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Radiation results

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Conclusion

Factors “Pro” of nuclear power plants: 1. Nuclear energy is by far the best type of energy production. Economical, high power, environmentally friendly when used correctly. 2. Nuclear power plants, compared to traditional thermal power plants, have an advantage in fuel costs, which is especially evident in those regions where there are difficulties in providing fuel and energy resources, as well as a steady upward trend in the cost of fossil fuel production. 3. Nuclear power plants are also not prone to polluting the natural environment with ash, flue gases with CO2, NOx, SOx, and waste water containing petroleum products. Factors “against” nuclear power plants: 1. Terrible consequences of accidents at nuclear power plants. 2. Local mechanical impact on the terrain - during construction. 3. Damage to individuals in technological systems - during operation. 4. Runoff of surface and groundwater containing chemical and radioactive components. 5. Changes in the nature of land use and metabolic processes in the immediate vicinity of the nuclear power plant. 6. Changes in microclimatic characteristics of adjacent areas.

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NUCLEAR energy (nuclear energy) - a branch of energy that uses nuclear energy for electrification and heating; a field of science and technology that develops methods and means for converting nuclear energy into electrical and thermal energy. The basis of nuclear energy is nuclear power plants. The first nuclear power plant (5 MW), which marked the beginning of the use of nuclear energy for peaceful purposes, was launched in the USSR in the beginning. 90s St. worked in 27 countries around the world. 430 nuclear power reactors with a total capacity of approx. 340 GW. According to experts, the share of nuclear energy in the overall structure of electricity generation in the world will continuously increase, provided that the basic principles of the safety concept for nuclear power plants are implemented. The main principles of this concept are a significant modernization of modern nuclear reactors, strengthening measures to protect the population and the environment from harmful technogenic impacts, training highly qualified personnel for nuclear power plants, developing reliable storage facilities for radioactive waste, etc.

Typically, to obtain nuclear energy, a nuclear chain reaction of fission of uranium-235 or plutonium nuclei is used. Nuclei fission when a neutron hits them, producing new neutrons and fission fragments. Fission neutrons and fission fragments have high kinetic energy. As a result of collisions of fragments with other atoms, this kinetic energy is quickly converted into heat. Although in any field of energy the primary source is nuclear energy (for example, the energy of solar nuclear reactions in hydroelectric and fossil fuel power plants, the energy of radioactive decay in geothermal power plants), nuclear energy refers only to the use of controlled reactions in nuclear reactors.

The main purpose of power plants is to supply electricity to industrial enterprises, agricultural production, electrified transport and the population. The inseparability of energy production and consumption places very high demands on the reliability of power plants, since interruptions in the supply of electricity and heat affect not only the economic indicators of the station itself, but also on the indicators of the industrial enterprises and transport it serves. Currently, nuclear power plants operate as condensing power plants. Sometimes they are also called nuclear power plants. Nuclear power plants designed to supply not only electricity, but also heat, are called nuclear combined heat and power plants (CHP). For now, only their projects are being developed.

A) Single-circuit B) Double-circuit C) Partially double-circuit D) Three-circuit 1 - reactor; 2 - steam turbine; 3 - electric generator; 4 - capacitor; 5 - feed pump; 6 - circulation pump: 7 - steam generator; 8 - volume compensator; 9 - drum separator; 10 - intermediate heat exchanger; 11 - liquid metal pump

The classification of nuclear power plants depends on the number of circuits on it. Nuclear power plants are classified as single-circuit, double-circuit, partially double-circuit and triple-circuit. If the contours of the coolant and working fluid coincide, then such a nuclear power plant; called single-circuit. Steam generation occurs in the reactor, the steam is sent to the turbine, where, expanding, it produces work, which is converted into electricity in the generator. After all the steam has condensed in the condenser, the condensate is pumped back into the reactor. Thus, the working fluid circuit is at the same time a coolant circuit, and sometimes a moderator circuit, and turns out to be closed. The reactor can operate with both natural and forced circulation of the coolant through an additional internal circuit of the reactor on which the corresponding pump is installed.

