The role of water in a nuclear reactor. How does a nuclear reactor work

I. Arrangement of a nuclear reactor

A nuclear reactor consists of the following five main elements:

1) nuclear fuel;

2) neutron moderator;

3) regulation systems;

4) cooling systems;

5) protective screen.

1. Nuclear fuel.

Nuclear fuel is a source of energy. Three types of fissile materials are currently known:

a) uranium 235, which is 0.7% in natural uranium, or 1/140 part;

6) plutonium 239, which is formed in some reactors based on uranium 238, which makes up almost the entire mass of natural uranium (99.3%, or 139/140 parts).

Capturing neutrons, uranium 238 nuclei turn into neptunium nuclei - element 93 of Mendeleev's periodic table; the latter, in turn, turn into plutonium nuclei - the 94th element of the periodic table. Plutonium is easily extracted from irradiated uranium by chemical means and can be used as a nuclear fuel;

c) uranium 233, which is an artificial isotope of uranium obtained from thorium.

Unlike uranium 235, which is found in natural uranium, plutonium 239 and uranium 233 are produced only by artificial means. Therefore, they are called secondary nuclear fuel; uranium 238 and thorium 232 serve as the source of such fuel.

Thus, among all the types of nuclear fuel listed above, uranium is the main one. This explains the tremendous scope that the search for and exploration of uranium deposits is taking in all countries.

The energy released in a nuclear reactor is sometimes compared with that released during a chemical combustion reaction. However, there is a fundamental difference between them.

The amount of heat obtained in the process of fission of uranium is immeasurably greater than the amount of heat obtained during the combustion of, for example, coal: 1 kg of uranium 235, equal in volume to a pack of cigarettes, could theoretically give as much energy as 2,600 tons of coal.

However, these energetic possibilities are not fully utilized, since not all uranium-235 can be separated from natural uranium. As a result, 1 kg of uranium, depending on the degree of its enrichment in uranium 235, is currently equivalent to about 10 tons of coal. But it should be borne in mind that the use of nuclear fuel facilitates transportation and, therefore, significantly reduces the cost of fuel. British experts have calculated that by enriching uranium they will be able to increase the heat received in the reactors by a factor of 10, which will equate 1 ton of uranium to 100 thousand tons of coal.

The second difference between the nuclear fission process, which proceeds with the release of heat, from chemical combustion is that oxygen is needed for the combustion reaction, while only a few neutrons and a certain mass of nuclear fuel are required to initiate a chain reaction, equal to the critical mass, the definition of which we already given in the section on the atomic bomb.

And finally, the invisible process of nuclear fission is accompanied by the emission of extremely harmful radiation, from which protection must be ensured.

2. Neutron moderator.

In order to avoid the spread of fission products in the reactor, nuclear fuel must be placed in special shells. For the manufacture of such shells, aluminum can be used (the temperature of the cooler should not exceed 200 °), and even better, beryllium or zirconium are new metals, the production of which in a pure form is fraught with great difficulties.

Formed in the process of nuclear fission, neutrons (on average 2–3 neutrons in the fission of one nucleus of a heavy element) have a certain energy. In order for the probability of the splitting of other nuclei by neutrons to be the greatest, without which the reaction will not be self-sustaining, it is necessary that these neutrons lose part of their speed. This is achieved by placing a moderator in the reactor, in which fast neutrons are converted into slow neutrons as a result of numerous successive collisions. Since the substance used as a moderator must have nuclei with a mass approximately equal to the mass of neutrons, that is, nuclei of light elements, heavy water was used from the very beginning as a moderator (D 2 0, where D is deuterium, which replaced light hydrogen in ordinary water H 2 0). However, now they are trying to use more and more graphite - it is cheaper and gives almost the same effect.

A ton of heavy water purchased from Sweden costs 70-80 million francs. At the Geneva Conference on the Peaceful Uses of Atomic Energy, the Americans announced that they would soon be able to sell heavy water at 22 million francs per ton.

A ton of graphite costs 400,000 francs, and a ton of beryllium oxide costs 20 million francs.

The material used as a moderator must be clean to avoid the loss of neutrons as they pass through the moderator. At the end of the run, the neutrons have an average speed of about 2200 m / s, while their initial speed was about 20 thousand km / s. In reactors, the release of heat occurs gradually and can be controlled, in contrast to the atomic bomb, where it occurs instantly and takes on the character of an explosion.

In some types of fast reactors, a moderator is not required.

