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Physics lesson in grade 9 on the topic NUCLEAR REACTOR Teacher: Serova Victoria Valerievna, GOU secondary school No. 2009slide 2
REVIEW 1. The mechanism of fission of uranium nuclei. 2. Tell us about the mechanism of the nuclear chain reaction. 3. Give an example of a nuclear fission reaction of the uranium nucleus. 4. What is called critical mass? 5. How goes chain reaction in uranium, if its mass is less than critical, more than critical?
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REVIEW 6. What is the critical mass of uranium 295, is it possible to reduce the critical mass? 7. What are the ways to change the course of a nuclear chain reaction? 8. What is the purpose of slowing down fast neutrons? 9. What substances are used as moderators? 10. Due to what factors can the number of free neutrons in a piece of uranium be increased, thereby ensuring the possibility of a reaction occurring in it?
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The first nuclear reactors The first nuclear chain reaction of uranium was carried out in the United States by a team of scientists led by Enrico Fermi in December 1942.
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The first nuclear reactors In our country, the first nuclear reactor was launched on December 25, 1946 by a team of physicists headed by the scientist Igor Vasilyevich Kurchatov
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A nuclear reactor is a device in which a controlled chain reaction of fission of some heavy nuclei is carried out and maintained.
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The main elements of a nuclear reactor: nuclear fuel (uranium 235, uranium 238, plutonium 239); neutron moderator (heavy water, graphite, etc.); coolant for the output of energy generated during the operation of the reactor (water, liquid sodium, etc.); Control rods (boron, cadmium) - strongly absorbing neutrons Protective shell that delays radiation (concrete with iron filler).
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The reactor is controlled by rods containing cadmium or boron. By pushing the rods into the core, it is possible at any time to stop the development of a chain reaction.
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Reactor on slow neutrons The most efficient fission of uranium-235 nuclei occurs under the action of slow neutrons. Such reactors are called slow neutron reactors. The secondary neutrons produced in the fission reaction are fast. In order for their subsequent interaction with uranium-235 nuclei in a chain reaction to be most effective, they are slowed down by introducing a moderator into the core - a substance that reduces the kinetic energy of neutrons.
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Fast neutron reactors Such reactors cannot operate on natural uranium. The reaction can only be maintained in an enriched mixture containing at least 15% of the uranium isotope. Advantage: when they work, a significant amount of plutonium is produced, which can then be used as nuclear fuel.
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Types of reactors are homogeneous: the active zone is a liquid, solid or gaseous homogeneous mixture of nuclear fuel, coolant and moderator. Heterogeneous: fuel in the form of blocks is placed in the moderator, i.e. fuel and moderator are spatially separated
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Energy conversion internal energy of uranium nuclei kinetic energy neutrons and nuclear fragments internal energy of water internal energy of steam kinetic energy of steam kinetic energy of turbine rotor and generator rotor electrical energy
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The Use of Nuclear Reactors Depending on the purpose, nuclear reactors are power, converters and breeders, research and multi-purpose, transport and industrial.
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Ecological disasters at a nuclear power plant in 1957 - an accident in the UK in 1966 - partial melting of the core after the failure of the reactor cooling near Detroit. 1971 - a lot of contaminated water went into the river USA 1979 - the largest accident in the USA 1982 - the release of radioactive steam into the atmosphere 1983 - a terrible accident in Canada (20 minutes radioactive water flowed out - a ton per minute) 1986 - an accident in the UK 1986 - accident in Germany 1986 - Chernobyl nuclear power plant 1988 - fire at a nuclear power plant in Japan
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Questions to reinforce 1. What is called a nuclear reactor? 2. What is the nuclear fuel in a reactor? 3. What substance serves as a neutron moderator in a nuclear reactor? 4. What is the purpose of a neutron moderator? 5. What are control rods for? How are they used? 6. What is used as a coolant in nuclear reactors? 7. Why is it necessary that the mass of each uranium rod be less than the critical mass?
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TEST 1. What particles are involved in the fission of uranium nuclei? A. protons; B. neutrons; B. electrons; G. helium nuclei.
