Nuclear power plant for missiles and underwater vehicles - how it works. Nuclear power plant Nuclear power plant principle

TO power plant nuclear-powered ships include a reactor, a steam generator and a turbine unit that drives the ship's propulsion system. A reactor is a facility for producing nuclear chain reactions, during which energy is generated that is further converted into mechanical energy. Operating principle nuclear reactor shown in Figure 8.

Operating principle of a nuclear reactor

It is known that the energy released when using 1 kg of uranium is approximately equal to the energy obtained from the combustion of 1500 tons of fuel oil. The heart of a nuclear installation is the reactor: a controlled nuclear reaction takes place in it, resulting in the formation of heat, which is removed using a coolant - water. Radioactive coolant water is pumped into a steam generator, where, due to its heat, steam is formed from non-radioactive water. The steam is directed to turbine disks, which drive turbogenerators powered by electric propulsion motors, which turn the propellers. The exhaust steam is sent to the condenser, where it is converted back into water and pumped into the steam generator. The operating principle of a nuclear power plant is shown in Figure 9.

diagram of a nuclear power plant with a reactor cooled by pressurized water

Much attention is paid to the safe operation of a nuclear installation, since people on the ship are to some extent exposed to the danger of radioactive radiation, therefore the nuclear reactor is isolated from the environment by a protective screen that does not allow harmful radioactive rays to pass through. Usually double screens are used. The primary shield surrounds the reactor and is made of polyethylene-coated lead plates and concrete. The secondary screen surrounds the steam generator and encloses the entire primary high-pressure circuit. This screen is mainly made of concrete with a thickness of 500 mm to 1095 mm, as well as lead plates with a thickness of 200 mm and polyethylene with a thickness of 100 mm. Both screens require a lot of space and are very heavy. The presence of such screens is a big disadvantage of nuclear power plants. The location of a nuclear power plant on a ship is shown in Figure 10. Another, even more significant drawback is, despite all protective measures, the danger of contamination of the environment both during the normal operation of the power plant due to waste of used fuel, the release of bilge water from the reactor compartment, etc. etc., and during accidental ship and nuclear accidents power plant.

nuclear power plant on a ship

Alternative energy installations

principle of operation of the Stirling engine

Even before the Second World War, shipbuilders made attempts to create for submarines some kind of alternative to a diesel-electric power plant - the so-called single engine for surface and underwater propulsion. For various reasons, at that time all these attempts did not leave the experimental stage, but already in the 1960s they were returned to again. This was caused by several reasons. Firstly, the Baltic Sea has been declared a nuclear-free zone, which means that the Baltic countries do not have ships with nuclear power plants. Secondly, for political reasons such warships Germany and Japan cannot be in service. Thirdly, the construction and maintenance of nuclear submarines is unaffordable for many countries. The most productive work on the creation of a single non-nuclear engine was in Sweden, the Netherlands, Great Britain and Germany.

But at the same time, for some types of ships, the electric motor is the only acceptable one. These are ships with frequent changes in the load conditions of the propulsion system, ships that require increased maneuvering qualities, operating for a long time with reduced power. Such vessels are icebreakers, tugs, ferries, whaling ships, dredgers and some others.

The Sterling engine is a thermal piston engine with an external heat supply, in a closed volume of which constant working heat (gas) circulates, heated from an external heat source and performing useful work due to its expansion. The operating principle of the Stirling engine is shown in Figure 11.

Unlike an internal combustion engine, the Sterling engine has two cavities in the cylinder that vary in volume - hot and cold. The working fluid is compressed in the cold cavity and enters the hot one, then after heating the gas moves in the opposite direction and enters the cold cavity, where, expanding, it produces useful work. This two-way movement of gas is ensured by the presence of two pistons in each cylinder: a displacer piston that regulates the flow of gas, and a working piston that performs useful work. The volume of the hot cavity and the upper part of the cylinder is regulated by the displacer piston, and the volume of the cold cavity located between both pistons is controlled by their joint movement. Both pistons are mechanically connected and perform a coordinated movement provided by a special mechanism that simultaneously replaces the crank mechanism.

During engine operation, four main sequential positions of the pistons can be distinguished, which determine the engine operating cycle: a) - the working piston is in the lowest position, the displacer piston is in the highest position. In this case, most of the gas is located between them in the cold space (cooling); b) - the displacer piston is in the upper position, and the working piston moves upward, compressing the cold gas (compression); c) - the displacer piston moves downwards, approaching the working piston and displacing gas into the hot cavity (heating); d) - hot gas expands, performing useful work by acting on the working piston (expansion). A regenerator is installed along the path of the gas, which takes away some of the heat when hot gas moves through it and releases it when it moves after cooling and compression in the opposite direction.

The presence of a regenerator theoretically allows increasing efficiency Stirling engine up to 70 percent. Engine power control is achieved by changing the amount of gas. Gases with high thermal properties (hydrogen, helium, air, etc.) are used as working heat.

Stirling engines have the following unique features: - the ability to use any heat source (liquid, solid, gaseous and nuclear fuel, solar energy, etc.); - work in a wide temperature range with a small pressure difference between compression and expansion; - power regulation by changing the amount of working heat in the cycle at constant highest and lowest gas temperatures;

These features provide Sterling engine over other installations the following advantages, such as multi-fuel and low toxicity of fuel combustion products; low noise and good balance; high efficiency at low power modes. Thanks to these advantages, Swedish submariners paid attention to the engine, turning the idea into reality on a modern submarine of the " Gotland" But while Stirling engines are comparable in efficiency to modern diesel engines, they are inferior to them in power. Therefore, they can only be used on submarines as additional engines to the classic diesel-electric propulsion system.

Nuclear power plant - a power plant operating on the energy of a chain reaction of nuclear fission. The nuclear power plant, which is basically a modification of the steam turbine, began to be used on ships in the late 50s. XX century The power plant of a nuclear-powered ship includes a reactor, a steam generator and a turbine unit that drives the ship's propulsion system. A reactor is a facility for producing nuclear chain reactions, during which energy is generated that is further converted into mechanical energy. In a nuclear reactor, conditions are created such that the number of nuclear fission per unit time is a constant value, i.e. the chain reaction occurs constantly.

Design and principle of operation of a nuclear reactor.

1 - steel body; 2 - moderator; 3 - reflector; 4 - protection; 5 - fuel elements; 6 - coolant inlet; 7 - coolant outlet; 8 - control rods.

Nuclear fuel contains fissile material, usually uranium or plutonium. When atomic nuclei split into so-called fragments, or free high-energy neutrons, a lot of energy is released. To reduce the high energy of neutrons, a moderator is used: graphite, beryllium or water. In order to minimize the possibility of neutron loss, a reflector is installed. It consists mainly of beryllium or graphite. To avoid too strong a neutron flux in the reactor, control rods made of neutron-absorbing materials (cadmium, boron, indium) are installed at an appropriate depth. Energy exchange in the reactor occurs with the help of coolants, water, organic liquids, alloys of low-melting metals, etc. Currently, reactors cooled by water under pressure are usually used on ships.

Diagram of a nuclear power plant with a reactor cooled by pressurized water.

1 - reactor; 2 - primary biological protection; 3 - secondary biological protection; 4 - steam generator; 5 - heating coil of the primary circuit; 6 - primary circuit circulation pump; 7 - high pressure turbine; 8 - low pressure turbine; 9 - gearbox; 10 - capacitor; 11 - secondary circuit pump; 12 - sea water inlet; 13 - sea water outlet.

This installation has two circulation circuits. The first circuit is the circulation of water under high pressure. The primary circuit water also serves as a coolant for the nuclear reactor and has a pressure of approximately 5.8 to 9.8 MPa. It flows through the reactor and is heated, for example on the ships Otto Hahn (Germany) and Mutsu (Japan), to 278 ° C. In this case, water pressure counteracts evaporation. Hot water from the primary circuit, flowing through the heating coil, gives up its heat to the steam generator, then it returns to the reactor again. Condensate is supplied to the steam generator from the second low-pressure circuit. The water heated in the steam generator evaporates. This steam with relatively low pressure (for example, on the American ship Savannah it is 3.14 MPa) serves to power turbines, which drive the propeller through a gearbox.

