In search of a cheaper source of energy that would not harm the environment, the world scientific community 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 directly purified uranium itself is considered chemically active substance. Considering the physical-mechanical and Chemical properties uranium, 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 with 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 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 the 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. Behind 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:

1. Beaverley;
2. Olympic Dam;
3. 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 the rather large area, Russia has only 5% of the world's 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. To date, uranium is often used as a fuel for rocket engines. In the production of 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:

1. 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.
2. 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.
3. The third method is to form wells into which sulfuric acid. 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 leaching

Recently, 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.

URANIUM ORES (a. uranium ores; n. Uranerze; f. minerais uraniferes, minerais d "uranium; and. minerales de urania, minerales uraniсos) - natural mineral formations containing uranium in such concentrations, quantities and compounds, in which its industrial mining is economically viable.

The main ore minerals: oxides - uraninite, uranium pitch, uranium black; silicates - coffinite; titanates - brannerite; uranyl silicates - uranophane, betauranotyl; uranyl vanadates - carnotite, tyuyamunite; uranyl phosphates - otenitis, torbernite. In addition, uranium in ores is often included in the composition 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 are 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 diverse in terms of formation conditions, the nature of occurrence, mineral composition, the presence of associated components, development methods. Sedimentary uranium ores (exogenous syngenetic) include bedded Paleogene deposits of the organogenic-phosphate type in (deposits of fish bone detritus enriched in U and TR) and Early Proterozoic quartz-pebble uranium-bearing conglomerates of the Elliot Lake region in Canada (with Th, Zr, Ti), Witwatersrand in South Africa (with Au) and Jacobina in Brazil (with Au). Ores are usually ordinary and wretched. Among the infiltration deposits (exogenous epigenetic), soil-, reservoir- and fissure-infiltration are distinguished. Leading among them are coffinite-chernium 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 are in the form of rolls (elongated sickle-shaped bodies) or lenses. The ores are predominantly ordinary and poor, sometimes complex with Se, Re, Mo, V, Sc (deposits in the arid regions of the CCCP, Wyoming in Niger).

Among soil-infiltration deposits, of industrial interest are mainly uranium-coal deposits, where uranium and associated mineralization is localized at the top of the layers, at contact with oxidized sands, as well as near-surface deposits of carnotite ores in "calcretes" and "hypcretes" (carbonate and gypsum soil formations of river paleovalleys) in Australia (the Yilirri deposit) and Namibia. This group is adjoined by stratiform uranium-bitumen deposits in terrigenous and carbonate rocks, where the ore substance is represented by pitchblende-bearing 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 deposits of the "sandstone" type (ordinary and poor ores). Their possible metamorphosed counterparts are the deposits of the Franceville ore region in Gabon, among them the unique Oklo deposit. Hydrothermal deposits (endogenous epigenetic medium-low temperature deposits) are mainly veined and vein-stockwork, less often sheetlike. 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, coffinite, brannerite (in uranium-thorium ores), uranium-containing fluorapatite (in phosphorus-uranium ores). Secondary uranyl silicates, uranyl phosphates, and uranyl arsenates are developed in the oxidation zones. The ores are ordinary and rich. This group includes deposits in volcano-tectonic structures and basement rocks in a number of areas of the CCCP, the Ore Mountains, the Central French Massif, the Beaverlodge and Great Bear Lake areas in Canada, the USA (Marysvale), Australia (Mount Isa and Westmoreland). The metasomatic deposits of the "unconformity" type, identified in Canada (ore areas of Rabbit Lake, Key Lake, etc.) and Northern Australia (the Alligator River region) adjoin this group. They are characterized by the control of mineralization by surfaces of stratigraphic unconformity, sheet-like or sheet-like-vein morphology, unusually high uranium contents in ores (0, n - n%). The main ore minerals are pitchblende, uraninite, coffinite, brannerite. A unique stratiform deposit of complex ores has been discovered in Australia. Uranium industry.

