What is called a nuclear reactor. Nuclear power plants. The importance of nuclear energy in the modern world
Especially the nuclei of the isotope and, most effectively capture slow neutrons. The probability of capturing slow neutrons with subsequent fission of nuclei is hundreds of times greater than that of fast ones. Therefore, in nuclear reactors fueled by natural uranium, neutron moderators are used to increase the neutron multiplication factor. The processes in a nuclear reactor are shown schematically in Figure 13.15.
The main elements of a nuclear reactor. Figure 13.16 shows a diagram of a power plant with a nuclear reactor.
The main elements of a nuclear reactor are: nuclear fuel, a neutron moderator (heavy or ordinary water, graphite, etc.), a coolant for removing the energy generated during the operation of the reactor (water, liquid sodium, etc.), and a device for regulating the reaction rate (introduced rods containing cadmium or boron - substances that absorb neutrons well from the reactor). Outside, the reactor is surrounded by a protective shell that blocks γ-radiation and neutrons. The shell is made of iron-filled concrete.
Fermi Enrico (1901 - 1954)- the great Italian physicist who made a great contribution to the development of modern theoretical and experimental physics. In 1938 he emigrated to the United States. Simultaneously with Dirac, he created the quantum statistical theory of electrons and other particles (Fermi - Dirac statistics). Developed a quantitative theory of p-decay - a prototype of the modern quantum theory of the interaction of elementary particles. He made a number of fundamental discoveries in neutron physics. Under his leadership, in 1942, a controlled nuclear reaction was carried out for the first time.
The best moderator is heavy water (see § 102). Ordinary water itself captures neutrons and turns into heavy water. Graphite, the nuclei of which does not absorb neutrons, is also considered a good moderator.
Critical mass. The multiplication factor k can become equal to unity only if the dimensions of the reactor and, accordingly, the mass of uranium exceed some critical values. The critical mass is the smallest mass of fissile matter at which a nuclear chain reaction can still proceed.
At small sizes, the neutron leakage through the surface of the reactor core (the volume in which the rods with uranium are located) is too large.
With an increase in the size of the system, the number of nuclei participating in fission increases in proportion to the volume, and the number of neutrons lost due to leakage increases in proportion to the surface area. Therefore, by increasing the size of the system, it is possible to achieve the value of the multiplication factor k 1. The system will have 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. The critical dimensions and, accordingly, the critical mass are determined by the type of nuclear fuel, moderator and design features of the reactor.
For pure (without moderator) uranium in the shape of a sphere, the critical mass is approximately 50 kg. In this case, the radius of the sphere is approximately 9 cm (uranium is a very heavy substance). By using neutron moderators and a neutron-reflecting beryllium shell, it was possible to reduce the critical mass to 250 g.
Kurchatov Igor Vasilievich (1903-1960)- Soviet physicist and organizer of scientific research, three times Hero of Socialist Labor. In 1943 he headed scientific work related to the atomic problem. Under his leadership, the first atomic reactor in Europe (1946) and the first Soviet atomic bomb (1949) were created. Early work related to the study of ferroelectrics, nuclear reactions caused by neutrons, artificial radioactivity. Discovered the existence of excited states of nuclei with a relatively long "lifetime".
The reactor is controlled by rods containing cadmium or boron. When the rods are extended from the reactor core k> 1, and when the rods are fully extended, k< 1. Вдвигая стержни внутрь активной зоны, можно в любой момент времени приостановить развитие цепной реакции. Управление ядерными реакторами осуществляется дистанционно с помощью ЭВМ.
Fast reactors. Reactors operating without a moderator on fast neutrons have been built. Since the probability of fission caused by fast neutrons is small, such reactors cannot operate on natural uranium.
The reaction can be maintained only in an enriched mixture containing at least 15% of the isotope. The advantage of fast reactors is that they generate a significant amount of plutonium, which can then be used as nuclear fuel. These reactors are called breeder reactors because they reproduce fissile material. Reactors with a breeding ratio of up to 1.5 are under construction. This means that fission of 1 kg of the isotope in the reactor produces up to 1.5 kg of plutonium. In conventional reactors, the breeding ratio is 0.6-0.7.
