The principle of operation of a nuclear power plant. reference

Nuclear power plant

Nuclear power plant (NPP)- a complex of technical structures designed to generate electrical energy by using the energy released during a controlled nuclear reaction.

In the second half of the 40s, even before the completion of work on the creation of the first atomic bomb (its test, as is known, took place on August 29, 1949), Soviet scientists began to develop the first projects for the peaceful use of atomic energy, the general direction of which immediately became electric power industry.

In 1948, at the suggestion of I.V. Kurchatov and in accordance with the task of the party and the government, the first work began on the practical application of atomic energy to generate electricity

In May 1950, near the village of Obninskoye, Kaluga Region, work began on the construction of the world's first nuclear power plant.

The world's first nuclear power plant with a capacity of 5 MW was launched on June 27, 1954 in the USSR, in the city of Obninsk, located in the Kaluga region. In 1958, the first stage of the Siberian Nuclear Power Plant with a capacity of 100 MW was put into operation (the total design capacity is 600 MW). In the same year, the construction of the Beloyarsk industrial nuclear power plant began, and on April 26, 1964, the generator of the 1st stage gave current to consumers. In September 1964, Unit 1 of the Novovoronezh NPP was put into operation with a capacity of 210 MW. The second unit with a capacity of 350 MW was put into operation in December 1969. In 1973 the Leningrad NPP was put into operation.

Outside the USSR, the first industrial-purpose nuclear power plant with a capacity of 46 MW was put into operation in 1956 at Calder Hall (Great Britain). A year later, a 60 MW nuclear power plant was put into operation in Shippingport (USA).

The world leaders in the production of nuclear electricity are: USA (788.6 billion kWh/year), France (426.8 billion kWh/year), Japan (273.8 billion kWh/year), Germany (158 .4 billion kWh/year) and Russia (154.7 billion kWh/year).

At the beginning of 2004, there were 441 nuclear power reactors operating in the world, the Russian TVEL OJSC supplies fuel for 75 of them.

The largest nuclear power plant in Europe is the Zaporozhye NPP near the city of Energodar (Zaporozhye region, Ukraine), the construction of which began in 1980 and by the middle of 2008, 6 nuclear reactors with a total capacity of 6 GigaWatt are operating.

The largest nuclear power plant in the world, Kashiwazaki-Kariwa in terms of installed capacity (as of 2008), is located in the Japanese city of Kashiwazaki, Niigata Prefecture - there are five boiling water reactors (BWR) and two advanced boiling nuclear reactors (ABWR) in operation, the total capacity of which is 8.212 GigaWatt.

Classification

By type of reactor

Nuclear power plants are classified according to the reactors installed on them:

Thermal neutron reactors using special moderators to increase the probability of absorption of a neutron by the nuclei of fuel atoms

light water reactors

heavy water reactors

Reactors on fast neutrons

Subcritical reactors using external neutron sources

Fusion reactors

By type of energy released

According to the type of energy supplied, nuclear power plants can be divided into:

Nuclear power plants (NPPs) designed to generate electricity only

Nuclear combined heat and power plants (NPP) generating both electricity and heat

However, all nuclear power plants in Russia have cogeneration plants designed to heat network water.

Operating principle

The figure shows a diagram of the operation of a nuclear power plant with a double-circuit water-cooled power reactor. The energy released in the reactor core is transferred to the primary coolant. Next, the coolant enters the heat exchanger (steam generator), where it heats the secondary circuit water to a boil. The resulting steam enters the turbines that rotate the electric generators. At the outlet of the turbines, the steam enters the condenser, where it is cooled by a large amount of water coming from the reservoir.

The pressure compensator is a rather complex and bulky design, which serves to equalize pressure fluctuations in the circuit during reactor operation, which arise due to the thermal expansion of the coolant. The pressure in the 1st circuit can reach up to 160 atmospheres (VVER-1000).

In addition to water, molten sodium or gas can also be used as a coolant in various reactors. The use of sodium makes it possible to simplify the design of the reactor core shell (unlike the water circuit, the pressure in the sodium circuit does not exceed atmospheric pressure), to get rid of the pressure compensator, but creates its own difficulties associated with the increased chemical activity of this metal.

The total number of circuits may vary for different reactors, the diagram in the figure is for VVER type reactors (Public Water Power Reactor). RBMK type reactors (High Power Channel Type Reactor) use one water circuit, and BN reactors (Fast Neutron Reactor) use two sodium and one water circuits.

If it is not possible to use a large amount of water to condense the steam, instead of using a reservoir, the water can be cooled in special cooling towers (cooling towers), which, due to their size, are usually the most visible part of a nuclear power plant.

Advantages and disadvantages

Advantages of nuclear power plants:

No harmful emissions;

Emissions of radioactive substances are several times less than coal el. stations of similar capacity (ash from coal-fired thermal power plants contains a percentage of uranium and thorium sufficient for their profitable extraction);

A small amount of fuel used and the possibility of its reuse after processing;

High power: 1000-1600 MW per unit;

Low cost of energy, especially heat.

Disadvantages of nuclear power plants:

Irradiated fuel is dangerous, requiring complex and expensive reprocessing and storage measures;

Variable power operation is undesirable for thermal neutron reactors;

The consequences of a possible incident are extremely severe, although its probability is quite low;

Large capital investments, both specific, per 1 MW of installed capacity for units with a capacity of less than 700-800 MW, and general, necessary for the construction of the station, its infrastructure, as well as in case of possible liquidation.

Safety of nuclear power plants

Rostekhnadzor oversees the safety of Russian NPPs.

Nuclear safety is regulated by the following documents:

General provisions for ensuring the safety of nuclear power plants. OPB-88/97 (PNAE G-01-011-97)

Nuclear Safety Rules for Reactor Installations at Nuclear Power Plants. NBY RU AS-89 (PNAE G - 1 - 024 - 90)

Radiation safety is regulated by the following documents:

Sanitary rules of nuclear power plants. SP AS-99

Basic rules for ensuring radiation safety. OSPORB-02

prospects

Despite these shortcomings, nuclear energy seems to be the most promising. Alternative ways of obtaining energy, due to the energy of tides, wind, the Sun, geothermal sources, etc. on this moment characterized by a low level of produced energy and its low concentration. In addition, these types of energy generation carry their own risks for the environment and tourism (“dirty” production of photovoltaic cells, the danger of wind farms for birds, and changes in wave dynamics.

Academician Anatoly Aleksandrov: "Nuclear energy on a large scale will be the greatest boon for mankind and will solve a number of acute problems."

Currently, international projects are being developed for new generation nuclear reactors, such as GT-MGR, which will improve safety and increase the efficiency of nuclear power plants.

Russia has begun construction of the world's first floating nuclear power plant, which will solve the problem of energy shortages in remote coastal areas of the country. [source?]

The USA and Japan are developing mini-nuclear power plants with a capacity of about 10-20 MW for the purpose of heat and power supply to individual industries, residential complexes, and in the future - individual houses. With a decrease in the capacity of the installation, the expected scale of production increases. Small-sized reactors (see, for example, Hyperion NPP) are created using safe technologies that greatly reduce the possibility of leakage of nuclear material.

