Presentation on the topic "use of radioactive isotopes." Applications of isotopes What are the possible applications of radioactive isotopes, give examples
Course work
On the topic: "Radioactivity.
Application of radioactive isotopes in technology"
Introduction
1. Types of radioactive radiation
2.Other types of radioactivity
3. Alpha decay
4.Beta decay
5. Gamma decay
6.The law of radioactive decay
7.Radioactive series
8. Effect of radioactive radiation on humans
9.Use of radioactive isotopes
List of used literature
Introduction
Radioactivity– the transformation of atomic nuclei into other nuclei, accompanied by the emission of various particles and electromagnetic radiation. Hence the name of the phenomenon: in Latin radio - radiate, activus - effective. This word was coined by Marie Curie. When an unstable nucleus - a radionuclide - decays, one or more high-energy particles fly out of it at high speed. The flow of these particles is called radioactive radiation or simply radiation.
X-rays. The discovery of radioactivity was directly related to the discovery of Roentgen. Moreover, for some time they thought that these were the same type of radiation. Late 19th century In general, he was rich in the discovery of various kinds of previously unknown “radiations.” In the 1880s, the English physicist Joseph John Thomson began studying elementary negative charge carriers; in 1891, the Irish physicist George Johnston Stoney (1826–1911) called these particles electrons. Finally, in December, Wilhelm Conrad Roentgen announced the discovery of a new type of ray, which he called X-rays. Until now, in most countries they are called that way, but in Germany and Russia the proposal of the German biologist Rudolf Albert von Kölliker (1817–1905) to call the rays X-rays has been accepted. These rays are created when electrons flying quickly in a vacuum (cathode rays) collide with an obstacle. It was known that when cathode rays hit glass, it emits visible light - green luminescence. X-ray discovered that at the same time some other invisible rays were emanating from the green spot on the glass. This happened by accident: in a dark room, a nearby screen covered with barium tetracyanoplatinate Ba (previously called barium platinum sulfide) was shining. This substance produces bright yellow-green luminescence under the influence of ultraviolet and cathode rays. But the cathode rays did not hit the screen, and moreover, when the device was covered with black paper, the screen continued to glow. Roentgen soon discovered that radiation passed through many opaque substances and caused blackening of a photographic plate wrapped in black paper or even placed in a metal case. The rays passed through a very thick book, through a 3 cm thick spruce board, through an aluminum plate 1.5 cm thick... Roentgen realized the possibilities of his discovery: “If you hold your hand between the discharge tube and the screen,” he wrote, “you can see dark shadows bones against the background of the lighter outlines of the hand.” This was the first fluoroscopic examination in history.
Roentgen's discovery instantly spread throughout the world and amazed not only specialists. On the eve of 1896, a photograph of a hand was exhibited in a bookstore in a German city. The bones of a living person were visible on it, and on one of the fingers was a wedding ring. It was an X-ray photograph of the hand of Roentgen's wife. Roentgen's first message “ About a new kind of rays" was published in the “Reports of the Würzburg Physico-Medical Society” on December 28, it was immediately translated and published in different countries, the most famous scientific journal “Nature” published in London published Roentgen’s article on January 23, 1896.
New rays began to be explored all over the world; in one year alone, over a thousand papers were published on this topic. X-ray machines of simple design also appeared in hospitals: the medical use of the new rays was obvious.
Now X-rays are widely used (and not only for medical purposes) throughout the world.
Becquerel's rays. Roentgen's discovery soon led to an equally remarkable discovery. It was made in 1896 by the French physicist Antoine Henri Becquerel. On January 20, 1896, he attended a meeting of the Academy, at which the physicist and philosopher Henri Poincaré spoke about the discovery of Roentgen and demonstrated X-ray photographs of a human hand taken in France. Poincare did not limit himself to talking about new rays. He suggested that these rays are associated with luminescence and, perhaps, always appear simultaneously with this type of glow, so that it is probably possible to do without cathode rays. The luminescence of substances under the influence of ultraviolet radiation - fluorescence or phosphorescence (in the 19th century there was no strict distinction between these concepts) was familiar to Becquerel: both his father Alexander Edmond Becquerel (1820-1891) and his grandfather Antoine Cesar Becquerel (1788-1878) were involved in it - both physicists; Antoine Henri Becquerel’s son, Jacques, also became a physicist, who “inherited” the chair of physics at the Paris Museum of Natural History; Becquerel headed this chair for 110 years, from 1838 to 1948.
Becquerel decided to test whether X-rays were associated with fluorescence. Some uranium salts, for example, uranyl nitrate UO 2 (NO 3) 2, exhibit bright yellow-green fluorescence. Such substances were in Becquerel’s laboratory, where he worked. His father also worked with uranium preparations, who showed that after the cessation of sunlight, their glow disappears very quickly - in less than a hundredth of a second. However, no one has checked whether this glow is accompanied by the emission of some other rays that can pass through opaque materials, as was the case with Roentgen. This is precisely what Becquerel decided to check after Poincaré’s report. On February 24, 1896, at the weekly meeting of the Academy, he said that he took a photographic plate wrapped in two layers of thick black paper, placed crystals of double potassium-uranyl sulfate K 2 UO 2 (SO 4) 2 2H2O on it and exposed it all for several hours sunlight, then after developing the photographic plate you can see a somewhat blurred outline of the crystals on it. If a coin or a figure cut out of tin is placed between the plate and the crystals, then after development a clear image of these objects appears on the plate.
All this could indicate a connection between fluorescence and X-ray radiation. The recently discovered X-rays can be obtained much more simply - without cathode rays and the vacuum tube and high voltage required for this, but it was necessary to check whether it turns out that the uranium salt, when heated in the sun, releases some kind of gas that penetrates under the black paper and acts on the photographic emulsion. To exclude this possibility, Becquerel placed a sheet of glass between the uranium salt and the photographic plate - it still lit up. “From here,” Becquerel concluded his brief message, “we can conclude that the luminous salt emits rays that penetrate through the black paper, opaque to light, and restore the silver salts in the photographic plate.” As if Poincaré was right and X-rays from X-rays can be obtained in a completely different way.
Becquerel began to carry out many experiments to better understand the conditions under which rays appear that illuminate a photographic plate, and to investigate the properties of these rays. He placed different substances between the crystals and the photographic plate - paper, glass, aluminum, copper, and lead plates of different thicknesses. The results were the same as those obtained by Roentgen, which could also serve as an argument in favor of the similarity of both radiations. In addition to direct sunlight, Becquerel illuminated the uranium salt with light reflected from a mirror or refracted by a prism. He received that the results of all previous experiments were in no way connected with the sun; all that mattered was how long the uranium salt was near the photographic plate. The next day, Becquerel reported about this at a meeting of the Academy, but, as it later turned out, he made the wrong conclusion: he decided that uranium salt, at least once “charged” in the light, is then capable of emitting invisible penetrating rays for a long time.
By the end of the year, Becquerel published nine articles on this topic, in one of them he wrote: “Different uranium salts were placed in a thick-walled lead box... Protected from the action of any known radiation, these substances continued to emit rays passing through glass and black paper..., in eight months.”
These rays came from any uranium compound, even those that do not glow in the sun. The radiation from metallic uranium turned out to be even stronger (about 3.5 times). It became obvious that the radiation, although similar in some manifestations to X-rays, had greater penetrating power and was somehow related to uranium, so Becquerel began to call it “uranium rays.”
Becquerel also discovered that “uranium rays” ionize the air, making it a conductor of electricity. Almost simultaneously, in November 1896, English physicists J. J. Thomson and Ernest Rutherford (discovered the ionization of air under the influence of X-rays. To measure the intensity of radiation, Becquerel used an electroscope in which the lightest gold leaves, suspended by their ends and charged electrostatically, repel and their free ends diverge. If the air conducts current, the charge drains from the leaves and they fall off - the faster the higher the electrical conductivity of the air and, therefore, the greater the intensity of the radiation.
The question remained of how a substance emits continuous radiation that does not weaken over many months without the supply of energy from an external source. Becquerel himself wrote that he was unable to understand where uranium received the energy that it continuously emits. A variety of hypotheses have been put forward on this matter, sometimes quite fantastic. For example, the English chemist and physicist William Ramsay wrote: “... physicists were perplexed where the inexhaustible supply of energy in uranium salts could come from. Lord Kelvin was inclined to suppose that uranium serves as a kind of trap, which catches otherwise undetectable radiant energy reaching us through space, and converts it into such a form as to make it capable of producing chemical effects."
Becquerel could neither accept this hypothesis, nor come up with something more plausible, nor abandon the principle of conservation of energy. It ended with him giving up work with uranium altogether for some time and taking up the splitting of spectral lines in a magnetic field. This effect was discovered almost simultaneously with the discovery of Becquerel by the young Dutch physicist Pieter Zeeman and explained by another Dutchman, Hendrik Anton Lorentz.
This completed the first stage of radioactivity research. Albert Einstein compared the discovery of radioactivity to the discovery of fire, since he believed that both fire and radioactivity were equally major milestones in the history of civilization.
1. Types of radioactive radiation
When powerful sources of radiation appeared in the hands of researchers, millions of times stronger than uranium (these were preparations of radium, polonium, actinium), it was possible to become more familiar with the properties of radioactive radiation. Ernest Rutherford, the spouses Maria and Pierre Curie, A. Becquerel, and many others took an active part in the first studies on this topic. First of all, the penetrating ability of the rays was studied, as well as the effect on the radiation of the magnetic field. It turned out that the radiation is not uniform, but is a mixture of “rays”. Pierre Curie discovered that when a magnetic field acts on radium radiation, some rays are deflected while others are not. It was known that a magnetic field deflects only charged flying particles, positive and negative in different directions. Based on the direction of deflection, we were convinced that the deflected β-rays were negatively charged. Further experiments showed that there was no fundamental difference between cathode and β-rays, which meant that they represented a flow of electrons.