The first nuclear reactors. For the first time the valuable nuclear fission reaction of uranium was carried out in the USA by a team of scientists led by Enrico Fermi in December 1942.
In our country, the first nuclear editor was launched on December 25, 1946 by a team of physicists headed by our remarkable scientist Igor Vasil'evich Kurchatov. Currently, various types of reactors have been created, differing from each other both in power and in their purpose.
In nuclear reactors, in addition to nuclear fuel, there is a neutron moderator and control rods. The released energy is removed by the heat carrier.
1. What is critical mass!
2. Why is a neutron moderator used in an atomic reactor!
Nuclear (nuclear) reactor
Nuclear reactor
Nuclear (nuclear) reactor
- an installation in which a self-sustaining controlled chain nuclear fission reaction is carried out. Nuclear reactors are used for nuclear power and research purposes. The main part of the reactor is its active zone, where nuclear fission occurs and nuclear energy is released. The core, which is usually in the form of a cylinder with a volume from fractions of a liter to many cubic meters, contains fissile material (nuclear fuel) in an amount exceeding the critical mass. Nuclear fuel (uranium, plutonium) is usually placed inside fuel elements (fuel rods), the number of which in the core can reach tens of thousands. Fuel rods are grouped into packages of several tens or hundreds of pieces. The core in most cases is a set of fuel rods immersed in a moderating medium (moderator) - a substance, due to elastic collisions with the atoms of which the energy of neutrons, causing and accompanying fission, is reduced to energies of thermal equilibrium with the medium. Such "thermal" neutrons have an increased ability to induce fission. Water (including heavy water, D 2 O) and graphite are usually used as moderators. The reactor core is surrounded by a reflector made of materials capable of scattering neutrons well. This layer returns neutrons emitted from the core back to this zone, increasing the rate of the chain reaction and decreasing the critical mass. Radiation biological shielding made of concrete and other materials is placed around the reflector to reduce radiation outside the reactor to an acceptable level.
In the core, huge energy is released in the form of heat as a result of fission. It is removed from the core with the help of gas, water or other substance (coolant), which is constantly pumped through the core, washing the fuel rods. This heat can be used to create hot steam that turns the power plant's turbine.
To control the rate of the fission chain reaction, control rods made of materials that strongly absorb neutrons are used. Their introduction into the core reduces the speed of the chain reaction and, if necessary, completely stops it, despite the fact that the mass of nuclear fuel exceeds the critical one. As the control rods are removed from the core, the neutron absorption decreases and the chain reaction can be brought to a self-sustaining stage.
The first reactor was launched in the USA in 1942. In Europe, the first reactor was launched in 1946 in the USSR.
For an ordinary person, modern high-tech devices are so mysterious and enigmatic that it is time to worship them like the ancients worshiped lightning. High school physics lessons, replete with math, do not solve the problem. But you can even tell interestingly about a nuclear reactor, the principle of operation of which is clear even to a teenager.
How does a nuclear reactor work?
The principle of operation of this high-tech device is as follows:
- When a neutron is absorbed, nuclear fuel (most often it is uranium-235 or plutonium-239) the fission of the atomic nucleus occurs;
- Kinetic energy, gamma radiation and free neutrons are released;
- Kinetic energy is converted into heat (when nuclei collide with surrounding atoms), gamma radiation is absorbed by the reactor itself and also turns into heat;
- Some of the generated neutrons are absorbed by the fuel atoms, which causes a chain reaction. Neutron absorbers and moderators are used to control it;
- With the help of a heat carrier (water, gas or liquid sodium), heat is removed from the place of the reaction;
- Pressurized steam from the heated water is used to drive steam turbines;
- With the help of a generator, the mechanical energy of rotation of the turbines is converted into alternating electric current.