The nuclear reactor is isolated from the environment by a protective shield that does not allow harmful radioactive rays to pass through. Usually double screens are used. The first (primary) screen surrounds the reactor and is made of polyethylene-coated lead plates and concrete. The secondary screen surrounds the steam generator and encloses the entire primary high-pressure circuit. This screen is mainly made of concrete with a thickness of 500 mm (Otto Hahn) to 1095 mm (Mutsu), as well as lead plates with a thickness of 200 mm and polyethylene with a thickness of 100 mm. Both screens require a lot of space and are very heavy. For example, the primary screen on the Savannah ship weighs 665 tons, and the secondary one weighs 2400 tons. The presence of such screens is a big disadvantage of nuclear power plants. Another, even more significant drawback is, despite all protective measures, the danger of environmental contamination both during the normal operation of the power plant due to waste of used fuel, release of bilge water from the reactor compartment, etc., and during accidental ship accidents and nuclear power plant.

The undeniable advantages include very low fuel consumption and an almost unlimited cruising range. For example, the ship "Otto Hahn" (Germany) did not even consume 20 kg of uranium in three years, while the fuel consumption of a conventional steam turbine power plant on a ship of this size was 40 thousand tons. The cruising range of the Japanese ship "Mutsu" is 145 thousand .miles Despite these advantages, nuclear power plants are widely used only on warships. It is especially advantageous to use them on large submarines, which can remain under water for a long time, since air is not required in the reactor to generate thermal energy. In addition, powerful icebreakers used in the northern latitudes of the globe are equipped with nuclear power plants.

1 - engine room; 2 - container with reactor; 3 - compartment of auxiliary mechanisms; 4 - spent fuel rod storage facility.

More than twenty-five years ago, the first power start-up of the IVG-1 nuclear reactor was carried out in Semipalatinsk, with the help of which development of the design of a nuclear rocket engine began. Even then it was assumed that such an engine would be needed during a human flight to Mars. Later, difficulties with funding science slowed down the work, but an expedition to Mars planned for 2017 has revived interest in nuclear propulsion. A nuclear engine is a reactor in which a gas flow—hydrogen—passes along fuel elements containing nuclear fuel. It cools the elements, but it itself heats up and flows out of the nozzle at high speed, creating engine thrust. This creates an impulse that pushes the rocket forward. The gas temperature at the outlet must be very high - at least 3000 °C, and the specific thrust - 950 s. Only under these conditions is a nuclear engine more efficient than a conventional engine running on liquid fuel.

Now in the field of nuclear rocket engines, despite the half-frozen state of work, we are 15-20 years ahead of the United States. Work on nuclear power plants (NPP) and power propulsion systems (NPP) is currently focused on the formation of advanced scientific and technical groundwork for the creation of basic unified elements, components and assemblies of nuclear power plants (NPP).

Priority areas of research that can show the advantages of nuclear power sources over other options include:

development of technologies that ensure the creation of nuclear power plants with a capacity of tens to hundreds of kilowatts (with the prospect of its further increase);

bringing the guaranteed resource of nuclear power plants to a level no less than that expected from solar energy (including up to 10 years or more in GSO);

development of technologies that ensure the creation of bimodal nuclear electric propulsion systems (operating both in the mode of nuclear rocket engines powered by hydrogen and in the electricity-generating mode to power the target and service equipment of a spacecraft or electric propulsion);

confirmation of nuclear and radiation safety of the development and operation of nuclear power plants (NPP).

As studies conducted by specialized domestic organizations have shown, with powers of 50...100 kW, preference can be given to nuclear power plants due to their noticeable advantages over traditional solar power plants in terms of weight, size, operational and economic indicators. Moreover, in the specified power range, second-generation thermionic nuclear power plants, based on the further development of the technology created under the Topaz program, an important element of which were successful flight tests in 1987-1988, have significant advantages. the world's first thermionic nuclear power plant “Topaz-1”. It is precisely this circumstance – the use of a nuclear power plant – that brings very significant specificity to the practice of spacecraft design, since layout diagram the latter becomes more dependent on the characteristics of the power plant than on the characteristics and parameters of the target equipment.

It is important that nuclear power plants are used both as a source of power supply for on-board equipment and in conjunction with electric rocket engines to launch a spacecraft from a radiation-safe orbit to a working one. Research performed to identify areas of application various types energy to supply the spacecraft indicate that already from the level of 300 kW with a service life of the spacecraft of more than one year, the use of nuclear power seems more preferable. The results of theoretical studies show that a nuclear power plant with thermionic energy conversion with a power of 7.5 MW and specific mass characteristics of 6 kg/kW can be created.

Nuclear power plants with turbomachine energy conversion (TEMP) may have advantages over thermionic and thermoelectric options due to:

significantly smaller mass of the reactor installation with equal electrical power; higher efficiency;

greater manufacturability due to a significantly lower temperature of the working fluid;

the fundamental possibility of testing the power circuit separately from the reactor;

higher reliability of TEMP due to the absence of restrictions on duplication of elements outside the reactor.

Therefore, it seems appropriate to consider the concept of nuclear power plants with TEMP. It should also be noted the extensive accumulated experience in the development of nuclear propulsion engines, the presence of a test bench base and highly qualified specialists in Russia, as well as a large scientific and technical reserve created in the USA under the Nerva program. At the selected level of electrical power (2 MW), the design of the reactor and radiation protection is close to optimal in terms of specific masses, configuration and fuel loading, and the specific masses of TEMP units are reduced to the level of 2-4 kg/kW.

The design and ballistic analysis of the space power transport vehicle (SET) determined the required electrical power parameters, as well as the characteristics of the electric rocket propulsion system.

The main restrictions adopted in the calculations:

the weight of the installation and dimensions should not exceed the capabilities of the Angara launch vehicle;

the radiation dose accumulated by the payload when crossing the Earth's radiation belts should not exceed 5 x 104 rad;

A circular orbit with an altitude of 600-800 km is considered radiation safe;

the service life of KETA onboard systems should be 1-2 years at the first stage, increasing to 5-7 years during subsequent testing;

number of KETA flights per resource – up to 10;

the total dose of radioactive radiation received in the instrument compartment from the operation of the reactor and the impact of the Earth's radiation belts: gamma radiation - no more than 106 rad; fast neutron fluence – no more than 1013 n/cm 2 .

The RRC “Kurchatov Institute” has developed a design for a nuclear power plant with a turbomachine energy converter designed for the following parameters:

thermal power – up to 10 MW;

electrical power – about 2 MW;

energy conversion system – turbomachine (Brayton cycle);

total operating time – at least 104 hours;

number of inclusions per resource – up to 30;

maximum temperature of the working fluid – up to 1500 K.

As a result of the studies carried out, the main design characteristics of the nuclear power plant were determined:

gas-cooled reactor mass – 1000 kg;

fuel – UC (U,Zr)C,UNc with 90% enrichment in U235, fuel cladding – Zr, W184, reflector – Be;

radiation protection mass (LiH,W,B4C) – 1000 kg;

weight of the energy converter (turbine, compressor and unipolar generator) – 3500 kg;

working fluid – helium-xenon mixture (1-3% Xe);

radiator refrigerators - on heat pipes at an average temperature of about 700 K, weight 3000 kg;

area of ​​the refrigerator-emitter (effective) – about 300 m2;

system mass automatic control, power supply systems – 1000 kg;

nuclear power plant structure weight – 1500 kg;

total mass of the nuclear power plant – 11,000 kg;

specific gravity – 5.5 kg/kW.

Structurally, KETA, which includes a nuclear power plant, consists of a power plant module with a nuclear reactor and protection; TEMP placed in the radiation protection cone; refrigerator-emitter on heat pipes, made according to the supporting circuit; four drop-down planes of refrigerator-emitters having a semi-cylindrical shape, as well as a retractable farm located inside the refrigerator-emitter.

On the retractable farm there are:

instrument compartment with a docking system, orientation, navigation, communications instruments and an additional propulsion system;

sustainer electric rocket propulsion system (specific impulse 4600 s); xenon fuel tank.

Main mass characteristics of KETA: nuclear power plant – 11,000 kg; ERDU – 5000 kg; retractable farm, fuel tank - 1000 kg; instrument compartment, docking system – 2000 kg; additional propulsion system, unaccounted for elements – 1000 kg; fuel (xenon) – 8000 kg; the total “dry” weight of KETA is 20,000 kg. KETA can provide extensive space research, the creation of a lunar base and the solution of a number of other national economic and defense problems.