NUCLEAR weapons - a set of nuclear weapons, means of delivering them to the target and control means. Refers to weapons of mass destruction; has enormous destructive power. Based on the power of charges and range, nuclear weapons are divided into tactical, operational-tactical and strategic. The use of nuclear weapons in war is disastrous for all humanity. Atomic bomb Hydrogen bomb

The first atomic bomb was used by the American army after World War II on Japanese territory. Effect of an atomic bomb Nuclear, or atomic, is a type of weapon in which an explosion occurs under the influence of energy released during the fission of atomic nuclei. This is the most dangerous type of weapon on our planet. If one atomic bomb explodes in a densely populated area, the number of human casualties will exceed several million. In addition to the effect of the shock wave generated during the explosion, its main impact is radioactive contamination of the area in the area of ​​the explosion, which persists for many years. Currently, the following officially have nuclear weapons: the USA, Russia, Great Britain (since 1952), France (since 1960), China (since 1964), India (since 1974), Pakistan (since 1998) and the DPRK (since 2006). A number of countries, such as Israel and Iran, have small stockpiles of nuclear weapons, but they are not yet officially considered nuclear powers.

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Hydroelectric power plants People have long been thinking about how to make rivers work. Already in ancient times - in Egypt, China, India - water mills for grinding grain appeared long before windmills - in the state of Urartu (in the territory of present-day Armenia), but were known back in the 13th century. BC e.One of the first power plants were “Hydroelectric Power Plants”. These power plants were built on mountain rivers with quite strong currents. The construction of hydroelectric power stations made it possible to make many rivers navigable, since the structure of the dams raised the water level and flooded river rapids, which prevented the free passage of river vessels.

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Conclusions: A dam is needed to create water pressure. However, hydroelectric dams worsen the living conditions of aquatic fauna. Dammed rivers, having slowed down, bloom, and vast areas of arable land go under water. Settled areas (if a dam is built) will be flooded, the damage that will be caused is incomparable with the benefits of building a hydroelectric power station. In addition, a system of locks is needed for the passage of ships and fish passages or water intake structures for irrigating fields and water supply. And although hydroelectric power plants have considerable advantages over thermal and nuclear power plants, since they do not require fuel and therefore generate cheaper electricity

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Thermal power plants At thermal power plants, the source of energy is fuel: coal, gas, oil, fuel oil, oil shale. The efficiency of thermal power plants reaches 40%. Most of the energy is lost along with the release of hot steam. From an environmental point of view, thermal power plants are the most polluting. The activity of thermal power plants is integrally associated with the combustion of huge amounts of oxygen and the formation of carbon dioxide and oxides of other chemical elements. When combined with water molecules, they form acids, which fall on our heads in the form of acid rain. Let's not forget about the "greenhouse effect" - its influence on climate change is already being observed!

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Nuclear power plant Supplies of energy sources are limited. According to various estimates, there are 400-500 years of coal deposits left in Russia at the current level of production, and even less gas - 30-60 years. And here nuclear energy comes first. Nuclear power plants are beginning to play an increasingly important role in the energy sector. Currently, nuclear power plants in our country provide about 15.7% of electricity. A nuclear power plant is the basis of the energy sector that uses nuclear energy for the purposes of electrification and heating.

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Conclusions: Nuclear energy is based on the fission of heavy nuclei by neutrons with the formation of two nuclei from each - fragments and several neutrons. This releases colossal energy, which is subsequently spent on heating the steam. The operation of any plant or machine, in general any human activity, is associated with the possibility of a risk to human health and the environment. People tend to be more wary of new technologies, especially if they have heard about possible accidents. And nuclear power plants are no exception.