Classification approaches
There are many reasons for a typology of reactors:
- By the type of nuclear reaction... Fission (all commercial installations) or fusion (thermonuclear energy, is widespread only in some research institutes);
- By coolant... In the vast majority of cases, water (boiling or heavy) is used for this purpose. Alternative solutions are sometimes used: liquid metal (sodium, lead-bismuth alloy, mercury), gas (helium, carbon dioxide or nitrogen), molten salt (fluoride salts);
- By generation. The first is early prototypes that didn't make any commercial sense. The second is the majority of currently used nuclear power plants, which were built before 1996. The third generation differs from the previous one with only minor improvements. Work on the fourth generation is still in progress;
- By state of aggregation fuel (gas still exists only on paper);
- By purpose of use(for electricity generation, engine starting, hydrogen production, desalination, transmutation of elements, obtaining neural radiation, theoretical and investigative purposes).
Atomic reactor device
The main components of reactors in most power plants are:
- Nuclear fuel - a substance that is required to generate heat for power turbines (usually low-enriched uranium);
- The active zone of the nuclear reactor - this is where the nuclear reaction takes place;
- Neutron moderator - reduces the speed of fast neutrons, converting them into thermal neutrons;
- Starting neutron source - used for a reliable and stable start of a nuclear reaction;
- Neutron absorber - available at some power plants to reduce the high reactivity of fresh fuel;
- Neutron howitzer - used to re-initiate the reaction after shutdown;
- Cooling liquid (purified water);
- Control rods - to regulate the fission rate of uranium or plutonium nuclei;
- Water pump - pumps water to the steam boiler;
- Steam turbine - converts thermal energy of steam into rotational mechanical energy;
- Cooling tower - a device for removing excess heat into the atmosphere;
- Radioactive waste reception and storage system;
- Safety systems (emergency diesel generators, emergency core cooling devices).
How the latest models work
The latest 4th generation of reactors will be available for commercial operation not earlier than 2030... Currently, the principle and structure of their work are under development. According to current data, these modifications will differ from existing models in such advantages:
- Rapid gas cooling system. It is assumed that helium will be used as a coolant. According to the design documentation, in this way it is possible to cool reactors with a temperature of 850 ° C. To work at such high temperatures, you will also need specific raw materials: composite ceramic materials and actinide compounds;
- It is possible to use lead or lead-bismuth alloy as the primary coolant. These materials have a low neutron absorption rate and a relatively low melting point;
- Also, a mixture of molten salts can be used as the main heat carrier. Thus, it will be possible to work at higher temperatures than modern counterparts with water cooling.
Natural analogues in nature
A nuclear reactor is perceived in the public mind exclusively as a product of high technologies. However, in fact, the first is the device is of natural origin... It was found in the Oklo region of the central African state of Gabon:
- The reactor was formed due to the flooding of uranium rocks by groundwater. They acted as neutron moderators;
- The heat energy released during the decay of uranium turns water into steam, and the chain reaction stops;
- After the coolant temperature drops, everything is repeated again;
- If the liquid had not boiled away and stopped the course of the reaction, humanity would have faced a new natural disaster;
- Self-sustained fission of nuclei began in this reactor about one and a half billion years ago. During this time, about 0.1 million watts of power output were allocated;
- Such a wonder of the world on Earth is the only one known. The emergence of new ones is impossible: the share of uranium-235 in natural raw materials is much lower than the level required to maintain a chain reaction.
How many nuclear reactors are there in South Korea?
Poor in natural resources, but industrialized and overpopulated, the Republic of Korea is in dire need of energy. Against the background of Germany's refusal from a peaceful atom, this country has high hopes for curbing nuclear technology:
- It is planned that by 2035 the share of electricity generated by nuclear power plants will reach 60%, and the total production - more than 40 gigawatts;
- The country does not have atomic weapons, but research in nuclear physics is ongoing. Korean scientists have developed projects for modern reactors: modular, hydrogen, with liquid metal, etc .;
- The success of local researchers makes it possible to sell technology abroad. The country is expected to export 80 such units in the next 15-20 years;
- But as of today, most of the nuclear power plant was built with the assistance of American or French scientists;
- The number of operating plants is relatively small (only four), but each of them has a significant number of reactors - 40 in total, and this figure will grow.
When bombarded with neutrons, nuclear fuel enters into a chain reaction that produces a huge amount of heat. The water in the system picks up this heat and turns into steam, which turns turbines that generate electricity. Here is a simple diagram of the operation of a nuclear reactor, the most powerful source of energy on Earth.