3. Regulation system.

A person should be able to induce, regulate and stop a nuclear reaction at will. This is achieved using control rods made of boron steel or cadmium, materials with the ability to absorb neutrons. Depending on the depth to which the control rods are lowered into the reactor, the number of neutrons in the core increases or decreases, which ultimately makes it possible to control the process. The control rods are controlled automatically by servo mechanisms; some of these rods can instantly fall into the core in case of danger.

At first, there were concerns that the explosion of the reactor would cause the same damage as the explosion of an atomic bomb. In order to prove that the explosion of the reactor occurs only in conditions different from usual and does not pose a serious danger to the population living in the vicinity of the nuclear plant, the Americans deliberately blew up one so-called "boiling" reactor. Indeed, there was an explosion that we can characterize as "classical", that is, non-nuclear; this proves once again that nuclear reactors can be built near populated areas without any particular danger to the latter.

4. Cooling system.

In the process of nuclear fission, a certain energy is released, which is transferred to the decay products and the resulting neutrons. This energy is converted into thermal energy as a result of numerous collisions of neutrons, therefore, in order to prevent the rapid failure of the reactor, heat must be removed. In reactors intended for the production of radioactive isotopes, this heat is not used, in reactors intended for the production of energy, on the contrary, it becomes the main product. Cooling can be carried out with the help of gas or water, which are circulated in the reactor under pressure through special tubes and then cooled in a heat exchanger. The released heat can be used to heat the steam, which rotates the turbine connected to the generator; such a device would be a nuclear power plant.

5. Protective screen.

In order to avoid the harmful effects of neutrons that can fly out of the reactor, and to protect yourself from the gamma radiation emitted during the reaction, reliable protection is necessary. Scientists have calculated that a reactor with a capacity of 100 thousand kW emits such an amount of radioactive radiation that a person located at a distance of 100 m will receive it in 2 minutes. lethal dose. To ensure the protection of the personnel serving the reactor, two-meter walls of special concrete with lead slabs are being built.

The first reactor was built in December 1942 by the Italian Fermi. By the end of 1955, there were about 50 nuclear reactors in the world (USA -2 1, England - 4, Canada - 2, France - 2). To this it should be added that by the beginning of 1956, about 50 more reactors were designed for research and industrial purposes (USA - 23, France - 4, England - 3, Canada - 1).

The types of these reactors are very diverse, ranging from slow reactors with graphite moderators and natural uranium as fuel to fast reactors that use uranium enriched with plutonium or uranium 233 artificially obtained from thorium as fuel.

In addition to these two opposite types, there are a number of reactors that differ from each other either in the composition of the nuclear fuel, or in the type of moderator, or in the coolant.

It is very important to note that, although the theoretical side of the issue is currently well studied by specialists in all countries, in the practical field, different countries have not yet reached the same level. The United States and Russia are ahead of other countries. It can be argued that the future of nuclear energy will depend mainly on the progress of technology.

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We are so used to electricity that we don’t think about where it comes from. Basically, it is produced in power plants that use various sources for this. Power plants are thermal, wind, geothermal, solar, hydroelectric, nuclear. It is the latter that cause the most controversy. They argue about their necessity, reliability.

In terms of productivity, nuclear power today is one of the most efficient and its share in the global production of electrical energy is quite significant, more than a quarter.

How is a nuclear power plant arranged, how does it generate energy? The main element of a nuclear power plant is a nuclear reactor. A nuclear chain reaction takes place in it, as a result of which heat is released. This reaction is controlled, which is why we can use energy gradually, and do not get a nuclear explosion.

The main elements of a nuclear reactor

Nuclear fuel: enriched uranium, uranium and plutonium isotopes. The most commonly used is uranium 235;
Coolant for the output of energy that is formed during the operation of the reactor: water, liquid sodium, etc.;
Regulating rods;
Neutron moderator;
Sheath for radiation protection.

Nuclear reactor video

How does a nuclear reactor work?

In the reactor core there are fuel elements (TVEL) - nuclear fuel. They are collected in cassettes, including several dozen fuel rods. The coolant flows through the channels through each cassette. Fuel rods regulate the power of the reactor. A nuclear reaction is possible only with a certain (critical) mass of the fuel rod. The mass of each rod is individually below the critical one. The reaction starts when all the rods are in the core. By immersing and removing fuel rods, the response can be controlled.

