Kuraleva Alena Yurievna Teacher of the first category Municipal government preschool educational institution “nursery-garden No. 27” of the municipal formation of the urban district of Yalta, Republic of Crimea
Kuraleva Alena Yurievna "PROJECT ACTIVITY IN DEE" TOPIC OF PEDAGOGICAL EXPERIENCE:
Kuraleva Alena Yuryevna Currently, the state has set a fairly clear and important task for educational institutions: to prepare the most active and inquisitive young generation possible. The issue of creating a system of work to introduce the project method into the educational process of preschool educational institutions becomes relevant. Most teachers are aware of the need to develop each child as a valuable individual. However, experts find it difficult to determine the factors influencing the success of a child’s progress in the educational process. A unique means of ensuring cooperation, co-creation between children and adults, and a way to implement a person-centered approach to education is design technology. . Relevance
Kuraleva Alena Yuryevna Project activity is the type of pedagogical work that will be in demand in connection with the implementation of federal state standards (FSES) in the practice of preschool educational institutions
Kuraleva Alena Yuryevna The project method is a way of organizing the pedagogical process, based on the interaction between teacher and student, a way of interacting with the environment, step-by-step practical activities to achieve the goal
Kuraleva Alena Yurievna in preschool institutions is the development of the free creative personality of the child. The main goal of the project method is the development of creative imagination and thinking, ensuring the psychological well-being and health of children, the development of communication skills, the development of cognitive abilities, and development tasks.
Kuraleva Alena Yurievna The tasks of research activities are specific for each age. In early preschool age, this is: children’s entry into a problematic play situation (the leading role of the teacher); activating the desire to look for ways to resolve a problem situation (together with the teacher); forming the initial prerequisites for research activities (practical experiments).
Kuraleva Alena Yuryevna In older preschool age this is: the formation of prerequisites for search activity, intellectual initiative; developing the ability to identify possible methods of solving a problem with the help of an adult, and then independently; developing the ability to apply these methods to help solve the problem, using various options; independent acquisition of missing knowledge from various sources; development of skills to use this knowledge to solve new cognitive and practical problems; development of abilities for analytical, critical, creative thinking; development of the most important competencies for modern life.
Kuraleva Alena Yurievna Position of children as project participants: Influence the choice of topic, forms of work within the project; Establish the sequence and total duration of self-selected activities: Act as initiators, active participants, and not executors of adult instructions; They realize their interests, needs for knowledge, communication, play and other activities, mainly independently, making a decision on participation or non-participation in a general project or specific action
Kuraleva Alena Yuryevna Position of adults as participants in the project: They have an equal right with children to contribute ideas regarding topics, content and types of activities; do not claim the right to the only true source of knowledge, limiting themselves to the status of a “resource personality”; they provide children with sufficient freedom to realize their own needs, delineating it within the framework of the accepted culture and forming an understanding of responsibility for their choices, actions and results
Kuraleva Alena Yurievna PROJECT is a “Model of Three Questions” (using the example of the project “WHERE DO SOAP BUBBLES COME FROM”) 1. WHAT DO WE KNOW ABOUT...? They can be colored (Kirill) Bubbles fly (Nastya) They are made from soap (Masha) 2. WHAT DO WE WANT TO KNOW? Who invented bubbles? (Esia) What can you do with bubbles? (Fedya) Why are they needed? (Vova) 3. WHAT SHOULD YOU DO TO FIND OUT? Read smart books (Masha) You can ask adults (Dasha) We’ll think and come up with ideas ourselves (Misha)
Kuraleva Alena Yurievna “WORK CENTERS”
Kuraleva Alena Yurievna 1 - P problem; 2 - Design (planning); 3 - Search for information; 4 - P product; 5 - P presentation. The sixth “P” of a project is its portfolio, a folder in which working materials are collected, including plans, reports, drawings, diagrams, maps, tables. A PROJECT IS THE 5 P’S EACH AUTHOR INTERPRETS A PROJECT IN A DIFFERENT WAY, SO THERE ARE MANY DEFINITIONS HERE’S ONE MORE
Kuraleva Alena Yuryevna Search: determining the topic of the project. Analytical: setting the project goal, defining tasks, preparatory stage. Practical: the main stage (working with children, parents, equipping a subject-development environment). Control: result, product of activity. Stages of work on the project
Kuraleva Alena Yuryevna INVOLVING PARENTS IN PROJECT ACTIVITIES CAN AND SHOULD INVOLVE PARENTS BY WRITING, FOR EXAMPLE, THE SUCH ANNOUNCEMENT: Dear moms and dads! We are still small, but when we grow up, we will definitely become astronauts or space tourists. Of course, you can’t fly into space without special training. We want to learn a lot about space, but we can’t do it without your help! We will be grateful if you bring us paper, old magazines, boxes, pictures and books about space. Your future cosmonauts.