Video: how nuclear reactors work
In this video, nuclear physicist Vladimir Chaikin will tell you how electricity is produced in nuclear reactors, their detailed structure:
The fission chain reaction is always accompanied by the release of enormous energy. The practical use of this energy is the main task of a nuclear reactor.
A nuclear reactor is a device in which a controlled, or controlled, nuclear fission reaction is carried out.
According to the principle of operation, nuclear reactors are divided into two groups: thermal reactors and fast reactors.
How a nuclear thermal reactor works
A typical nuclear reactor contains:
- Active zone and moderator;
- Reflector of neutrons;
- Heat carrier;
- Chain reaction control system, emergency protection;
- Monitoring and radiation protection system;
- Remote control system.
1 - active zone; 2 - reflector; 3 - protection; 4 - control rods; 5 - coolant; 6 - pumps; 7 - heat exchanger; 8 - turbine; 9 - generator; 10 - capacitor.
Active zone and retarder
It is in the core that the controlled fission chain reaction takes place.
Most nuclear reactors use the heavy isotopes of uranium-235. But in natural samples of uranium ore, its content is only 0.72%. This concentration is not enough for a chain reaction to develop. Therefore, the ore is artificially enriched, bringing the content of this isotope to 3%.
Fissile material, or nuclear fuel, in the form of pellets is placed in hermetically sealed rods called fuel rods (fuel rods). They permeate the entire core filled with moderator neutrons.
Why do you need a neutron moderator in a nuclear reactor?
The fact is that the neutrons born after the decay of uranium-235 nuclei have a very high speed. The probability of their capture by other uranium nuclei is hundreds of times less than the probability of the capture of slow neutrons. And if their speed is not reduced, the nuclear reaction can die out over time. The moderator also solves the problem of reducing the speed of neutrons. If water or graphite is placed in the path of fast neutrons, their speed can be artificially reduced and thus the number of particles captured by atoms can be increased. At the same time, for a chain reaction in the reactor, less nuclear fuel is needed.
As a result of the deceleration process, thermal neutrons, the speed of which is practically equal to the speed of thermal motion of gas molecules at room temperature.
Water, heavy water (deuterium oxide D 2 O), beryllium, graphite are used as a moderator in nuclear reactors. But the best moderator is heavy water D 2 O.
Neutron reflector
To avoid leakage of neutrons into the environment, the core of a nuclear reactor is surrounded by neutron reflector... The materials used for reflectors are often the same as those used for retarders.
Heat carrier
The heat released during a nuclear reaction is removed using a coolant. As a coolant in nuclear reactors, ordinary natural water, previously purified from various impurities and gases, is often used. But since water boils already at a temperature of 100 0 C and a pressure of 1 atm, in order to increase the boiling point, the pressure in the primary coolant circuit is increased. The water in the primary circuit, circulating through the reactor core, washes the fuel rods, heating up to a temperature of 320 0 C. Then, inside the heat exchanger, it gives off heat to the water in the secondary circuit. The exchange passes through heat exchange tubes, so there is no contact with the water of the second circuit. This excludes the ingress of radioactive substances into the second loop of the heat exchanger.
And then everything happens as in a thermal power plant. The water in the second circuit turns into steam. The steam turns a turbine, which drives an electric generator, which generates an electric current.
In heavy water reactors, heavy water D 2 O serves as the coolant, and molten metal is used in reactors with liquid metal coolants.
Chain reaction control system
The current state of the reactor is characterized by a quantity called reactivity.
ρ = ( k -1) / k ,
k = n i / n i -1 ,
where k - neutron multiplication factor,
n i - the number of next generation neutrons in a nuclear fission reaction,
n i -1 , - the number of neutrons of the previous generation in the same reaction.
If k ˃ 1 , the chain reaction grows, the system is called supercritically th. If k< 1 , the chain reaction dies out, and the system is called subcritical... At k = 1 the reactor is in stable critical condition, since the number of fissile nuclei does not change. In this state, reactivity ρ = 0 .
The critical state of the reactor (the required neutron multiplication factor in a nuclear reactor) is maintained by moving control rods... The material from which they are made includes substances that absorb neutrons. By extending or sliding these rods into the core, the rate of the nuclear fission reaction is controlled.