In the 21st century more energy-intensive tasks will have to be solved: the creation of space production complexes, research of comets, asteroids, etc. To solve them, more powerful remote control is needed. The power requirements of a propulsion system are determined by flight time, payload mass, specific mass of the power plant (kg/kW), specific impulse and engine efficiency. The power required for a cargo flight to the Moon, a 600-day cargo flight to Mars with a payload of hundreds of tons, is estimated at 1-10 MW. A manned flight to Mars requires power supplies with a power of several tens of MW. This allows, taking into account domestic and foreign experience consider the concept of creating a CET with a nuclear propulsion system based on a power plant with an electrical power of several MW.

Nuclear power plant with an electrical power of 2 MW for a space power transport vehicle. Space energy transport vehicles with a nuclear power plant with a power of about 2 MW and electric rocket engines can provide significant progress in the exploration of the planets of the solar system, the creation of a lunar base, conducting some purely scientific high-energy experiments in space and, finally, with their use the cost can be reduced several times delivery of 1 kg of payload to geostationary and other high orbits.

KETA is a space shuttle (inter-orbital tug). KETA is launched into low orbit by the Angara launch vehicle. It is quite obvious that programs for exploring distant planets, creating a lunar base, a manned expedition to Mars and, finally, projects for global space telephony require a decisive intensive increase in the transport capabilities of space technology, which predetermines a sharp increase in the power supply of spacecraft.

Nuclear electric rocket propulsion systems with an electrical power of 2-10 MW. From the preliminary design and ballistic analysis it follows that for nuclear power plants the most appropriate level of electrical power is ~3 MW as the most optimal in accordance with the following criteria:

the maximum possible mass of payload launched into geostationary orbit using a nuclear propulsion propulsion system is placed in a PG container during launch from the Earth to the Energia launch vehicle;

the time of transportation of cargo to the GEO does not exceed 100 days (the condition of not exceeding the permissible radiation dose when passing through the Earth's radiation belts);

the specific impulse of an electric rocket engine (EP) is 5000 s;

the selected power level is universal for solving a number of other problems (transporting cargo to Mars, the Moon, Venus, changing the inclination of the orbits of large space objects such as scientific stations, conducting scientific experiments and organizing industrial production in orbit).

Among the powerful electric propulsion systems, the most developed ones both in terms of flight parameters and the development of subsystems are magnetoplasma and ion electric ones. rocket engines. Currently, the possibilities of creating a magnetoplasmodynamic (MPD) engine with a power of 2.5 MW with an external field, operating at a discharge current of 10 kA and a voltage of 250 V have been investigated. The engine resource required for most space missions is assumed to be 10 thousand hours, so developments are aimed at mainly to increase the service life of an individual engine. The possibility of operating MTD engines with a power of up to 40 MW in a quasi-stationary mode has been demonstrated. The plasma flow is satisfactorily described by the equations of ideal magnetohydrodynamics.

The use of powerful MTD engines in space experiments conducted in recent decades has not been considered due to the low level of onboard energy of existing spacecraft. Operating the plant at low power levels is disadvantageous for two reasons. Firstly, this reduces the efficiency of converting electrical energy into traction to an unacceptably low value. Secondly, high efficiency at low levels of average power can only be achieved in the pulsed operating mode of the propulsion system. To ensure pulsed operation, an energy converter with auxiliary devices is required, the mass of which is quite significant. Therefore, low-power propulsion systems with pulsed MTD engines cannot compete with other electric propulsion engines.

The ballistic calculations carried out also showed that it is very promising to use an MPD engine in a propulsion system for interorbital flights if the spacecraft has an onboard megawatt energy source, at which stationary MPD engines achieve satisfactory propulsion characteristics. To transport a large energy source from a low satellite orbit to a geostationary orbit using a motor on chemical fuel requires a mass of fuel 10 times the mass of the payload. When using an MTD engine, the mass of the working fluid is reduced by 5-10 times. If we take into account that the mass of the MTD engine is of the same order as that of a chemical fuel engine, then the gain in the initial mass of the spacecraft in low Earth orbit turns out to be significant. To perform such tasks, a reliable installation design with an MTD motor with a power of several megawatts is required.

The most optimal for a spacecraft of the selected power level is a fast neutron reactor plant, the core concept of which is based on the use of uranium-intensive high-temperature compositions in the form of twisted rod fuel elements or free backfilling of bead fuel elements with axial coolant flow. The choice of a fast neutron reactor is determined by: minimal dimensions and weight; the absence of a moderator, which eliminates the problem of its stability and cooling; virtual absence of reactivity effects associated with burnout and slagging; small initial margin and negative temperature effect of reactivity.

Nuclear safety at all stages life cycle In normal and emergency situations, spacecraft is provided using active and passive means, including the following elements:

control drums in the side reflector;

retractable absorber rods;

resonant absorbers placed in the core; programmable change in reactor geometry in emergency situations.

Radiation protection of the payload and control system - shadow, in the form of a truncated cone - is determined by the maximum permissible level of radiation. Boron-activated zirconium hydride and lithium hydride are considered as the main protection components. The choice of the turbomachine conversion method according to the Brayton thermodynamic cycle is due to the low specific mass of the conversion system - less than 10 kg/kW, which is significantly less than its value for other conversion methods (30 kg/kW); high degree technological readiness, perfection of the main components of the gas circuit; the ability to ensure that the output parameters of the electric generator correspond to the needs of the load; high energy conversion efficiency (-30%). Among dynamic methods of energy conversion, the Brayton cycle is distinguished by the fact that it provides ease of start-up, chemical inertness and radiation inactivability of the working fluid.

The proposed power plant uses a direct regenerative closed Brayton cycle, the main components in the implementation of which are a turbocompressor-generator, a recuperative heat exchanger and a refrigerator-radiator (CI). The maximum cycle temperature is 1500 K, which is quite justified when using modern structural materials based on ceramics for the manufacture of turbine disks and heat-resistant alloys for housing components and supply pipes. Materials operating at such temperatures, however, have increased fragility at lower temperatures, which requires development of the algorithm for starting turbines. The design of the recuperative heat exchanger, consisting of a series of stamped sheets, provides high-intensity heat exchange and thereby allows the creation of a compact and lightweight heat exchanger.

The spacecraft consists of a power plant module based on a nuclear reactor, a propulsion module, an accelerator and a payload compartment. The power plant module includes a reactor plant, shadow radiation protection, an energy conversion system (ECS), radiator refrigerators based on heat pipes and a sliding truss. The propulsion module contains a block of electric propulsion engines, a fuel tank, an engine control system, a spacecraft control system, and a nuclear power plant control system. The radiator coolers of the electric rocket propulsion system are located on the surface of the propulsion module.

The accelerator is a jettisonable rocket stage consisting of an oxidizer tank (oxygen), a fuel tank (kerosene) and two engines with a total thrust of about 1 tf, located on a jettisonable truss. The truss is fixed on the surface of the power frame of the SEP and is dropped along with tanks and engines in a circular orbit with an altitude of Ncr ~ 800 km. The payload compartment has a total volume of about 800 m3 and is separated from the spacecraft at the GSO along the plane of docking with the propulsion module.

When inserted into low orbit, the spacecraft is placed in the payload container of the Energia launch vehicle. The payload container is opened and dropped after the launch vehicle is launched at an altitude of Nkr - ~ 200 km. Then the accelerator engines are turned on, and when the spacecraft reaches the reference orbit with an altitude of Ncr ~ 600... 800 km, the accelerators are reset. In the reference orbit, upon command from the Earth, operations of moving the CI trusses and opening them are carried out. Next, the reactor is started and the power supply system is brought to the specified power level. After testing the spacecraft subsystems, it is transferred to the gravitational orientation position. The main propulsion engines are switched on.

According to calculations, the time for launching a spacecraft with the specified parameters to geostationary orbit will be approximately 60 days, while most time, the spacecraft will be in radiation belts of different intensities. If the protection of the spacecraft control and payload is made of aluminum, ensuring its specific gravity up to 1 g/cm2, the total radiation dose will not exceed 2*104 rad. After insertion into orbit, the payload is separated from the spacecraft, and the spacecraft, if necessary, is transferred to a geocentric orbit.