Kuraleva Alena Yuryevna Typology of projects in preschool educational institutions (according to E.S. Evdokimova) By dominant activity (Research, information, creative, gaming, adventure, practice-oriented) By the nature of contacts (Within one age group, in contact with another age group, within Preschool educational institution, in contact with family, cultural institutions, public organizations) By the nature of the content (Child and family, child and nature, child and the man-made world, child and society and its cultural values) By the number of participants (Individual, pair, group, frontal) By the nature of the child’s participation in the project (Customer, expert, performer, participant from inception to obtaining results) By duration (Short-term, medium-term, long-term) PROJECTS
Kuraleva Alena Yurievna FROM WORK EXPERIENCE
Kuraleva Alena Yurievna
Kuraleva Alena Yurievna
Kuraleva Alena Yurievna
Kuraleva Alena Yurievna
Thus, during the implementation of the project, each child develops a certain position on a specific issue; children get the opportunity to reveal their creative streak and show everyone their individuality. All this has an extremely beneficial effect on the development of the child’s personality and contributes to the formation of normal self-esteem. Simply put, projects ideally prepare preschoolers for their further education at school. CONCLUSION: Kuraleva Alena Yurievna
Kuraleva Alena Yurievna THANK YOU FOR YOUR ATTENTION!
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. Poincaré did not limit himself to talking about new rays. He suggested that these rays are associated with luminescence and, perhaps, always arise 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; The son of Antoine Henri Becquerel, Jacques, also became a physicist, who “by inheritance” took over 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 location. 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
Isotopes are varieties of chemical elements in which the nuclei of atoms differ in the number of neutrons, but contain the same number of protons, and therefore occupy the same place in Mendeleev’s Periodic Table of Elements. There are stable (stable) and radioactive isotopes. The term "isotopes" was first proposed in 1910. Frederick Soddy (1877-1956), famous English radiochemist, Nobel Prize laureate in 1921, who experimentally proved the formation of radium from uranium.
Radioactive isotopes are widely used not only in nuclear energy, but also in a variety of instruments and equipment to determine the density, homogeneity of a substance, its hygroscopicity, etc. With the help of radioactive indicators, it is possible to monitor the movement of chemical compounds in physical, technological, biological and chemical processes, for which radioactive indicators (labeled atoms) of certain elements are introduced into the object under study and then their movement is observed. This method makes it possible to study reaction mechanisms during the transformation of substances under difficult conditions, for example at high temperatures, in a blast furnace or in the aggressive environment of a chemical reactor, as well as to study metabolic processes in living organisms. The oxygen isotope-18 helps to clarify the mechanism of respiration of living organisms.
The radioactive method of analyzing a substance makes it possible to determine the content of various metals in it, from calcium to zinc, in extremely small concentrations - up to 1 -10 g (only 10 -12 g of the substance is required). Radioactive drugs are widely used in medical practice to treat many diseases, including malignant tumors. Isotopes of plutonium-238 and curium-224 are used to produce low-power batteries for heart rhythm stabilizers. For their continuous operation for 10 years, only 150-200 mg of plutonium is enough (conventional batteries last up to four years).