Hydrogen production

The US government has adopted the Atomic Hydrogen Initiative. Work is underway (together with South Korea) to create a new generation of nuclear reactors capable of producing hydrogen in large quantities. INEEL (Idaho National Engineering Environmental Laboratory) predicts that one next-generation nuclear power plant will produce hydrogen equivalent to 750,000 liters of gasoline daily.

Research is being funded to produce hydrogen at existing nuclear power plants.

Thermonuclear energy

Even more interesting, albeit a relatively distant prospect, is the use of nuclear fusion energy. Thermonuclear reactors, according to calculations, will consume less fuel per unit of energy, and both this fuel itself (deuterium, lithium, helium-3) and their synthesis products are non-radioactive and, therefore, environmentally safe.

At present, with the participation of Russia in the south of France, the construction of the international experimental thermonuclear reactor ITER is underway.

NPP construction

Site selection

One of the main requirements in assessing the possibility of building a nuclear power plant is to ensure the safety of its operation for the surrounding population, which is regulated by radiation safety standards. One of the protection measures environment- territory and population from harmful effects during NPP operation is the organization of a sanitary protection zone around it. When choosing a NPP construction site, the possibility of creating a sanitary protection zone defined by a circle, the center of which is the NPP ventilation stack, should be taken into account. Residents are prohibited from living in the sanitary protection zone. Special attention should be directed to the study of wind regimes in the area of ​​nuclear power plant construction in order to locate the nuclear power plant on the leeward side in relation to settlements. Based on the possibility of emergency leakage of active fluids, preference is given to sites with deep standing groundwater.

When choosing a site for the construction of a nuclear power plant, technical water supply is of great importance. The nuclear power plant is a major water user. The water consumption of NPPs is negligible, and the use of water is large, that is, the water is mostly returned to the water supply source. Nuclear power plants, as well as all industrial facilities under construction, are subject to environmental requirements. When choosing a site for the construction of a nuclear power plant, the following requirements must be followed:

lands allotted for the construction of nuclear power plants are unsuitable or unsuitable for agricultural production;

the construction site is located near reservoirs and rivers, in coastal areas that are not flooded by flood waters;

the soils of the site allow the construction of buildings and structures without additional costly measures;

the groundwater level is below the depth of the basements of buildings and underground engineering communications, and no additional costs are required for dewatering during the construction of a nuclear power plant;

the site has a relatively flat surface with a slope that provides surface drainage, while earthworks are kept to a minimum.

NPP construction sites, as a rule, are not allowed to be located:

in active karst zones;

in areas of heavy (mass) landslides and mudflows;

in areas of possible action of snow avalanches;

in swampy and waterlogged areas with a constant influx of pressure groundwater,

in areas of large failures as a result of mine workings;

in areas subject to catastrophic events such as tsunamis, etc.

in areas where minerals occur;

In order to determine the possibility of building a nuclear power plant in the designated areas and to compare options in terms of geological, topographical and hydrometeorological conditions, at the stage of site selection, specific surveys are carried out for each considered option for placing a power plant.

Engineering-geological surveys are carried out in two stages. At the first stage, materials are collected on previously conducted surveys in the area under consideration and the degree of knowledge of the proposed construction site is determined. At the second stage, if necessary, special engineering and geological surveys are carried out with well drilling and soil sampling, as well as a reconnaissance geological survey of the site. Based on the results of office processing of the collected data and additional surveys, an engineering-geological characteristic of the construction area should be obtained, which determines:

relief and geomorphology of the territory;

stratigraphy, thickness and lithological composition of primary and Quaternary deposits, common in the area to a depth of 50-100 m;

the quantity, nature, level of occurrence and conditions for the distribution of individual aquifers within the total depth;

the nature and intensity of physical and geological processes and phenomena.

When conducting engineering and geological surveys at the site selection stage, information is collected on the availability of local building materials - developed quarries and deposits of stone, sand, gravel and other building materials. In the same period, the possibilities of using groundwater for technological and domestic water supply are determined. When designing nuclear power plants, as well as other large industrial complexes, situational construction plans, schemes of general plans and general plans for the industrial site of a nuclear power plant are carried out.

Space-planning solutions for buildings

The goal of designing nuclear power plants is to create the most rational design. The main requirements that nuclear power plant buildings must meet:

convenience for the implementation of the main technological process for which they are intended (functional expediency of the building);

reliability when exposed to the environment, strength and durability (technical feasibility of the building);

profitability, but not at the expense of durability (economic feasibility).

aesthetics (architectural and artistic expediency);

The layout of the nuclear power plant is created by a team of designers of various specialties.

Building structures of buildings and structures

The composition of the nuclear power plant includes buildings and structures for various purposes and, accordingly, of various designs. This is a multi-storey and multi-span building of the main building with massive reinforced concrete structures enclosing the radioactive circuit; stand-alone buildings of auxiliary systems, for example, chemical water treatment, diesel generator, nitrogen station, usually made in prefabricated reinforced concrete standard structures; underground channels and tunnels, passable and impassable for placement of cable flows and communication pipelines between systems; elevated overpasses connecting the main building and auxiliary buildings and structures, as well as the buildings of the administrative sanitary building. The most complex and responsible building of a nuclear power plant is the main building, which is a system of structures formed in the general case by frame building structures and arrays of the reactor compartment.

Features of engineering equipment

A feature of nuclear power plants, as well as any buildings of nuclear installations, is the presence of ionizing radiation during operation. This main distinguishing factor must be taken into account when designing. The main source of radiation at nuclear power plants is a nuclear reactor, in which the fission reaction of fuel nuclei occurs. This reaction is accompanied by all known types of radiation.

Nuclear fuel cycle. Nuclear power is a complex industry that includes many industrial processes that together form the fuel cycle. There are different types of fuel cycles, depending on the type of reactor and how the final stage of the cycle proceeds.

Typically, the fuel cycle consists of the following processes. Uranium ore is mined in the mines. The ore is crushed to separate the uranium dioxide, and the radioactive waste is dumped. The resulting uranium oxide (yellow cake) is converted into uranium hexafluoride, a gaseous compound. To increase the concentration of uranium-235, uranium hexafluoride is enriched at isotope separation plants. The enriched uranium is then converted back into solid uranium dioxide, from which fuel pellets are made. Fuel elements (fuel rods) are assembled from pellets, which are combined into assemblies for introduction into the core of a nuclear reactor of a nuclear power plant. The spent fuel extracted from the reactor has a high level of radiation and, after cooling on the territory of the power plant, is sent to a special storage facility. It also provides for the disposal of waste with a low level of radiation that accumulates during the operation and maintenance of the station. At the end of the service life, the reactor itself must be decommissioned (with decontamination and disposal of the reactor units). Each stage of the fuel cycle is regulated in such a way as to ensure the safety of people and the protection of the environment.

Power plants in Bulgaria Nuclear power plants Inside the case, the pressure reaches 160 ... they will seriously compete with hydroelectric power plants, power and atomic power plants because they are environmentally friendly...

Nuclear power plant- a complex of necessary systems, devices, equipment and structures intended for the production of electrical energy. The station uses uranium-235 as fuel. The presence of a nuclear reactor distinguishes nuclear power plants from other power plants.