Thus, the research conducted shows the following:

the use of the Energia launch vehicle and a 3 MW nuclear propulsion propulsion system with turbomachine conversion and an MPD engine with an efficiency of ~ 0.7 and a specific impulse of 5000 s makes it possible to launch a payload weighing 35 tons into the geostationary orbit in 60 days;

the use of a nuclear propulsion propulsion system doubles the mass and volume of the payload launched to the geostationary orbit compared to a liquid propellant rocket engine;

nuclear safety of spacecraft at all stages of its life cycle in normal and emergency situations can be ensured using active and passive means of protection;

The feasibility of the proposed concept of an electric rocket engine is confirmed by a number of experimental and theoretical studies carried out in Russia and abroad.

Currently, Russia has the capabilities to solve this problem, since it has a powerful Energia launch vehicle, as well as scientific and technical resources for space nuclear and propulsion systems. Along with nuclear power plants, which have an increased radiation hazard, further development Rocket engines of traditional designs will also be available.

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The developing nuclear energy industry requires a constant influx of specialists into the industry.

This book is part of a five-volume teaching aid“Nuclear Reactors and Power Plants” and is designed to train designers of nuclear power plants (NPP).
The volumes of the first edition were published in 1981 - 1983. and included the following books: Emelyanov I. Ya., Efanov A. I., Konstantinov L. V. “Scientific and technical foundations of control of nuclear reactors” (M.: Energoizdat, 1981) Ganev I. X. “Physics and calculation of the reactor" (M.: Energoizdat, 1981) Egorov Yu. A. "Fundamentals of radiation safety of nuclear power plants" (M.: Energoizdat, 1982) Emelyanov I. Ya., Mikhan V. I., Solonin V. I. and etc. “Design of nuclear reactors” (M.: Energoizdat, 1982) Ganchev B.G., Kalishevsky L.L., Demeshev R.S. et al. “Nuclear power plants” (M.: Energoatomizdat, 1983). Nowadays, first edition books have become difficult to access for students. In the second edition of the book, the material from the first edition is supplemented and partially revised.
The authors of the book made an attempt to cover in a concise form the main issues related to the calculation and design of nuclear power plants for various purposes: for stationary nuclear power plants, water transport and space objects, which corresponds to the established practice of training nuclear power plant designers. In accordance with the needs of industry, the main attention is paid to stationary nuclear power plants. Features of installations and their elements for other purposes are given more briefly.
At modern development technical equipment, the nuclear power plant designer must be able not only to select the required composition of the equipment, justify its main parameters, but also carry out design
structural calculation, at least at the level of preliminary design, to justify the task for the developers of one or another type of heating, power and other equipment, to justify the efficiency and reliability of the decisions made. This is all the more important because when creating a new type of reactor installation, it is necessary to re-develop almost all the equipment.
The peculiarities of this book include the fact that within the framework of one volume, issues previously covered in various textbooks, teaching aids and monographs are presented in a concise form and from a unified position.
The authors set the task, within the framework of one volume, to provide primary information on the calculation and design of nuclear power plants as a whole and individual elements of its equipment, accompanying each section with a list of recommended literature for a more in-depth study of the issue.
The main content of the book is divided into four parts. The first discusses general issues in the design of nuclear power plants. Particular attention is paid to the calculation and justification of the thermal design of the installation and economic issues.
The second part is devoted to nuclear power plant equipment. The basic principles and methods of calculation and design of heat exchange and machinery equipment, pipelines and fittings are considered. Issues of strength calculations are included in a separate chapter. The third part examines systems and equipment for emergency cooling, fuel reloading, cleaning and replenishment of coolant, technical water supply, and ventilation.
The book concludes with the fourth part, which examines the design and layout of nuclear power plants at nuclear power plants, on ships and on space objects.
The authors express confidence that, having mastered the material in the book, the student will be ready for independent practical work and a more in-depth study of the necessary issues.
Introduction, § 1.1, 1.2, 6.1 - 6.6, 6.8, 7.1 - 7.9, 8.2, 8.3, as well as Ch. 9 written by B. G. Ganchev ch. 2, § 1.3, 6.7, 6.9 prepared by S.V. Selikhovkin § 3.1 - 3.7, Ch. 4, § 8.1, ch. 14 and 15 were written by L. L. Kalishevsky ch. 5 and § 7.10, 7.11 were written by E. B. Kolosov; material § 1.4, 3.8, 6.10, Ch. 11 and 13 prepared by L. A. Kuznetsov Ch. 10 - R. S. Lemeshev ch. 12 -
N. F. Rexney § 6.2 - L. E. Kostikov. B. I. Katorgin, Yu. V. Zhuravsky, V. V. Lozovetsky also took part in the preparation of the material for the first edition.
The authors express deep gratitude to the reviewer of this edition of the book, Doctor of Technical Sciences, Professor of Moscow Power Engineering Institute L.P. Kabanov.