Deflected rays had a stronger ability to penetrate various materials, while non-deviated rays were easily absorbed even by thin aluminum foil - this is how, for example, the radiation of the new element polonium behaved - its radiation did not penetrate even through the cardboard walls of the box in which the drug was stored.
When using stronger magnets, it turned out that α-rays are also deflected, only much weaker than β-rays, and in the other direction. It followed from this that they were positively charged and had a significantly larger mass (as it was later found out, the mass of α-particles is 7740 times greater than the mass of the electron). This phenomenon was first discovered in 1899 by A. Becquerel and F. Giesel. Later it turned out that α-particles are the nuclei of helium atoms (nuclide 4 He) with a charge of +2 and a mass of 4 units. When in 1900 the French physicist Paul Villar (1860–1934) studied in more detail the deviation of α- and β-rays, he discovered in the radiation of radium a third type of rays that do not deviate in the strongest magnetic fields; this discovery was soon confirmed by Becquerel. This type of radiation, by analogy with alpha and beta rays, was called gamma rays; the designation of different radiations with the first letters of the Greek alphabet was proposed by Rutherford. Gamma rays turned out to be similar to X-rays, i.e. they are electromagnetic radiation, but with shorter wavelengths and therefore more energy. All these types of radiation were described by M. Curie in her monograph “Radium and Radioactivity”. Instead of a magnetic field, an electric field can be used to “split” radiation, only the charged particles in it will not be deflected perpendicular to the lines of force, but along them - towards the deflection plates.
For a long time it was unclear where all these rays come from. Over the course of several decades, through the work of many physicists, the nature of radioactive radiation and its properties were clarified, and new types of radioactivity were discovered.γ
Alpha rays are emitted mainly by the nuclei of the heaviest and therefore less stable atoms (they are located after lead in the periodic table). These are high energy particles. Usually several groups of α particles are observed, each of which has a strictly defined energy. Thus, almost all α particles emitted from 226 Ra nuclei have an energy of 4.78 MeV (megaelectron volts) and a small fraction of α particles have an energy of 4.60 MeV. Another radium isotope, 221 Ra, emits four groups of α particles with energies of 6.76, 6.67, 6.61 and 6.59 MeV. This indicates the presence of several energy levels in nuclei; their difference corresponds to the energy of α-quanta emitted by the nucleus. “Pure” alpha emitters are also known (for example, 222 Rn).
According to the formula E = mu 2 /2 it is possible to calculate the speed of α-particles with a certain energy. For example, 1 mol α particles with E= 4.78 MeV has energy (in SI units) E= 4.78 10 6 eV 96500 J/(eV mol) = 4.61 10 11 J/mol and mass m= 0.004 kg/mol, from where uα 15200 km/s, which is tens of thousands of times faster than the speed of a pistol bullet. Alpha particles have the strongest ionizing effect: when they collide with any other atoms in a gas, liquid or solid, they “strip” electrons from them, creating charged particles. In this case, α-particles lose energy very quickly: they are retained even by a sheet of paper. In air, α-radiation from radium travels only 3.3 cm, α-radiation from thorium – 2.6 cm, etc. Ultimately, the α particle, which has lost kinetic energy, captures two electrons and turns into a helium atom. The first ionization potential of a helium atom (He – e → He +) is 24.6 eV, the second (He + – e → He +2) is 54.4 eV, which is much higher than that of any other atoms. When electrons are captured by α-particles, enormous energy is released (more than 7600 kJ/mol), so not a single atom, except the atoms of helium itself, is able to retain its electrons if an α-particle happens to be nearby.
The very high kinetic energy of α-particles makes it possible to “see” them with the naked eye (or with the help of an ordinary magnifying glass), this was first demonstrated in 1903 by the English physicist and chemist William Crookes (1832 - 1919. He glued a grain of radium salt to the tip of a needle, barely visible to the eye, and strengthened the needle in a wide glass tube. At one end of this tube, not far from the tip of the needle, was placed a plate covered with a layer of phosphor (it was zinc sulfide), and at the other end there was a magnifying glass. If you examine the phosphor in the dark, you can see: the entire field vision is dotted with sparks flashing and now dying out. Each spark is the result of the impact of one α-particle. Crookes called this device a spinthariscope (from the Greek spintharis - spark and skopeo - look, observe). Using this simple method of counting α-particles, A number of studies have been carried out, for example, using this method it was possible to quite accurately determine Avogadro's constant.
In the nucleus, protons and neutrons are held together by nuclear forces. Therefore, it was not clear how an alpha particle, consisting of two protons and two neutrons, could leave the nucleus. The answer was given in 1928 by the American physicist (who emigrated from the USSR in 1933) George (Georgi Antonovich) Gamow). According to the laws of quantum mechanics, α-particles, like any particles of low mass, have a wave nature and therefore they have some small probability of ending up outside the nucleus, on a small (about 6 · 10–12 cm) distance from it. As soon as this happens, the particle begins to experience Coulomb repulsion from a very nearby positively charged nucleus.
It is mainly heavy nuclei that are subject to alpha decay - more than 200 of them are known; alpha particles are emitted by most isotopes of elements following bismuth. Lighter alpha emitters are known, mainly atoms of rare earth elements. But why do alpha particles fly out of the nucleus, and not individual protons? Qualitatively, this is explained by the energy gain during α-decay (α-particles - helium nuclei are stable). The quantitative theory of α-decay was created only in the 1980s; domestic physicists also took part in its development, including Lev Davidovich Landau, Arkady Beinusovich Migdal (1911–1991), head of the department of nuclear physics at Voronezh University Stanislav Georgievich Kadmensky and colleagues .
The departure of an alpha particle from the nucleus leads to the nucleus of another chemical element, which is shifted two cells to the left in the periodic table. An example is the transformation of seven isotopes of polonium (nuclear charge 84) into different isotopes of lead (nuclear charge 82): 218 Po → 214 Pb, 214 Po → 210 Pb, 210 Po → 206 Pb, 211 Po → 207 Pb, 215 Po → 211 Pb, 212 Po → 208 Pb, 216 Po → 212 Pb. Lead isotopes 206 Pb, 207 Pb and 208 Pb are stable, the rest are radioactive.
Beta decay occurs in both heavy and light nuclei, such as tritium. These light particles (fast electrons) have higher penetrating power. Thus, in air, β-particles can fly several tens of centimeters, in liquid and solid substances - from fractions of a millimeter to about 1 cm. Unlike α-particles, the energy spectrum of β-rays is not discrete. The energy of electrons escaping from the nucleus can vary from almost zero to a certain maximum value characteristic of a given radionuclide. Typically, the average energy of β particles is much less than that of α particles; for example, the energy of β-radiation from 228 Ra is 0.04 MeV. But there are exceptions; so the β-radiation of the short-lived nuclide 11 Be carries an energy of 11.5 MeV. For a long time it was unclear how particles fly out from identical atoms of the same element at different speeds. When the structure of the atom and the atomic nucleus became clear, a new mystery arose: where do the β-particles escaping from the nucleus come from - after all, there are no electrons in the nucleus. After the English physicist James Chadwick discovered the neutron in 1932, Russian physicists Dmitry Dmitrievich Ivanenko (1904–1994) and Igor Evgenievich Tamm and independently the German physicist Werner Heisenberg suggested that atomic nuclei consist of protons and neutrons. In this case, β-particles should be formed as a result of the intranuclear process of converting a neutron into a proton and an electron: n → p + e. The mass of a neutron is slightly greater than the combined mass of a proton and an electron, an excess of mass, in accordance with Einstein's formula E = mc 2, gives the kinetic energy of an electron escaping from the nucleus, therefore β-decay is observed mainly in nuclei with an excess number of neutrons. For example, the nuclide 226 Ra is an α-emitter, and all the heavier isotopes of radium (227 Ra, 228 Ra, 229 Ra and 230 Ra) are β-emitters.
It remained to find out why β-particles, unlike α-particles, have a continuous energy spectrum, which meant that some of them have very low energy, while others have very high energy (and at the same time move at a speed close to the speed of light) . Moreover, the total energy of all these electrons (it was measured using a calorimeter) turned out to be less than the difference in the energy of the original nucleus and the product of its decay. Once again, physicists were faced with a “violation” of the law of conservation of energy: part of the energy of the original nucleus disappeared to an unknown destination. The unshakable physical law was “saved” in 1931 by the Swiss physicist Wolfgang Pauli, who suggested that during β-decay two particles fly out of the nucleus: an electron and a hypothetical neutral particle - a neutrino with almost zero mass, which carries away excess energy. The continuous spectrum of β-radiation is explained by the distribution of energy between electrons and this particle. Neutrinos (as it later turned out, the so-called electron antineutrino is formed during beta decay) interact very weakly with matter (for example, they easily pierce the diameter of the globe and even a huge star) and therefore were not detected for a long time - experimentally free neutrinos were registered only in 1956 Thus, the refined beta decay scheme is as follows: n → p +. The quantitative theory of β-decay, based on Pauli’s ideas about neutrinos, was developed in 1933 by the Italian physicist Enrico Fermi, who also proposed the name neutrino (in Italian “neutron”).