There are three mutual transformations of forms of energy at nuclear power plants

Nuclear power

goes into heat

Thermal energy

goes into mechanical

mechanical energy

converted to electrical

1. Nuclear energy turns into heat

The basis of the station is the reactor - a structurally allocated volume where nuclear fuel is loaded and where a controlled chain reaction takes place. Uranium-235 is fissile with slow (thermal) neutrons. As a result, a huge amount of heat is released.

STEAM GENERATOR

2. Thermal energy is converted into mechanical

Heat is removed from the reactor core by a coolant - a liquid or gaseous substance passing through its volume. This thermal energy is used to produce water vapor in a steam generator.

POWER GENERATOR

3. Mechanical energy is converted into electrical energy

The mechanical energy of the steam is sent to the turbogenerator, where it is converted into electrical energy and then goes to the consumers through the wires.

What is a nuclear power plant made of?

A nuclear power plant is a complex of buildings that house technological equipment. The main building is the main building where the reactor hall is located. It houses the reactor itself, the nuclear fuel holding pool, the refueling machine (for fuel refueling), all this is monitored by operators from the block control room (BCR).

The main element of the reactor is the active zone (1) . It is located in a concrete shaft. Mandatory components of any reactor are the control and protection system, which allows to carry out the selected mode of the controlled fission chain reaction, as well as the emergency protection system - to quickly stop the reaction in the event of emergency. All this is mounted in the main building.

There is also a second building where the turbine hall (2) is located: steam generators, the turbine itself. Next along the technological chain are capacitors and high-voltage power lines that go beyond the station site.

On the territory there is a building for reloading and storage of spent nuclear fuel in special pools. In addition, the stations are equipped with elements of a circulating cooling system - cooling towers (3) (a concrete tower tapering upwards), a cooling pond (natural or artificially created reservoir) and spray pools.

What are nuclear power plants?

Depending on the type of reactor, nuclear power plants can have 1, 2 or 3 coolant operation circuits. In Russia, bypass NPPs with VVER-type reactors (pressure-cooled power reactor) are most widely used.

NPP WITH 1-LOOP REACTORS

NPP WITH 1-LOOP REACTORS

The single-circuit scheme is used at nuclear power plants with RBMK-1000 type reactors. The reactor operates in a block with two condensing turbines and two generators. In this case, the boiling reactor itself is a steam generator, which makes it possible to use a single-loop scheme. The single-loop scheme is relatively simple, but the radioactivity in this case extends to all elements of the block, which complicates biological protection.

Currently, there are 4 nuclear power plants with single-loop reactors operating in Russia

NPP WITH 2-LOOP REACTORS

NPP WITH 2-LOOP REACTORS

The double-circuit scheme is used at nuclear power plants with water-cooled reactors of the VVER type. Pressurized water is supplied to the reactor core, which is heated. The energy of the coolant is used in the steam generator to form saturated steam. The second circuit is non-radioactive. The unit consists of one 1000 MW condensing turbine or two 500 MW turbines with associated generators.

Currently, Russia has 5 nuclear power plants with double-loop reactors

NPP WITH 3-LOOP REACTORS

NPP WITH 3-LOOP REACTORS

The three-loop scheme is used at nuclear power plants with fast neutron reactors with a sodium coolant of the BN type. To exclude the contact of radioactive sodium with water, a second circuit is constructed with non-radioactive sodium. Thus, the circuit turns out to be three-circuit.

1. Introduction ……………………………………………………. Page 1

2.Physical foundations of nuclear energy…………………P.2

3. Nucleus of an atom……………………………………………………P.4

4. Radioactivity…………………………………………….P.4

5. Nuclear reactions…………………………………………… Page 4

6. Nuclear fission…………………………………………………… Page 4

7. Nuclear chain reactions………………………………… Page 5

8. Fundamentals of the theory of reactors………………………………… Page 5

9. Principles of reactor power control……… Page 6

10. Classification of reactors………………………………… Page 7

11. Structural schemes of reactors…………………………P.9

13.NPP equipment design………………………………………………………………………………………………………………………………………………………………………………

14. Scheme of a three-loop NPP …………………………………P.16

15.Heat exchangers of NPP……………………………………… P.19

16.Turbomachines of NPP………………………………………… Page 20

17. Auxiliary equipment of NPP……………………… Pp. twenty

18. NPP equipment layout…………………………… P.21

19. Safety issues at nuclear power plants…………………… P.21

20. Mobile nuclear power plants …………………………………………P. 24

21. Literature used…………………………………… Page 26

Introduction.

Status and prospects for the development of nuclear power.

The development of industry, transport, agriculture and communal services requires a continuous increase in electricity production.

The global increase in energy consumption is growing every year.

For example: in 1952 it was 540 million tons in conventional units, and already in 1980 it was 3567 million tons. in almost 28 years has increased by more than 6.6 times. At the same time, it should be noted that the reserves of nuclear fuel are 22 times higher than the reserves of organic fuel.

At the 5th World Energy Conference, fuel reserves were estimated as follows:

1. Nuclear fuel…………………………..520х106

2. Coal…………………………………………55.5х106

3. Oil…………………………………………0.37x106

4. Natural gas ………………………….0.22x106

5. Oil shale……………………………0.89х106

6. Tar……………………………………..1.5x 106

7. Peat………………………………………. 0.37x10

Total 58.85x106

At the current level of energy consumption, according to various estimates, the world's reserves will run out in 100-400 years.

According to scientists' forecasts, energy consumption will differ by 7 times from 1950 to 2050. Stocks of nuclear fuel can meet the energy needs of the population for a much longer period.

Despite the rich natural resources of Russia, in fossil fuels, as well as the hydropower resources of large rivers (1200 billion kWh) or 137 million kW. an hour already today, the president of the country paid special attention to the development of nuclear energy. Given that coal, oil, gas, shale, peat are valuable raw materials for various branches of the chemical industry. Coal is used to produce coke for metallurgy. Therefore, the task is to preserve organic fuel reserves for some industries. Such trends are followed by world practice.

Considering that the cost of energy received at nuclear power plants is expected to be lower than that of coal and close to the cost of energy at hydroelectric power plants, the urgency of increasing the construction of nuclear power plants becomes apparent. Despite the fact that nuclear power plants carry increased danger, (radioactivity in case of accident)

Everything the developed countries, both Europe and America have recently been actively building up their construction, not to mention the use of atomic energy, both in civil and military equipment, these are nuclear-powered ships, submarines, aircraft carriers.

Both in civil and military areas, the palm belonged and still belongs to Russia.

Solving the problem of direct conversion of the energy of the fission of the atomic nucleus into electrical energy will significantly reduce the cost of generated electricity.

Physical foundations of nuclear energy.

All substances in nature are made up of tiny particles - molecules that are in continuous motion. Body heat is the result of the movement of molecules.

The state of complete rest of molecules corresponds to absolute zero temperature.

Molecules of matter are made up of atoms of one or more chemical elements.

Molecule is the smallest particle given substance. If you divide the molecule of a complex substance into its constituent parts, then you get atoms of other substances.

Atom- the smallest particle of a given chemical element. It cannot be further divided chemically into even smaller particles, although the atom also has its own internal structure and consists of a positively charged nucleus and a negatively charged electron shell.