INTRODUCTION

Nuclear energy is an important and integral part of the global economy. By the beginning of 1988, more than 420 power units with a total installed capacity of about 300,103 MW were operated at nuclear power plants (NPPs) in 26 countries around the world. Their share in electricity generation is 16%. It is assumed that by the end of the 20th century. In the global fuel balance structure, the share of nuclear fuel will be 20%.
In the USSR, by the beginning of 1988, 16 nuclear power plants operated 45 power units with a total installed capacity of 34.4X x 103 MW. The share of nuclear power plants in the total electricity generation in the country was 11.2%.
The development of nuclear energy began with the launch of the First Nuclear Power Plant with a capacity of 5000 kW on June 27, 1954 in the USSR in Obninsk. Its operation convincingly proved the technical feasibility of converting nuclear energy into electrical energy on an industrial scale. Humanity has the opportunity to use a new, extremely high-calorie source of energy, which in the future will allow us to sharply reduce the consumption of traditional fossil fuels for electricity generation. The possibility of creating and using materials, equipment and instruments at nuclear power plants of such quality and with such characteristics that ensure a high level of reliability and operational safety in relation to the environment, population and operating personnel was demonstrated.
After the launch of the First Nuclear Power Plant, construction of more powerful nuclear power plants began, with the goal of proving their economic competitiveness with fossil fuel power plants. This period practically ended in the 60s. Since the 70s, widespread construction of powerful nuclear power plants has begun. In 1975, the installed capacity of nuclear power plants in the world amounted to 76 GW, in 1985 - 248.6 GW, by 2000 it is expected that the installed capacity will increase to 505 GW. The pace of development of nuclear energy is determined by specific conditions and, above all, the fossil fuel resources of a particular country. In countries supplied with fossil fuels, at the first stage, the expansion of nuclear power plant capacities proceeded at a slower pace, but as nuclear power plant technology improved and their efficiency increased, they increased. Thus, if in 1975 the share of CMEA member countries accounted for about 10% of the installed capacity at nuclear power plants, then by 2000 this share will increase.
Accelerated development of nuclear energy was envisaged comprehensive program scientific and technological progress CMEA member countries until 2000.
The main prerequisites for the rapid growth of nuclear energy are as follows:
Nuclear fuel is characterized by high calorific value (the specific heat release of nuclear fuel is approximately 2X X 106 times higher than that of organic fuel). Therefore, on the basis of nuclear energy, it is possible to develop the energy base of areas deprived of their own reserves of energy raw materials, without increasing transport costs for its delivery. Such areas include the European part of the USSR, where over 60% of the population lives and over 80% of industrial products are produced. Therefore, it was in the European part that the construction of powerful nuclear power plants began on a broad front.
Another important advantage of nuclear installations is low environmental pollution under normal operating conditions. During operation, traditional power plants consume a huge amount of oxygen to burn fuel, emit fuel combustion products into the environment, including harmful substances such as nitrogen and sulfur oxides, and when operating on solid fuels, significant amounts of ash. The total production of electricity at nuclear power plants per year is currently equivalent to the combustion of 550x106 tons of coal or 350-106 tons of oil at thermal power plants. A thermal power plant with an electrical capacity of 1000 MW consumes 3-106 tons of coal per year, producing 7-106 tons of carbon dioxide, 120-103 tons of sulfur dioxide, 20X103 tons of nitrogen oxides and 750-103 tons of ash. Harmful heavy metals contained in the ash (arsenic, lead, cadmium, etc.) remain in the biosphere. The work process in nuclear power installations (NPP) is practically unrelated to the environment, with the exception of heat discharge - thermal pollution at the cold source of the cycle (cooling turbine condensers), but traditional thermal power plants(TES).
More than 30 years of experience in operating nuclear power plants around the world has shown that they can indeed be economical (on average Electric Energy, produced at nuclear power plants, is 2 times cheaper than at thermal power plants burning coal) and environmentally friendly. But the same experience shows that in re-6
As a result of violation of the rules of operation of stations, leaks of radioactive media may occur, as happened in the USA, Germany, Great Britain and in the USSR - in Chernobyl. A nuclear reactor and nuclear power plant are, in general, extremely complex technical systems that require a particularly responsible approach during design, manufacturing, and operation. As in other complex technical systems, the problem of interaction between man and machine is especially clearly highlighted here. Modern industrial facilities such as large hydraulic structures, chemical plants, gas storage facilities, nuclear fuel production and reprocessing plants, and rocket and space technology pose a high potential danger. The accident at the Chernobyl nuclear power plant, at the American Three Mile Island nuclear power plant, an explosion at a chemical plant in the Indian city of Bhopal, the death of the American space shuttle Challenger, disasters at sea and on railway showed that the problem of interaction between man and machine has not yet been fully resolved and requires tireless attention. As Academician V. A. Legasov emphasized when commenting on the causes of the Chernobyl accident, the enemy is not technology itself, but our incompetent, irresponsible handling of it. The main reason The Chernobyl accident, according to the conclusions of the government commission, was a consistent violation of a number of provisions of the operating regulations. Additionally, it was stated that the design of the reactor did not exclude the possibility of an accident due to erroneous actions of personnel. The design changes introduced after the accident eliminate the possibility of similar accidents in reactors of this type. The task has been set to create a new generation of reactors with more high level"internal" security.
The Chernobyl accident has intensified the debate about the advisability of further use of nuclear energy. Scientists various countries the world give a clear answer about the possibility of safe and economical use of nuclear energy. According to the Commission of the European Economic Community (EEC) for environmental protection, consumer protection and nuclear safety, humanity has no alternative to the development of nuclear power plants that is acceptable from an economic, environmental and energy point of view. Despite significant efforts made by the EEC to develop stringent standards for emissions of sulfur and nitrogen oxides and particulate matter, significant progress in this matter has not been achieved since 1983. The accumulation in the atmosphere of carbon dioxide and a number of other products of combustion of organic fuels by 2030 may lead to a greenhouse effect and a global temperature increase of 4.5 1 as a result, the level of the world sea will rise by 0.8 - 1.7 m. Under these conditions the need to continue construction of nuclear power plants becomes obvious.
Moreover, nuclear energy occupies such a significant place in the economies of many countries that abandoning it is simply impossible. Below are data on the share of nuclear power plants in electricity generation in some countries in 1989:
The use of nuclear energy has become one of the areas of technological progress.
The development of nuclear energy in the USSR until now has been based on two main types of nuclear reactors: pressurized water reactors in double-circuit plants and channel reactors with a graphite moderator in single-circuit plants. Both types of plants use a steam turbine cycle. Pressurized water reactors are the most common type in the world energy industry.
Pressurized water reactors can be used in double-circuit schemes with non-boiling water under pressure in the primary circuit and in single-circuit schemes with boiling water in the core. In domestic practice, mainly pressurized water reactors are used, which in stationary power engineering are called water-cooled power reactors (WWER) (Fig. B.1, B.2). The advantages of such reactors (compared to channel ones) are their greater compactness, which allows all primary circuit equipment to be sealed in a protective shell, simple communications, and simpler conditions for controlling the operation of the reactor. However, they require heavy, thick-walled, large-diameter housings operating at high pressures under conditions of irradiation with powerful neutron fluxes, the fuel is overloaded and the reactor is shut down; the possibilities for increasing the steam parameters in front of the turbine are limited; nuclear superheating of the steam is impossible.
Reactors of the VVER type have been used at nuclear power plants in our country since 1964 (Unit I Novovoronezh NPP them. 50th anniversary of the USSR). Currently, they are also successfully operated at the Kola, Rivne, Zaporozhye, Kalinin, Balakovo and other nuclear power plants in the USSR and abroad: they are also being built at a number of new nuclear power plants in the German Democratic Republic, Finland and Belarus.
A powerful impetus to the use of pressurized water reactors at domestic nuclear power plants was the creation of a specialized production association"Atommash" in Volgodonsk. After 1986 (after the Chernobyl accident), a decision was made 8
Switzerland. 41.6% France. .74.6% Belgium. . 60.8% Finland. 35.4% Germany. . . .34.3%
Czechoslovakia. . . 27.6% NRB. . . .32.9% Japan. . . 27.8% USA 19.1% USSR. . . 12.3%
Rice. IN 1. VVER-440 reactor (central hall)
on the development of domestic nuclear energy based on VVER-type reactors. At all operating units, measures were taken to increase the efficiency of emergency protection, improve accident localization systems, and increase reliability technological equipment. A design has been developed for the high-safety power unit NPP-88, which provides for additional passive safety systems. The first unit of the new project will be commissioned in 1993.
The design of a channel reactor with a graphite moderator (Fig. B.3) was proposed in the USSR in the 40s. For you-
For electricity generation, channel reactors were used at the First NPP, Siberian NPP (1958), Beloyarsk NPP
them. I.V. Kurchatov (1964), at a number of powerful nuclear power plants - Leningradskaya named after. V.I. Lenin (1973), Kursk, Smolensk, Ignalinsk, etc.
The main advantages of this type of reactor include the following:
the possibility of implementing large unit capacities; the absence of a single heavy vessel, which complicates the manufacture and transportation of the reactor
Rice. VZ. RBMK reactor (central hall)
the possibility of sectioning the reactor and creating reactors of various powers from standard factory-made sections
the possibility of nuclear superheating of steam in the reactor core, obtaining high parameters, and consequently increasing the efficiency of the cycle
Possibility of continuous fuel reloading without shutting down the reactor.
The use of channel reactors ensured a rapid increase in capacity at nuclear power plants before the launch of Atommash. In 1987, they accounted for about half of the installed capacity (13 units with a capacity of up to 1000 MW and 2 units of 1500 MW each).
Accident at Unit IV Chernobyl nuclear power plant in 1986, with the destruction of the reactor and the release of radioactive products into the environment, reactors of this type attracted the close attention of specialists and the world community. The scenario for the development of the accident, its causes and directions for improving reactors are discussed in detail in other volumes of the textbook. Here we note once again that the cause of the accident was a consistent violation of operating regulations. Under these conditions, shortcomings in the reactor design also appeared: a positive steam coefficient of reactivity, and at reduced power, a positive power coefficient of reactivity, which makes the reactor unstable at low power levels; insufficient response speed of emergency protection systems; insufficiency technical means, automatically bringing the reactor into a safe state in the event of personnel actions that do not comply with the requirements of the technological regulations.
Organizational and technical measures carried out at all operating power units with RBMK-YOO and RBMK-1500 reactors completely exclude the possibility of rapid uncontrolled acceleration of the reactor. The positive vapor coefficient of reactivity has been reduced by reducing the graphite content in the core and increasing the fuel enrichment with 235U nuclide to 2.4%. The protection response time has been reduced from 18 - 20 to 10 - 12 s. Additional absorber rods have been installed. A rapid emergency protection (BAZ) has been developed and tested at two units of the Leningrad and Ignalina NPPs, ensuring the insertion of absorber rods into the core in 2 - 2.5 s. Similar BAZ systems have been implemented since 1989 at all operating power units with channel reactors.
As a comprehensive analysis carried out by experts shows, none of the shortcomings of RBMK reactors that appeared during the accident at Unit IV of the Chernobyl nuclear power plant are irremovable in nuclear channel water-graphite reactors and are not inherent in reactors of this type.
The types of reactors considered operate on thermal neutrons, and they use 235U as a fissile nuclide (the content of which in natural uranium is about 0.7%). The prospects for the development of nuclear energy are associated with the construction of fast neutron reactors, the introduction of which into widespread operation will make it possible to use the raw material nuclide 238U. In the USSR in 1973, the world's first large fast neutron power reactor BN-350 (Fig. B.4) with an electrical power of 150 MW was launched; in the 10th Five-Year Plan, the BN-600 reactor with an electrical power of 600 MW was launched (Beloyarsk NPP). The installations are made according to a three-circuit scheme. Liquid sodium is used as the primary coolant in the reactors. Widespread use of such reactors at nuclear power plants can be expected by the end of this century - at the beginning of the next. Reactors of other types - fast and thermal neutrons with a gas coolant, thermal neutrons with an organic coolant, water-water reactors with boiling coolant (widespread abroad), etc. - were not widespread in the nuclear energy industry of the USSR.
Let us list the main trends observed in stationary nuclear energy to date.
Rice. AT 5. Increasing the unit electrical power of power units at nuclear power plants in the USSR:
K1 - First NPP K2 - I block of the Siberian NPP: KZ - II block of the Beloyarsk NPP K4 - I block of the Leningrad NPP Kb - I block of the Ignalina NPP Bl, V2, VZ, V4 - respectively I, II, III and V blocks of the Novovoronezh NPP B1 - BN-350 in Shevchenko: B2 - BN-600, Unit III at Beloyarsk NPP
1. Increasing the unit capacity of nuclear power plant units. Thus, the power of channel reactors increased from 5 MW at the First NPP to 1000 MW at the Leningrad, Kursk, Chernobyl, Smolensk NPPs and up to 1500 MW at the Ignalina NPP (Fig. B.5). The power of both VVER and fast neutron reactors is growing. Along with the increase in the power of the unit, the unit power of the equipment included in it increases - steam generators in double-circuit units, steam turbine units (the power of steam turbines at nuclear power plants is 500 and 1000 MW), pumping equipment, etc. The possibility and feasibility of further growth in the unit power of power units is discussed. There are no clear and obvious solutions on this issue yet.
2. Increasing the power of nuclear power plants. The installed capacities of nuclear power plants already reach 4000 MW (Leningrad NPP - four units of 1000 MW each). The design capacity of a number of other stations is 4000 - 6000 MW.
3. Increasing the parameters of the primary coolant and the parameters of the steam in front of the turbine. This is especially clearly seen in the example of the development of units at the Novovoronezh NPP (Fig. B.6).
4. Due to the rapid growth of the share of nuclear power plants in the energy system, the requirements for their maneuverability with the ability to change the load in the range from 100 to 50% are increasing.
The vast majority of nuclear power plants currently operate on saturated steam. At the Beloyarsk NPP, for the first time in the world, nuclear superheating of steam to 783 K was carried out, which made it possible to obtain a high efficiency (~37%). When developing the new generation RBMK-YOO channel reactors, their creators temporarily abandoned steam overheating. Broad prospects for the use of superheated steam are opening up with the use of fast neutron reactors with liquid metal as a coolant. Due to the high temperature of sodium at the outlet of the reactor, superheated steam of high parameters can be obtained.
With the development of nuclear energy, more and more attention began to be drawn to the use of power reactors for district heating purposes.