In the 80s. profitable for mining were uranium ores worth less than 80 dollars / kg of uranium. The total reserves and resources of uranium, including potential ones, in industrially developed capitalist and developing countries are estimated at 14 million tons (excluding associated uranium). The main reserves of uranium ores (thousand 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 in deposits of the "unconformity" type, 25% - of the "sandstone" type, 16% - of uranium-bearing conglomerates, 14% - of the "porphyry" type, etc.

The world annual production of uranium concentrates in these countries in 1988 was 37.4 thousand tons of uranium at an average cost of $30 per kg (beginning of 1989).

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 neutron flux, which occurs just during a supernova explosion. It would seem that later, when condensing from the cloud of new star systems formed by it, uranium, having gathered in a protoplanetary cloud and being very heavy, should sink into the depths of the planets. But it's not. Uranium is a radioactive element and it releases heat when it decays. The calculation shows that if uranium were evenly distributed throughout the entire thickness of the planet, at least with the same concentration as on the surface, then it would release too much heat. Moreover, its flow should decrease as uranium is consumed. Since nothing of the kind is 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? Uranium on Earth is not so small - in terms of prevalence, it is in 38th place. And most of all this element is 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. About 15 uranium minerals are of industrial importance. This is uranium pitch - its base is tetravalent uranium oxide, uranium mica - various silicates, phosphates and more complex compounds with vanadium or titanium based on hexavalent uranium.

What are Becquerel rays? After the discovery of X-rays by Wolfgang Roentgen, the French physicist Antoine-Henri Becquerel became interested in the glow of uranium salts, which occurs under the action 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, and the photographic plate still darkened. When a metal object was placed between the salt and the photographic plate, the darkening under it was less. Consequently, the new rays did not arise at all due to the excitation of uranium by light and did not partially pass through the metal. They were called at first "Becquerel rays". Subsequently, it was found 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 high is the radioactivity of 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. The next is uranium-235 - 0.7 billion years. Both of them undergo alpha decay and become the corresponding isotopes of thorium. Uranium-238 makes up over 99% of all natural uranium. Because of its long half-life, the radioactivity of this element is low, and besides, alpha particles are not able to overcome the stratum corneum on the surface of the human body. They say that IV Kurchatov, after working with uranium, 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. For example, here is a recent article by Canadian and American experts who analyzed the health data of more than 17,000 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 also showed that mine workers have a lower incidence of various types of blood cancer than the average Canadian. At the same time, the main source of radiation is considered not uranium itself, but the gaseous radon generated by it 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. The most dangerous uranium is in water, so the WHO set a limit: at first 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 for nine months with water supplemented with depleted uranium, and in a relatively high concentration - from 0.2 to 120 mg / l. The lower value is water near the mine, while the upper one is not found anywhere - the maximum concentration of uranium, measured in the same Finland, is 20 mg / l. To the surprise of the authors - the article is titled: "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, put on weight properly, did not complain of illness and did not die of cancer. Uranium, as it should be, was deposited primarily in the kidneys and bones, and in a hundredfold smaller amount - in the liver, and its accumulation, as expected, depended on the content in the water. However, this did not lead to renal failure, or even to the noticeable appearance of any molecular markers of inflammation. The authors suggested starting a review of the strict WHO guidelines. However, there is one caveat: the effect on the brain. There was less uranium in the brains of rats than in the liver, but its content did not depend on the amount in water. But uranium affected the work of the antioxidant system of the brain: the activity of catalase increased by 20%, glutathione peroxidase increased by 68–90%, while the activity of superoxide dismutase fell by 50% regardless of the dose. This means that uranium clearly caused oxidative stress in the brain and the body reacted to it. Such an effect - a strong effect of uranium on the brain in the absence of its accumulation in it, by the way, as well as in the genital organs - was noticed earlier. Moreover, water with uranium at a concentration of 75–150 mg/l, which researchers from the University of Nebraska fed to 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 the lines, stood up on their hind legs, and brushed their fur, unlike the control ones. There is evidence that uranium also leads to memory impairment in animals. The change in behavior correlated with the level of lipid oxidation in the brain. It turns out that rats from uranium water became healthy, but stupid. These data will still be useful to us in the analysis of the so-called Persian Gulf syndrome (Gulf War Syndrome).