The number of electrons in the shell ranges from one to one hundred and one. The last number of electrons has an element called Mendelevium.

This element is named Mendelevium after D.I. Mendeleev, who discovered in 1869 the periodic law, according to which the physicochemical properties of all elements depend on the atomic weight, and after certain periods there are elements with similar physicochemical properties.

The nucleus of an atom.

The nucleus of an atom contains most of its mass. The mass of the electron shell is only a fraction of a percent of the mass of an atom. Atomic nuclei are complex formations consisting of elementary particles-protons with a positive electric charge, and particles without an electric charge-neutrons.

Positively charged particles - protons and electrically neutral particles - neutrons are collectively called nucleons. Protons and neutrons in the nucleus of an atom are connected by the so-called nuclear forces.

The binding energy of a nucleus is the amount of energy required to separate the nucleus into individual nucleons. Since nuclear forces are millions of times greater than the forces of chemical bonds, it follows from this that the nucleus is a compound whose strength immeasurably exceeds the strength of the connection of atoms in a molecule.

During the synthesis of 1 kg of helium from a hydrogen atom, an amount of heat is released that is equivalent to the amount of heat during the combustion of 16,000 tons of coal, while the splitting of 1 kg of uranium releases an amount of heat equal to the heat released during the combustion of 2,700 tons of coal.

Radioactivity.

Radioactivity is the ability to spontaneously convert unstable isotopes of one chemical element into isotopes of another element accompanied by the emission of alpha, beta and gamma rays.

The transformation of elementary particles (neutrons, mesons) is also sometimes called radioactivity.

Nuclear reactions.

Nuclear reactions are the transformations of atomic nuclei as a result of their interaction with elementary particles and with each other.

In chemical reactions, the outer electron shells of atoms are rearranged, and the energy of these reactions is measured in electron volts.

In nuclear reactions, the nucleus of an atom is rearranged, and in many cases the result of the rearrangement is the transformation of one chemical element into another. The energy of nuclear reactions is measured in millions of electron volts.

Nuclear fission .

The discovery of fission of uranium nuclei, its experimental confirmation in 1930 made it possible to see the inexhaustible possibilities of application in various fields national economy, including energy production in the construction of nuclear installations.

Chain nuclear reaction.

A nuclear chain reaction is the reaction of fission of the nuclei of atoms of heavy elements under the action of neutrons, in each act of which the number of neutrons increases, as a result of which the self-sustaining process of fission increases.

Nuclear chain reactions belong to the class of exothermic, that is, accompanied by the release of energy.

Fundamentals of the theory of reactors.

A nuclear power reactor is a unit designed to produce heat from nuclear fuel through a self-sustaining controlled chain reaction, the fission of atoms of this fuel.

During the operation of a nuclear reactor, in order to exclude the occurrence of a chain reaction, moderators are used to artificially extinguish the reaction by automatically introducing moderator elements into the reactor. To maintain the reactor power at a constant level, it is necessary to observe the condition of constancy of the average rate of nuclear fission, the so-called neutron multiplication factor.

A nuclear reactor is characterized by critical dimensions of the active zone, at which the neutron multiplication factor is K=1. Asking the composition of the nuclear fissile material, construction materials, moderator and coolant, choose the option in which K = ∞ has a maximum value.

The effective multiplication factor is the ratio of the number of neutron productions to the number of neutron deaths due to absorption and leakage.

A reactor using a reflector reduces the critical dimensions of the core, evens out the distribution of the neutron flux and increases the specific power of the reactor, related to 1 kg of nuclear fuel loaded into the reactor. Calculation of the dimensions of the active zone is carried out by complex methods.

Reactors are characterized by cycles and types of reactors.

The fuel cycle or nuclear fuel cycle is a set of successive fuel transformations in the reactor, as well as during the processing of irradiated fuel after its removal from the reactor in order to isolate secondary fuel and unburned primary fuel.

The fuel cycle determines the type of nuclear reactor: reactor-convector;

breeder reactor; reactors on fast, intermediate and thermal neutrons, a reactor on solid, liquid and gaseous fuels; homogeneous reactors and heterogeneous reactors and others.

Principles of reactor power control.

The power reactor must operate stably at various power levels. Changes in the level of heat release in the reactor should occur quickly enough, but smoothly, without jumps in power acceleration.

The control system is designed to compensate for changes in the K factor (reactivity) that occur with changes in the mode, including starting and stopping. To do this, during operation, graphite rods are introduced into the core as necessary, the material of which strongly absorbs thermal neutrons. To reduce or increase the power, respectively, the indicated rods are removed or introduced, thereby adjusting the coefficient K. The rods are used both regulating and compensating, and in general they can be called control or protective.

Classification of reactors.

Nuclear reactors can be classified according to various criteria:

1) By appointment

2) According to the energy level of neutrons that cause most fissions of fuel nuclei;

3) By the type of neutron moderator

4) By type and state of aggregation of the coolant;

5) On the basis of the reproduction of nuclear fuel;

6) According to the principle of placing nuclear fuel in the moderator,

7) According to the state of aggregation of nuclear fuel.

Reactors designed to generate electrical or thermal energy are called power reactors, as well as technological and dual-purpose reactors.

According to the energy level, reactors are subdivided: on thermal neutrons, on fast neutrons, on intermediate neutrons.

By type of neutron moderators: water, heavy water, graphite, organic, beryllium.

By type of coolant: water, heavy water, liquid metal, organic, gas.

According to the principle of reproduction of nuclear fuel:

Reactors on a pure fissile isotope. With the reproduction of nuclear fuel (regenerative) with expanded reproduction (breeder reactors).

According to the principle of nuclear fuel: heterogeneous and homogeneous

According to the principle of the state of aggregation of the dividing material:

In the form of a solid body, less often in the form of liquid and gas.

If we restrict ourselves to the main features, then the following system for designating reactor types can be proposed

1. Reactor with water as moderator and low-enriched uranium coolant (WWR-Uno) or pressurized water reactor (WWR).

2. Reactor with heavy water as a moderator and ordinary water as a coolant on natural uranium. Designation: natural uranium heavy water reactor (TVR-Up) or heavy water reactor (HWR) When using heavy water and as

The coolant will be (TTR)

3. A reactor with graphite as a moderator and water as a coolant on weakly enriched uranium will be called a graffiti-water reactor on weakly enriched uranium (GVR-Uno) or a graffiti-water reactor (GVR)

4. Reactor with graphite as a moderator and gas as a coolant on natural uranium (GGR-Up) or graffito-gas reactor (GGR)

5. A reactor with boiling water as a coolant moderator can be designated VVKR, the same heavy water reactor - TTKR.

6. A reactor with graphite as a moderator and sodium as a coolant can be designated GNR

7. A reactor with an organic moderator and a coolant may be designated OOR

Main characteristics of nuclear power plant reactors

Structural scheme of the reactor.

The main structural components of a heterogeneous nuclear reactor are: a body; core, consisting of fuel elements, moderator and control and protection system; neutron reflector; heat removal system; thermal protection; biological protection; system for loading and unloading fuel elements. Breeder reactors also have a nuclear fuel breeding zone with its own heat removal system. In homogeneous reactors, instead of fuel elements, there is a reservoir with a solution of salts or a suspension of fissile coolant materials.