Heat from condensing stations has been used for a long time to supply heat to villages near nuclear power plants.
The most efficient from an economic point of view is the combined production of heat and electricity at the ATPP. But this will require moving closer to major industrial centers. Currently, it is considered rational to locate nuclear power plants at a distance of 20 - 40 km from large cities. In 1973, the Bilibino ATPP was commissioned. Four heating units were built on it based on channel-type reactors with a total electrical power of 48 MW with a total heat output of about 100 Gcalch (116.3 MW). Successful operating experience indicates the possibility of creating reliable and cost-effective small power nuclear power plants.
ACT are designed to produce only low parameter steam and hot water. In this regard, the parameters (pressure, temperature) of the operating circuit of the reactor installation itself are reduced, which reduces its cost and makes safety measures simpler, allowing the ACT to be brought closer to heat consumers. Currently, the first large ACTs are being built in Gorky and Voronezh with water-cooled reactors with a thermal capacity of 500 MW. Systems that limit the development of an accident and localize its consequences will be completely built on a passive principle.
Stationary nuclear power is one of the main areas of use of nuclear power plants. Another direction is to use
Rice. AT 7. Control panel for the power plant of the nuclear-powered icebreaker "Lenin"
use of nuclear power plants on naval vessels. The use of nuclear power plants makes it possible to impart qualities to ships that are unattainable when operating on fossil fuels. First of all, this is an almost unlimited cruising range when operating at high power and long-term autonomy. These qualities are especially important for icebreakers. Nuclear icebreakers, without requiring replenishment of fuel, can operate without leaving the route during the entire navigation.
In our country, since 1959, the world's first nuclear-powered icebreaker “Lenin” has been in operation (Fig. B.7). In 1975, the nuclear-powered icebreaker "Arktika" was put into operation, which opened a series of nuclear-powered icebreakers of this type (nuclear-powered icebreakers "Sibir", "Russia", " Soviet Union"). The successful operation of Soviet nuclear-powered ships clearly demonstrated the advantages of the nuclear-powered icebreaker fleet. The icebreaker Arktika became the first surface vessel to reach the North Pole.
In table B.1 are given comparative characteristics nuclear and diesel icebreakers of approximately the same time of construction.
The data presented show the advantage of nuclear icebreakers both in terms of power plant power, speed, and specific thrust.
In 1986, the first nuclear-powered lighter-container carrier "Sevmorput" with a capacity of
29.5 MW (40,000 hp) with a speed of 20 knots. The nuclear-powered ship takes on board 74 lighters, each of which is capable of carrying 350 tons of cargo. The vessel is characterized by a high degree of safety. The power plant will not be damaged, for example, if it collides with another ship or falls onto the deck of an aircraft.
Nuclear power plants are widely used on navies of highly developed countries of the world. According to foreign press data, at the beginning of the 80s, the US Navy alone operated more than 120 submarines and over 10 surface ships.
A promising area of ​​use for nuclear power plants is space technology. In the near future, power of tens, hundreds and thousands of kilowatts will be required on board space objects with a service life of 1 year or more. Such energy supply is possible only with the use of nuclear power plants, since the power of chemical sources and solar panels currently used is insufficient.
In the Soviet Union, for the first time in the world, the Topaz nuclear power plant with a power of 7 - 10 kW was developed, created and tested, in which the machineless conversion of thermal energy into electrical energy was carried out directly in a nuclear reactor.
Nuclear power plants are used on some artificial Earth satellites of the Cosmos series. For example, according to TASS, Kosmos-1402 was equipped with such an installation.
A presentation of the fundamentals of calculation and design of main and auxiliary equipment, with the exception of the reactor itself, nuclear power plants for various purposes is main task of this tutorial.