Does uranium pollute shale gas mining 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 has explored the Marcelus Shale, which stretches from western New York State through Pennsylvania and Ohio to West Virginia. It turned out that uranium is chemically bound precisely with the source of hydrocarbons (recall that related carbonaceous shales have the highest uranium content). Experiments have shown that the solution used for fracturing the seam perfectly dissolves uranium. “When the uranium in these waters is on the surface, it can cause pollution of the surrounding area. It does not carry a radiation risk, but uranium is a poisonous element, ”Tracey Bank notes in a university press release dated October 25, 2010. Detailed articles on the risk of environmental pollution with uranium or thorium during the extraction of shale gas have not yet been prepared.

Why is uranium needed? Previously, it was used as a pigment for the manufacture of ceramics and colored glass. Now uranium is the basis of nuclear energy and nuclear weapons. In doing so, it uses unique property- the ability of the nucleus to divide.

What is nuclear fission? The disintegration of the nucleus into two unequal large pieces. It is precisely 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. Usually such a nucleus ejects 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, the uranium nucleus, in addition to emitting alpha and beta particles, 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 everything they had to the newly discovered radiation. Here is how Otto Frisch, a participant in the events, writes about this (“Successes physical sciences ", 1968, 96, 4). After the discovery of beryllium rays - neutrons - Enrico Fermi irradiated them, in particular, uranium to cause beta decay - he hoped to get the next, 93rd element, now called neptunium, at his expense. It was he who discovered a new type of radioactivity in irradiated uranium, which he associated with the appearance of transuranium elements. In this case, slowing down neutrons, for which the beryllium source was covered with a layer of paraffin, increased this induced radioactivity. The 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 in this case. Together with Lise Meitner, in early 1938, Hahn suggested, based on the results of experiments, that whole chains of radioactive elements are formed, arising from multiple beta decays of uranium-238 nuclei that absorbed a neutron 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, continuing his experiments with Fritz Strassmann, discovered that among the products there was also barium, element number 56, which could not have been obtained from uranium in any way: all chains of uranium alpha decays end in 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 Lise Meitner in Gothenburg. There, at Christmas 1938, her nephew, Otto Frisch, visited her, and, walking in the vicinity of the winter city - he is on skis, his aunt is on foot - they discussed the possibility of the appearance of barium during irradiation of uranium due to nuclear fission (for more on Lise Meitner, see "Chemistry and Life ", 2013, No. 4). Returning to Copenhagen, Frisch, literally on the gangway of a steamer departing for the USA, caught Niels Bohr and informed him about the idea of ​​division. Bor, slapping his forehead, said: “Oh, what fools we were! We should have noticed this sooner." In January 1939, Frisch and Meitner published an article on the fission of uranium nuclei under the action of neutrons. By that time, Otto Frisch had already set up a control experiment, as well as many American groups that received a 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 Strassman revised their experiments and found, just like their colleagues, that the radioactivity of irradiated uranium is not associated with transuraniums, but with the decay of radioactive elements formed during fission from the middle of the periodic table.