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Wind power plants For a very long time, seeing the destruction that storms and hurricanes can bring, people thought about whether it was possible to use wind energy. Wind energy is very strong. This energy can be obtained without polluting the environment. But wind has two significant drawbacks: energy is highly dispersed in space and the wind is unpredictable - it often changes direction, suddenly dies down even in the windiest areas of the globe, and sometimes reaches such strength that it breaks windmills. To obtain wind energy, a variety of designs are used: from multi-bladed “daisy” and propellers like airplane propellers with three, two, or even one blade to vertical rotors. Vertical structures are good because they catch wind from any direction; the rest have to turn with the wind.

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Conclusions: The construction, maintenance and repair of wind turbines that operate 24 hours a day in the open air in any weather are not cheap. Wind power plants of the same capacity as hydroelectric power plants, thermal power plants or nuclear power plants, in comparison with them, must occupy a very large area in order to somehow compensate for the variability of the wind. Windmills are placed so that they do not block each other. Therefore, they build huge “wind farms” in which wind turbines stand in rows over a vast space and work for a single network. In calm weather, such a power plant can use water collected at night. The placement of wind turbines and reservoirs require large areas that are used for arable land. In addition, wind power plants are not harmless: they interfere with the flights of birds and insects, make noise, reflect radio waves with rotating blades, interfering with the reception of television programs in nearby populated areas.

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Solar power plants In the thermal balance of the Earth, solar radiation plays a decisive role. The power of radiation incident on the Earth determines the maximum power that can be generated on Earth without significantly disturbing the thermal balance. The intensity of solar radiation and the duration of sunshine in the southern regions of the country make it possible, with the help of solar panels, to obtain a sufficiently high temperature of the working fluid for its use in thermal installations.

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Conclusions: Great dissipation of energy and instability of its supply are the disadvantages of solar energy. These shortcomings are partially compensated by the use of storage devices, but still the Earth’s atmosphere interferes with the production and use of “clean” solar energy. To increase the power of solar power plants, it is necessary to install a large number of mirrors and solar panels - heliostats, which must be equipped with an automatic tracking system for the position of the sun. The transformation of one type of energy into another is inevitably accompanied by the release of heat, which leads to overheating of the earth's atmosphere.

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Geothermal energy About 4% of all water reserves on our planet are concentrated underground - in rock strata. Waters whose temperature exceeds 20 degrees Celsius are called thermal. Groundwater is heated as a result of radioactive processes occurring in the bowels of the earth. People have learned to use the deep heat of the Earth for economic purposes. In countries where thermal waters come close to the surface of the earth, geothermal power plants (geothermal power plants) are built. Geothermal power plants are designed relatively simply: there is no boiler room, fuel supply equipment, ash collectors and many other devices necessary for thermal power plants. Since the fuel at such power plants is free, the cost of generated electricity is low.

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Nuclear energy The energy sector that uses nuclear energy for electrification and heating; A field of science and technology that develops methods and means for converting nuclear energy into electrical and thermal energy. The basis of nuclear energy is nuclear power plants. The first nuclear power plant (5 MW), which marked the beginning of the use of nuclear energy for peaceful purposes, was launched in the USSR in 1954. By the beginning of the 90s. Over 430 nuclear power reactors with a total capacity of about 340 GW operated in 27 countries around the world. According to experts, the share of nuclear energy in the overall structure of electricity generation in the world will continuously increase, provided that the basic principles of the safety concept for nuclear power plants are implemented.

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Development of nuclear energy 1942 in the USA, under the leadership of Enrico Fermi, the first nuclear reactor was built FERMI (Fermi) Enrico (1901-54), Italian physicist, one of the creators of nuclear and neutron physics, founder of scientific schools in Italy and the USA, foreign corresponding member USSR Academy of Sciences (1929). In 1938 he emigrated to the USA. Developed quantum statistics (Fermi-Dirac statistics; 1925), the theory of beta decay (1934). Discovered (with collaborators) artificial radioactivity caused by neutrons, the moderation of neutrons in matter (1934). He built the first nuclear reactor and was the first to carry out a nuclear chain reaction in it (December 2, 1942). Nobel Prize (1938).