The control system provides control of the reactor during its start-up, scheduled shutdown, operation at power, as well as emergency protection of the nuclear reactor. This is achieved by changing the position of the control rods.
If any of the reactor parameters (temperature, pressure, rate of power rise, fuel consumption, etc.) deviates from the norm, and this can lead to an accident, special emergency rods and there is a rapid cessation of the nuclear reaction.
To ensure that the parameters of the reactor comply with the standards, they are monitored monitoring and radiation protection systems.
To protect the environment from radioactive radiation, the reactor is placed in a thick concrete case.
Remote control systems
All signals about the state of the nuclear reactor (coolant temperature, radiation level in different parts of the reactor, etc.) are sent to the reactor control panel and processed in computer systems. The operator receives all the necessary information and recommendations for eliminating certain deviations.
Fast Reactors
The difference between reactors of this type and reactors on thermal neutrons is that fast neutrons arising after the decay of uranium-235 are not slowed down, but are absorbed by uranium-238, followed by its transformation into plutonium-239. Therefore, fast reactors are used to obtain weapons-grade plutonium-239 and thermal energy, which the generators of the nuclear power plant convert into electrical energy.
The nuclear fuel in such reactors is uranium-238, and the raw material is uranium-235.
In natural uranium ore, 99.2745% is accounted for by uranium-238. When a thermal neutron is absorbed, it does not divide, but becomes an isotope of uranium-239.
Some time after β-decay, uranium-239 turns into the nucleus of neptunium-239:
239 92 U → 239 93 Np + 0 -1 e
After the second β-decay, fissile plutonium-239 is formed:
239 9 3 Np → 239 94 Pu + 0 -1 e
And finally, after alpha decay, plutonium-239 nuclei get uranium-235:
239 94 Pu → 235 92 U + 4 2 He
Fuel rods with raw materials (enriched with uranium-235) are located in the reactor core. This zone is surrounded by a breeding zone, which consists of fuel rods with fuel (depleted uranium-238). Fast neutrons emitted from the core after the decay of uranium-235 are captured by the nuclei of uranium-238. The result is plutonium-239. Thus, new nuclear fuel is produced in fast reactors.
Liquid metals or their mixtures are used as coolants in fast-neutron nuclear reactors.
Classification and application of nuclear reactors
The main application of nuclear reactors is found in nuclear power plants. With their help, electric and thermal energy is obtained on an industrial scale. Such reactors are called energy .
Nuclear reactors are widely used in propulsion systems of modern nuclear submarines, surface ships, and in space technology. They supply electrical energy to motors and are called transport reactors .
For scientific research in the field of nuclear physics and radiation chemistry, fluxes of neutrons and gamma quanta are used, which are obtained in the core. research reactors. The energy generated by them does not exceed 100 MW and is not used for industrial purposes.
Power experimental reactors even less. It reaches a value of only a few kW. Various physical quantities are studied at these reactors, the importance of which is important in the design of nuclear reactions.
TO industrial reactors include reactors for producing radioactive isotopes used for medical purposes, as well as in various fields of industry and technology. Reactors for seawater desalination are also classified as industrial reactors.
Topic: Physical foundations of nuclear energy. Nuclear reactor.
Lesson objectives: updating existing knowledge; continue the formation of concepts: fission of uranium nuclei, nuclear chain reaction, conditions of its course, critical mass; introduce new concepts: a nuclear reactor, the main elements of a nuclear reactor, the design of a nuclear reactor and the principle of its operation, control of a nuclear reaction, the classification of nuclear reactors and their use; continue the formation of skills to observe and draw conclusions, as well as develop the intellectual abilities and curiosity of students; continue fostering an attitude towards physics as an experimental science; to cultivate a conscientious attitude towards work, discipline, a positive attitude towards knowledge.
Lesson type: learning new material.
During the classes
1. Organizational moment.
Today in the lesson we will repeat the fission of uranium nuclei, the nuclear chain reaction, the conditions for its course, the critical mass, we will learn what a nuclear reactor is, the main elements of a nuclear reactor, the design of a nuclear reactor and its principle of operation, control of a nuclear reaction, the classification of nuclear reactors and their use.