How does a chain reaction work in uranium? Shortly 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 amount), Niels Bohr and John Wheeler, who worked at Princeton, and also independently 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 related to the threshold absorption of fast neutrons. According to him, to initiate fission, the neutron must have a rather high energy, more than 1 MeV for the nuclei of the main isotopes - uranium-238 and thorium-232. At lower energies, the absorption of a neutron by uranium-238 has a resonant character. Thus, a neutron with an energy of 25 eV has a capture cross section 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, the one 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, followed by the third more or less common fissile isotope - uranium-235 (as well as plutonium-239 and uranium-233, which are absent in nature): by absorbing any neutron, even a slow one, the so-called thermal, with an energy of for molecules participating in thermal motion - 0.025 eV, such a nucleus will be divided. And this is very good: for thermal neutrons, the capture cross-sectional area is four times higher than for fast, megaelectronvolt ones. 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 hitting 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 fly out. If they fall into the nuclei of the same uranium, they will cause neutron multiplication in geometric progression- a chain reaction will start, 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 in this way: after all, during fission, neutrons with an average energy of 1-3 MeV are emitted, 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 neutrons will have to be slowed down to thermal energy so that they interact with uranium-235 nuclei as efficiently as possible. 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 acting as a moderator, it is possible to maintain neutron multiplication at a constant level and prevent an explosion - to control a chain reaction.

The calculation carried out by Ya. B. Zeldovich and Yu. B. Khariton in the same fateful 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 by at least 1.83 times. Then this idea seemed to them pure fantasy: “It should be noted that approximately double the enrichment of those fairly significant amounts 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 up to 3.5% for power plants.

What is spontaneous nuclear fission? In 1940, G. N. Flerov and K. A. Petrzhak discovered that uranium fission 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 fly away 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 power needed? Zel'dovich 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 implementing a nuclear fission reaction in uranium with infinitely branching chains. If such a reaction is feasible, then the reaction rate is automatically adjusted to ensure that it proceeds smoothly, despite great amount energy at the disposal of the experimenter. This circumstance is exceptionally favorable for the energy utilization of the reaction. Therefore, although this is a division of the skin of an unkilled bear, we present some numbers that characterize the possibilities for the energy use of uranium. If the fission process proceeds on 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 about 4000 times cheaper than from coal (unless, of course, the processes of "burning" 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, taking into account that the abundance of the isotope U235 is 0.007, is 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 manually controlled by pushing and pulling out graphite rods 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 work? Most reactors now operate on slow neutrons. Enriched uranium in the form of a metal, an alloy, for example with aluminum, or in the form of an oxide is put into long cylinders - fuel elements. They are installed in a certain way in the reactor, and rods from the moderator are introduced between them, which control the chain reaction. Over time, reactor poisons accumulate in the fuel element - uranium fission products, also capable of absorbing neutrons. When the uranium-235 concentration falls below the critical level, the element is decommissioned. However, it contains many fission fragments with strong radioactivity, which decreases over the years, which is why the elements emit a significant amount of heat for a long time. They are kept in cooling pools, and then they are either buried or they try to process them - to extract unburned uranium-235, accumulated plutonium (it was used to make atomic bombs) and other isotopes that can be used. The unused part is sent to the burial grounds.

In so-called fast neutron reactors, or breeder reactors, reflectors of uranium-238 or thorium-232 are installed around the elements. They slow down and send too fast neutrons back to the reaction zone. Slowed down to resonant speeds, neutrons absorb these isotopes, turning into plutonium-239 or uranium-233, respectively, which can serve as fuel for a nuclear power plant. Since fast neutrons do not react well with uranium-235, it is necessary to significantly increase its concentration, but this pays off with a stronger neutron flux. Despite the fact that breeder reactors are considered the future of nuclear energy, since they provide more nuclear fuel than they consume, experiments have shown that it is difficult to control them. 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, the main point in the arguments of opponents of nuclear energy today was the proposal to add to the calculation of its effectiveness the costs of protecting the environment after decommissioning the plant and when working with fuel. In both cases, the task of reliable disposal of radioactive waste arises, and these are the costs that the state bears. There is an opinion that if they are shifted 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 - are absent in nature due to a half-life of thousands of years. And they are obtained just as a result of the fission of uranium-235. If it ends, the beautiful will disappear natural source neutrons for a nuclear chain reaction. As a result of such extravagance, humanity will lose the opportunity in the future to involve thorium-232 in the energy cycle, the reserves of which are several times greater than those of uranium.