So, when the critical mass is exceeded, radioactive fuel elements emit neutrons that collide with atoms. The result is an unstable isotope that decays immediately, releasing energy in the form of gamma radiation and heat. Particles, colliding, impart kinetic energy to each other, and the number of decays increases exponentially. This is a chain reaction - the principle of operation of a nuclear reactor. Without control, it happens at lightning speed, which leads to an explosion. But in a nuclear reactor, the process is under control.

Thus, thermal energy is released in the core, which is transferred to the water that bathes this zone (primary circuit). Here the water temperature is 250-300 degrees. Further, the water gives off heat to the second circuit, after that - to the turbine blades that generate energy. Conversion of nuclear energy into electrical energy can be represented schematically:

Internal energy of the uranium core,
Kinetic energy of fragments of decayed nuclei and released neutrons,
Internal energy of water and steam,
Kinetic energy of water and steam,
Kinetic energy of turbine and generator rotors,
Electric Energy.

The reactor core consists of hundreds of cassettes united by a metal shell. This shell also plays the role of a neutron reflector. Control rods are inserted among the cassettes to adjust the reaction rate and emergency protection rods of the reactor. Further, thermal insulation is installed around the reflector. On top of the thermal insulation there is a protective concrete shell, which retains radioactive substances and does not let them into the surrounding space.

Where are nuclear reactors used?

Power nuclear reactors are used at nuclear power plants, in ship electrical installations, at nuclear power plants for heat supply.
Convector reactors and breeders are used for the production of secondary nuclear fuel.
Research reactors are needed for radiochemical and biological research, and for the production of isotopes.

Despite all the controversy and disagreement over nuclear power, nuclear power plants continue to be built and operated. One of the reasons is economy. A simple example: 40 tanks of fuel oil or 60 cars of coal produce as much energy as 30 kilograms of uranium.

When German chemists Otto Hahn and Fritz Strassmann first succeeded in fissioning a uranium nucleus by neutron irradiation in 1938, they were in no hurry to inform the public about the scale of their discovery. These experiments laid the foundation for the use of atomic energy, both for peaceful and military purposes.

A byproduct of the atomic bomb

Otto Hahn, who collaborated with the Austrian physicist Lisa Meitner before his emigration in 1938, was well aware that the fission of a uranium nucleus — an unstoppable chain reaction — meant an atomic bomb. The United States, eager to get ahead of Germany in the creation of nuclear weapons, launched the Manhattan Project, an enterprise of unprecedented proportions. Three cities have sprung up in the Nevada desert. 40,000 people worked here in deep secrecy. Under the leadership of Robsrg Oppenheimer, "the father of the atomic bomb", about 40 research institutions, laboratories and factories were established in record time. For plutonium mining, the first nuclear reactor was built under the podium of the University of Chicago football stadium. Here, under the leadership of Enrico Fermi, the first controlled self-sustaining chain reaction was launched in 1942. At that time, no useful application was found for the heat released as a result.

Electrical energy from a nuclear reaction

In 1954, the first nuclear power plant in the world was launched in the USSR. It was located in Obninsk, about 100 km from Moscow, and had a capacity of 5 MW. In 1956, the first large nuclear reactor began operation in the English town of Calder Hall. This nuclear power plant was gas-cooled, which ensured relatively safe operation. But in the world market, the pressurized water-cooled water-cooled nuclear reactors developed in the USA in 1957 have become more widespread. Such plants can be built at relatively low costs, but their reliability is poor. At the Ukrainian nuclear power plant Chernobyl, the melting of the reactor core led to an explosion with the release of radioactive substances into the environment. The catastrophe, which led to the death and serious illness of thousands of people, led to numerous protests, especially in Europe, against the use of atomic energy.

1896: Henri Bequerel discovered radioactive radiation from uranium.
Chapter 1919 Ernest Rutherford for the first time succeeded in the art of causing a nuclear reaction by bombarding nitrogen atoms with alpha particles, which was converted into oxygen.
1932: James Chadwick discovers neutrons by bombarding beryllium atoms with alpha particles.
19.38: Otto Hahn for the first time achieves a chain reaction in the laboratory, splitting the uranium nucleus with neutrons.

The nuclear reactor works smoothly and accurately. Otherwise, as you know, there will be trouble. But what's going on inside? Let us try to formulate the principle of operation of a nuclear (atomic) reactor briefly, clearly, with stops.

In fact, the same process is going on there as in a nuclear explosion. Only now the explosion occurs very quickly, but in the reactor all this is stretched out for a long time. As a result, everything remains safe and sound, and we receive energy. Not so much that everything around was immediately blown up, but quite enough to provide the city with electricity.