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2. What is the critical mass of uranium? A. the largest at which a chain reaction is possible; B. any mass; V. the smallest at which a chain reaction is possible; D. the mass at which the reaction will stop.
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3. What is the approximate critical mass of uranium 235? A. 9 kg; B. 20 kg; B. 50 kg; G. 90 kg.
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4. Which of the following substances can be used in nuclear reactors as neutron moderators? A. graphite; B. cadmium; B. heavy water; G. bor.
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5. For a nuclear chain reaction to take place at a nuclear power plant, it is necessary that the neutron multiplication factor be: A. equal to 1; B. more than 1; V. less than 1.
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6. Regulation of the fission rate of nuclei of heavy atoms in nuclear reactors is carried out: A. due to the absorption of neutrons when lowering rods with an absorber; B. due to an increase in heat removal with an increase in the speed of the coolant; B. by increasing the supply of electricity to consumers; G. by reducing the mass of nuclear fuel in the core when removing the fuel rods.
A nuclear (or atomic) reactor is a device in which a controlled nuclear fission reaction is carried out. Nuclei of uranium (especially an isotope) capture slow neutrons most efficiently. The probability of capture of slow neutrons with subsequent nuclear fission is hundreds of times greater than that of fast ones. Nuclear reactors fueled with natural uranium use neutron moderators to increase neutron multiplication factors. Uchim.net
The main elements of a nuclear reactor: 1) nuclear fuel (, etc.); 2) neutron moderator (heavy or ordinary water, graphite, etc.); 3) coolant for the output of energy generated during the operation of the reactor (water, liquid sodium, etc.); 4) A device for regulating the reaction rate (rods containing cadmium or boron introduced into the working space of the reactor - substances that absorb neutrons well). Outside, the reactor is surrounded by a protective shell that traps γ-radiation and neutrons. The shell is made of concrete with iron filler. Uchim.net
Critical mass. Critical mass is the smallest mass of fissile material at which a nuclear chain reaction can proceed. At small sizes, the leakage of neutrons through the surface of the reactor core (the volume in which the uranium rods are located) is high. With an increase in the size of the system, the number of nuclei involved in fission increases in proportion to the volume, and the number of neutrons lost due to leakage increases in proportion to the surface area. By increasing the system, it is possible to achieve values of the multiplication factor k=1. The system will be of critical dimensions if the number of neutrons lost due to capture and leakage is equal to the number of neutrons obtained in the fission process. Critical dimensions (critical mass) are determined by: 1) the type of nuclear fuel; 2) moderator; 3) design features of the reactor. Uchim.net
The reactor is controlled by rods containing cadmium or boron. With the rods extended from the reactor core, k>1. With fully inserted rods k 1. With the rods fully retracted k"> 1. With the rods fully retracted k"> 1. With the rods fully retracted k" title="The reactor is controlled using rods containing cadmium or boron. When extended from the core reactor rods k> 1. With fully inserted rods k"> title="The reactor is controlled by rods containing cadmium or boron. With the rods extended from the reactor core, k>1. With fully inserted rods k"> !}
Fast neutron reactors: Reactors operating without a moderator on fast neutrons have been built. The probability of fission caused by fast neutrons is small; such reactors cannot operate on natural uranium. The reaction can only be maintained in an enriched mixture containing at least 15% of the isotope. Advantage: when they work, a significant amount of plutonium is produced, which can then be used as nuclear fuel. These reactors are called breeder reactors because they breed fissile material. Uchim.net
The first nuclear reactors The first nuclear chain reaction of uranium was carried out in the United States by a team of scientists led by Enrico Fermi in December 1942. In our country, the first nuclear reactor was launched on December 25, 1946 by a team of physicists, headed by the scientist Igor Vasilievich Kurchatov (). Enrico Fermi () Igor Vasilyevich Kurchatov () Uchim.net
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Nuclear reactor A nuclear reactor is a device for carrying out a controlled nuclear reaction. Slow neutron reactor - a reactor in which uranium - 235 is mainly used as fuel. Uranium - 235 - is most efficiently divided under the action of slow neutrons. Fast neutrons are formed in the fission of nuclei, so a neutron moderator is used in the reactor.