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Development of nuclear energy In 1946, the first European reactor was created in the Soviet Union under the leadership of Igor Vasilyevich Kurchatov. KURCHATOV Igor Vasilyevich (1902/03-1960), Russian physicist, organizer and leader of work on atomic science and technology in the USSR, academician of the USSR Academy of Sciences (1943), three times Hero of Socialist Labor (1949, 1951, 1954). Researched ferroelectrics. Together with his colleagues, he discovered nuclear isomerism. Under the leadership of Kurchatov, the first domestic cyclotron was built (1939), the spontaneous fission of uranium nuclei was discovered (1940), mine protection for ships was developed, the first nuclear reactor in Europe (1946), the first atomic bomb in the USSR (1949), and the world's first thermonuclear bomb ( 1953) and nuclear power plant (1954). Founder and first director of the Institute of Atomic Energy (since 1943, since 1960 - named after Kurchatov).

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The whole world, covering from earth to heaven, Having alarmed more than one generation, Scientific progress is sweeping across the planet. What is behind this phenomenon? Man went into space and was on the moon. Nature has fewer and fewer secrets. But any discovery is an aid to war: The same atom and the same missiles... How to use knowledge is the concern of people. It’s not science – the scientist is in charge. Who gave people fire - was Prometheus right? How will progress turn out for the planet?

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Discovery of Antoine Becquerel February 1896 Paris Experiment: A cross was placed under a saucer of uranium salts placed on a photographic plate wrapped in opaque paper. But the exhibition of salts had to be postponed due to cloudy weather. And while waiting for the sun, I placed the entire structure in a drawer of the cupboard. On Sunday, March 1, 1896, without waiting for clear weather, he decided, just in case, to develop a photographic plate and, to his surprise, discovered the clear contours of a cross on it. Uranium salts emitted radiation that penetrated through layers of opaque paper and left a clear mark on the photographic plate without “recharging” with light 1903 Nobel Prize for the discovery of natural radioactivity

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Discovery of radium Pierre Curie 1859 - 1906 Maria Sklodowska - Curie 1867 - 1934 The rays discovered by A. Becquerel interested Marie Curie. It turned out that such rays come not only from uranium. The word "ray" is Latin for "radius". Therefore, Maria proposed calling all substances that emit invisible rays radioactive. Maria's work greatly interested her husband Pierre. Soon they discovered rays that were sent by an unknown element! They called this element polonium, and some time later they discovered radium. And not only discover, but also extract a tiny piece of radium. Awarded the Nobel Prize for the discovery of the phenomenon of radioactivity

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In 1961 N.S. Khrushchev loudly declared that the USSR had a bomb containing 100 million tons of TNT. “But,” he noted, “we will not detonate such a bomb, because if we detonate it even in the most remote places, then even then we can break out our windows.” From the history

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Igor Vasilyevich Kurchatov is the man who gave the country security 01/02/1903 - 02/07/1960 1932. Kurchatov was one of the first in Russia to study the physics of the atomic nucleus. In 1934, he investigated artificial radioactivity and discovered nuclear isomerism - the decay of identical atoms at different rates. In 1940, Kurchatov, together with G.N. Flerov and K.A. Petrzhak, discovered that uranium atomic nuclei can undergo fission without the help of neutron irradiation - spontaneously. In 1943 he began working on a project to create atomic weapons. 1946 - the first European reactor under the leadership of I.V. Kurchatov in Obninsk. The creation of the domestic atomic bomb was completed by 1949, and in 1953 the hydrogen bomb appeared. The name of Kurchatov is also associated with the construction of the world’s first nuclear power plant, which produced electricity in 1954. It is noteworthy that it was Kurchatov who wrote the words “The atom should be a worker, not a soldier.”

