littered vast areas, releasing 8 tons of uranium fuel and decay products as a result of the explosion, which spread across Europe. The second polluted and, three years after the accident, continues to pollute the Pacific Ocean in fishing areas. Eliminating the consequences of these accidents was very expensive, and if these costs were broken down into the cost of electricity, it would increase significantly.

A separate issue is the consequences for human health. According to official statistics, many people who survived the bombing or living in contaminated areas benefited from radiation - the former have a higher life expectancy, the latter have less cancer, and experts attribute some increase in mortality to social stress. The number of people who died precisely from the consequences of accidents or as a result of their liquidation amounts to hundreds of people. Opponents of nuclear power plants point out that the accidents have led to several million premature deaths on the European continent, but they are simply invisible in the statistical context.

Removing lands from human use in accident zones leads to an interesting result: they become a kind of nature reserves where biodiversity grows. True, some animals suffer from radiation-related diseases. The question of how quickly they will adapt to the increased background remains open. There is also an opinion that the consequence of chronic irradiation is “selection for fools” (see “Chemistry and Life”, 2010, No. 5): even at the embryonic stage, more primitive organisms survive. In particular, in relation to people, this should lead to a decrease in mental abilities in the generation born in contaminated areas shortly after the accident.

What is depleted uranium? This is uranium-238, remaining after the separation of uranium-235 from it. The volumes of waste from the production of weapons-grade uranium and fuel elements are large - in the United States alone, 600 thousand tons of such uranium hexafluoride have accumulated (for problems with it, see Chemistry and Life, 2008, No. 5). The content of uranium-235 in it is 0.2%. This waste must either be stored until better times, when fast neutron reactors will be created and it will be possible to process uranium-238 into plutonium, or used somehow.

They found a use for it. Uranium, like other transition elements, is used as a catalyst. For example, the authors of the article in ACS Nano dated June 30, 2014, they write that a catalyst made of uranium or thorium with graphene for the reduction of oxygen and hydrogen peroxide “has enormous potential for use in the energy sector.” Because uranium has a high density, it serves as ballast for ships and counterweights for aircraft. This metal is also suitable for radiation protection in medical devices with radiation sources.

What weapons can be made from depleted uranium? Bullets and cores for armor-piercing projectiles. The calculation here is as follows. The heavier the projectile, the higher its kinetic energy. But the larger the projectile, the less concentrated its impact. This means that heavy metals with high density are needed. Bullets are made of lead (Ural hunters at one time also used native platinum, until they realized that it was a precious metal), while the shell cores are made of tungsten alloy. Environmentalists point out that lead contaminates the soil in places of military operations or hunting and it would be better to replace it with something less harmful, for example, tungsten. But tungsten is not cheap, and uranium, similar in density, is a harmful waste. At the same time, the permissible contamination of soil and water with uranium is approximately twice as high as for lead. This happens because the weak radioactivity of depleted uranium (and it is also 40% less than that of natural uranium) is neglected and a truly dangerous chemical factor is taken into account: uranium, as we remember, is poisonous. At the same time, its density is 1.7 times greater than that of lead, which means that the size of uranium bullets can be reduced by half; uranium is much more refractory and hard than lead - it evaporates less when fired, and when it hits a target it produces fewer microparticles. In general, a uranium bullet is less polluting than a lead bullet, although such use of uranium is not known for certain.

But it is known that plates made of depleted uranium are used to strengthen the armor of American tanks (this is facilitated by its high density and melting point), and also instead of tungsten alloy in cores for armor-piercing projectiles. The uranium core is also good because uranium is pyrophoric: its hot small particles formed upon impact with the armor flare up and set fire to everything around. Both applications are considered radiation safe. Thus, the calculation showed that even after sitting for a year in a tank with uranium armor loaded with uranium ammunition, the crew would receive only a quarter of the permissible dose. And to get the annual permissible dose, you need to screw such ammunition to the surface of the skin for 250 hours.