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Uranium is widely distributed in nature, but there are no rich deposits of uranium ores (like, say, iron or coal). Industrial uranium-containing ores have a very low concentration: 0.1-0.5% and even less than 0.08-0.05%. True, there are rich, unique deposits with a content of up to 10%, but they are very few and the uranium reserves in them are relatively small. IN earth's crust there is a lot of uranium, but almost all of it is in a dispersed state and not in uranium proper, but in uranium-containing minerals, where it isomorphically replaces thorium, zirconium, and rare earth elements.
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Uranium is found in both granites and basalts, but its concentration there is so low (4-10~4 and 1-10~*%, respectively) that extraction will become possible only in the very distant future. According to some forecasts, the reserves of uranium and thorium in the earth's crust can provide mankind with energy for 3 billion years. In terms of production, the United States ranks first, Canada is second, and South Africa is third. In nature, there is only one isotope of uranium that can support the chain reaction of fission of the uranium nucleus - this is uranium-235. In one act of fission of the uranium nucleus, energy is released per atom 200 million times greater than in any chemical reaction. If all isotopes in 1 g of uranium underwent fission, then energy of 20 million kcal would be released, which corresponds to 23 thousand kWh of thermal energy.
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The core contains nuclear fuel in the form of uranium rods and a neutron moderator water. The mass of each uranium rod is much less than the critical mass, so a chain reaction cannot occur in one rod. It occurs after the immersion of all uranium rods into the core, i.e. when the mass of uranium becomes critical. The core is surrounded by a neutron reflector and a protective shell made of concrete that traps neutrons and other particles.
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The nuclear reaction takes place in the reactor core, which is filled with a moderator and pierced with rods containing an enriched mixture of uranium isotopes with a high content of uranium-235 (up to 3%). Control rods containing cadmium or boron are introduced into the core, which intensively absorb neutrons. The introduction of rods into the core allows you to control the speed of the chain reaction.
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The core is cooled by a pumped coolant, which can be water or a metal with a low melting point (for example, sodium, which has a melting point of 98 °C). In a steam generator, the heat transfer medium transfers heat energy to water, converting it into high-pressure steam. The steam is sent to a turbine connected to an electric generator.
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The steam is sent to a turbine connected to an electric generator. From the turbine, steam enters the condenser. To avoid leakage of radiation, the circuits of coolant I and steam generator II operate in closed cycles.
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for the production of 1000 MW electrical power the thermal power of the reactor should reach 3000 MW. 2000 MW must be carried away by the water cooling the condenser. This leads to local overheating of natural water bodies and the subsequent occurrence environmental issues
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However, the main problem is to ensure complete radiation safety people working in nuclear power plants and the prevention of accidental releases of radioactive substances that in large numbers accumulate in the reactor core.
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A bit of history The first nuclear reactor was put into operation in the United States on December 2, 1942 under the leadership of the Italian scientist Enrico Fermi. The atomic bomb was created by the efforts of scientists from many countries of the world who emigrated to the United States during World War II. Its test was carried out on July 16, 1945 in the desert area of New Mexico, and in August 1945 two atomic bombs were dropped on the Japanese cities of Hiroshima and Nagasaki.
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The order to bomb Japanese cities was given by American President Harry Truman on July 31, 1945: to bomb after August 2, as soon as the weather allows. On the morning of August 6, 1945, the American B-29 Enola Gay bomber (crew commander Colonel Paul Tibbets) dropped the Little Boy atomic bomb on the Japanese city of Hiroshima. Three days later atomic bomb Fat Man ("Fat Man") was dropped on the city of Nagasaki.
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The Americans needed a target to match the destructive power of the bomb. The relief features embodied in geographical names- the word Hiroshima means "wide island", the word Nagasaki - "long bay". Hiroshima, located at the mouth of the river, surrounded by mountains, suffered much more than Nagasaki, stretched along a winding gorge. During the bombing, there were 6 more aircraft next to the bomber - one safety aircraft, three reconnaissance aircraft and two witnesses, who were stuffed with photographic equipment and instruments to record the results of their work.