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1 g. U - 75 MJ = 3 tons of coal 1 g. deuterium-tritium mixture – 300 MJ =? tons of coal. Energy yield of reactions

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Thermonuclear fusion is an inexhaustible and environmentally friendly source of energy. Conclusion:

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(Controlled thermonuclear fusion) Tokamak project (current chamber-magnet) At high temperatures (on the order of hundreds of millions of degrees), keep the plasma inside the installation for 0.1 - 1 s. TCB problem

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Scheme of a nuclear bomb 1-conventional explosive; 2-plutonium or uranium (the charge is divided into 6 parts, the mass of each of which is less than the critical mass, but their total mass is greater than the critical mass). If you connect these parts, a chain reaction will begin, occurring in millionths of a second - an atomic explosion will occur. To do this, the parts of the charge are connected using a conventional explosive. The connection occurs either by “shooting” two blocks of fissile substance of subcritical mass towards each other. The second scheme involves obtaining a supercritical state by compressing the fissile material with a focused shock wave created by the explosion of a conventional chemical explosive, which is given a very complex shape for focusing and detonation is carried out simultaneously at several points.

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Uncontrolled nuclear chain reaction. Nuclear weapon. Combat properties 1. Shock wave. It is formed as a result of a sharp and exceptionally strong increase in pressure in the nuclear reaction zone. It is a wave of highly compressed and heated air rapidly propagating about the center of the explosion (from 40 to 60% of energy) 2. Light radiation 30-50% of energy) 3. Radioactive contamination - 5-10% of energy) - contamination of the area in the area of ​​the epicenter at air explosion is caused mainly by radioactivity arising in the soil as a result of exposure to neutrons. 4. Penetrating radiation. Penetrating radiation is the flow of gamma rays and neutrons emitted at the moment of an atomic explosion. The main source of penetrating radiation is fission fragments of charge matter (5% of energy) 5. Electromagnetic pulse (2-3% of energy)

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Tests of nuclear weapons were first carried out on July 16, 1945 in the USA (in the desert part of New Mexico.) A plutonium nuclear device mounted on a steel tower was successfully detonated. The energy of the explosion approximately corresponded to 20 kt of TNT. The explosion created a mushroom cloud, turned the tower into steam, and melted the typical desert soil underneath into a highly radioactive glassy substance. (16 years after the explosion, the level of radioactivity in this place was still above normal.) In 1945 there were Bombs were dropped on the cities of Hiroshima and Nagasaki

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The first atomic bomb of the USSR - “RDS-1” The nuclear charge was first tested on August 29, 1949 at the Semipalatinsk test site. Charge power up to 20 kilotons of TNT equivalent.

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Nuclear bomb for use from supersonic aircraft Warhead of an intercontinental ballistic missile

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1. 1953 - in the USSR, 2. 1956 - in the USA, 3. 1957 - in England, 4. 1967 - in China, 5. 1968 - in France. Hydrogen bomb More than 50 thousand hydrogen bombs have been accumulated in the arsenals of various countries!

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The BZHRK includes: 1. Three minimum starting modules 2. A command module consisting of 7 cars 3. A tank car with reserves of fuel and lubricants 4. Three DM62 diesel locomotives. The minimum launch module includes three cars: 1. Launcher control center 2. Launcher 3. Support unit Combat railway missile system BZHRK 15P961 “Molodets” with an intercontinental nuclear missile.

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An explosion of a thermonuclear charge with a power of 20 Mt will destroy all life at a distance of up to 140 km from its epicenter.

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Was Prometheus right when he gave people fire? The world rushed forward, the world broke from its springs, A dragon grew from a beautiful swan, A genie was released from a forbidden bottle “It was as if light had appeared from the depths of the Earth, the light not of this world, but of many Suns brought together. This huge fireball rose, changing color from purple to orange, increasing in size, the natural silt came into action, freed from the bonds that had been bound for billions of years. "W. Lawrence A small group of stunned observers looked at the unprecedented spectacle that unfolded ten kilometers from them . One stood with his hand outstretched, palm up. There were small scraps of paper on the palm. Picked up by the shock wave, the pieces of paper flew off the man’s hand and fell at a distance of about a meter from him.