1st type(s) - a reactor in which graphite is the moderator and reflector of neutrons. Graphite blocks (parallepipeds of a prism with internal channels and fuel elements placed in them form an active zone, usually in the form of a cylinder or a polyhedral prism. Channels in graphite blocks run along the entire height of the active zone. Pipes are inserted into these channels to accommodate fuel elements. Along the annular gap coolant flows between the fuel elements and the guide tubes.Water, liquid metal or gas can be used as the coolant.Part of the channels of the core is used to place the rods of the control and protection system.A neutron reflector is located around the core, also in the form of a laying of graphite blocks.Channels of fuel elements pass both through the core masonry and through the reflector masonry.

During the operation of the reactor, graphite is heated to a temperature at which it can oxidize. To prevent oxidation, the graphite masonry is enclosed in a steel hermetic casing filled with neutral gas (nitrogen, helium). Channels of fuel elements can be placed both vertically and horizontally. Outside the steel casing is placed biological protection - special concrete. Between the casing and the concrete, a concrete cooling channel can be provided through which the cooling medium (air, water) circulates. In the case of using sodium as a coolant, graphite blocks are covered with a protective shell (for example, from zirconium). To prevent impregnation of graphite with sodium when it leaks from the circulation circuit. Automatic drives of control rods receive a pulse from ionization chambers or counters of neutrons. In an ionization chamber filled with gas, fast charged particles cause a voltage drop between the electrodes to which a potential difference is applied. The voltage drop in the electrode circuit is proportional to the change in the flux density of particles that ionize the gas. The electrode surfaces of ionization chambers coated with boron absorb neutrons, causing a flow of alpha particles that also produce ionization. In such devices, changes in the current strength in the circuit are proportional to the change in the neutron flux density. The weak current generated in the circuit of the ionization chamber is amplified by electronic or other amplifiers. With an increase in the neutron flux in the reactor, the current in the circuit of the ionization chamber increases and the automatic control servomotor lowers the control rod into the core to the appropriate depth. When the neutron flux in the reactor decreases, the current in the ionization chamber circuit decreases and the drive of the control rods automatically raises them to the appropriate height.

The graphite-water reactor, when cooled by non-boiling water, has a relatively low outlet water temperature, which also causes relatively low initial parameters of the generated steam and, accordingly, low plant efficiency.

In the event of steam overheating in the reactor core, the efficiency of the installation can be significantly increased. The use of gas or liquid metals in the reactor according to Scheme 1 will also make it possible to obtain higher steam generation parameters and, accordingly, a higher plant efficiency. Graffiti water, pressurized water and graffiti liquid metal reactors require the use of enriched uranium.

Figure 1 shows the schematic diagram of the RBMK NPP.

1 Fig.1

1-Graphite blocks

(Moderator)

2-core reactor

2. Heavy water-gas reactor 2 can operate on natural uranium. The fuel element of such a reactor is immersed in a steel or aluminum tank filled to a certain level with heavy water. Around the tank is a graphite reflector - biological protection. The fuel elements have internal channels for the passage of the heat-removing gas. Heavy water, which serves as a moderator, also heats up and requires its own cooling system. This is done by circulating heavy water using a special pump and cooling it in a heat exchanger with running water. Such a reactor has a sufficiently high efficiency and a relatively low fuel cost of the generated electricity.

Since the fuel is natural uranium, the high cost of heavy water and the heat loss associated with its cooling are its disadvantages.

3. Figure c) shows a pressurized water or heavy water reactor in which water or heavy water serves as a moderator and coolant. (VVER).

4 Fig d) gives an idea of ​​the design scheme of a boiling-type reactor. This type makes it possible to produce them with a smaller wall thickness, as well as their positive property is the possibility of self-regulation.

5. the breeder reactor operates on fast neutrons i.e. on enriched uranium. These types of reactors require higher biological protection and, accordingly, the use of more expensive materials.

6. homogeneous reactor where, when natural uranium is used, only heavy water can act as a moderator, while ordinary water can act as a moderator when enriched uranium. Here, nuclear fission on fast neutrons is absent. The relatively low density of uranium and resonant absorption require a higher degree of fuel enrichment in fissile isotope.

All reactor designs have both positive and negative aspects, which must always be taken into account when designing, taking into account the linkage of construction to specific regional conditions, based on the possibility of supplying raw materials, the risk of environmental pollution, water supply sources and groundwater.

When designing nuclear power plants, complex mathematical calculations are used, which, despite the modern analytical capabilities of computer technology, cannot guarantee the correctness of all parameters. Therefore, all calculations are rechecked by experimental verification.

This is especially important when checking the critical dimensions of a natural uranium reactor. If you trust only the theoretical calculation, then you can make a serious miscalculation, which will be very expensive and difficult to correct.

Periodic refueling of nuclear power plants requires very careful preparation and is usually carried out with the reactor shut down, since increased radioactivity requires the absence of personnel during loading and unloading, despite the fact that the refueling scheme occurs in automatic mode using special containers that provide not only automatic mode, but also all safety requirements with constant cooling.

The containers have thick lead shells that provide an acceptable radiation background.

NPP equipment designs.

Graffiti-water reactors.

The graffiti-water reactor of the NPP AN is the first reactor created for the production of electricity.

In the central part of the graphite masonry, 4.6 m high and 3 m in diameter, there are 157 vertical holes with a diameter of 65 mm arranged along a triangular lattice with a step of 120 mm. They contain channels with TVE. The active zone, in which channels with TVE are located, has a diameter of 1.6 meters and a height of 1.7 meters. It is surrounded on all sides by a graphite reflector 0.7 m thick, the graphite masonry is enclosed in a steel case welded to the lower steel plate. From above, the masonry is closed with a massive cast-iron slab through which TVE channels and control systems pass. The steel case is filled with an inert gas that protects the graphite from oxidation. Around the body there is an annular water protection tank with a water layer thickness of 1m. The reactor is located in a concrete shaft with a wall thickness of 3 m, which serves as the outer layer of biological protection. There are 12 vertical pipes in the water shield, in which ionization chambers are located at the height of the active zone. There are 128 TVE channels in the active zone. The design of such a channel is shown in figure 2.

A cylindrical channel with a diameter of 65 mm is assembled from graphite bushings with five holes through which tubular TVEs pass. Water descends through the central tube from top to bottom and returns up through the 4 tubular TBE. Uranus is located outside these tubes at a height of 1.7m. The heat flux of channels in the central part of the active zone reaches 1.8 * 106 Kcal/m2 per hour.

24 channels are occupied by boron carbide control rods. Four rods for automatic control of the reactor power are located along the periphery of the core. Eighteen manual control rods are located in the center of the active zone (6 pcs) along the periphery (12 pcs.) They serve to compensate for the reactivity margin.

There are also emergency rods for an emergency shutdown of the reactor. All channels of the rods are cooled with water at a pressure of 5 atm. And temperatures from 30 to 60 degrees. The thermal power of such a reactor is 30 MW. The total load of the reactor is 550 kg of uranium containing 5% uranium 235, i.e. the amount of uranium 235 loaded into the reactor is 27.5 kg. Uranium consumption per day is about 30 gr.