The transformation of a neutron into a proton during beta decay practically does not change the mass of the nuclide, but increases the charge of the nucleus by one. Consequently, a new element is formed, shifted one cell to the right in the periodic table, for example: →, →, →, etc. (an electron and an antineutrino fly out from the nucleus at the same time).
2. Other types of radioactivity
In addition to alpha and beta decays, other types of spontaneous radioactive transformations are known. In 1938, American physicist Louis Walter Alvarez discovered a third type of radioactive transformation - electron capture (E-capture). In this case, the nucleus captures an electron from the energy shell closest to it (K-shell). When an electron interacts with a proton, a neutron is formed, and a neutrino flies out of the nucleus, carrying away excess energy. The transformation of a proton into a neutron does not change the mass of the nuclide, but reduces the charge of the nucleus by one. Consequently, a new element is formed, located one cell to the left in the periodic table, for example, a stable nuclide is obtained (it was in this example that Alvarez discovered this type of radioactivity).
During K-capture in the electron shell of an atom, an electron from a higher energy level “descends” to the place of the disappeared electron, the excess energy is either released in the form of X-rays or is spent on the departure from the atom of more weakly bound one or more electrons - the so-called Auger electrons , named after the French physicist Pierre Auger (1899–1993), who discovered this effect in 1923 (he used ionizing radiation to knock out internal electrons).
In 1940, Georgy Nikolaevich Flerov (1913–1990) and Konstantin Antonovich Petrzhak (1907–1998), using the example of uranium, discovered spontaneous fission, in which an unstable nucleus decays into two lighter nuclei, the masses of which do not differ very much, for example: → + + 2n. This type of decay is observed only in uranium and heavier elements - more than 50 nuclides in total. In the case of uranium, spontaneous fission occurs very slowly: the average lifetime of a 238 U atom is 6.5 billion years. In 1938, the German physicist and chemist Otto Hahn, the Austrian radiochemist and physicist Lise Meitner (the element Mt - meitnerium is named after her) and the German physical chemist Fritz Strassmann (1902–1980) discovered that when bombarded by neutrons, uranium nuclei are divided into fragments, and those emitted from neutrons can cause fission of neighboring uranium nuclei, which leads to a chain reaction). This process is accompanied by the release of enormous (compared to chemical reactions) energy, which led to the creation of nuclear weapons and the construction of nuclear power plants.
In 1934, Marie Curie's daughter Irène Joliot-Curie and her husband Frédéric Joliot-Curie discovered positron decay. In this process, one of the protons of the nucleus turns into a neutron and an antielectron (positron) - a particle with the same mass, but positively charged; simultaneously, a neutrino flies out of the nucleus: p → n + e + + 238. The mass of the nucleus does not change, but a shift occurs, unlike β – decay, to the left, β+ decay is characteristic of nuclei with an excess of protons (the so-called neutron-deficient nuclei ). Thus, the heavy isotopes of oxygen 19 O, 20 O and 21 O β - are active, and its light isotopes 14 O and 15 O β + are active, for example: 14 O → 14 N + e + + 238. Like antiparticles, positrons are immediately they are destroyed (annihilated) when they meet electrons with the formation of two γ quanta. Positron decay often competes with K-capture.
In 1982, proton radioactivity was discovered: the emission of a proton by a nucleus (this is only possible for some artificially produced nuclei with excess energy). In 1960, physical chemist Vitaly Iosifovich Goldansky (1923–2001) theoretically predicted two-proton radioactivity: the ejection of two protons with paired spins from a nucleus. It was first observed in 1970. Two-neutron radioactivity is also very rarely observed (discovered in 1979).
In 1984, cluster radioactivity was discovered (from the English cluster - bunch, swarm). In this case, in contrast to spontaneous fission, the nucleus decays into fragments with very different masses, for example, nuclei with masses from 14 to 34 fly out from a heavy nucleus. Cluster decay is also observed very rarely, and this has made it difficult to detect for a long time.
Some nuclei are capable of decaying in different directions. For example, 221 Rn decays 80% with the emission of α-particles and 20% with β-particles; many isotopes of rare earth elements (137 Pr, 141 Nd, 141 Pm, 142 Sm, etc.) decay either by electron capture or with positron emission. Various types of radioactive radiation are often (but not always) accompanied by γ-radiation. This happens because the resulting nucleus may have excess energy, from which it is released by emitting gamma rays. The energy of γ-radiation lies within a wide range, for example, during the decay of 226 Ra it is equal to 0.186 MeV, and during the decay of 11 Be it reaches 8 MeV.
Almost 90% of the known 2500 atomic nuclei are unstable. An unstable nucleus spontaneously transforms into other nuclei, emitting particles. This property of nuclei is called radioactivity. In large nuclei, instability arises due to competition between the attraction of nucleons by nuclear forces and the Coulomb repulsion of protons. There are no stable nuclei with a charge number Z > 83 and a mass number A > 209. But atomic nuclei with significantly lower values of the Z and A numbers can also be radioactive. If the nucleus contains significantly more protons than neutrons, then the instability is caused by an excess of Coulomb interaction energy . Nuclei that would contain a large excess of neutrons over the number of protons turn out to be unstable due to the fact that the mass of the neutron exceeds the mass of the proton. An increase in the mass of the nucleus leads to an increase in its energy.
The phenomenon of radioactivity was discovered in 1896 by the French physicist A. Becquerel, who discovered that uranium salts emit unknown radiation that can penetrate barriers opaque to light and cause blackening of the photographic emulsion. Two years later, French physicists M. and P. Curie discovered the radioactivity of thorium and discovered two new radioactive elements - polonium and radium
In subsequent years, many physicists, including E. Rutherford and his students, studied the nature of radioactive radiation. It was found that radioactive nuclei can emit particles of three types: positively and negatively charged and neutral. These three types of radiation were called α-, β- and γ-radiation. These three types of radioactive radiation differ greatly from each other in their ability to ionize atoms of matter and, therefore, in their penetrating ability. α-radiation has the least penetrating ability. In air under normal conditions, α-rays travel a distance of several centimeters. β-rays are much less absorbed by matter. They are able to pass through a layer of aluminum several millimeters thick. γ-rays have the greatest penetrating ability, capable of passing through a layer of lead 5–10 cm thick.
In the second decade of the 20th century, after E. Rutherford’s discovery of the nuclear structure of atoms, it was firmly established that radioactivity is a property of atomic nuclei. Research has shown that α-rays represent a flow of α-particles - helium nuclei, β-rays are a flow of electrons, γ-rays are short-wave electromagnetic radiation with an extremely short wavelength λ< 10 –10 м и вследствие этого – ярко выраженными корпускулярными свойствами, т.е. является потоком частиц – γ-квантов.
3. Alpha decay
Alpha decay is the spontaneous transformation of an atomic nucleus with the number of protons Z and neutrons N into another (daughter) nucleus containing the number of protons Z – 2 and neutrons N – 2. In this case, an α particle is emitted - the nucleus of a helium atom. An example of such a process is the α-decay of radium: 
Alpha particles emitted by the nuclei of radium atoms were used by Rutherford in experiments on scattering by the nuclei of heavy elements. The speed of α-particles emitted during the α-decay of radium nuclei, measured from the curvature of the trajectory in a magnetic field, is approximately 1.5 10 7 m/s, and the corresponding kinetic energy is about 7.5 10 –13 J (approximately 4. 8 MeV). This value can be easily determined from the known values of the masses of the mother and daughter nuclei and the helium nucleus. Although the speed of the escaping α particle is enormous, it is still only 5% of the speed of light, so when calculating, you can use a non-relativistic expression for kinetic energy. Research has shown that a radioactive substance can emit alpha particles with several discrete energies. This is explained by the fact that nuclei can be, like atoms, in different excited states. The daughter nucleus may end up in one of these excited states during α decay.
During the subsequent transition of this nucleus to the ground state, a γ-quantum is emitted. A diagram of the α-decay of radium with the emission of α-particles with two values of kinetic energies is shown in Fig. 2. Thus, α-decay of nuclei is in many cases accompanied by γ-radiation.
In the theory of α-decay, it is assumed that groups consisting of two protons and two neutrons can be formed inside nuclei, i.e. α particle. The mother nucleus is a potential well for α particles, which is limited by a potential barrier. The energy of the α particle in the nucleus is not sufficient to overcome this barrier (Fig. 3). The escape of an alpha particle from the nucleus is possible only due to a quantum mechanical phenomenon called the tunneling effect. According to quantum mechanics, there is a non-zero probability of a particle passing under a potential barrier. The phenomenon of tunneling is probabilistic in nature.
4. Beta decay
During beta decay, an electron is ejected from the nucleus. Electrons cannot exist inside nuclei; they arise during beta decay as a result of the transformation of a neutron into a proton. This process can occur not only inside the nucleus, but also with free neutrons. The average lifetime of a free neutron is about 15 minutes. During decay, a neutron turns into a proton and an electron
Measurements have shown that in this process there is an apparent violation of the law of conservation of energy, since the total energy of the proton and electron resulting from the decay of a neutron is less than the energy of the neutron. In 1931, W. Pauli suggested that during the decay of a neutron, another particle with zero mass and charge is released, which takes away part of the energy. The new particle is called a neutrino (small neutron). Due to the lack of charge and mass of a neutrino, this particle interacts very weakly with the atoms of matter, so it is extremely difficult to detect in experiment. The ionizing ability of neutrinos is so small that one ionization event in the air occurs approximately 500 km of the way. This particle was discovered only in 1953. It is now known that there are several types of neutrinos. During the decay of a neutron, a particle is created, which is called an electron antineutrino. It is indicated by the symbol. Therefore, the neutron decay reaction is written in the form
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A similar process occurs inside nuclei during β-decay. An electron formed as a result of the decay of one of the nuclear neutrons is immediately ejected from the “parental home” (nucleus) at enormous speed, which can differ from the speed of light by only a fraction of a percent. Since the distribution of energy released during β-decay between the electron, neutrino and daughter nucleus is random, β-electrons can have different velocities over a wide range.