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A nuclear reactor is a facility in which a controlled chain reaction of fission of heavy nuclei is carried out. The first nuclear reactor: USA, 1942, E. Fermi, fission of uranium nuclei. In Russia: December 25, 1946, I.V. Kurchatov The world's first pilot nuclear power plant with a capacity of 5 MW was launched in the USSR on June 27, 1954 in Obninsk. Abroad, the first industrial nuclear power plant with a capacity of 46 MW was put into operation in 1956 in Calder Hall (England).

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Chernobyl is a world synonym for an environmental disaster - April 26, 1986. Destroyed 4th power unit Sarcophagus On the first day of the accident, 31 people died, 15 years after the disaster, 55 thousand liquidators died, another 150 thousand became disabled, 300 thousand people died from radiation diseases, a total of 3 million 200 thousand people received increased doses of radiation

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Nuclear energy VVER – pressurized water power reactor RBMK – high-power channel nuclear reactor BN – fast neutron nuclear reactor EGP – nuclear power graphite reactor with steam superheating

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Sources of external radiation, cosmic rays (0.3 mSv/year), provide slightly less than half of the total external radiation received by the population. When a person is located, the higher he rises above sea level, the stronger the radiation becomes, because. The thickness of the air layer and its density decrease as it rises, and therefore the protective properties decrease. Earthly radiation comes mainly from those mineral rocks that contain potassium - 40, rubidium - 87, uranium - 238, thorium - 232.

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Internal exposure of the population Entering the body with food, water, air. The radioactive gas radon is an invisible, tasteless, odorless gas that is 7.5 times heavier than air. Alumina. Industrial waste used in construction, for example, red clay bricks, blast furnace slag, fly ash. We also must not forget that when coal is burned, a significant part of its components is sintered into slag or ash, where radioactive substances are concentrated.

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Nuclear explosions Nuclear explosions also contribute to increasing the radiation dose to humans (what happened in Chernobyl). Radioactive fallout from testing in the atmosphere spreads throughout the planet, increasing the overall level of pollution. In total, nuclear tests in the atmosphere were carried out by: China - 193, USSR - 142, France - 45, USA - 22, Great Britain - 21. After 1980, explosions in the atmosphere practically stopped. Underground testing is still ongoing.

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Exposure to ionizing radiation Any type of ionizing radiation causes biological changes in the body, both during external (the source is outside the body) and internal irradiation (radioactive substances, i.e. particles, enter the body with food, through the respiratory system). A single exposure to radiation causes biological damage that depends on the total absorbed dose. So with a dose of up to 0.25 Gy. There are no visible violations, but already at 4 - 5 Gy. deaths account for 50% of the total number of victims, and at 6 Gy. and more - 100% of victims. (Here: Gr. - gray). The main mechanism of action is associated with the processes of ionization of atoms and molecules of living matter, in particular water molecules contained in cells. The degree of exposure to ionizing radiation on a living organism depends on the radiation dose rate, the duration of this exposure and the type of radiation and radionuclide that entered the body. The equivalent dose value, measured in sieverts, has been introduced (1 Sv. = 1 J/kg). A sievert is a unit of absorbed dose multiplied by a coefficient that takes into account the unequal radioactive danger to the body of different types of ionizing radiation.

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Equivalent radiation dose: N=D*K K - quality factor D – absorbed radiation dose Absorbed radiation dose: D=E/m E – energy of the absorbed body m – body mass

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As for the genetic consequences of radiation, they manifest themselves in the form of chromosomal aberrations (including changes in the number or structure of chromosomes) and gene mutations. Gene mutations appear immediately in the first generation (dominant mutations) or only if both parents have the same gene mutated (recessive mutations), which is unlikely. A dose of 1 Gy received at low background radiation by males (for women, estimates are less certain) causes the appearance of 1000 to 2000 mutations leading to serious consequences, and from 30 to 1000 chromosomal aberrations for every million living newborns.