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

What is weapon-grade uranium? This is highly enriched uranium-235. Its critical mass - it corresponds to the size of a piece of matter in which a chain reaction spontaneously occurs - is small enough to make a munition. Such uranium can be used to make 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. Having escaped from control due to an oversight or due to intent, this energy can do a lot of trouble. The two most monstrous 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 on nuclear power plants and enterprises of the nuclear cycle. First major accident happened in 1949 in the USSR at the Mayak plant near Chelyabinsk, where plutonium was produced; liquid radioactive waste got into the river Techa. In September 1957, an explosion occurred on it with the release of a large amount of radioactive material. Eleven days later, the British plutonium reactor at Windscale burned down, a cloud of explosion products dissipated over Western Europe. In 1979, the reactor at the Trimail Island nuclear power plant in Pennsylvania burned down. Accidents at the Chernobyl nuclear power plant(1986) and the nuclear power plant in Fukushima (2011), when millions of people were exposed to radiation. The first littered vast lands, throwing out 8 tons of uranium fuel with decay products as a result of the explosion, which spread throughout Europe. The second polluted and, three years after the accident, continues to pollute the water area Pacific Ocean in fishing areas. The elimination of the consequences of these accidents was very expensive, and if these costs were decomposed 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 live in contaminated areas benefited from exposure - the former have a higher life expectancy, the latter have fewer cancers, 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 is estimated at hundreds of people. Opponents of nuclear power plants point out that accidents have led to several million premature deaths in European continent, they are simply invisible against the statistical background.

The withdrawal of lands from human use in accident zones leads to an interesting result: they become a kind of reserves, where biodiversity grows. True, some animals suffer from diseases associated with radiation. 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 a fool” (see Chemistry and Life, 2010, No. 5): more primitive organisms survive even at the embryonic stage. In particular, in relation to people, this should lead to a decrease in the mental abilities of the generation born in the contaminated territories shortly after the accident.

What is depleted uranium? This is uranium-238 left over from the extraction of uranium-235. 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%. These wastes 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 somehow used.

They found a use for it. Uranium, like other transition elements, is used as a catalyst. For example, the authors of an article in ACS Nano dated June 30, 2014, they write that a uranium or thorium catalyst with graphene for the reduction of oxygen and hydrogen peroxide "has great potential for energy applications." Because of its high density, uranium serves as ballast for ships and counterweights for aircraft. This metal is 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. Here is the calculation. The heavier the projectile, the higher its kinetic energy. But the larger the projectile, the less concentrated its impact. So we need heavy metals with high density. 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 cores of the shells were made of a tungsten alloy. Conservationists point out that lead pollutes the soil in places of war or hunting and it would be better to replace it with something less harmful, for example, with the same tungsten. But tungsten is not cheap, and uranium, similar in density to it, 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 the really dangerous chemical factor: 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 harder than lead - when fired, it evaporates less, and when it hits a target, it produces fewer microparticles. In general, a uranium bullet pollutes less environment than lead, however, it is not known for certain about such use of uranium.

But it is known that depleted uranium plates 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 when they hit the armor, flare up and set fire to everything around. Both applications are considered radiation safe. So, the calculation showed that, even after spending a year without getting out in a tank with uranium armor loaded with uranium ammunition, the crew would receive only a quarter of the allowable dose. And in order to obtain an annual allowable dose, such ammunition must be screwed to the surface of the skin for 250 hours.