During β-decay, the charge number Z increases by one, but the mass number A remains unchanged. The daughter nucleus turns out to be the nucleus of one of the isotopes of the element, the serial number of which in the periodic table is one higher than the serial number of the original nucleus. A typical example of β-decay is the transformation of thorium isotone resulting from the α-decay of uranium into palladium
5. Gamma decay
Unlike α- and β-radioactivity, γ-radioactivity of nuclei is not associated with a change in the internal structure of the nucleus and is not accompanied by a change in charge or mass numbers. Both during α- and β-decay, the daughter nucleus may find itself in some excited state and have an excess of energy. The transition of a nucleus from an excited state to a ground state is accompanied by the emission of one or more γ quanta, the energy of which can reach several MeV.
6. The law of radioactive decay
Any sample of a radioactive substance contains a huge number of radioactive atoms. Since radioactive decay is random in nature and does not depend on external conditions, the law of decrease in the number N(t) of nuclei that have not decayed by a given time t can serve as an important statistical characteristic of the radioactive decay process.
Let the number of undecayed nuclei N(t) change by ΔN over a short period of time Δt< 0. Так как вероятность распада каждого ядра неизменна во времени, что число распадов будет пропорционально количеству ядер N(t) и промежутку времени Δt:
The proportionality coefficient λ is the probability of nuclear decay in time Δt = 1 s. This formula means that the rate of change of the function N(t) is directly proportional to the function itself.
where N 0 is the initial number of radioactive nuclei at t = 0. During the time τ = 1 / λ, the number of undecayed nuclei will decrease by e ≈ 2.7 times. The value τ is called the average lifetime of a radioactive nucleus.
For practical use, it is convenient to write the law of radioactive decay in a different form, using the number 2 rather than e as the base:
The T value is called the half-life. During time T, half of the original number of radioactive nuclei decays. The quantities T and τ are related by the relation
Half-life is the main quantity characterizing the rate of radioactive decay. The shorter the half-life, the more intense the decay. So, for uranium T ≈ 4.5 billion years, and for radium T ≈ 1600 years. Therefore, the activity of radium is much higher than that of uranium. There are radioactive elements with half-lives of a fraction of a second.
During α- and β-radioactive decay, the daughter nucleus may also become unstable. Therefore, a series of successive radioactive decays are possible, which end in the formation of stable nuclei. There are several such series in nature. The longest is a series consisting of 14 consecutive decays (8 alpha decays and 6 beta decays). This series ends with a stable isotope of lead (Fig. 5).
In nature, there are several more radioactive series similar to the series. There is also a series known that begins with neptunium, not found in natural conditions, and ends with bismuth. This series of radioactive decays occurs in nuclear reactors.
Offset rule. The displacement rule specifies exactly what transformations a chemical element undergoes when emitting radioactive radiation.
7. Radioactive series
The displacement rule made it possible to trace the transformations of natural radioactive elements and build from them three family trees, the ancestors of which are uranium-238, uranium-235 and thorium-232. Each family begins with an extremely long-lived radioactive element. The uranium family, for example, is headed by uranium with a mass number of 238 and a half-life of 4.5·10 9 years (in Table 1, in accordance with the original name, designated as uranium I).
| Table 1. Radioactive family of uranium | |||||
| Radioactive element | Z | Chemical element | A | Radiation type |
Half-life |
| Uranus I | 92 | Uranus | 238 | | 4.510 9 years |
| Uranium X 1 | 90 | Thorium | 234 | | 24.1 days |
| Uranium X 2 Uranium Z |
Protactinium Protactinium |
–
(99,88%) (0,12%) |
|||
| Uranus II | 92 | Uranus | 234 | | 2.510 5 years |
| Ionium | 90 | Thorium | 230 | | 810 4 years |
| Radium | 88 | Radium | 226 | | 1620 years |
| Radon | 86 | Radon | 222 | | 3.8 days |
| Radium A | 84 | Polonium | 218 | | 3.05 min |
| Radium B | 82 | Lead | 214 | | 26.8 min |
| 83 83 |
Bismuth Bismuth |
214 214 |
(99,96%) (0,04%) |
||
| Radium C | 84 | Polonium | 214 | | 1.610 –4 s |
| Radium C | 81 | Thallium | 210 | | 1.3 min |
| Radium D | 82 | Lead | 210 | | 25 years |
| Radium E | 83 | Bismuth | 210 | | 4.85 days |
| Radium F | 84 | Polonium | 210 | | 138 days |
| Radium G | 82 | Lead | 206 | Stable | |
Uranium family. Most of the properties of radioactive transformations discussed above can be traced to the elements of the uranium family. For example, the third member of the family exhibits nuclear isomerism. Uranium X 2, emitting beta particles, turns into uranium II (T = 1.14 min). This corresponds to beta decay of the excited state of protactinium-234. However, in 0.12% of cases, excited protactinium-234 (uranium X 2) emits a gamma quantum and passes to the ground state (uranium Z). The beta decay of uranium Z, which also leads to the formation of uranium II, occurs in 6.7 hours.
Radium C is interesting because it can decay in two ways: emitting either an alpha or a beta particle. These processes compete with each other, but in 99.96% of cases beta decay occurs with the formation of radium C. In 0.04% of cases, radium C emits an alpha particle and turns into radium C (RaC). In turn, RaC and RaC are converted into radium D by the emission of alpha and beta particles, respectively.
Isotopes. Among the members of the uranium family, there are those whose atoms have the same atomic number (the same nuclear charge) and different mass numbers. They are identical in chemical properties, but differ in the nature of radioactivity. For example, radium B, radium D and radium G, which have the same atomic number 82 as lead, are similar to lead in chemical behavior. It is obvious that chemical properties do not depend on mass number; they are determined by the structure of the electron shells of the atom (hence, Z). On the other hand, the mass number is critical to the nuclear stability of the radioactive properties of an atom. Atoms with the same atomic number and different mass numbers are called isotopes. Isotopes of radioactive elements were discovered by F. Soddy in 1913, but soon F. Aston, using mass spectroscopy, proved that many stable elements also have isotopes.
8. Effect of radioactive radiation on humans
Radioactive radiation of all types (alpha, beta, gamma, neutrons), as well as electromagnetic radiation (X-rays) have a very strong biological effect on living organisms, which consists in the processes of excitation and ionization of atoms and molecules that make up living cells. Under the influence of ionizing radiation, complex molecules and cellular structures are destroyed, which leads to radiation damage to the body. Therefore, when working with any source of radiation, it is necessary to take all measures to protect people who may be exposed to radiation.
However, a person can be exposed to ionizing radiation at home. The inert, colorless, radioactive gas radon can pose a serious danger to human health. As can be seen from the diagram shown in Fig. 5, radon is a product of the α-decay of radium and has a half-life T = 3.82 days. Radium is found in small quantities in soil, stones, and various building structures. Despite the relatively short lifetime, the concentration of radon is continuously replenished due to new decays of radium nuclei, so radon can accumulate in enclosed spaces. Once in the lungs, radon emits α-particles and turns into polonium, which is not a chemically inert substance. What follows is a chain of radioactive transformations of the uranium series (Fig. 5). According to the American Commission on Radiation Safety and Control, the average person receives 55% of ionizing radiation from radon and only 11% from medical care. The contribution of cosmic rays is approximately 8%. The total radiation dose that a person receives during his life is many times less than the maximum permissible dose (MAD), which is established for people in certain professions who are subject to additional exposure to ionizing radiation.
9. Application of radioactive isotopes
One of the most outstanding studies carried out using “tagged atoms” was the study of metabolism in organisms. It has been proven that in a relatively short time the body undergoes almost complete renewal. The atoms that make it up are replaced by new ones. Only iron, as experiments on isotope studies of blood have shown, is an exception to this rule. Iron is part of the hemoglobin of red blood cells. When radioactive iron atoms were introduced into food, it was found that the free oxygen released during photosynthesis was originally part of water, not carbon dioxide. Radioactive isotopes are used in medicine both for diagnosis and for therapeutic purposes. Radioactive sodium, injected in small quantities into the blood, is used to study blood circulation; iodine is intensively deposited in the thyroid gland, especially in Graves' disease. By observing radioactive iodine deposition using a meter, a diagnosis can be made quickly. Large doses of radioactive iodine cause partial destruction of abnormally developing tissues, and therefore radioactive iodine is used to treat Graves' disease. Intense cobalt gamma radiation is used in the treatment of cancer (cobalt gun).
No less extensive are the applications of radioactive isotopes in industry. One example of this is the following method for monitoring piston ring wear in internal combustion engines. By irradiating the piston ring with neutrons, they cause nuclear reactions in it and make it radioactive. When the engine operates, particles of ring material enter the lubricating oil. By examining the level of radioactivity in the oil after a certain time of engine operation, ring wear is determined. Radioactive isotopes make it possible to judge the diffusion of metals, processes in blast furnaces, etc.
Powerful gamma radiation from radioactive drugs is used to examine the internal structure of metal castings in order to detect defects in them.