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Genetic effects of radiation

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Nuclear energy

School No. 625 N.M. Turlakova

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§66. Fission of uranium nuclei. §67. Chain reaction. §68. Nuclear reactor. §69. Nuclear power. §70. Biological effects of radiation. §71. Production and use of radioactive isotopes. §72. Thermonuclear reaction. §73. Elementary particles. Antiparticles.

Nuclear power

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§66. Uranium nuclear fission

Who and when discovered the fission of uranium nuclei? What is the mechanism of nuclear fission? What forces act in the nucleus? What happens when a nucleus fissions? What happens to energy when a uranium nucleus fissions? How does the ambient temperature change when uranium nuclei fission? How much energy is released?

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Unlike the radioactive decay of nuclei, which is accompanied by the emission of α- or β-particles, fission reactions are a process in which an unstable nucleus is divided into two large fragments of comparable masses. In 1939, German scientists O. Hahn and F. Strassmann discovered the fission of uranium nuclei. Continuing the research begun by Fermi, they established that when uranium is bombarded with neutrons, elements of the middle part of the periodic table arise - radioactive isotopes of barium (Z = 56), krypton (Z = 36), etc. Uranium occurs in nature in the form of two isotopes: uranium- 238 and uranium-235 (99.3%) and (0.7%). When bombarded by neutrons, the nuclei of both isotopes can split into two fragments. In this case, the fission reaction of uranium-235 occurs most intensively with slow (thermal) neutrons, while uranium-238 nuclei enter into a fission reaction only with fast neutrons with an energy of about 1 MeV.

Fission of heavy nuclei.

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The main interest for nuclear energy is the fission reaction of the uranium-235 nucleus. Currently, about 100 different isotopes with mass numbers from about 90 to 145 are known, resulting from the fission of this nucleus. Two typical fission reactions of this nucleus are: Note that fission of a nucleus initiated by a neutron produces new neutrons that can cause fission reactions of other nuclei. The fission products of uranium-235 nuclei can also be other isotopes of barium, xenon, strontium, rubidium, etc.

Chain reaction

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The diagram of the development of a chain reaction of fission of uranium nuclei is shown in the figure

When a uranium-235 nucleus fissions, which is caused by a collision with a neutron, 2 or 3 neutrons are released. Under favorable conditions, these neutrons can hit other uranium nuclei and cause them to fission. At this stage, from 4 to 9 neutrons will appear, capable of causing new decays of uranium nuclei, etc. Such an avalanche-like process is called a chain reaction

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For a chain reaction to occur, it is necessary that the so-called neutron multiplication factor be greater than one. In other words, in each subsequent generation there should be more neutrons than in the previous one. The multiplication coefficient is determined not only by the number of neutrons produced in each elementary act, but also by the conditions under which the reaction occurs - some of the neutrons can be absorbed by other nuclei or leave the reaction zone. Neutrons released during the fission of uranium-235 nuclei are capable of causing the fission of only the nuclei of the same uranium, which accounts for only 0.7% of natural uranium.

Reproduction rate

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The smallest mass of uranium at which a chain reaction can occur is called critical mass. Ways to reduce neutron loss: Using a reflective shell (from beryllium), Reducing the amount of impurities, Using a neutron moderator (graphite, heavy water), For uranium-235 - M cr = 50 kg (r = 9 cm).

Critical mass

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Nuclear reactor diagram

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In the core of a nuclear reactor, a controlled nuclear reaction occurs, releasing a large amount of energy.