Part one
GENERAL ISSUES IN DESIGNING NUCLEAR POWER INSTALLATIONS

Chapter 1
DIAGRAMS AND COMPOSITION OF EQUIPMENT
NUCLEAR POWER INSTALLATIONS

1.1. CIRCUIT DIAGRAMS
Energy released as a result of nuclear fission heavy elements, is removed from the reactor in the form of heat. Next, the thermal energy is converted into another type of energy needed by the external consumer. A set of equipment that ensures the operation of a nuclear reactor, the removal of thermal energy from the reactor and its conversion into another type of energy constitutes a nuclear power plant (NPP).
All consumers according to the type of energy used can be divided into three groups: 1) thermal energy consumers
2) consumers of mechanical energy 3) consumers of electrical energy. Nuclear power plants can also be divided into similar groups. In the installations of the first group, thermal energy is supplied to the consumer. This includes, for example, Atom stations heat supply (ACT), thermal desalination plants, energy technology.
The installations of the second group use mechanical energy. These include transport and rocket engines. For example, on ships, a turbine unit converts thermal energy into mechanical energy, which is transmitted to the propellers using a mechanical transmission.
In installations of the third group, electrical energy is supplied to the consumer. These are primarily nuclear power plants, as well as transport installations with an electric drive or propulsion (for example, electric jet engines).
Thermal energy removed from the reactor using a special medium called coolant. Water and water vapor, liquid metals, various gases (inert or dissociating), and organic liquids are used as coolants in nuclear energy. The choice of coolant is determined by the type of reactor and the specified coolant temperature.
The units of the first group are connected to an external consumer through an end heat exchanger. Consequently, a nuclear power plant of the first type includes a nuclear reactor and an end heat exchanger (Fig. 1.1,a). They are connected to each other by a pipeline system. The coolant is moved from the reactor to the heat exchanger and back by a circulator. As the latter, depending on the properties of the coolant and its parameters, you can use pumps, gas blowers, and compressors.
In Fig. 1.1a shows a single-circuit installation. Its distinctive feature is that heat is removed from the reactor and transferred to the end heat exchanger using the same coolant (it can change its phase state, for example, evaporate during boiling in the reactor and condense in the end heat exchanger). The main advantage of single-circuit installations is the simplicity of the thermal circuit. However, the coolant leaving the reactor may have high induced activity, and in some cases contain radioactive fission products. Therefore, the entire circuit, including the end heat exchanger, must have reliable biological protection. In the end heat exchanger, thermal energy is transferred to the consumer directly from the radioactive coolant. In principle, there is a possibility of radioactive products entering the consumer’s working environment in the event of a heat exchanger de-sealing. Therefore, single-circuit installations cannot be used in cases where the possibility of radioactive contamination must be excluded in principle, including in emergency situations. From this point of view, conditions in multi-circuit installations are more favorable.
In Fig. 1.1.6 given circuit diagram double-circuit installation. Her distinctive feature consists in the fact that heat is removed from the reactor and transferred to an external consumer using two different coolants that are not in direct contact. Heat transfer from one coolant to another occurs in an intermediate heat exchanger (HE). The reactor and the PT with the piping system form the first closed circuit, and the PT, the end heat exchanger and piping form the second. Each circuit has its own circulator. Between the first PT and the end heat exchanger, another PT can be connected, once again separating the coolant, then the nuclear power plant is a three-circuit one.
The multi-circuit circuit practically eliminates contact of the radioactive coolant with the consumer’s working environment. In addition, in a multi-circuit installation, coolants for the first and subsequent circuits can be selected with different optimal properties for operation in the reactor and in the end heat exchanger. The design of a multi-circuit nuclear power plant is more complex than a single-circuit nuclear power plant, since additional equipment is required: PT, circulators, pipelines, etc.
In installations of the second group, mechanical energy is given to the consumer. In Fig. 1.2, a, c show schematic diagrams of steam turbine single- and double-circuit transport units with a turbo-gear unit (TPA). In a single-circuit plant, saturated or superheated steam is produced in the reactor. Steam enters the flow part of the turbine, where, when it expands, thermal energy is converted into mechanical (kinetic) energy of the steam flow, which rotates the turbine rotor, its rotational energy is transmitted through the gearbox to the ship's propellers. The turbine and gearbox form the TPA. The steam leaving the turbine is condensed in a condenser, and the condensate is returned to the reactor using a pump (circulator). The medium used to convert thermal energy into mechanical energy is usually called the working fluid. Thus, in a single-circuit installation, the same medium is both the coolant and the working fluid. And these concepts are equivalent. In double-circuit (multi-circuit) installations operating in a steam turbine cycle, steam is generated in a special steam generator 7 (Fig. 1.2, c).
Rice. 1.2. Single-circuit (c, b) and double-circuit (c) nuclear power plants for mechanical energy consumers:
- nuclear reactor 2 - turbine 3 - condenser 4 - circulator 5 - tank b - nozzle 7 - steam generator 8, 9 - circulators of the primary and secondary circuits
The steam generator is heated by the primary coolant in a similar way to the previously discussed installations for thermal energy consumers.
In single-circuit gas turbine plants (GTUs) and in the second circuit of double-circuit gas turbine plants, non-condensable gases, such as helium, are used as a working fluid. The schematic diagrams are similar to those with a steam turbine cycle, but the equipment is designed to operate on gas. The TZA includes a gas turbine, an end cooler is used instead of a condenser, a compressor plays the role of a circulator, and instead of a steam generator in a dual-circuit circuit, a heat exchanger should be used to heat the gas.
The installations of the second group also include nuclear rocket engines with jet propulsion (Fig. 1.2,6). The working fluid from the tank is fed through a circulator into a nuclear reactor, where it is gasified and “heated to significant temperatures (2500 - 3000 K). Upon exiting the reactor, the working fluid expands in a supersonic nozzle, while thermal energy is converted into kinetic energy of the flow. The flow leaves the nozzle, forming rocket thrust. To drive the circulator, a part of the working fluid is used, which after the reactor is sent to a special drive turbine.
In installations of the third group, thermal energy is ultimately converted into electrical energy. They can be divided into installations: with thermionic converters (TEC), with a thermoelectric generator (TEG), with a magnetohydrodynamic (MHC) generator, with a machine-type electric generator.
In a TEC installation, the thermal energy of the reactor is used to heat the cathode. TEP can be either remote (Fig. 1.3,a) or built into a nuclear reactor. In the latter case we talk about reactor-generators. The use of generator reactors is one of the promising directions nuclear energy, especially space. However, at present they have insufficient operating life and relatively low efficiency (about 10 - 15%).
In installations with TEG, the thermal energy of the reactor is used to heat the hot junctions of dissimilar electrodes (Fig. 1.3,6). In a circuit containing hot and cold junctions of dissimilar conductors, an electric current arises, which is given to the consumer. Just like TEC, TEG can be remote or built into the reactor. The main area of ​​application of TEGs is low-power space installations (the achieved efficiency does not exceed 3%). In installations with an MHD generator, the phenomenon of excitation of electric current when a conductor moves in a magnetic field is used, while the role of the conductor is played by one heated in the reactor to high temperatures flow of ionized gas. In the reactor (Fig. 1.3c), the gas is heated to a temperature of ~3000 K, and ionizing additives are introduced into the working fluid to increase the degree of ionization. Upon exiting the MHD generator, the gas is returned to the reactor by a circulator. Until now, the issue of industrial use of installations with an MHD generator cannot be considered resolved. Their main disadvantages are the relatively low efficiency (~10%) and the bulkiness of the equipment.
The main way to obtain electricity in a nuclear power plant is the use of machine-type electric generators with a mechanical drive from a steam turbine, or less often from a gas turbine.
Thermal energy of the coolant in the flow part steam turbine when it expands, it is converted into mechanical (kinetic) energy of the steam flow, which is used to rotate the turbine rotor of the electric generator. The exhaust steam behind the turbine is condensed and returned in the form of feed water to the reactor (single-circuit diagram, Fig. 1.3,d) or to the steam generator (double-circuit scheme, Fig. 1.3,2).
In a single-circuit gas turbine installation, gas (helium, carbon dioxide etc.) is heated in the reactor and sent to the gas turbine, where, when it expands, mechanical energy is released and transferred to the turbine rotor. Upon exiting the turbine, the gas is cooled into regenerative-22
heat exchanger and end cooler and enters the compressor, where it is compressed to a given pressure. After the compressor, the gas, passing through a regenerative heat exchanger, is heated by cooling the gas leaving the turbine and enters the reactor core for heating. The mechanical energy of rotation of the gas turbine rotor is used partly to drive the compressor, and mainly goes to drive the electric generator. In real installations, the compressor and generator are often driven by different turbines.
The considered circuit diagram refers to a closed-cycle gas turbine unit. In traditional energy, the most common is an open cycle using fuel combustion products in air as a working fluid. In this case, the exhaust gas after the turbine is discharged into the atmosphere and fresh air is sucked from the atmosphere into the compressor. In single-circuit nuclear power plants, an open cycle is unacceptable due to radiation safety conditions. In multi-circuit installations, the gas is heated in an intermediate heat exchanger, so an open cycle can also be used.
Gas turbines become competitive with steam turbine plants when using gas with a temperature in front of the turbine of more than 1100 K. Such temperatures are just being mastered in nuclear power reactors.
All types of installations considered include a nuclear reactor - a source of energy, heat exchange equipment for transferring heat from one coolant to another or an external consumer, connecting communications (pipelines) and machinery for various purposes (circulators - machines-tools for transferring energy to the coolant or working fluid and motor machines for converting thermal energy working environment to mechanical).
The operating conditions of installations and the requirements for them vary significantly depending on the purpose. Thus, for stationary nuclear power plants, the main requirements are reliability and high efficiency during long-term operation (design service life 30 years). For ship installations, in addition to the specified requirements, the weight and size ratio of the equipment and ensuring the safe operation of the equipment in the limited volumes of the vessel become essential. The design service life can be reduced, and there is a requirement for high maneuverability of the installation. For space nuclear power plants, while maintaining the requirements for reliability and efficiency, even more stringent requirements appear for weight and size ratios with a relatively short service life, as well as for stability under large mechanical loads. Below we will dwell in more detail on the necessary composition and operating conditions of the main equipment of stationary, ship and space nuclear power plants.
END OF PARAGMEHTA BOOKS

The principle of operation and design of power reactors under pressure.