Pressurized reactor NPP (VVER)

Pressurized pressurized water reactors have a vessel that can withstand the operating pressure of the coolant (Fig. 3). Fuel assemblies with nuclear fuel are loaded into the reactor core. The heat released during the fission of nuclear fuel heats the water in the reactor pressure vessel, a slightly radioactive, saturated steam is formed, which enters the secondary circuit steam generator. In the steam generator, weakly radioactive steam gives off heat to water, and saturated non-radioactive steam is formed, which is directed to the steam turbine. When the heat of radioactive steam is transferred to non-radioactive water of the secondary circuit, additional (compared to RBMK) heat losses occur in the steam generator, which reduces the efficiency of NPPs with VVER reactors to 30%.

Nuclear power plants with fast neutron reactors have a three-dimensional scheme: in the first circuit, the coolant is radioactive sodium (or potassium), in the second - non-radioactive sodium (or potassium), in the third - non-radioactive water heated in the steam generator by the heat of non-radioactive sodium of the second circuit. Non-radioactive saturated steam of the third circuit enters the steam turbine. The efficiency of nuclear power plants with fast neutron reactors is about 35%.

1 circuit 2 circuit

EG Fig.3

MCP 1 Schematic diagram

MCP1, MCP2 -

Main circulation

Pumps of the first and nuclear power plants. 1-metal case

Second circuits of the MCP 2 reactors; 2-active zone;

3-water; 4-steam generator.

The diagram shows:

1. Nuclear reactor with primary biological protection.

2. Secondary biological protection.

3. Turbine.

4. Generator.

5. Capacitor.

6. Circulation pumps.

7. Regenerative heat exchanger.

8. Water tank.

9. Steam generator.

10. Intermediate heat exchanger.

T - step-up transformer.

TSN - auxiliary transformer.

RU VN - high voltage switchgear (110 kV and above).

RU SN - switchgear of own needs.

I; II; III– NPP circuits.

A plant in which a controlled nuclear chain reaction takes place is called a nuclear reactor. 1 . It is loaded with nuclear fuel, for example - uranium-238. A nuclear reactor is used to heat the coolant and is, in principle, a boiler.

Biological protection 2 acts as an insulator of the reactor from the surrounding space so that powerful neutron fluxes, alpha, beta, gamma rays and fission fragments do not penetrate into it. Biological protection is designed to create safe working conditions for service personnel.

Turbine 3 is designed to convert steam energy into mechanical energy of rotation of the rotor of an electric generator. Generator 4 generates electrical energy, which is fed to a step-up transformer T, where it is converted to the required values ​​for further transmission to power lines. Part of the energy is also transferred to TSN- step-down transformer for own needs.

The exhaust steam from the turbine enters the condenser. Capacitor 5 serves to cool the steam, which, condensing, is then supplied by a circulation pump 6 through a regenerative exchanger 7 into the steam generator 9 . In the regenerative exchanger, the water is cooled to its original value.

The primary coolant heated in the reactor ( Na) gives off heat in the intermediate heat exchanger 10 secondary coolant ( Na). And that, in turn, gives off heat to the working body ( H2 O) in the steam generator.

Circulation pumps are used to move the coolant in the circuit circuits, as well as to supply cooling water to the condenser from the tank 8 .

Thus, nuclear power plants fundamentally differ from thermal power plants only in that the working fluid in them receives heat in the steam generator when nuclear fuel is burned in a nuclear reactor, and not organic fuel in boilers, as is the case at thermal power plants.

The multi-loop scheme of the NPP ensures radiation safety and creates convenience for equipment maintenance. The choice of the number of circuits is determined depending on the type of reactor and the properties of the coolant, which characterize its suitability for use as a working fluid in a turbine.

NPP heat exchangers.

Nuclear power plant heat exchangers have specific design features and significantly higher specific heat loads compared to conventional power plant heat exchangers. Reducing the dimensions of the heat exchangers of the reactor plant makes it possible to reduce the size and weight of the biological shield, and, consequently, the investment in the construction of nuclear power plants.

Heat exchangers, through which a radioactive and corrosive medium flows, are made of relatively expensive stainless steel. In order to save this steel, heating surfaces, tube sheets and heat exchanger shells tend to be made with minimal thicknesses, avoiding excessive strength margins, but ensuring the necessary reliability of their long-term operation.

The steam generator set consists of horizontal saturated steam generators with a pressure of 32 and 231o C.

Water from the reactor at a temperature of 275°C is fed into a vertical collector with a diameter of 750 mm, from which it is distributed over tube bundles, then it enters the circulation pump of the cooling circuit.

The tube bundles are immersed in the water volume of the secondary circuit, the water filling the annular space evaporates, the resulting steam passes through the steam separators and then enters the collecting steam pipeline to the turbine.

The heating surface of the steam generator is 1290 m2. It consists of two in-line packages of 975 tubes with a diameter of 21 mm and a wall thickness of 1.5 mm. The pitch of the tubes in the package is 36 mm. The pipe package has 5 vertical corridors that improve natural circulation.

NPP turbomachines.

Condensing steam turbines are used at operating, constructing and designing nuclear power plants.

At nuclear power plants with high-temperature reactors, special types of turbines are used that operate on saturated or slightly superheated steam.

There are special grooves in the turbine housing to trap dripping moisture. Drip moisture separators can be centrifugal and inertial. Passing through the channels of the two-way screw in the steam flow, drops of moisture are thrown by centrifugal forces onto the walls of the housing and flow down to the drainage hole.

When the steam flow is rotated by 180°, centrifugal force also develops at the entrance to the inner pipe of the separator, which throws moisture drops down.

In inertial type separators, the separation of drop moisture from the flow occurs when the flow hits the strip grid.

Auxiliary equipment.

Auxiliary equipment of NPP gas blowers, pumps, fittings, measuring instruments have specific features that should provide higher reliability providing a longer service life without maintenance. Ensuring the exclusion of leakage of radioactive gas. Increased resistance to corrosion. Sealless design pumps must provide high tightness.

All fittings are made with a bellows stem seal.

All measuring equipment also has its own design features that provide higher accuracy and reliability.

Layout of NPP equipment.

Basic requirements for equipment layout:

1. Simplicity of the technological scheme providing straight and short pipelines, water and gas lines. Cable routes

2. Convenience and ease of maintenance, easy access to all units.

3. Good lighting.

4. Compact arrangement of units

5. Ventilation providing fast and exciting all volumes of the building.

6. Increased foundation rigidity.

7. Transport mobile devices should be provided to ensure the decontamination of the premises with their equipment and devices.

Safety issues at nuclear power plants.

Safety issues at nuclear power plants are given extremely great attention. The safety of the NPP personnel and the population of the areas adjacent to its territory is ensured by a system of measures provided for the design of the NPP and the selection of a site for its construction. The maximum permissible radioactivity of water and the degree of pollution of water bodies are regulated by the "Sanitary Rules for the Transportation, Storage, Accounting and Work with Radioactive Substances" approved by the Chief Sanitary Inspector of Russia.

These regulations set temporary limits on acceptable levels of radiation.

The system of biological safety and dosimetric control of nuclear power plants, adopted for nuclear power plants of the Academy of Sciences of Russia, is strictly controlled by higher authorities.