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140,000 people died in Hiroshima from the explosion and its aftermath; a similar estimate for Nagasaki is 74,000. In both cities, the vast majority of victims were civilians.
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Many of the remarks of Captain Lewis, who dropped the first bomb, are extremely expressive. “In the first minute, no one knew what might happen,” the pilot writes. - The flash was terrible. There is no doubt that this is the most powerful explosion that man has ever seen. My God, what have we done!”
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According to Lewis, the mushroom cloud, rising to a height of 17 kilometers, was visible even from a distance of 400 miles from the epicenter. In Hiroshima, 140 thousand people died, in Nagasaki - about 74 thousand. In total, almost 227 thousand people died over a 58-year period.
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In the Soviet Union, all work related to the fission of the atomic nucleus was interrupted with the outbreak of war and resumed again only in the middle of 1943, but already in December 1946 in Moscow on the territory of the Institute atomic energy(now bearing the name of its founder I. V. Kurchatov) the first research nuclear reactor in Europe and Asia was put into operation.
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A presentation on the topic "chemical reactors" can be downloaded absolutely free of charge on our website. Project subject: Chemistry. Colorful slides and illustrations will help you keep your classmates or audience interested. To view the content, use the player, or if you want to download the report, click on the appropriate text under the player. The presentation contains 11 slide(s).
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Chemical reactor - a unit for carrying out chemical reactions with a volume from several milliliters to tens of cubic meters. Depending on the reaction conditions and technological requirements, the reactors are divided into: reactors for reactions in homogeneous systems and in heterogeneous systems; low, medium and high pressure reactors; low-temperature and high-temperature reactors; batch, semi-continuous and continuous reactors.
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The purpose of the reactor is to produce the final product from the initial components while meeting the requirements for the maximum efficiency of the process:
Creation of a sustainable and stable reaction mode; high energy performance; minimum cost of the reactor; ease of operation and repair. The processes occurring in chemical reactors can be described in terms of several ideal models: ideal mixing, where the concentration of the target product instantly jumps from the initial to the steady state in the reactor; ideal displacement, where a moving stream can be represented as several volumes that do not mix with each other and the nature of their movement is piston-like; one-parameter diffusion model - it is assumed that only longitudinal diffusion takes place in the flow; cell model - the flow is represented as a set of cells, each of which is ideally mixed, and there is no mass transfer between them.
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Application by reactor volume
Chemical reactors with an internal volume of up to 10 liters are mainly used in laboratories for research purposes and in pilot plants. Reactors with a volume of 100 liters or more are used in the chemical, pharmaceutical, cellulose, perfume industries and others. Chemical reactors are used to conduct various chemical reactions, evaporation, crystallization, melting and homogenization of the initial components or reaction products.
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Batch reactor
A batch reactor is loaded with a certain amount of reagents at a time, which is in it until the desired degree of conversion is reached. After that, the reactor is unloaded. In such a reactor, the distribution of concentration at any degree of mixing over time is similar to a plug-flow reactor. The amount of the initial substance that reacts per unit of time is determined by the formula: Material balance equation: Characteristic equation:
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Reactor of full mixing flow
The flow mixing reactor is an apparatus in which the reactants are intensively mixed, for example, using a stirrer. Reagents are continuously fed into it and reaction products are continuously removed. Particles of matter entering the apparatus of this type instantly mix with the particles in it, that is, they are evenly distributed in the volume of the apparatus. As a result, at all points of the reaction volume, the parameters characterizing the process are instantly aligned. Figure 25 shows the dependences of the concentration (a), the degree of conversion (b), and the reaction rate (c).