Radioactive isotopes are increasingly used in agriculture. Irradiation of plant seeds (cotton, cabbage, radishes, etc.) with small doses of gamma rays from radioactive drugs leads to a noticeable increase in yield. Large doses of radiation cause mutations in plants and microorganisms, which in some cases leads to the appearance of mutants with new valuable properties (radio selection). This is how valuable varieties of wheat, beans and other crops were developed, and highly productive microorganisms used in the production of antibiotics were obtained. Gamma radiation from radioactive isotopes is also used to combat harmful insects and for food preservation. “Tagged atoms" are widely used in agricultural technology. For example, to find out which phosphorus fertilizer is better absorbed by the plant, various fertilizers are labeled with radioactive phosphorus 15 32P. Researching Then the plants are tested for radioactivity, and the amount of phosphorus they have absorbed from different types of fertilizer can be determined.
An interesting application of radioactivity is the method of dating archaeological and geological finds by the concentration of radioactive isotopes. The most commonly used method of dating is radiocarbon dating. An unstable isotope of carbon appears in the atmosphere due to nuclear reactions caused by cosmic rays. A small percentage of this isotope is found in the air along with the usual stable isotope. Plants and other organisms take up carbon from the air, and both isotopes accumulate in them in the same proportion as in the air. After the plants die, they stop consuming carbon and the unstable isotope gradually turns into nitrogen as a result of β-decay with a half-life of 5730 years. By accurately measuring the relative concentration of radioactive carbon in the remains of ancient organisms, the time of their death can be determined.
List of used literature
1. The doctrine of radioactivity. History and modernity. M. Nauka, 1973 2. Nuclear radiation in science and technology. M. Nauka, 1984 Furman V.I. 3. Alpha decay and related nuclear reactions. M. Nauka, 1985
4. Landsberg G.S. Elementary textbook of physics. Volume III. – M.: Nauka, 19865. Seleznev Yu. A. Fundamentals of elementary physics. –M.: Nauka, 1964.6. CD ROM "Big Encyclopedia of Cyril and Methodius", 1997.
7. Curie M., Radioactivity, trans. from French, 2nd ed., M. - L., 1960
8. Murin A.N., Introduction to radioactivity, Leningrad, 1955
9. Davydov A.S., Theory of the atomic nucleus, M., 1958
10. Gaisinsky M.N., Nuclear chemistry and its applications, trans. from French, M., 1961
11. Experimental Nuclear Physics, ed. E. Segre, trans. from English, vol. 3, M., 1961; INTERNET tools
Slide 2
In biology and medicine - in industry - in agriculture - in archiology
Slide 3
Isotopes in medicine and biology
Slide 4
Table 1. Main characteristics of radionuclides - γ-emitters for use for diagnostic purposes
Slide 5
Slide 6
Co60 is used to treat malignant tumors located both on the surface of the body and inside the body. To treat tumors located superficially (for example, skin cancer), cobalt is used in the form of tubes that are applied to the tumor, or in the form of needles that are injected into it. The tubes and needles containing radiocobalt are kept in this position until the tumor is destroyed. In this case, the healthy tissue surrounding the tumor should not suffer much. If the tumor is located deep in the body (stomach or lung cancer), special γ-devices containing radioactive cobalt are used. This installation creates a narrow, very powerful beam of γ-rays, which is directed to the place where the tumor is located. Radiation does not cause any pain, patients do not feel it.
Slide 7
Digital radiographic camera for fluorographic devices KRTS 01-"PONI"
Slide 8
Mammograph is a modern mammography system, with a low radiation dose and high resolution, which provides high-quality images of the breast necessary for accurate diagnosis
Slide 9
The digital fluorographic device FC-01 "Electron" is intended for conducting mass preventive X-ray examinations of the population in order to timely detect tuberculosis, cancer and other pulmonary diseases with low radiation exposure.
Slide 10
computed tomograph Computed tomography is a method of layer-by-layer x-ray examination of organs and tissues. It is based on computer processing of multiple X-ray images of the transverse layer taken at different angles.
Slide 11
Brachytherapy is not a radical, but an almost outpatient operation, during which we inject titanium grains containing an isotope into the affected organ. This radioactive nuclide kills the tumor to death. In Russia, so far only four clinics perform such an operation, two of which are in Moscow, Obninsk and Yekaterinburg, although the country needs 300-400 centers where brachytherapy is used.
Slide 12
Isotopes in industry
Slide 13
Control of wear of piston rings in internal combustion engines. By irradiating the piston ring with neutrons, they cause nuclear reactions in it and make it radioactive. When the engine operates, particles of ring material enter the lubricating oil. By examining the level of radioactivity in the oil after a certain time of engine operation, ring wear is determined.
Slide 14
Powerful y-radiation of drugs is used to study the internal structure of metal castings in order to detect defects in them.
Slide 15
Radioactive materials make it possible to judge the diffusion of materials, processes in blast furnaces, etc.
Slide 16
Isotopes in agriculture
Slide 17
Irradiation of plant seeds (cotton, cabbage, radishes, etc.) with small doses of y-rays from radioactive drugs leads to a noticeable increase in yield.
Slide 18
Large doses of radiation cause mutations in plants and microorganisms, which in some cases leads to the appearance of mutants with new valuable properties (radio selection). This is how valuable varieties of wheat, beans and other crops were developed. This is how valuable varieties of wheat, beans and other crops were developed, and highly productive microorganisms used in the production of antibiotics were obtained.
Slide 19
Gamma radiation from radioactive isotopes is also used to control harmful insects and for food preservation.
Slide 20
Isotopes in archiology
Slide 21
The radioactive carbon method has received an interesting application for determining the age of ancient objects of organic origin (wood, charcoal, fabrics, etc.). Plants always contain the B-radioactive carbon isotope 166C with a half-life of T=5700 years. It is formed in the Earth's atmosphere in small quantities from nitrogen under the influence of neutrons. The latter arise due to nuclear reactions caused by fast particles that enter the atmosphere from space (cosmic rays). Combining with oxygen, this carbon forms carbon dioxide, which is absorbed by plants, and through them, by animals. One gram of carbon from young forest samples emits about fifteen B particles per second.
Slide 22
After the death of the organism, its replenishment with radioactive carbon stops. The available amount of this isotope decreases due to radioactivity. By determining the percentage of radioactive carbon in organic remains, it is possible to determine their age if it lies in the range from 1000 to 50,000 and even up to 100,000 years. In this way, the age of Egyptian mummies, remains of prehistoric fires, etc. is known.
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State autonomous educational institution
secondary vocational education -
Novokuybyshevsk State College of Humanities and Technology
Essay
by discipline:"Chemistry"
topic: “The use of radioactive isotopes in technology”
Grazhdankina Daria Igorevna
1st year students group 16
specialty 230115
2013
1. What are isotopes and their production
Bibliography
radioactive isotope atom flaw detection
1. What are isotopes?
Isotopes are varieties of any chemical element in the periodic table D.I. Mendeleev, having different atomic weights. Different isotopes of any chemical element have the same number of protons in the nucleus and the same number of electrons on the shells of the atom, have the same atomic number and occupy certain places in the D.I. table, characteristic of a given chemical element. Mendeleev. The difference in atomic weight between isotopes is explained by the fact that the nuclei of their atoms contain different numbers of neutrons.
Radioactive isotopes are isotopes of any element of D.I. Mendeleev’s periodic table, the atoms of which have unstable nuclei and pass into a stable state through radioactive decay accompanied by radiation. For elements with atomic numbers greater than 82, all isotopes are radioactive and decay by alpha or beta decay. These are the so-called natural radioactive isotopes, usually found in nature. The atoms formed during the decay of these elements, if they have an atomic number above 82, in turn undergo radioactive decay, the products of which can also be radioactive. It turns out to be a sequential chain, or a so-called family of radioactive isotopes. There are three known natural radioactive families, called after the first element of the series, the families of uranium, thorium and actinouranium (or actinium). The uranium family includes radium and radon. The last element of each series transforms as a result of decay into one of the stable isotopes of lead with serial number 82. In addition to these families, certain natural radioactive isotopes of elements with serial numbers less than 82 are known. These are potassium-40 and some others. Of these, potassium-40 is important, as it is found in any living organism.
Radioactive isotopes of all chemical elements can be obtained artificially.
There are several ways to obtain them. Radioactive isotopes of elements such as strontium, iodine, bromine and others, occupying middle places in the periodic table, are fission products of the uranium nucleus. From a mixture of such products obtained in a nuclear reactor, they are isolated using radiochemical and other methods. Radioactive isotopes of almost all elements can be produced in a particle accelerator by bombarding certain stable atoms with protons or deuterons. A common method of producing radioactive isotopes from stable isotopes of the same element is by irradiating them with neutrons in a nuclear reactor. The method is based on the so-called radiation capture reaction. If a substance is irradiated with neutrons, the latter, having no charge, can freely approach the nucleus of an atom and, as it were, “stick” to it, forming a new nucleus of the same element, but with one extra neutron. In this case, a certain amount of energy is released in the form of gamma radiation, which is why the process is called radiation capture. Nuclei with an excess of neutrons are unstable, so the resulting isotope is radioactive. With rare exceptions, radioactive isotopes of any element can be obtained in this way.
When an isotope decays, an isotope that is also radioactive can be formed. For example, strontium-90 turns into yttrium-90, barium-140 into lanthanum-140, etc.
Transuranium elements unknown in nature with a serial number greater than 92 (neptunium, plutonium, americium, curium, etc.), all isotopes of which are radioactive, were artificially obtained. One of them gives rise to another radioactive family - the neptunium family.