Shells with uranium cores - for 30-mm aircraft cannons or artillery sub-calibers - have been used by the Americans in recent wars, starting with the Iraq campaign of 1991. That year they rained down on Iraqi armored units in Kuwait and during their retreat, 300 tons of depleted uranium, of which 250 tons, or 780 thousand rounds, were fired at aircraft guns. In Bosnia and Herzegovina, during the bombing of the army of the unrecognized Republika Srpska, 2.75 tons of uranium were spent, and during the shelling of the Yugoslav army in the region of Kosovo and Metohija - 8.5 tons, or 31 thousand rounds. Since WHO was by that time concerned about the consequences of the use of uranium, monitoring was carried out. He showed that one salvo consisted of approximately 300 rounds, of which 80% contained depleted uranium. 10% hit targets, and 82% fell within 100 meters of them. The rest dispersed within 1.85 km. A shell that hit a tank burned up and turned into an aerosol; the uranium shell pierced through light targets like armored personnel carriers. Thus, at most one and a half tons of shells could turn into uranium dust in Iraq. According to experts from the American strategic research center RAND Corporation, more, from 10 to 35% of the used uranium, turned into aerosol. Croatian anti-uranium munitions activist Asaf Durakovic, who has worked in a variety of organizations from Riyadh's King Faisal Hospital to the Washington Uranium Medical Research Center, estimates that in southern Iraq alone in 1991, 3-6 tons of submicron uranium particles were formed, which were scattered over a wide area , that is, uranium contamination there is comparable to Chernobyl.

In search of a cheaper source of energy that would not harm the environment, the world scientific community has paid attention to the field of nuclear energy. Today, 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 ground contains 1000 times more uranium ore than gold. It is processed to obtain fuel for nuclear power plants.

Characteristics of uranium ores

Uranium ore in its free form is a gray-white metal, which can have a fairly large amount of various impurities. It is worth considering that the purified uranium itself is considered a chemically active substance. Considering the physical, mechanical and chemical properties of uranium, we note the following points:

1. The boiling point of this chemical element is 4,200 degrees Celsius, which significantly complicates the process of its processing.
2. In air, uranium oxidizes, can dissolve in acids and react to exposure to water. However, this chemical element does not interact with alkalis, which can be called its feature.
3. With a certain impact, the substance becomes a source of quite a large amount of energy. In this case, a relatively small amount of waste is generated, the disposal of which today poses quite a lot of problems.

It is worth considering that uranium is considered by many to be a rare chemical element, since its concentration in the earth’s crust is 0.002%. With such a relatively low concentration of this chemical element, no alternative substance has yet been found. Of course, for now there are enough reserves to continuously mine uranium and power 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 increase in the need for the material, its cost is increasing. Recently, quite a large number of uranium deposits have been discovered; Australia is considered to be the leader in its production. Studies indicate that more than 30% of all reserves are concentrated in this country. The largest deposits are considered:

1. Beverly;
2. Olympic Dam;
3. Ranger.

An interesting point is that Kazakhstan is considered to be Australia’s main competitor in the field of uranium ore mining. More than 12% of the world's reserves are concentrated in this country. Despite its fairly large area, Russia has only 5% of the world's reserves.

According to some information, Russia's reserves amount to 400 thousand tons of uranium. At the end of 2017, 16 fields 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 fuel, which determines the ongoing search for its deposits. Today, uranium is often used as fuel for rocket engines. In the production of nuclear weapons, this element is used to increase their power. Some manufacturers use it to produce pigments that are used in painting.

Mining of uranium ores

Uranium ore mining is established in many countries. It is worth considering that today three technologies can be used for ore mining:

1. When uranium is close to the surface of the earth, 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 being picked up and loaded onto 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 whose area can reach several square kilometers. It is worth considering that this method of ore mining causes irreparable harm to the environment. A fairly large number of large mining companies are engaged in surface mining of uranium.
2. When the ore is located deep in the earth, mines are created. The technology is quite complex to implement and also involves mechanical extraction of material. There are quite a large number of mines in which uranium and other ores are mined. This method of rock extraction is associated with quite high risks, since gas pockets or underwater rivers may be located deep in 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, if the rock in question is deeply buried, it is almost impossible to extract it any other way.
3. The third method is to form wells into which sulfuric acid is pumped. Near the previously drilled well, a second one is created, which is intended to raise the already obtained solution. After the sorption process is completed, equipment is installed that can lift resin-like substances to the surface. After the resulting resin is raised to the surface, it is processed and uranium is separated.

In-situ leaching

Recently, the third method of uranium mining has become increasingly used. This is due to the fact that it allows you to achieve a high concentration of the required substance with a minimum content of polluting chemical elements. However, such technology requires accurate geological research, since well drilling must be carried out over the deposit of the chemical substance in question. Otherwise, when adding acid, the sorption process at a low concentration of uranium will take quite a long time.