Nuclear power plants (NPP). Currently, the issue of widespread use of nuclear fuel in ship power plants is becoming increasingly relevant. Interest in ships with nuclear power plants especially increased in 1973-1974, when, as a result of the global energy crisis, prices for fossil fuels sharply increased. The main advantage of ships with nuclear power plants is their virtually unlimited cruising range, which is very important for icebreakers, Arctic vessels, research vessels, hydrographic vessels, etc.

The daily consumption of nuclear fuel does not exceed several tens of grams, and the fuel elements in the reactor can be changed once every two to four years. NPP at transport ships, especially on those that make long-distance voyages at high speed, allows you to significantly increase the vessel's carrying capacity due to the almost complete absence of fuel reserves (this gives a greater gain than losses due to the significant mass of the nuclear power plant). In addition, the nuclear power plant can operate without air access, which is very important for underwater vessels. However, the fuel consumed by nuclear power plants is still very expensive. In addition, on ships with nuclear power plants it is necessary to provide special biological protection from radioactive radiation, which makes the installation heavier. It must be assumed that progress in the development of nuclear technology and in the creation of new designs and materials will make it possible to gradually eliminate these shortcomings of ship nuclear power plants.

All modern ship nuclear power plants use the heat released during the fission of nuclear fuel to form steam or heat gases, which then enter the steam or gas turbine. The main link of the nuclear steam generating plant APPU reactor, in which a nuclear reaction occurs. Various fissile substances are used as nuclear fuel, in which the process of nuclear fission is accompanied by the release of a large amount of energy. These substances include isotopes of uranium, plutonium and thorium.

Rice. 6.1. Nuclear reactor diagram.

1- active zone; 2 -- uranium rods; 3 - moderator; 4 - reflector; 5 - coolant; 6 - biological protection; 7 - heat shield; 8 - regulation system

The most important elements of ship reactors are (Figure 6.2) active zone, in which uranium rods and a moderator are located, necessary to absorb the energy of neutron particles released during the decay of nuclei; neutron reflector, returning part of the neutrons emitted outside the core to the core; coolant to remove heat released during the fission of uranium from the core and transfer this heat to another working fluid in a heat exchanger; biological protection screen, preventing the spread of harmful radiation from the reactor; control and protection system, regulating the course of the reaction in the reactor and stopping it in the event of an emergency increase in power.

The moderator in nuclear reactors is graphite, heavy and ordinary water, and the coolant is liquid metals with a low melting point (sodium, potassium, bismuth), gases (helium, nitrogen, carbon dioxide, air) or water.

Reactors in which both the moderator and coolant are distilled water have become widespread in ship nuclear power plants, hence their name. pressurized water reactors. These reactors are simpler in design, more compact, more reliable in operation than other types, and cheaper. Depending on the method of transferring thermal energy from the reactor to the actuator (turbine), single-circuit, double-circuit and three-circuit nuclear power plant schemes are distinguished.

By single-circuit diagram(Fig. 6.2, A) the working substance - steam - is formed in the reactor, from where it enters directly into the turbine and from it through the condenser with the help of a circulation pump returns to the reactor.

By double-circuit circuit(Fig. 6.2, b) The coolant circulating in the reactor gives up its heat in a heat exchanger - a steam generator - to water, which forms steam, which enters the turbine. In this case, the coolant is passed through the reactor and steam generator by a circulation pump or blower, and the condensate formed in the turbine condenser is pumped by a condensate pump through the heating, filtration and make-up system and again supplied to the steam generator by the feed pump.

Three-circuit scheme(Fig. 6.2, V) is a double-circuit circuit with an additional intermediate circuit connected between the first and second circuits.

The single-circuit design requires biological protection around the entire circuit, including the turbine, which complicates maintenance and control and increases the danger for the crew. The double-circuit circuit is safer, since here the second circuit is no longer dangerous for I crew. Therefore, dual-circuit circuits are almost always used on nuclear ships. Three-loop circuits are used if the coolant in the reactor is highly activated and it must be carefully separated from the working substance, which is what the intermediate loop is designed for.

Rice. 6.2. Thermal diagrams of nuclear power plants:

A- single-circuit; b- double-circuit; V- three-circuit.

1 -reactor; 2 - turbine; 3 - capacitor; 4 - circulation pump; 5 - steam generator; 6 - condensate pump; 7 - filtration and recharge heating system; 8 - feed pump; 9 - heat exchanger; 10 - biological protection

Operating principle and design of power reactors. On ships with nuclear power plants, the main source of energy is a nuclear reactor. The heat released during the fission of nuclear fuel serves to generate steam, which then enters the steam turbine.

The reactor plant, like a conventional steam boiler, contains pumps, heat exchangers and other auxiliary equipment. A special feature of a nuclear reactor is its radioactive radiation, which requires special protection for operating personnel.

Safety. Massive biological protection has to be installed around the reactor. Common radiation shielding materials are concrete, lead, water, plastics and steel.

There is a problem of storing liquid and gaseous radioactive waste. Liquid waste is stored in special containers, and gaseous waste is absorbed by activated charcoal. The waste is then transported ashore to recycling facilities.

Ship nuclear reactors. The main elements of a nuclear reactor are rods with fissile material (fuel rods), control rods, coolant (coolant), moderator and reflector. These elements are enclosed in a sealed housing and arranged to ensure a controlled nuclear reaction and removal of the generated heat.

The fuel can be uranium-235, plutonium, or a mixture of both; these elements can be chemically bonded with other elements and be in the liquid or solid phase. Heavy or light water, liquid metals, organic compounds or gases are used to cool the reactor. The coolant can be used to transfer heat to another working fluid and produce steam, or it can be used directly to rotate the turbine. The moderator serves to reduce the speed of the neutrons produced to a value that is most effective for the fission reaction. The reflector returns neutrons to the core. The moderator and reflector are usually heavy and light water, liquid metals, graphite and beryllium.

On all naval vessels, on the first nuclear icebreaker“Lenin”, on the first cargo and passenger ship “Savanna” there are power plants made according to a dual-circuit scheme. In the primary circuit of such a reactor, water is under pressure up to 13 MPa and therefore does not boil at a temperature of 270 0 C, usual for the reactor cooling path. Water heated in the primary circuit serves as a coolant for producing steam in the secondary circuit.

Liquid metals can also be used in the primary circuit. This scheme was used on the US Navy submarine Sea Wolf, where the coolant is a mixture of liquid sodium and liquid potassium. The pressure in the system of such a scheme is relatively low.

The same advantage can be realized by using paraffin-like organic substances - biphenyls and triphenyls - as a coolant. In the first case, the disadvantage is the problem of corrosion, and in the second, the formation of resinous deposits.

There are single-circuit schemes in which the working fluid, heated in the reactor, circulates between it and the main engine. Gas-cooled reactors operate using a single-circuit design. The working fluid is a gas, for example helium, which is heated in a reactor and then rotates a gas turbine.

Protection. Its main function is to protect the crew and equipment from radiation emitted by the reactor and other elements that come into contact with radioactive substances. This radiation is divided into two categories: neutrons, released during nuclear fission, and gamma radiation, produced in the core and in activated materials.

In general, ships have two containment shells. The first is located directly around the reactor vessel. Secondary (biological) protection covers steam generating equipment, cleaning systems and waste containers. The primary shield absorbs most of the reactor's neutrons and gamma radiation. This reduces the radioactivity of reactor auxiliary equipment.

Primary protection can be a double-shell sealed tank with a space between the shells filled with water and an outer lead shield 2 to 10 cm thick. Water absorbs most of the neutrons, and gamma radiation is partially absorbed by the walls of the housing, water and lead.

The main function of the secondary protection is to reduce the radiation of the radioactive nitrogen isotope 16N, which is formed in the coolant passing through the reactor. For secondary protection, water containers, concrete, lead and polyethylene are used.

Efficiency of ships with nuclear power plants. For warships, the cost of construction and operating costs are less important than the advantages of an almost unlimited cruising range, greater power and speed of ships, compact installation and reduction of maintenance personnel. These advantages of nuclear power plants have led to their widespread use on submarines. The use of atomic energy on icebreakers is also justified.

Self-test questions:

What is the source of energy for nuclear power plants?

What is a double shell sealed tank?