During the operation of reactors and accelerators, radioactive isotopes are formed in the materials and parts of these installations and surrounding equipment. This "induced activity", which persists for a more or less long time after the installations have stopped operating, represents an undesirable source of radiation. Induced activity also occurs in a living organism exposed to neutrons, for example during an accident or an atomic explosion.
The activity of radioactive isotopes is measured in units of curie or its derivatives - millicurie and microcurie.
In terms of chemical and physicochemical properties, radioactive isotopes are practically no different from natural elements; their admixture to any substance does not change its behavior in a living organism.
It is possible to replace stable isotopes in various chemical compounds with such labeled atoms. The properties of the latter will not change as a result, and if introduced into the body, they will behave like ordinary, unlabeled substances. However, thanks to radiation, it is easy to detect their presence in the blood, tissues, cells, etc. The radioactive isotopes in these substances thus serve as indicators, or indicators, of the distribution and fate of substances introduced into the body. That's why they are called "radioactive tracers." A variety of inorganic and organic compounds labeled with various radioactive isotopes have been synthesized for radioisotope diagnostics and for various experimental studies.
2. Application of radioactive isotopes in technology
One of the most outstanding studies carried out using “tagged atoms” was the study of metabolism in organisms. It has been proven that in a relatively short time the body undergoes almost complete renewal. The atoms that make it up are replaced by new ones. Only iron, as experiments on isotope studies of blood have shown, is an exception to this rule. Iron is part of the hemoglobin of red blood cells. When radioactive iron atoms were introduced into food, it was found that the free oxygen released during photosynthesis was originally part of water, not carbon dioxide. The scope of application of radioactive isotopes in industry is extensive. One example of this is the following method for monitoring piston ring wear in internal combustion engines. By irradiating the piston ring with neutrons, they cause nuclear reactions in it and make it radioactive. When the engine operates, particles of ring material enter the lubricating oil. By examining the level of radioactivity in the oil after a certain time of engine operation, ring wear is determined. Radioactive isotopes make it possible to judge the diffusion of metals, processes in blast furnaces, etc.
Powerful gamma radiation from radioactive drugs is used to examine the internal structure of metal castings in order to detect defects in them.
Radioactive isotopes that emit gamma rays can be used instead of bulky X-ray units for transilluminating products, since the properties of gamma rays are similar to the properties of X-rays. A gamma ray source is placed on one side of the product being tested, and photographic film is placed on the other. This testing method is called gamma flaw detection. In this way, ferrous and non-ferrous castings, finished products (steel products up to 300 mm thick) and the quality of welds are currently checked. With the help of radioactive isotopes, it is easy to measure the thickness of a metal strip or rolled metal sheets on the go and without contact and automatically maintain a constant thickness. A source of beta particles is placed under the moving belt running out from under the rollers of the machine. A change in the thickness of the tape therefore leads to a change in the current in the meter. This current is amplified and sent either to a measuring device or to an automatic machine, which will instantly bring the rollers closer together or, conversely, push them apart. Devices of this type are also used in the paper, rubber and leather industries. Radioisotope sources of electrical energy have been created. They use the heat generated in a sample that absorbs radiation. With the help of thermoelements, this heat is converted into electric current. A source weighing several kilograms provides power of several tens of watts for 10 years of uninterrupted operation. Such sources are used to power automatic beacons and automatic weather stations operating in hard-to-reach areas. More powerful sources were installed on Soviet lunar rovers launched to the Moon. They worked reliably at temperatures from -140 to +120.
One of the most outstanding studies carried out using “tagged atoms” was the study of metabolism in organisms. It has been proven that in a relatively short time the body undergoes almost complete renewal. The atoms that make it up are replaced by new ones. Only iron, as experiments on isotope studies of blood have shown, is an exception to this rule. Iron is part of the hemoglobin of red blood cells. When radioactive iron atoms were introduced into food, it was found that the free oxygen released during photosynthesis was originally part of water, not carbon dioxide. Radioactive isotopes are used in medicine both for diagnosis and for therapeutic purposes. Radioactive sodium, injected in small quantities into the blood, is used to study blood circulation; iodine is intensively deposited in the thyroid gland, especially in Graves' disease. By observing radioactive iodine deposition using a meter, a diagnosis can be made quickly. Large doses of radioactive iodine cause partial destruction of abnormally developing tissues, and therefore radioactive iodine is used to treat Graves' disease. Intense cobalt gamma radiation is used in the treatment of cancer (cobalt gun).
List of used literature
1. Gaisinsky M.N., Nuclear chemistry and its applications, trans. from French, M., 1961
2. Experimental Nuclear Physics, ed. E. Segre, trans. from English, vol. 3, M., 1961; INTERNET tools
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Preparation and application of radioactive isotopes Student of group 1 BC Galtsova Vlada
ISOTOPES are varieties of the same chemical element that are similar in their physicochemical properties, but have different atomic masses. An atom of any chemical element consists of a positively charged nucleus and a cloud of negatively charged electrons surrounding it (see also ATOM NUCLEUS). The position of a chemical element in the periodic table of Mendeleev (its serial number) is determined by the charge of the nucleus of its atoms. Isotopes are therefore called varieties of the same chemical element, the atoms of which have the same nuclear charge (and, therefore, practically the same electron shells), but differ in nuclear mass values. According to the figurative expression of F. Soddy, the atoms of isotopes are the same “outside”, but different “inside”.
History of the discovery of isotopes The first evidence that substances having the same chemical behavior can have different physical properties was obtained from the study of radioactive transformations of atoms of heavy elements. In 1906-07, it turned out that the product of radioactive decay of uranium - ionium and the product of radioactive decay of thorium - radiothorium, have the same chemical properties as thorium, but differ from it in atomic mass and radioactive decay characteristics. In 1932, the neutron was discovered - a particle that has no charge, with a mass close to the mass of the nucleus of a hydrogen atom - a proton, and a proton-neutron model of the nucleus was created. As a result, science has established the final modern definition of the concept of isotopes
Production of radioactive isotopes Radioactive isotopes are produced in nuclear reactors and particle accelerators
Application of radioactive isotopes biology medicine agricultural archeology industry
Radioactive isotopes in biology. One of the most outstanding studies carried out using “tagged atoms” was the study of metabolism in organisms.
Radioactive isotopes in medicine For diagnosis and for therapeutic purposes. Radioactive sodium is used to study blood circulation. Iodine is intensively deposited in the thyroid gland, especially in Graves' disease.
Radioactive isotopes on the farm Irradiation of plant seeds (cotton, cabbage, radish). Radiation causes mutations in plants and microorganisms.
Radioactive isotopes in archeology An interesting application for determining the age of ancient objects of organic origin (wood, charcoal). This method is used to determine the age of Egyptian mummies and the remains of prehistoric fires.
Radioactive isotopes in industry A method for monitoring wear of piston rings in internal combustion engines. Allows to judge the diffusion of metals and processes in blast furnaces
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Municipal educational institution "Pobedinskaya secondary school" Shegarsky district, Tomsk region
STATE (FINAL) CERTIFICATION OF IX CLASS GRADUATES
ABSTRACT ON PHYSICS
RADIOACTIVITY PHENOMENON. ITS IMPORTANCE IN SCIENCE, TECHNOLOGY, MEDICINE
Completed: Dadaev Aslan, 9th grade student
Supervisor: Gagarina Lyubov Alekseevna, physics teacher
Pobeda 2010
1. Introduction……………………………………………………………...page 1
2. The phenomenon of radioactivity………..……………………….................page 2
2.1.Discovery of radioactivity…………………………………………………….page 2
2.2. Sources of radiation…………………………………………………….. page 6
3. Production and use of radioactive isotopes……………..page 8
3.1.Use of isotopes in medicine……………………........page 8
3.2. Radioactive isotopes in agriculture………………page 10
3.3.Radiation chronometry…………………………………p.11
3.4. Application of radioactive isotopes in industry...p. 12
3.5. The use of isotopes in science……………………………...page 12
4. Conclusion…………………………………………………………...page 13
5. Literature………………………………………………………..page 14
INTRODUCTION
The idea of atoms as immutable tiny particles of matter was destroyed by the discovery of the electron, as well as the phenomenon of natural radioactive decay discovered by the French physicist A. Becquerel. A significant contribution to the study of this phenomenon was made by the outstanding French physicists Maria Sklodowska-Curie and Pierre Curie.
Natural radioactivity has existed for billions of years and is literally everywhere. Ionizing radiation existed on Earth long before the origin of life on it and was present in space before the emergence of the Earth itself. Radioactive materials have been part of the Earth since its birth. Any person is slightly radioactive: in the tissues of the human body, one of the main sources of natural radiation is potassium - 40 and rubidium - 87, and there is no way to get rid of them.
By carrying out nuclear reactions by bombarding the nuclei of aluminum atoms with a-particles, the famous French physicists Frederic and Irene Curie-Joliot managed to artificially create radioactive nuclei in 1934. Artificial radioactivity is fundamentally no different from natural radioactivity and obeys the same laws.
Currently, artificial radioactive isotopes are produced in different ways. The most common is the irradiation of a target (future radioactive drug) in a nuclear reactor. It is possible to irradiate a target with charged particles in special installations where the particles are accelerated to high energies.
Target: find out in which areas of life the phenomenon of radioactivity is used.
Tasks:
· Study the history of the discovery of radioactivity.
· Find out what happens to a substance during radioactive radiation.