In 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.

Currently, nuclear energy is used on a fairly 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 electricity and used for completely peaceful purposes. Nuclear engines are also being created, which are used, for example, in submarines.

The main radioactive material used to produce 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 “uranium pitch.” A new chemical element has been named after a recently discovered planet in the 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 contained in small quantities in sea water (10–9 g/l). Due to its chemical activity, uranium is found only in compounds and is not found in free form on Earth.

Uranium ores are natural mineral formations containing uranium or its compounds in quantities at which its use is possible and economically feasible. 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 (coffinit), titanites (Davidite and brannerite), as well as hydrous phosphates and uranium micas.

Uranium ores are classified according to various criteria. In particular, they are distinguished by educational conditions. One of the types are 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 during the process of accumulation (syngenetic ores) or as a result (epigenetic ores). They occur predominantly on the surface of young platforms. Metamorphogenic ores that arose during the redistribution of primary dispersed uranium during the metamorphism of sedimentary strata. Metamorphogenic ores are characteristic of ancient platforms.

In addition, uranium ores are divided into natural types and technological grades. According to the nature of uranium mineralization, they are distinguished: primary uranium ores - (U 4 + content of at least 75% of the total amount), oxidized uranium ores (contain mainly U 6 +) and mixed uranium ores, in which U 4 + and U 6 + are found in approximately equal proportions. The technology for their processing depends on the degree of oxidation of uranium. Based on the degree of unevenness of the U content in the lump fraction of the rock (“contrast”), highly contrasting, contrasting, weakly contrasting and non-contrasting uranium ores are distinguished. This parameter determines the possibility and feasibility of enriching uranium ores.

According to the sizes of aggregates and grains of uranium minerals, they 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 grain sizes of uranium minerals also determine the possibility of ore enrichment. 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% carbonate minerals), iron oxide (iron-uranium ores), sulfide (more than 8–10% sulfide minerals) and caustobiolite consisting mainly of organic matter.

The chemical composition of ores often determines how they are processed. Uranium is separated from silicate ores by acids, and from carbonate ores by soda solutions. Iron oxide ores are subjected to blast furnace smelting. Caustobiolite uranium ores are sometimes enriched by combustion.

As mentioned above, the content of uranium in the earth's crust is quite low. There are several deposits of uranium ores in Russia:

Zherlovoe and Argunskoye fields. They are located in the Krasnokamensky district of the Chita region. The reserves of the Zherlovoye deposit amount to 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%). C1 category uranium reserves at the Argun deposit amount to 13,025 thousand tons of ore, 27,957 tons of uranium (average content 0.215%) and 3,598 tons of molybdenum (average content 0.048%). Reserves in category C2 are: 7,990 thousand tons of ore, 9,481 tons of uranium (with an average content of 0.12%) and 3,191 tons of molybdenum (with an average content of 0.0489%). Approximately 93% of all Russian uranium is mined here.

5 uranium deposits ( Istochnoye, Kolichkanskoye, Dybrynskoye, Namarusskoye, Koretkondinskoye) 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.

Khiagdinskoye uranium deposit. Extraction is carried out using 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 quantities to glass to give it color. Uranium is a component of various metal alloys and is used in photography and other fields.

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

Uranium does not exist in nature in its pure form - 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 of the 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 of a 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:

1. Conditions of formation - endogenous, exogenous and metamorphogenic ores.
2. The nature of uranium mineralization is primary, oxidized and mixed uranium ores.
3. Aggregate and grain size of minerals - coarse-grained, medium-grained, fine-grained, fine-grained and dispersed fractions of ore.
4. Usefulness of impurities - molybdenum, vanadium, etc.
5. 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 reducing economic costs, although there are a number of restrictions on its use.

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 recent years, the topic of nuclear energy has become increasingly relevant. To produce nuclear energy, it is common to use a material such as uranium. It is a chemical element belonging to the actinide family.

The chemical activity of this element determines the fact that it is not contained in free form. For its production, mineral formations called uranium ores are used. They concentrate such an amount of fuel that allows the extraction of this chemical element to be considered economically rational and profitable. At the moment, in the bowels of our planet the content of this metal exceeds the reserves of gold in 1000 times(cm. ). In general, deposits of this chemical element in soil, aquatic environment and rock are estimated at more than 5 million tons.