The first nuclear reactor was built in 1942 in the USA under the leadership of E. Fermi. In our country, the first reactor was built in 1946 under the leadership of I.V. Kurchatov

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§66. Fission of uranium nuclei. §67. Chain reaction. §68. Nuclear reactor. Answer the questions. Draw a diagram of the reactor. What substances and how are they used in a nuclear reactor? (written)

Homework

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Fusion reactions of light nuclei are called thermonuclear reactions, since they can only occur at very high temperatures.

Thermonuclear reactions.

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The second way to release nuclear energy is associated with fusion reactions. When light nuclei fuse and form a new nucleus, a large amount of energy must be released.

Of particular great practical importance is that during a thermonuclear reaction, much more energy is released per nucleon than during a nuclear reaction, for example, during the fusion of a helium nucleus from hydrogen nuclei, an energy equal to 6 MeV is released, and during the fission of a uranium nucleus, one nucleon accounts for " 0.9 MeV.

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In order for two nuclei to enter into a fusion reaction, they must approach each other to a distance of nuclear forces of the order of 2·10–15 m, overcoming the electrical repulsion of their positive charges. For this, the average kinetic energy of the thermal motion of molecules must exceed the potential energy of the Coulomb interaction. Calculation of the temperature T required for this leads to a value of the order of 108–109 K. This is an extremely high temperature. At this temperature, the substance is in a fully ionized state called plasma.

Conditions for a thermonuclear reaction

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Energetically favorable reaction. However, it can only occur at very high temperatures (on the order of several hundred million degrees). At a high density of matter, such a temperature can be achieved by creating powerful electronic discharges in the plasma. In this case, a problem arises - it is difficult to contain the plasma.

Controlled thermonuclear reaction

Self-sustaining thermonuclear reactions occur in stars

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has become a real threat to humanity. In this regard, scientists have proposed extracting the heavy hydrogen isotope - deuterium - from seawater and subjecting it to a nuclear meltdown reaction at temperatures of about 100 million degrees Celsius. In a nuclear meltdown, deuterium obtained from one kilogram of seawater will be able to produce the same amount of energy as released when burning 300 liters of gasoline ___

Energy crisis

TOKAMAK (toroidal magnetic chamber with current)

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The most powerful modern TOKAMAK, serving only for research purposes, is located in the city of Abingdon near Oxford. 10 meters high, it produces plasma and keeps her alive for only about 1 second.

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This is an electrophysical device whose main purpose is the formation of plasma. The plasma is held not by the walls of the chamber, which are not able to withstand its temperature, but by a specially created magnetic field, which is possible at temperatures of about 100 million degrees, and its preservation for quite a long time in a given volume. The possibility of producing plasma at ultra-high temperatures makes it possible to carry out a thermonuclear reaction of fusion of helium nuclei from feedstock, hydrogen isotopes (deuterium and tritium

TOKAMAK (TORoidal CHAMBER with MAGNETIC COILS)

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M.A. Leontovich near Tokamak

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The foundations of the theory of controlled thermonuclear fusion were laid in 1950 by I. E. Tamm and A. D. Sakharov, who proposed to contain the hot plasma formed as a result of reactions by a magnetic field. This idea led to the creation of thermonuclear reactors - tokamaks. At a high density of matter, the required high temperature of hundreds of millions of degrees can be achieved by creating powerful electronic discharges in the plasma. Problem: Plasma is difficult to retain. Modern tokamak installations are not thermonuclear reactors, but research installations in which the existence and preservation of plasma is possible only for a while.

Controlled thermonuclear reactions

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The founding fathers of the Soviet peaceful thermonuclear fusion were academicians Andrei Sakharov (left), the creator of the hydrogen bomb, and Evgeniy Velikhov (right), one of the developers of the tokamak - the prototype of the thermonuclear reactor

Slide 23

The spherical tokamak Globus-M is a new large physical installation built at the Physico-Technical Institute named after. A.F. Ioffe of the Russian Academy of Sciences in 1999

"Globe"

Slide 24

§72. Thermonuclear reaction. Answer the questions. §70. Biological effects of radiation. §71. Production and use of radioactive isotopes. Reports.