· Find out how to obtain radioactive isotopes and where they will be used.
· Develop skills in working with additional literature.
· Perform a computer-based presentation of the material.
MAIN PART
2.The phenomenon of radioactivity
2.1.Discovery of radioactivity
Story radioactivity began with the French physicist Henri Becquerel's work on luminescence and X-rays in 1896.
The discovery of radioactivity, the most striking evidence of the complex structure of the atom .
Commenting on Roentgen's discovery, scientists hypothesize that X-rays are emitted during phosphorescence, regardless of the presence of cathode rays. A. Becquerel decided to test this hypothesis. Wrapping the photographic plate in black paper, he placed on it a bizarrely shaped metal plate coated with a layer of uranium salt. After exposing it to sunlight for four hours, Becquerel developed the photographic plate and saw on it the exact silhouette of a metal figure. He repeated the experiments with large variations, obtaining prints of a coin and a key. All experiments confirmed the hypothesis being tested, which Becquerel reported on February 24 at a meeting of the Academy of Sciences. However, Becquerel does not stop experiments, preparing more and more new options.
Henri Becquerel Welhelm Conrad Roentgen
On February 26, 1896, the weather over Paris deteriorated and the prepared photographic plates with pieces of uranium salt had to be placed in a dark desk drawer until the sun appeared. It appeared over Paris on March 1, and the experiments could be continued. Taking the records, Becquerel decided to develop them. Having developed the plates, the scientist saw silhouettes of uranium samples on them. Not understanding anything, Becquerel decided to repeat the random experiment.
He placed two plates in a lightproof box, poured uranium salt on them, having first placed glass on one of them and an aluminum plate on the other. All this was in a dark room for five hours, after which Becquerel developed the photographic plates. And well, the silhouettes of the samples are clearly visible again. This means that some rays are formed in uranium salts. They look like X rays, but where do they come from? One thing is clear: there is no connection between X-rays and phosphorescence.
He reported this at a meeting of the Academy of Sciences on March 2, 1896, completely confusing all its members.
Becquerel also established that the intensity of radiation from the same sample does not change over time and that new radiation is capable of discharging electrified bodies.
The majority of members of the Paris Academy, after Becquerel’s next report at the meeting on March 26, believed that he was right.
The phenomenon discovered by Becquerel was called radioactivity, at the suggestion of Maria Sklodowska-Curie.
Maria Skłodowska – Curie
Radioactivity - the ability of atoms of some chemical elements to spontaneously emit.
In 1897, Maria, while pursuing her doctoral dissertation, having chosen a topic for research - the discovery of Becquerel (Pierre Curie advised his wife to choose this topic), decided to find the answer to the question: what is the true source of uranium radiation? To this end, she decides to examine a large number of samples of minerals and salts and find out whether only uranium has the property of radiating. Working with samples of thorium, she discovers that, like uranium, it produces the same rays and about the same intensity. This means that this phenomenon turns out to be a property not only of uranium, and it needs to be given a special name. Uranium and thorium were called radioactive elements. Work continued with new minerals.
Pierre, as a physicist, feels the importance of the work and, temporarily leaving the study of crystals, begins to work together with his wife. As a result of this joint work, new radioactive elements were discovered: polonium, radium, etc.
In November 1903, the Royal Society awarded Pierre and Marie Curie one of England's highest scientific awards, the Davy Medal.
On November 13, the Curies and Becquerel received a telegram from Stockholm announcing that the three of them had been awarded the Nobel Prize in Physics for their outstanding discoveries in the field of radioactivity.
The work started by the Curies was taken up by their students, among whom were daughter Irene and son-in-law Frédéric Joliot, who became Nobel Prize laureates for the discovery in 1935 artificial radioactivity .
Irene and Frederic Curie - Joliot
English physicists E. Rutherford And F. Soddy It has been proven that in all radioactive processes mutual transformations of the atomic nuclei of chemical elements occur. A study of the properties of radiation accompanying these processes in magnetic and electric fields showed that it is divided into a-particles, b-particles and g-rays (electromagnetic radiation with a very short wavelength).
E. Rutherford F. Soddy
Some time later, as a result of studying various physical characteristics and properties of these particles (electric charge, mass, etc.), it was possible to establish that the b particle is an electron, and the a particle is a fully ionized atom of the chemical element helium (i.e. an atom helium that has lost both electrons).
In addition, it turned out that radioactivity is the ability of some atomic nuclei to spontaneously transform into other nuclei with the emission of particles.
For example, several varieties of uranium atoms were found: with nuclear masses approximately equal to 234 amu, 235 amu, 238 amu. and 239 amu Moreover, all these atoms had the same chemical properties. They entered into chemical reactions in the same way, forming the same compounds.
Some nuclear reactions produce highly penetrating radiation. These rays penetrate a layer of lead several meters thick. This radiation is a stream of neutrally charged particles. These particles are named neutrons.
Some nuclear reactions produce highly penetrating radiation. These rays come in different types and have different penetrating powers. For example, neutron flux penetrates through a layer of lead several meters thick.
2.2. Sources of radiation
Radiation is very numerous and varied, but we can distinguish about seven its main sources.
The first source is our Earth. This radiation is explained by the presence of radioactive elements in the Earth, the concentration of which varies widely in different places.
The second source radiation - space, from where a stream of high-energy particles constantly falls onto the Earth. The sources of cosmic radiation are stellar explosions in the Galaxy and solar flares.
Third source Radiation are radioactive natural materials used by humans for the construction of residential and industrial premises. On average, the dose rate inside buildings is 18% - 50% greater than outside. A person spends three quarters of his life indoors. A person constantly staying in a room built of granite can receive - 400 mrem/year, from red brick – 189 mrem/year, from concrete – 100 mrem/year, from wood – 30 mrem/year.
Fourth The source of radioactivity is little known to the population, but no less dangerous. These are radioactive materials that humans use in everyday activities.
The inks for printing bank checks include radioactive carbon, which ensures easy identification of forged documents.
Uranium is used to produce paint or enamel on ceramics or jewelry.
Uranium and thorium are used in glass production.
Artificial porcelain teeth are reinforced with uranium and cerium. At the same time, radiation to the mucous membranes adjacent to the teeth can reach 66 rem/year, while the annual rate for the entire body should not exceed 0.5 rem (i.e. 33 times more)
A TV screen emits 2-3 mrem/year per person.
Fifth source – enterprises for transportation and processing of radioactive materials.
Sixth The source of radiation is nuclear power plants. At nuclear power plants,
In addition to solid waste, there are also liquid (contaminated water from reactor cooling circuits) and gaseous waste contained in the carbon dioxide used for cooling.
Seventh The source of radioactive radiation is medical installations. Despite the commonality of their use in everyday practice, the danger of radiation from them is much greater than from all the sources discussed above and sometimes reaches tens of rems. One of the common diagnostic methods is an X-ray machine. So, with radiography of teeth - 3 rem, with fluoroscopy of the stomach - the same, with fluorography - 370 mrem.
What happens to matter during radioactive radiation?
Firstly, the amazing consistency with which radioactive elements emit radiation. Over the course of days, months, years, the radiation intensity does not change noticeably. It is not affected by heating or increased pressure; the chemical reactions into which the radioactive element entered also did not affect the intensity of the radiation.
Secondly, radioactivity is accompanied by the release of energy, and it is released continuously over a number of years. Where does this energy come from? When a substance becomes radioactive, it experiences some profound changes. It was assumed that the atoms themselves undergo transformations.
The presence of the same chemical properties means that all these atoms have the same number of electrons in the electron shell, and therefore the same nuclear charges.
If the charges of the atomic nuclei are the same, then these atoms belong to the same chemical element (despite the differences in their masses) and have the same atomic number in the D.I. table. Mendeleev. Varieties of the same chemical element that differ in the mass of atomic nuclei are called isotopes .
3. Production and use of radioactive isotopes
Radioactive isotopes found in nature are called natural. But many chemical elements occur in nature only in a stable (i.e., radioactive) state.
In 1934, French scientists Irène and Frédéric Joliot-Curie discovered that radioactive isotopes could be created artificially as a result of nuclear reactions. These isotopes were called artificial .
Nuclear reactors and particle accelerators are usually used to produce artificial radioactive isotopes. There is an industry specializing in the production of such elements.
Subsequently, artificial isotopes of all chemical elements were obtained. In total, approximately 2000 radioactive isotopes are currently known, and 300 of them are natural.
Currently, radioactive isotopes are widely used in various fields of scientific and practical activity: technology, medicine, agriculture, communications, military and some others. In this case, the so-called tagged atom method.
3.1.Use of isotopes in medicine
Application of isotopes One of the most outstanding studies carried out using “tagged atoms” was the study of metabolism in organisms.
With the help of isotopes, the development mechanisms (pathogenesis) of a number of diseases were revealed; They are also used to study metabolism and diagnose many diseases.
Isotopes are introduced into the human body in extremely small quantities (safe for health) and are not capable of causing any pathological changes. They are distributed unevenly throughout the body by blood. The radiation produced during the decay of an isotope is recorded by instruments (special particle counters, photography) located near the human body. As a result, you can get an image of any internal organ. From this image one can judge the size and shape of this organ, the increased or decreased concentration of the isotope in
its various parts. You can also evaluate the functional state (i.e., work) of internal organs by the rate of accumulation and removal of the radioisotope by them.