Projectiles with uranium cores - for 30-mm aircraft guns or for artillery sub-calibers - were used by the Americans in recent wars, starting with the 1991 Iraq campaign of the year. That year, they poured 300 tons of depleted uranium on Iraqi armored units in Kuwait, and during their retreat, 250 tons, or 780,000 rounds, fell on aircraft guns. In Bosnia and Herzegovina, during the bombing of the army of the unrecognized Republika Srpska, 2.75 tons of uranium were used, and during the shelling of the Yugoslav army in the province of Kosovo and Metohija - 8.5 tons, or 31,000 rounds. Since the WHO had by that time taken care of the consequences of the use of uranium, monitoring was carried out. He showed that one volley consisted of approximately 300 rounds, of which 80% contained depleted uranium. 10% hit the targets, and 82% fell within 100 meters of them. The rest dispersed within 1.85 km. The shell that hit the tank burned down and turned into an aerosol, light targets like armored personnel carriers were pierced through by a uranium shell. Thus, one and a half tons of shells could turn into uranium dust in Iraq at the most. According to experts from the American strategic research center RAND Corporation, more than 10 to 35% of the used uranium has turned into an aerosol. Croatian uranium munitions fighter Asaf Durakovich, who has worked in a variety of organizations from the King Faisal Hospital in Riyadh to the Washington Uranium Medical Research Center, believes that in southern Iraq alone in 1991, 3-6 tons of submicron uranium particles were formed, which scattered over a wide area , that is, uranium pollution there is comparable to Chernobyl.

Uranium ore is a natural mineral formation in which uranium contains such an amount that it is economically profitable to extract it.

By the amount of uranium mineral ores there are:

• the super rich. Such ores contain 0.3% U, and the ore itself in such deposits is over 50 thousand tons.
• rich, containing from 0.1 to 0.3%.
• ordinary, have in their composition 0.05-0.10%
• miserable. In such ores there is 0.03-0.05% uranium
• off-balance sheet, in which only 0.01-0.03% is present.

Most uranium is present in acidic rocks, which contain a lot of silicon. The most important uranium ores include uranium pitch (uraninite) and carnotite.

Table 1. List of uranium minerals

Uranium mining

Uranium is mined in three ways:

• the open method is suitable in cases where the ore lies in close proximity to the surface of the earth. For mining, it is necessary to dig a deep and wide hole with the help of bulldozers, and then load the mined ore into dump trucks with excavators, which will deliver the rock to the processing complex
• underground mining is used if the ore lies at a considerable depth. This method is significantly more expensive than the previous one. It is used only in cases where a high concentration of uranium in the rock has been proven. To implement this method, it is necessary to drill a vertical shaft, from which horizontal workings should be diverted. Uranium mines can be located at a depth of two kilometers. Miners extract ore, use freight elevators to deliver it to the top, after which it is sent for processing
• borehole in-situ leaching (ISL). For production by this method, it is necessary to drill 6 wells at the corners of the hexagon. These wells pump sulfuric acid into uranium deposits. In the center of the entire structure, another well is being drilled, through which a solution saturated with uranium salts is pumped out. Next, the solution is subjected to adsorption several times. The end product is uranium oxide.

uranium mines

According to the latest data, there are 440 commercial reactors on our planet, which require 67 thousand tons of uranium annually.
Uranium mining in the world is concentrated in the three states of Australia, Kazakhstan and Russia. Australia has 31% of the world's uranium, Kazakhstan - 12%, Russia and Canada - 9% each. Uranium mining in Russia is carried out mainly on the territory of the Republic of Sakha in Yakutia. Total in Russian Federation there are 550 thousand tons of uranium deposits. In addition to Yakutia, there are uranium deposits in Transbaikalia and Buryatia.
Interestingly, the world's reserves are located in countries that have nothing to do with nuclear energy. For example, French companies mine uranium in Niger for their own needs. But in the USA, China, India, France, Japan, South Korea, there is an acute shortage of uranium. Therefore, today there are hostilities between countries for control over deposits of uranium ore. The toughest situation is in Africa. There, because of uranium, they are kindled civil wars and many people die.

This fact was first discovered back in the 60s of the last century, but at that time almost no attention was paid to it. When replacing worn-out equipment at a number of oil fields in the Trans-Volga region, it turned out quite by accident that the pipes extracted from wells, which had lain at great depths for 20-30 years, have a truly prohibitive level of ionizing radiation - sometimes up to 5000 microroentgens per hour. And this is more than 400 times higher than natural radiation background(Fig. 1).