In the free state, uranium is a gray-white metal, which is characterized by 3 allotropic modifications: rhombic crystalline, tetragonal and body-centered cubic lattices. The boiling point of this chemical element is 4200 °C.

Uranium is a chemically active material. In air, this element slowly oxidizes, easily dissolves in acids, reacts with water, but does not interact with alkalis.

Uranium ores in Russia are usually classified according to various criteria. Most often they differ in terms of education. Yes, there are endogenous, exogenous and metamorphogenic ores. In the first case, they are mineral formations formed under the influence of high temperatures, humidity and pegmatite melts. Exogenous uranium mineral formations occur in surface conditions. They can form directly on the surface of the earth. This occurs due to the circulation of groundwater and the accumulation of sediments. Metamorphogenic mineral formations appear as a result of the redistribution of initially dispersed uranium.

According to the level of uranium content, these natural formations can be:

• super rich (over 0.3%);
• rich (from 0.1 to 0.3%);
• privates (from 0.05 to 0.1%);
• poor (from 0.03 to 0.05%);
• off-balance sheet (from 0.01 to 0.03%).

Modern uses of uranium

Today, uranium is most often used as fuel for rocket engines and nuclear reactors. Given the properties of this material, it is also intended to increase the power of a nuclear weapon. This chemical element has also found its use in painting. It is actively used as yellow, green, brown and black pigments. Uranium is also used to make cores for armor-piercing projectiles.

Mining uranium ore in Russia: what is needed for this?

The extraction of radioactive ores is carried out using three main technologies. If ore deposits are concentrated as close as possible to the surface of the earth, then it is customary to use open-pit technology for their extraction. It involves the use of bulldozers and excavators, which dig large holes and load the resulting minerals into dump trucks. Then it is sent to the processing complex.

When this mineral formation is located deeply, it is customary to use underground mining technology, which involves creating a mine up to 2 kilometers deep. The third technology differs significantly from the previous ones. In-ground leaching to develop uranium deposits involves drilling wells through which sulfuric acid is pumped into the deposits. Next, another well is drilled, which is necessary to pump the resulting solution to the surface of the earth. Then it goes through a sorption process, which allows the salts of this metal to be collected on a special resin. The last stage of SPV technology is cyclic treatment of the resin with sulfuric acid. Thanks to this technology, the concentration of this metal becomes maximum.

Uranium ore deposits in Russia

Russia is considered one of the world leaders in the mining of uranium ores. Over the past few decades, Russia has consistently ranked among the top 7 leading countries in this indicator.

The largest deposits of these natural mineral formations are:

The largest uranium mining deposits in the world - leading countries

Australia is considered the world leader in uranium mining. More than 30% of all world reserves are concentrated in this state. The largest Australian deposits are Olympic Dam, Beverly, Ranger and Honemoon.

Australia's main competitor is Kazakhstan, which contains almost 12% of the world's fuel reserves. Canada and South Africa each contain 11% of the world's uranium reserves, Namibia - 8%, Brazil - 7%. Russia closes the top seven with 5%. The list of leaders also includes countries such as Namibia, Ukraine and China.

The world's largest uranium deposits are:

Field	A country	Start processing
Olympic Dam	Australia	1988
Rossing	Namibia	1976
McArthur River	Canada	1999
Inkai	Kazakhstan	2007
Dominion	South Africa	2007
Ranger	Australia	1980
Kharasan	Kazakhstan	2008

Reserves and production volumes of uranium ore in Russia

The explored reserves of uranium in our country are estimated at more than 400 thousand tons. At the same time, the predicted resources are more than 830 thousand tons. As of 2017, there are 16 uranium deposits in Russia. Moreover, 15 of them are concentrated in Transbaikalia. The main deposit of uranium ore is considered to be the Streltsovskoe ore field. In most domestic deposits, production is carried out using the shaft method.

• Uranium was discovered back in the 18th century. In 1789, the German scientist Martin Klaproth managed to produce metal-like uranium from ore. Interestingly, this scientist is also the discoverer of titanium and zirconium.
• Uranium compounds are actively used in the field of photography. This element is used to color positives and enhance negatives.
• The main difference between uranium and other chemical elements is its natural radioactivity. Uranium atoms tend to change independently over time. At the same time, they emit rays invisible to the human eye. These rays are divided into 3 types - gamma, beta and alpha radiation (see).