The main sources of radioactive contamination at nuclear power plants are water from the reactor cooling circuit and nitrogen filling the graphite stack.

The activity of air emitted into the atmosphere is determined by the activity of argon.

Water with its long-lived dry residues of sodium, manganese, calcium and other components is strictly tested for permissible doses of activity.

The radioactive air from the overflow space is diluted in the general ventilation system until the activity drops to an acceptable level.

The emitted radioactive water is processed in a special workshop, subjected to aging, dilution and purification of impurities, including evaporation.

Discharged water from the primary circuit has low activity and contains short-lived isotopes. It is aged and diluted. The exposure time is 10-15 days. During this period, radioactivity decreases to an acceptable level. drinking water and goes down the drain. In particular, in the building of the NPP of the Academy of Sciences of Russia there are 28 ventilation systems for ventilating air from one room to another.

Particular attention is paid to the space above the reactor, from where radioactive gas can penetrate into the reactor hall. The air between the reactor shell and the water shield is not ventilated, as it is highly radioactive and its release into the atmosphere through a pipe is not allowed, in order to avoid environmental pollution.

There is a system of dosimetric control, both stationary and individual. In addition, air is constantly taken from various rooms and tested for radioactivity in separate dosimetric control laboratories. All working personnel have pocket photo cassettes and pocket dosimeters.

During the repair and maintenance of equipment, the regulated working hours of the personnel are introduced. When working, they use: pneumosuits, gas masks, gloves, goggles and other personal protective equipment.

Preliminary decontamination of equipment and places of planned work is being carried out.

To avoid the removal of radioactivity on overalls, special medical posts are organized.

When leaving the zone of radioactivity, the personnel take off their protective clothing, take a shower and change into clean clothes.

Used clothes are given to a special laundry or destroyed.

Violations of the dosimetric control rules can lead to irreparable consequences.

The world history of nuclear power plant operation knows many examples that took place in the countries of Canada and the USA. France, England. Yugoslavia. The events of the Chernobyl accident are still fresh. All cases that led to one or more complex, and often severe consequences were the cause of certain imperfections, sometimes negligence or disregard for the rules of operation of nuclear power plants.

Literature.

1. Nuclear power plants………………… A.A. Kanaev 1961

2. Almost everything about the chain reactor………………………… L. Matveev 1990

3. Nuclear power……………………………… A.P. Alexandrov 1978

4. Energy of the future…………………………………… A I. Protsenko 1985

5. Economics of the electric power industry …………………… Fomina 2005

Nuclear power plant (NPP) - a complex of technical structures designed to generate electrical energy by using the energy released during a controlled nuclear reaction.

Uranium is used as a common fuel for nuclear power plants. The fission reaction is carried out in the main unit of a nuclear power plant - a nuclear reactor.

The reactor is mounted in a steel case designed for high pressure - up to 1.6 x 107 Pa, or 160 atmospheres.
The main parts of VVER-1000 are:

1. The core, where nuclear fuel is located, a chain reaction of nuclear fission proceeds and energy is released.
2. Neutron reflector surrounding the core.
3. Coolant.
4. Protection control system (CPS).
5. Radiation protection.

Heat in the reactor is released due to the chain reaction of fission of nuclear fuel under the action of thermal neutrons. In this case, nuclear fission products are formed, among which there are both solids and gases - xenon, krypton. Fission products have a very high radioactivity, so the fuel (uranium dioxide tablets) is placed in sealed zirconium tubes - TVELs (fuel elements). These tubes are combined several pieces side by side into a single fuel assembly. To control and protect a nuclear reactor, control rods are used that can be moved along the entire height of the core. The rods are made from substances that strongly absorb neutrons, such as boron or cadmium. With the deep introduction of the rods, the chain reaction becomes impossible, since the neutrons are strongly absorbed and removed from the reaction zone. The rods are moved remotely from the control panel. With a small movement of the rods, the chain process will either develop or decay. In this way, the power of the reactor is regulated.

The scheme of the station is two-circuit. The first, radioactive, circuit consists of one VVER 1000 reactor and four circulation cooling loops. The second circuit, non-radioactive, includes steam generator and water supply units and one turbine unit with a capacity of 1030 MW. The primary coolant is high-purity non-boiling water at a pressure of 16 MPa with the addition of a solution of boric acid, a strong neutron absorber, which is used to control the power of the reactor.

1. The main circulation pumps pump water through the reactor core, where it is heated to a temperature of 320 degrees due to the heat released during a nuclear reaction.
2. The heated coolant gives off its heat to the water of the secondary circuit (working fluid), evaporating it in the steam generator.
3. The cooled coolant enters the reactor again.
4. The steam generator produces saturated steam at a pressure of 6.4 MPa, which is fed to the steam turbine.
5. The turbine drives the rotor of the electric generator.
6. The exhaust steam is condensed in the condenser and fed back to the steam generator by the condensate pump. To maintain a constant pressure in the circuit, a steam volume compensator is installed.
7. The heat of steam condensation is removed from the condenser by circulating water, which is supplied by a feed pump from the cooling pond.
8. Both the first and second circuits of the reactor are sealed. This ensures the safety of the reactor for personnel and the public.

If it is impossible to use a large amount of water for steam condensation, instead of using a reservoir, the water can be cooled in special cooling towers (cooling towers).

The safety and environmental friendliness of the reactor operation are ensured by strict compliance with the regulations (operational rules) and big amount control equipment. All of it is designed for thoughtful and effective management reactor.
Emergency protection of a nuclear reactor - a set of devices designed to quickly stop a nuclear chain reaction in the reactor core.

Active emergency protection is automatically triggered when one of the parameters of a nuclear reactor reaches a value that can lead to an accident. Such parameters can be: temperature, pressure and flow rate of the coolant, level and rate of power increase.

The executive elements of emergency protection are, in most cases, rods with a substance that absorbs neutrons well (boron or cadmium). Sometimes a liquid scavenger is injected into the coolant loop to shut down the reactor.

In addition to active protection, many modern projects also include elements of passive protection. For example, modern versions of VVER reactors include the "Emergency Core Cooling System" (ECCS) - special tanks with boric acid located above the reactor. In the event of a maximum design basis accident (rupture of the primary cooling circuit of the reactor), the contents of these tanks are by gravity inside the reactor core and the nuclear chain reaction is quenched by a large amount of a boron-containing substance that absorbs neutrons well.

According to the "Nuclear Safety Rules for Reactor Installations of Nuclear Power Plants", at least one of the provided reactor shutdown systems must perform the function of emergency protection (EP). Emergency protection must have at least two independent groups of working bodies. At the signal of the AZ, the working bodies of the AZ must be actuated from any working or intermediate positions.
The AZ equipment must consist of at least two independent sets.

Each set of AZ equipment must be designed in such a way that, in the range of neutron flux density changes from 7% to 120% of the nominal value, protection is provided for:
1. According to the density of the neutron flux - at least three independent channels;
2. According to the rate of neutron flux density increase - by at least three independent channels.

Each set of AZ equipment must be designed in such a way that, in the entire range of process parameters change established in the reactor plant (RP) design, emergency protection is provided by at least three independent channels for each process parameter for which protection is necessary.