2. Verification of the studied material.
Fission mechanism of uranium nuclei.
Tell us about the mechanism of the nuclear chain reaction.
Give an example of a nuclear fission reaction of a uranium nucleus.
What is called critical mass?
How is the chain reaction going in uranium if its mass is less than critical, more than critical?
What is the critical mass of uranium 295, is it possible to reduce the critical mass?
In what ways can the course of a nuclear chain reaction be changed?
What is the purpose of slowing down fast neutrons?
What substances are used as moderators?
3. Explanation of the new material.
: What is the main part of any nuclear power plant? ( nuclear reactor)
Well done. So, guys, now let's dwell on this issue in more detail.
Historical reference.
Igor Vasilievich Kurchatov is an outstanding Soviet physicist, academician, founder and first director of the Institute of Atomic Energy from 1943 to 1960, the chief scientific leader of the atomic problem in the USSR, one of the founders of the use of nuclear energy for peaceful purposes. Academician of the USSR Academy of Sciences (1943). The tests of the first Soviet atomic bomb were carried out in 1949. Four years later, the world's first hydrogen bomb was successfully tested. And in 1949, Igor Vasilyevich Kurchatov began work on a project for a nuclear power plant. Nuclear power plant - a bulletin of the peaceful uses of atomic energy. The project was successfully completed: on July 27, 1954, our nuclear power plant became the first in the world! Kurchatov was jubilant and merry like a child!
Definition of a nuclear reactor.
A nuclear reactor is a device in which a controlled chain reaction of fission of some heavy nuclei is carried out and maintained.
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 IV Kurchatov.
The main elements of a nuclear reactor are:
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) - highly absorbing neutrons
Radiation-retarding protective shell (iron-filled concrete).
Operating principle nuclear reactor
Nuclear fuel is located in the core in the form of vertical rods called fuel elements (fuel rods). Fuel rods are designed to regulate the power of the reactor.
The mass of each fuel rod is much less than the critical one, therefore, a chain reaction cannot occur in one rod. It begins after all uranium rods are immersed in the core.
The core is surrounded by a layer of material that reflects neutrons (reflector) and a protective shell made of concrete that traps neutrons and other particles.
Removing heat from fuel cells. Heat carrier - water washes the rod, heated to 300 ° C at high pressure, enters the heat exchangers.
The role of the heat exchanger is that water heated to 300 ° C gives off heat to ordinary water, turns into steam.
Nuclear reaction management
The reactor is controlled by rods containing cadmium or boron. With the rods extended from the reactor core K> 1, and with fully retracted - K< 1. Вдвигая стержни внутрь активной зоны, можно в любой момент времени приостановить развитие цепной реакции. Управление ядерными реакторами осуществляется дистанционно с помощью ЭВМ.
Slow neutron reactor.
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 by 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.
Fast neutron reactor.
Fast reactors cannot run on natural uranium. The reaction can be maintained only in an enriched mixture containing at least 15% of the uranium isotope. The advantage of fast reactors is that they generate a significant amount of plutonium, which can then be used as nuclear fuel.
Homogeneous and heterogeneous reactors.
Nuclear reactors, depending on the relative placement of the fuel and the moderator, are subdivided into homogeneous and heterogeneous. In a homogeneous reactor, the core is a homogeneous mass of fuel, moderator and coolant in the form of a solution, mixture, or melt. A reactor is called heterogeneous, in which fuel in the form of blocks or fuel assemblies is placed in a moderator, forming a regular geometric lattice in it.
Converting the internal energy of atomic nuclei into electrical energy.
A nuclear reactor is the main element of a nuclear power plant (NPP), which converts thermal nuclear energy into electrical energy. Energy conversion takes place according to the following scheme:
internal energy of uranium nuclei -
kinetic energy of neutrons and nuclear fragments -
internal energy of water -
internal energy of steam -
kinetic energy of steam -
kinetic energy of the turbine rotor and generator rotor -
Electric Energy.
Use of nuclear reactors.
Depending on the purpose, nuclear reactors are power, converters and breeders, research and multipurpose, transport and industrial.