Dangerous elements

It was only in the late 1980s that experts began to understand this fact. It turned out that over decades of operation of oilfield equipment, a layer of oil sediment had formed on the walls of pipes, on valves and on other units. It was this sediment that accumulated rare radionuclides - radium-226 and radium-228. But where did they come from in the European part of the USSR?

It was then that it became clear that at this point earth's crust at a depth of 400 to 800 meters, there are layers with a high content of natural uranium, the decay product of which is precisely radium. And oilfield equipment accumulated so many of these radionuclides over 20-30 years of operation that they began to really threaten the health of people working in the fields. In this regard, since the end of the 80s, radiation monitoring has been introduced in many oil fields, which, if the permitted radiation level is exceeded, issues an order to replace "dirty" equipment.

Reference. Uranium is a chemical element No. 92 of the periodic table of Mendeleev. In its purest form, it is silver white metal, which is the heaviest element currently found in nature. In natural ores, it is present as a mixture of three isotopes: uranium-238 (99.28%), uranium-235 (0.71%) and uranium-234 (0.005%). Currently, the largest proven uranium reserves are in Canada, South Africa, Namibia, Australia and Kazakhstan. In Russia, 93% of this metal is mined at the Krasnokamenskoye deposit in the Trans-Baikal Territory, the rest - in Buryatia and the Kurgan region (Fig. 2).

It was for the uranium isotope with an atomic weight of 235 that theoretical physicists predicted in the 1930s the possibility of carrying out a fission chain reaction atomic nuclei, which releases a lot of energy. In practice, such a reaction was first carried out in July 1945 in the United States in the form of an atomic bomb explosion. After that, the Americans dropped such bombs on the Japanese cities of Hiroshima and Nagasaki. For peaceful purposes, the controlled fission reaction of uranium nuclei was first used in the USSR at Obninskaya nuclear power plant in 1954. Currently, uranium from natural deposits is used as fuel for nuclear power plants, as well as as a raw material for obtaining plutonium-239, which is the stuffing of nuclear weapons.

Radiation from underground

Usually, the word "radiation" immediately brings to mind the image of a nuclear power plant and the catastrophe that occurred in 1986 at the Chernobyl nuclear power plant. Meanwhile, for millions of years, all life on the planet Earth has been developing under the conditions of incessant natural radiation coming to us from two sides at once - from outer space and from the bowels of the earth's crust.

Cosmic radiation is almost completely retained by the ozone layer of the atmosphere, thereby preserving the very possibility of the existence of living organisms on the planet. But the natural radiation coming to us from the depths of the Earth, at different points in the earth's crust can reach different levels, depending on the concentration of radium, uranium and thorium in the rocks.

In particular, in a number of regions of our planet, for example, in the Himalayan foothills of India, local rocks sometimes emit up to 300-500 micro-roentgens per hour due to the high content of radioactive elements in them. These figures are 15-25 times higher than the level of natural background radiation for central Russia. Nevertheless, people have been living in this area for hundreds of years, and at the same time they do not have radiation sickness. Moreover, it was from such "radioactive" Indian villages that the British colonialists at one time recruited the strongest and tallest soldiers. According to a number of scientists, this fact proves that in small doses, radiation is not only not harmful, but even beneficial to the human body. However, their opponents believe that good health natives of these regions of India is explained only by simple village food, clean air and distance from civilization.

Geological studies of the 80s - 90s in the European part of Russia show that rocks with an increased level of radiation at a number of points Samara region also come to the surface of the earth's crust (Fig. 3, 4).

So, in the Lysaya Gora gravel pit, which is located within the city of Syzran, local construction organizations have been taking stone for their needs for decades. Everything was fine, and there were no complaints about the quality of the material during the entire period of work. However, in the 1990s, at one fine moment, during a radiometric survey of the area, it turned out quite by chance that at some points in the quarry, the level of rock radiation jumps to 320 microroentgens per hour, which is 25-30 times higher than the natural background.