Before you understand how a controlled nuclear reaction is going, you need to know what is nuclear reaction generally.

Nuclear reaction Is the process of transformation (fission) of atomic nuclei during their interaction with elementary particles and gamma quanta.

Nuclear reactions can take place with both absorption and release of energy. Second reactions are used in the reactor.

Nuclear reactor Is a device whose purpose is to maintain a controlled nuclear reaction with the release of energy.

Often a nuclear reactor is also called atomic. Note that there is no fundamental difference here, but from the point of view of science, it is more correct to use the word "nuclear". There are many types of nuclear reactors now. These are huge industrial reactors designed to generate energy at power plants, nuclear reactors in submarines, small experimental reactors used in scientific experiments. There are even reactors used for desalination of seawater.

The history of the creation of a nuclear reactor

The first nuclear reactor was launched in the not so distant 1942. It happened in the USA under the leadership of Fermi. This reactor was called the "Chicago Woodpile".

In 1946, the first Soviet reactor started up under the leadership of Kurchatov. The body of this reactor was a ball of seven meters in diameter. The first reactors did not have a cooling system, and their power was minimal. By the way, the Soviet reactor had an average power of 20 watts, while the American one had only 1 watt. For comparison: the average power of modern power reactors is 5 Gigawatts. Less than ten years after the launch of the first reactor, the world's first industrial nuclear power plant was opened in the city of Obninsk.

The principle of operation of a nuclear (atomic) reactor

Any nuclear reactor has several parts: active zone with fuel and moderator , neutron reflector , coolant , control and protection system ... Isotopes are most often used as fuel in reactors uranium (235, 238, 233), plutonium (239) and thorium (232). The active zone is a boiler through which ordinary water (heat carrier) flows. Among other coolants, “heavy water” and liquid graphite are less commonly used. If we talk about the operation of a nuclear power plant, then a nuclear reactor is used to generate heat. Electricity itself is generated by the same method as in other types of power plants - steam rotates a turbine, and the energy of motion is converted into electrical energy.

Below is a diagram of the operation of a nuclear reactor.

As we have already said, during the decay of a heavy uranium nucleus, lighter elements and several neutrons are formed. The resulting neutrons collide with other nuclei, also causing their fission. In this case, the number of neutrons grows like an avalanche.

It needs to be mentioned here neutron multiplication factor ... So, if this coefficient exceeds a value equal to one, a nuclear explosion occurs. If the value is less than one, there are too few neutrons and the reaction is extinguished. But if you maintain the value of the coefficient equal to one, the reaction will proceed for a long time and stably.

The question is how to do this? In the reactor, the fuel is in the so-called fuel elements (TVELakh). These are rods in which, in the form of small tablets, there is nuclear fuel ... The fuel rods are connected in hexagonal cassettes, of which there can be hundreds in the reactor. Cassettes with fuel rods are positioned vertically, with each fuel rod having a system that allows you to adjust the depth of its immersion in the core. In addition to the cassettes themselves, among them there are control rods and emergency protection rods ... The rods are made of a material that absorbs neutrons well. Thus, the control rods can be lowered to different depths in the core, thereby adjusting the neutron multiplication factor. The emergency rods are designed to shut down the reactor in case of an emergency.

How is a nuclear reactor started?

We figured out the very principle of operation, but how to start and make the reactor work? Roughly speaking, here it is - a piece of uranium, but a chain reaction does not start in it by itself. The fact is that in nuclear physics there is a concept critical mass .

The critical mass is the mass of fissile matter necessary for the start of a nuclear chain reaction.

With the help of fuel rods and control rods, a critical mass of nuclear fuel is first created in the reactor, and then the reactor is brought to the optimal power level in several stages.

In this article, we have tried to give you a general idea of the structure and principle of operation of a nuclear (atomic) reactor. If you have any questions on the topic or at the university asked a problem in nuclear physics, please contact specialists of our company... We, as usual, are ready to help you solve any pressing issue in your studies. In the meantime, we are doing this, your attention is another educational video!

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Lesson objectives:

Educational: 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;
Developing: continue the formation of skills to observe and draw conclusions, as well as develop the intellectual abilities and curiosity of students;
Educational: 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.

Equipment: multimedia installation.

During the classes

1. Organizational moment.

Guys! 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?
What factors can increase the number of free neutrons in a piece of uranium, thereby ensuring the possibility of a reaction in it?

3. Explanation of the new material.

Guys, answer this question: 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, to 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 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;
E. the 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?

THANKS FOR WORKING IN THE LESSON!