As a result of radiation-chemical reactions, ozone is formed from oxygen, and hydrogen and complex compounds of low molecular weight olefins are formed from gaseous paraffins. Irradiation of polyethylene, polyvinyl chloride and other polymers leads to an increase in their heat resistance and strength. There are many examples of the practical use of isotopes and radioactive radiation. Despite this, people's attitudes towards radiation, especially in recent decades, have changed dramatically. Over about a hundred-year history, radioactive sources have come a long way from the elixir of life to a symbol of evil. Concepts of modern natural science: Textbook. manual for universities / A.A. Gorelov.- M.: VLADOS., 2000.- P. 285-288.
After the discovery of X-rays, many believed that radiation could cure all diseases and solve all problems. At that time, people did not want to see the dangers of radiation exposure. When Wilhelm Roentgen (1845-1923) discovered a new type of irradiation in 1895, a wave of delight swept the entire civilized world. The discovery not only shook the foundations of classical physics. It promised unlimited possibilities - in medicine they immediately began to use it for diagnosis, and a little later - for the treatment of a wide variety of diseases. X-ray diagnostics and radiotherapy have saved the lives of many people. Doctors, however, after some time began to limit the permissible number of x-rays for one patient, but no one seriously paid attention to the burns that occur after x-rays. The French physicist A. Becquerel, for example, had the habit of carrying a radium device in his trouser pocket. After some time, he noticed inflammation on his leg. To make sure that the device was the cause of the illness, he moved it to another pocket. But even the ulcer that appeared on the other leg could not sober up the scientist, who, like the rest, was euphoric from the new discovery. Radioactive radiation at that time was considered as a universal healing agent, the elixir of life. Radium proved effective in the treatment of benign tumors, and its “popularity” increased dramatically. Radium pillows, radioactive toothpaste and cosmetics appeared on the public market.
However, the first warning signs soon appeared. In 1911 It was discovered that Berlin doctors who dealt with radiation often developed leukemia. Later, the German physicist Max von Laue (1879-1960) experimentally proved that radioactive radiation adversely affects living organisms, and in 1925-1927. It became known that under the influence of radiation, changes in the hereditary substance - mutations - occur.
Complete sobering came after the atomic bombing of Hiroshima and Nagasaki. Almost all the survivors of the nuclear explosion were exposed to large doses of radiation and died of cancer, and their children inherited some genetic disorders caused by the radiation. This was first discussed openly in 1950, when the number of leukemia patients among victims of atomic explosions began to grow catastrophically. After the Chernobyl accident, mistrust of radiation grew into real nuclear hysteria.
Thus, if at the beginning of the 20th century. people stubbornly did not want to see the harm from radiation, then at the end of it they began to fear radiation even when it does not pose a real danger. The cause of both phenomena is the same - human ignorance. One can only hope that in the future a person will learn to adhere to the golden mean and turn knowledge about natural phenomena to his own benefit.
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In biology and medicine - in industry - in agriculture - in archiology
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Isotopes in medicine and biology
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Table 1. Main characteristics of radionuclides - γ-emitters for use for diagnostic purposes
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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.
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Digital radiographic camera for fluorographic devices KRTS 01-"PONI"
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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
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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.
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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.
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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.
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Isotopes in industry
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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.
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Powerful y-radiation of drugs is used to study the internal structure of metal castings in order to detect defects in them.
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Radioactive materials make it possible to judge the diffusion of materials, processes in blast furnaces, etc.
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Isotopes in agriculture
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Irradiation of plant seeds (cotton, cabbage, radishes, etc.) with small doses of y-rays from radioactive drugs leads to a noticeable increase in yield.
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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.
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Gamma radiation from radioactive isotopes is also used to control harmful insects and for food preservation.
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Isotopes in archiology
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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.
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After the death of the organism, its replenishment with radioactive carbon ceases. 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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