The control commands of each set for AZ actuators must be transmitted over at least two channels. When one channel is taken out of operation in one of the AZ equipment sets without this set being taken out of operation, an alarm signal should be automatically generated for this channel.

Tripping of emergency protection should occur at least in the following cases:
1. Upon reaching the AZ setpoint in terms of neutron flux density.
2. Upon reaching the AZ setpoint in terms of the rate of increase in the neutron flux density.
3. In the event of a power failure in any set of AZ equipment and CPS power supply buses that have not been taken out of operation.
4. In case of failure of any two of the three protection channels in terms of the neutron flux density or in terms of the rate of neutron flux increase in any set of AZ equipment that has not been decommissioned.
5. When the AZ settings are reached by the technological parameters, according to which it is necessary to carry out protection.
6. When initiating the operation of the AZ from the key from the block control point (BCR) or the backup control point (RCP).

The material was prepared by the online editors www.rian.ru based on information from RIA Novosti and open sources

In the middle of the twentieth century, the best minds of mankind worked hard on two tasks at once: on the creation of an atomic bomb, and also on how the energy of the atom could be used for peaceful purposes. So the first in the world appeared. What is the principle of operation of nuclear power plants? And where in the world are the largest of these power plants located?

History and features of nuclear energy

"Energy is the head of everything" - this is how the well-known proverb can be paraphrased, given the objective realities of the 21st century. With every new turn technical progress humanity needs more and more of it. Today, the energy of the "peaceful atom" is actively used in the economy and production, and not only in the energy sector.

Electricity produced at so-called nuclear power plants (the principle of operation of which is very simple in nature) is widely used in industry, space exploration, medicine and agriculture.

Nuclear energy is a branch of heavy industry that extracts heat and electricity from the kinetic energy of the atom.

When did the first nuclear power plants appear? Soviet scientists studied the principle of operation of such power plants back in the 40s. By the way, in parallel they also invented the first atomic bomb. Thus, the atom was both "peaceful" and deadly at the same time.

In 1948, I. V. Kurchatov suggested that the Soviet government begin to carry out direct work on the extraction of atomic energy. Two years later, in the Soviet Union (in the city of Obninsk, Kaluga region), the construction of the very first nuclear power plant on the planet began.

The principle of operation of all is similar, and it is not at all difficult to understand it. This will be discussed further.

NPP: principle of operation (photo and description)

At the heart of any work is a powerful reaction that occurs when the nucleus of an atom divides. Uranium-235 or plutonium atoms are most often involved in this process. The nucleus of atoms divides the neutron that enters them from the outside. In this case, new neutrons are produced, as well as fission fragments, which have a huge kinetic energy. It is this energy that is the main and key product of the activity of any nuclear power plant.

This is how you can describe the principle of operation of a nuclear power plant reactor. In the next photo you can see what it looks like from the inside.

There are three main types of nuclear reactors:

• high power channel reactor (abbreviated as RBMK);
• pressurized water reactor (VVER);
• fast neutron reactor (FN).

Separately, it is worth describing the principle of operation of nuclear power plants as a whole. How it works will be discussed in the next article.

The principle of operation of nuclear power plants (diagram)

Works in certain conditions and in strictly specified modes. In addition to (one or more), the structure of a nuclear power plant includes other systems, special facilities and highly qualified personnel. What is the principle of operation of nuclear power plants? Briefly, it can be described as follows.

The main element of any nuclear power plant is a nuclear reactor, in which all the main processes take place. We wrote about what happens in the reactor in the previous section. (as a rule, most often it is uranium) in the form of small black tablets is fed into this huge cauldron.

The energy released during the reactions taking place in a nuclear reactor is converted into heat and transferred to the coolant (usually water). It should be noted that the coolant in this process receives a certain dose of radiation.

Further, the heat from the coolant is transferred to ordinary water (through special devices - heat exchangers), which boils as a result. The resulting water vapor drives the turbine. A generator is connected to the latter, which generates electrical energy.

Thus, according to the principle of operation of a nuclear power plant, this is the same thermal power plant. The only difference is how the steam is generated.

Geography of nuclear power

The top five countries in terms of nuclear energy production are as follows:

1. France.
2. Japan.
3. Russia.
4. South Korea.

At the same time, the United States of America, generating about 864 billion kWh per year, produces up to 20% of the entire electricity of the planet.

There are 31 states in the world that operate nuclear power plants. Of all the continents of the planet, only two (Antarctica and Australia) are completely free from nuclear energy.

Today, there are 388 nuclear reactors operating in the world. True, 45 of them have not generated electricity for a year and a half. Most of the nuclear reactors are located in Japan and the United States. Their full geography is presented on the following map. Green indicates countries with valid nuclear reactors, their total number in a particular state is also indicated.

The development of nuclear energy in different countries

In general, as of 2014, there is a general decline in the development of nuclear power. The leaders in the construction of new nuclear reactors are three countries: Russia, India and China. In addition, a number of states that do not have nuclear power plants are planning to build them in the near future. These include Kazakhstan, Mongolia, Indonesia, Saudi Arabia and several North African countries.

On the other hand, a number of states have taken a course towards a gradual reduction in the number of nuclear power plants. These include Germany, Belgium and Switzerland. And in some countries (Italy, Austria, Denmark, Uruguay) nuclear power is prohibited at the legislative level.

The main problems of nuclear power

With the development of nuclear power is associated with one significant ecological problem. This is the so-called environment. So, according to many experts, nuclear power plants emit more heat than the same power thermal power plants. Especially dangerous is thermal pollution of waters, which disrupts the lives of biological organisms and leads to the death of many species of fish.

Another acute problem associated with nuclear power concerns nuclear safety in general. For the first time, mankind seriously thought about this problem after the Chernobyl disaster in 1986. The principle of operation of the Chernobyl nuclear power plant was not much different from that of other nuclear power plants. However, this did not save her from a major and serious accident, which entailed very serious consequences for the whole of Eastern Europe.

Moreover, the danger of nuclear energy is not limited to possible industrial accidents. So, big problems arise with the disposal of nuclear waste.

Advantages of nuclear energy

Nevertheless, supporters of the development of nuclear energy also name the obvious advantages of the operation of nuclear power plants. Thus, in particular, the World Nuclear Association recently published its report with very interesting data. According to him, the number of human casualties accompanying the production of one gigawatt of electricity at nuclear power plants is 43 times less than at traditional thermal power plants.

There are other equally important benefits. Namely:

• low cost of electricity production;
• environmental cleanliness of nuclear energy (with the exception of only thermal pollution of water);
• the absence of a strict geographical reference of nuclear power plants to large sources of fuel.

Instead of a conclusion

In 1950, the world's first nuclear power plant was built. The principle of operation of nuclear power plants is the fission of an atom with the help of a neutron. As a result of this process, an enormous amount of energy is released.

It would seem that nuclear energy is an exceptional boon for mankind. However, history has proven otherwise. In particular, two major tragedies - the accident at the Soviet Chernobyl nuclear power plant in 1986 and the accident at the Japanese power plant Fukushima-1 in 2011 - demonstrated the danger posed by the "peaceful" atom. And many countries of the world today began to think about the partial or even complete rejection of nuclear energy.