Thus, the state of cardiac circulation, blood flow velocity, and the image of the heart cavities are determined using compounds including isotopes of sodium, iodine, and technetium; isotopes of technetium and xenon are used to study pulmonary ventilation and diseases of the spinal cord; macroaggregates of human serum albumin with an iodine isotope are used to diagnose various inflammatory processes in the lungs, their tumors and for various diseases of the thyroid gland.
Use of isotopes in medicine
The concentration and excretory functions of the liver are studied using Bengal rose paint with an isotope of iodine and gold. Images of the intestines and stomach are obtained using a technetium isotope; the spleen is obtained using red blood cells with a technetium or chromium isotope; Pancreatic diseases are diagnosed using a selenium isotope. All this data allows us to make a correct diagnosis of the disease.
Using the “labeled atoms” method, various abnormalities in the functioning of the circulatory system are also studied and tumors are detected (since it is in them that some radioisotopes accumulate). Thanks to this method, it was discovered that in a relatively short time the human body is almost completely renewed. The only exception is iron, which is part of the blood: it begins to be absorbed by the body from food only when its reserves are depleted.
When choosing an isotope, important issues include the sensitivity of the isotope analysis method, as well as the type of radioactive decay and radiation energy.
In medicine, radioactive isotopes are used not only for diagnosis, but also for the treatment of certain diseases, such as cancer, Graves' disease, etc.
Due to the use of very small doses of radioisotopes, radiation exposure to the body during radiation diagnostics and treatment does not pose a danger to patients.
3.2. Radioactive isotopes in agriculture
Radioactive isotopes are becoming increasingly used in agriculture. Irradiation of plant seeds (cotton, cabbage, radishes, etc.) with small doses of gamma rays from radioactive drugs leads to a noticeable increase in yield. Large doses of radiation cause mutations in plants and microorganisms, which in some cases leads to the emergence of mutants with new valuable properties ( radio selection). This is how valuable varieties of wheat, beans and other crops were developed, and highly productive microorganisms used in the production of antibiotics were obtained.
Gamma radiation from radioactive isotopes is also used to combat harmful insects and for food preservation. “Tagged atoms” are widely used in agricultural technology. For example, to find out which phosphorus fertilizer is better absorbed by a plant, various fertilizers are labeled with radioactive phosphorus. By then examining the plants for radioactivity, it is possible to determine the amount of phosphorus they have absorbed from different types of fertilizer.
The radioactive carbon method has received an interesting application for determining the age of ancient objects of organic origin (wood, charcoal, fabrics, etc.). Plants always contain a beta radioactive isotope of carbon with a half-life of T = 5700 years. It is formed in the Earth's atmosphere in small quantities from nitrogen under the influence of neutrons. The latter arise due to nuclear reactions caused by fast particles that enter the atmosphere from space (cosmic rays). Combining with oxygen, this carbon forms carbon dioxide, which is absorbed by plants, and through them, by animals.
Isotopes are widely used to determine the physical properties of soil
and reserves of plant food elements in it, to study the interaction of soil and fertilizers, the processes of absorption of nutrients by plants, and the entry of mineral food into plants through leaves. Isotopes are used to identify the effect of pesticides on the plant organism, which makes it possible to determine the concentration and timing of their treatment of crops. Using the isotope method, the most important biological properties of agricultural crops are studied (when assessing and selecting breeding material) yield, early ripening, and cold resistance.
IN livestock farming they study the physiological processes occurring in the body of animals, analyze feed for the content of toxic substances (small doses of which are difficult to determine by chemical methods) and microelements. With the help of isotopes, techniques are being developed to automate production processes, for example, separating root crops from stones and lumps of soil when harvesting with a combine on rocky and heavy soils.
3.3.Radiation chronometry
Some radioactive isotopes can be successfully used to determine the age of various fossils ( radiation chronometry). The most common and effective method of radiation chronometry is based on measuring the radioactivity of organic substances, which is caused by radioactive carbon (14C).
Research has shown that for every gram of carbon in any organism, 16 radioactive beta decays occur per minute (more precisely, 15.3 ± 0.1). After 5730 years, in each gram of carbon only 8 atoms per minute will decay, after 11,460 years - 4 atoms.
One gram of carbon from young forest samples emits about fifteen beta particles per second. After the death of the organism, its replenishment with radioactive carbon stops. The available amount of this isotope decreases due to radioactivity. By determining the percentage of radioactive carbon in organic remains, it is possible to determine their age if it lies in the range from 1000 to 50,000 and even up to 100,000 years.
The number of radioactive decays, i.e., the radioactivity of the samples under study, is measured by radioactive radiation detectors.
Thus, by measuring the number of radioactive decays per minute in a certain weight amount of the material of the sample under study and recalculating this number per gram of carbon, we can determine the age of the object from which the sample was taken. This method is used to determine the age of Egyptian mummies, remains of prehistoric fires, etc.
3.4. Application of radioactive isotopes in industry
One example is the following method for monitoring piston ring wear in internal combustion engines. By irradiating the piston ring with neutrons, they cause nuclear reactions in it and make it radioactive. When the engine operates, particles of ring material enter the lubricating oil. By examining the level of radioactivity in the oil after a certain time of engine operation, ring wear is determined. Radioactive isotopes make it possible to judge the diffusion of metals, processes in blast furnaces, etc. Powerful gamma radiation from radioactive drugs is used to study the internal structure of metal castings in order to detect defects in them.
Isotopes are also used in nuclear physics equipment for the manufacture of neutron counters, which makes it possible to increase the counting efficiency by more than 5 times, and in nuclear energy as neutron moderators and absorbers.
3.5. Use of isotopes in science
Use of isotopes in biology led to a revision of previous ideas about the nature of photosynthesis, as well as about the mechanisms that ensure the assimilation by plants of inorganic substances of carbonates, nitrates, phosphates, etc. Using isotopes, the movement of populations in the biosphere and individuals within a given population, the migration of microbes, as well as individual compounds within body. By introducing a label into organisms with food or by injection, it was possible to study the speed and migration routes of many insects (mosquitoes, flies, locusts), birds, rodents and other small animals and obtain data on the size of their populations.
In area physiology and biochemistry of plants With the help of isotopes, a number of theoretical and applied problems have been solved: the routes of entry of minerals, liquids and gases into plants, as well as the role of various chemical elements, including microelements, in plant life have been clarified. It has been shown, in particular, that carbon enters plants not only through the leaves, but also through the root system; the paths and speeds of movement of a number of substances from the root system to the stem and leaves and from these organs to the roots have been established.
In area physiology and biochemistry of animals and humans the rates of entry of various substances into their tissues have been studied (including the rate of incorporation of iron into hemoglobin, phosphorus into nervous and muscle tissue, calcium into bones). The use of “labeled” food led to a new understanding of the rates of absorption and distribution of nutrients, their “fate” in the body and helped to monitor the influence of internal and external factors (starvation, asphyxia, overwork, etc.) on metabolism.
CONCLUSION
Outstanding French physicists Maria Sklodowska-Curie and Pierre Curie, their daughter Irene and son-in-law Frédéric Joliot and many other scientists not only made a great contribution to the development of nuclear physics, but were passionate fighters for peace. They carried out significant work on the peaceful use of atomic energy.
In the Soviet Union, work on atomic energy began in 1943 under the leadership of the outstanding Soviet scientist I.V. Kurchatov. In the difficult conditions of an unprecedented war, Soviet scientists solved the most complex scientific and technical problems related to the mastery of atomic energy. On December 25, 1946, under the leadership of I.V. Kurchatov, a chain reaction was carried out for the first time on the continent of Europe and Asia. Began in the Soviet Union era of the peaceful atom.
In the course of my work, I found out that radioactive isotopes obtained artificially have found wide application in science, technology, agriculture, industry, medicine, archeology and other fields. This is due to the following properties of radioactive isotopes:
· a radioactive substance continuously emits a certain type of particle and the intensity does not change over time;
· radiation has a certain penetrating ability;
· radioactivity is accompanied by the release of energy;
· under the influence of radiation, changes can occur in the irradiated substance;
· radiation can be detected in different ways: with special particle counters, photography, etc.
LITERATURE
1. F.M. Diaghilev “From the history of physics and the life of its creators” - M.: Education, 1986.
2. A.S. Enokhin, O.F. Kabardin and others. “Anthology on Physics” - M.: Education, 1982.
3. P.S. Kudryavtsev. “History of Physics” - M.: Education, 1971.
4. G.Ya. Myakishev, B.B. Bukhovtsev “Physics 11th grade.” - M.: Education, 2004.
5. A.V. Peryshkin, E.V. Gutnik "Physics 9th grade." - M.: Bustard, 2005.
6. Internet resources.
Review
for an examination essay in physics “The phenomenon of radioactivity. Its significance in science, technology, medicine."
The author sees the relevance of the chosen topic in the possibility of using nuclear energy for peaceful purposes. Radioactive isotopes obtained artificially have found wide application in various fields of scientific and practical activity: science, technology, agriculture, industry, medicine, archeology, etc.
However, the “Introduction” section does not indicate the relevance and interest of the author in the chosen topic of the abstract.
The discovery of radioactivity is explained in an accessible, logical manner; research carried out using “tagged atoms”.
The formatting of the abstract does not in all cases meet the requirements:
· Pages are not numbered;
· Each section is not printed from a new page;
· There are no references to illustrations in the text;
· The “Literature” section does not list Internet resource sites.
In general, despite minor shortcomings in the compilation and design, we can say that the abstract “The phenomenon of radioactivity. Its significance in science, technology, and medicine deserves a “good” rating.
Physics teacher, Municipal Educational Institution "Pobedinskaya Secondary School": ___________/L.A. Gagarin/