The survey helped to establish that here again the whole point is the high concentration of uranium and radium isotopes in underground layers, which in the Syzran region come very close to the surface of the earth. Of course, work on the dangerous section of the quarry was immediately curtailed, and it was decided to fill up the uranium vein with mining waste. And after shields with a sign of radiation danger were placed here, few of the local residents risk going into the "uranium" quarry for a long time.

Treatment on the waters

In connection with the above facts, during the 80s, the Middle Volga region was surveyed by geological parties for the location of deposits of uranium and radium ores. It turned out that layers with a high content of these elements are distributed over a vast territory - approximately from the Penza region to the southern foothills of the Urals. On average, the depth of occurrence of such rocks ranges from 400 meters to 1 kilometer from the upper edge of the earth's crust, but at a number of points, such as, for example, in the aforementioned quarry near Syzran, radioactive layers approach almost the very surface.

This fact is confirmed by the results of the work of a search and survey geological expedition, which in 1996 studied water sources on the border of the Samara and Ulyanovsk regions. In these places, at different depths, reserves of underground mineral waters were found in the Upper Carboniferous deposits with a high content of radon in them - a natural radioactive chemical element, which is also a decay product of uranium isotopes.

And on the territory of the Syzran region already mentioned above, namely, near the village of Repyevka, it was also possible to find in the bowels of the earth another group of healing waters - not only radon, but also sulfide and iodine-bromine, confined to the same deposits. At the same time, medical studies have established that radon waters are very effective against many ailments - in particular, in the treatment of chronic diseases of the central nervous system, musculoskeletal system, peripheral nerve trunks and blood vessels, some diseases of the heart muscle, valvular apparatus, diseases and metabolic disorders, diseases of the skin, and so on. But at the same time, experts note that in order to obtain more specific data on the radon waters of the Middle Volga region, more detailed search and evaluation work is needed, for which no one has allocated funds yet.

Nowadays, theoretical geologists call the Middle Volga region one of the promising regions of Russia in terms of uranium mining. Moreover, uranium ore occurrences are now known not only in the Syzran region. In particular, a group of uranium anomalies in Paleozoic rocks on the Bolshoi Kinel River is already being discussed in terms of detailed geological exploration. There are traces of uranium also on the Samarskaya Luka, and even in the immediate vicinity of Samara.

It is with natural radiation that some physicists also associate the appearance in a number of areas of the Samarskaya Luka of the so-called "pillars of light" - the phenomenon of vertical airglow, which has been repeatedly noted by residents of Zhiguli villages for hundreds of years. As eyewitnesses describe this phenomenon, "pillars" can suddenly appear at night over the mountains and, as it were, hang in one place for different times - from several minutes to several hours.

Experts believe that the glow of the air can be caused by its ionization, and it, in turn, usually occurs in the zone of action of powerful electromagnetic or radiation radiation. And since the latest geological studies in the Middle Volga region show that the Samara Territory is included in the distribution zone of underground deposits of uranium and radium, it is quite possible that there are “windows” in the Zhiguli Mountains through which this natural radiation periodically breaks out. Then columns of ionized luminous air appear above the mountain range.

... I remember that in Soviet times, when there was no current glasnost, there were persistent legends among the people that all prisoners sentenced to death for serious crimes were sent to uranium mines instead of a death row. It is not known whether this was actually the case, but the addresses of the deposits where raw materials for the country's nuclear shield were mined were on everyone's lips. These included, in particular, uranium deposits in the territory Central Asia. However, after the collapse of the USSR, many of these mines ended up far beyond the borders of Russia.

Therefore, it is possible that with the depletion of uranium deposits in Transbaikalia and the Southern Urals, the development of underground deposits of this metal in the Middle Volga region will be recognized as economically viable. And then it is quite possible that uranium mines will appear in the immediate vicinity of Samara (Fig. 5).

Valery EROFEEV.

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