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Plug-flow reactor
An example of such a reactor is a tubular reactor for the production of maleic anhydride. In such a reactor, all particles move in a given direction without mixing with those moving in front and behind and completely displacing the flow particles in front (piston flow movement) like a piston. The residence time of all particles in the ideal displacement apparatus is the same, that is, the time characteristic of the reactor is the equation:
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Temperature regime of the reactor
Temperature significantly affects the result of the chemical-technological process in general and especially on chemical reaction. Depending on the temperature regime, the following main types of reactors are distinguished: adiabatic, isothermal and polythermal. Adiabatic reactors are called ideal displacement reactors that operate without the supply and removal of heat in environment through the walls of the reactor or with the help of heat exchange elements. In this case, all the heat released (absorbed) in the reactor is accumulated by the reaction mixture. Isothermal reactors are reactors in which the process proceeds at a constant temperature throughout the entire volume of the reactor. Isothermality is achieved by intensive mixing of the reagents. The required temperature is set either by supplying or removing heat of reaction, or by controlling the temperature of the incoming reaction mixture. This mode can also be achieved in a plug-flow reactor when carrying out processes with low thermal effects. Reactors are called polythermal, which are characterized by a partial supply of heat or heat removal from the reaction zone in accordance with a given program for changing the temperature along the length (height) of the plug-in or incomplete mixing reactor. Polythermal reactors in time are fully mixed batch reactors. When studying and quantifying the processes occurring in the reactor, heat balances are used to derive the equations for the temperature regime.
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Completed by: 10th grade student Vasina Lyudmila Nikolaevna Supervisor: Vasin N.V. - teacher of physics, MOU "Secondary School with. Krasnoarmeiskoye, Kalininsky District, Saratov Region"slide 2
A nuclear (or atomic) reactor is a device in which a controlled chain reaction of fission of some heavy nuclei is carried out and maintained. slow neutron reactor: (enrich natural uranium, i.e. bring the content in it to 5%). Natural uranium contains 0.7%. fast neutron reactor: (enriched natural uranium contains 15%). Types of nuclear reactors
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The first nuclear chain reaction of uranium was carried out in the United States by a team of scientists led by Enrico Fermi in December 1942. In our country, the first nuclear reactor was launched on December 25, 1946 by a team of physicists headed by the scientist Igor Vasilievich Kurchatov (1903-1960). Enrico Fermi (1901-1954) Igor Vasilyevich Kurchatov (1903-1960)
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1) nuclear fuel (, etc.); 2) neutron moderator (heavy or ordinary water, graphite, etc.); 3) coolant for the output of energy generated during the operation of the reactor (water, liquid sodium, etc.); 4) A device for regulating the reaction rate (rods containing cadmium or boron introduced into the working space of the reactor - substances that absorb neutrons well). Outside, the reactor is surrounded by a protective shell that traps γ-radiation and neutrons. The shell is made of concrete with iron filler.
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Critical mass is the smallest mass of fissile material at which a nuclear chain reaction can proceed. At small sizes, the leakage of neutrons through the surface of the reactor core (the volume in which the uranium rods are located) is high. With an increase in the size of the system, the number of nuclei involved in fission increases in proportion to the volume, and the number of neutrons lost due to leakage increases in proportion to the surface area. By increasing the system, it is possible to achieve values of the multiplication factor k=1. The system will be of critical dimensions if the number of neutrons lost due to capture and leakage is equal to the number of neutrons obtained in the fission process. Critical dimensions (critical mass) are determined by: the type of nuclear fuel; moderator; design features of the reactor.
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The reactor is controlled by rods containing cadmium or boron. With the rods extended from the reactor core, k>1. With fully inserted rods k
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depending on the average energy of the neutron spectrum, the reactors are divided into: fast, intermediate thermal; according to the design features of the core, the reactors are divided into: pressure vessel; by type of coolant for: water heavy water, sodium; by type of moderator: water, graphite, heavy water, etc.
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Energy Converters Breeders Research Multi-purpose Transport and industrial Used to generate electricity For the production of secondary nuclear fuel from natural uranium and thorium Expanded reproduction of nuclear fuel is carried out: more is obtained than was spent. For studies of the interaction of neutrons with matter, production of isotopes, biological research. Serving multiple purposes. Nuclear submarines and icebreakers, combined heat and power plants (CHP), heat supply stations (NPP).
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at nuclear power plants; on nuclear icebreakers; on nuclear submarines; during the operation of nuclear rocket engines (in particular, on AMS).
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pressurized water reactors with non-boiling or pressurized boiling water; uranium-graphite reactors with boiling water or cooled with carbon dioxide; heavy water channel reactors, etc.