Nuclear power reactors are used to generate electricity in nuclear power plants, ship power plants, nuclear power plants, and nuclear heating plants.
Reactors designed to produce secondary nuclear fuel from natural uranium and thorium are called converters or breeders. In the reactor-converter secondary nuclear fuel is formed less than the initially consumed.
In the breeder reactor, an expanded breeding of nuclear fuel is carried out, i.e. it turns out more than it was spent.
Research reactors are used to study the processes of interaction of neutrons with matter, study the behavior of reactor materials in intense fields of neutron and gamma radiation, radiochemical in biological research, production of isotopes, experimental research of the physics of nuclear reactors.
The reactors have different capacities, stationary or pulsed operation. Multipurpose reactors are those that serve multiple purposes, such as power generation and nuclear fuel.
Environmental disasters at nuclear power plants
1957 - an accident in the UK
1966 - partial melting of the core after failure of the reactor cooling near Detroit.
1971 - A lot of contaminated water went into the US river
1979 - the largest accident in the United States
1982 - release of radioactive steam into the atmosphere
1983 - a terrible accident in Canada (radioactive water leaked out for 20 minutes - a ton per minute)
1986 - an accident in the UK
1986 - an accident in Germany
1986 - Chernobyl nuclear power plant
1988 - a fire at a nuclear power plant in Japan
Modern nuclear power plants are equipped with PCs, and earlier, even after an accident, the reactors continued to operate, since there was no automatic shutdown system.
4. Securing the material.
What is called a nuclear reactor?
What is nuclear fuel in a reactor?
What substance serves as a neutron moderator in a nuclear reactor?
What is the purpose of a neutron moderator?
What are control rods for? How are they used?
What is used as a coolant in nuclear reactors?
Why do you need the mass of each uranium rod to be less than the critical mass?
5. Execution of the test.
What particles are involved in the fission of uranium nuclei?
A. protons;
B. neutrons;
V. electrons;
G. helium nucleus.
What is the critical mass of uranium?
A. the highest, at which a chain reaction is possible;
B. any mass;
V. is the smallest, at which a chain reaction is possible;
G. the mass at which the reaction will stop.
What is the approximate critical mass of uranium 235?
A. 9 kg;
B. 20 kg;
H. 50 kg;
G. 90 kg.
Which substances from the following can be used in nuclear reactors as neutron moderators?
A. graphite;
B. cadmium;
B. heavy water;
G. bor.
For a nuclear chain reaction to occur at a nuclear power plant, the neutron multiplication factor must be:
A. is equal to 1;
B. is greater than 1;
V. less than 1.
Regulation of the rate of fission of nuclei of heavy atoms in nuclear reactors is carried out:
A. due to 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.
What energy transformations take place in a nuclear reactor?
A. the internal energy of atomic nuclei is converted into light energy;
B. the internal energy of atomic nuclei is converted into mechanical energy;
C. the internal energy of atomic nuclei is converted into electrical energy;
G. Among the answers there is no correct one.
In 1946, the first nuclear reactor was built in the Soviet Union. Who was the leader of this project?
A. S. Korolev;
B. I. Kurchatov;
V. D. Sakharov;
G. A. Prokhorov.
Which way do you consider the most acceptable for increasing the reliability of nuclear power plants and preventing contamination of the external environment?
A. development of reactors capable of automatically cooling the reactor core regardless of the operator's will;
B. increasing the literacy of NPP operation, the level of professional preparedness of NPP operators;
B. development of highly efficient technologies for dismantling nuclear power plants and processing radioactive waste;
D. location of reactors deep underground;
D. refusal to build and operate a nuclear power plant.
What sources of environmental pollution are associated with the operation of a nuclear power plant?
A. uranium industry;
B. nuclear reactors of various types;
B. radiochemical industry;
D. places of processing and disposal of radioactive waste;
D. use of radionuclides in the national economy; E. nuclear explosions.
Answers: 1 B; 2 B; 3V; 4 A, B; 5 A; 6 A; 7 B ;. 8 B; 9 B. V; 10 A, B, C, D, E.
6. Lesson summary.
What new have you learned in the lesson today?
What did you like in the lesson?
What questions do you have?
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