Nuclear power plants are the main types of nuclear reactors. How a nuclear power plant works

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

In fact, the same process is going on there as in a nuclear explosion. Only now the explosion occurs very quickly, and in the reactor all this stretches for a long time. In the end, everything remains safe and sound, and we get energy. Not so much that everything around immediately smashed, but quite enough to provide electricity to the city.

Before you can understand how a controlled nuclear reaction works, you need to know what nuclear reaction at all.

nuclear reaction - this is the process of transformation (fission) of atomic nuclei during their interaction with elementary particles and gamma quanta.

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

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

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

The history of the creation of a nuclear reactor

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

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

The principle of operation of a nuclear (atomic) reactor

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

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

As we have already said, the decay of a heavy uranium nucleus produces lighter elements and a few neutrons. The resulting neutrons collide with other nuclei, also causing them to fission. In this case, the number of neutrons grows like an avalanche.

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

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

How is a nuclear reactor started?

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

Critical mass is the mass of fissile material necessary to start a nuclear chain reaction.

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

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

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Nuclear power plants (NPPs) can be condensing, heating plants (ATES), as well as nuclear heat supply plants (ACT) and nuclear industrial heat supply plants (ACPT). Nuclear power plants are built according to the block principle, both in the thermal and electrical parts.
Nuclear reactors of nuclear power plants are classified according to various criteria. According to the level of neutron energy, reactors are divided into two main classes: thermal (using thermal neutrons) and fast (using fast neutrons). According to the type of neutron moderator, reactors are water, heavy water, graphite, and according to the type of coolant - water, heavy water, gas, liquid metal. Water-cooled reactors are also classified according to their design: vessel and channel.
From the point of view of the organization of equipment repair, the classification according to the number of circuits is of the greatest importance for nuclear power plants. The number of circuits is chosen taking into account the requirements for ensuring the safe operation of the unit in all possible emergency situations. An increase in the number of circuits is associated with the appearance of additional losses in the cycle and, accordingly, a decrease in the NPP efficiency.
In the system of any nuclear power plant, a coolant and a working fluid are distinguished. The working body, i.e. the medium that does the work, converting thermal energy into mechanical energy, is water vapor. The purpose of the coolant at nuclear power plants is to remove the heat released in the reactor. If the circuits of the coolant and the working fluid are not separated, the NPP is called single-circuit (Fig. 1).

Fig.1. NPP thermal scheme:
a - single-circuit; b - double-circuit; in - three-circuit; 1 - reactor; 2 - turbine; 3- turbogenerator; 4- condensing unit; 5- condensate pump; b - system of regenerative heating of feed water; 7 - feed pump; 8 - steam generator; 9 - circulation pump of the reactor circuit; 10 - intermediate circuit circulation pump

In single-circuit schemes, all equipment operates in radiation-active conditions, which complicates its repair. NPPs with RBMK-1000 and RBMK-1500 type reactors operate according to a single-loop scheme.
If the circuits of the coolant and the working fluid are separated, then the nuclear power plant is called a double-circuit one. Accordingly, the coolant circuit is called the first, and the working fluid circuit is called the second. In such schemes, the reactor is cooled by a coolant pumped through it, and the steam generator is cooled by the main circulation pump. The coolant loop formed in this way is radioactive, but it does not include all the plant equipment, but only part of it. The second circuit includes equipment that operates in the absence of radiation activity - this simplifies equipment repair. At a double-circuit station, a steam generator is required, which separates the first and second circuits.
NPPs with reactors of the VVER-440 and VVER-1000 types operate according to the two-loop scheme. There are coolants that interact intensively with steam and water. This may create a risk of release of radioactive substances into the serviced premises. Such a coolant is, for example, liquid sodium. Therefore, an additional (intermediate) circuit is created in order to avoid contact of radioactive sodium with water or water vapor even in emergency conditions. Such nuclear power plants are called three-loop. NPPs with reactors of the BN-350 and BN-600 types operate according to the three-circuit scheme. At present, power units with a capacity of 350–1500 MW with reactors of the VVER-440, VVER-1000, RBMK-1000, RBMK-1500, BN types are mainly installed at nuclear power plants. -350 and BN-600. The main characteristics of the reactors are given in Table. one.

Table 1. Main characteristics of nuclear power plant reactors

Nuclear power plants where reactors are installed: VVER-440 - Rovno and others; VVER-1000 - Zaporozhye, Balakovo, Novovoronezh, Kalinin, South-Ukrainian, etc.; RBMK-1000 - Leningrad, Chernobyl, Kursk, Smolensk, etc.; RBMK-1500 - Ignalina; BN-350 - Shevchenkovskaya; BN-600 - Beloyarskaya.
A pressurized water power reactor (VVER) is a vessel-type reactor. Moderator and coolant - pressurized water. The working fluid at nuclear power plants with VVER reactors is water vapor.
Reactor high power boiling water (RBMK) is a channel reactor, in which graphite serves as a moderator, and water and a steam-water mixture serve as a coolant.
In fast neutron reactors, sodium is the coolant of the primary and secondary circuits, thereby eliminating the possibility of contact of radioactive metal with water. On fig. 2 shows a schematic process diagram of a nuclear power plant with VVER. Thermal energy from the reactor core 5 to steam generator 1 is transferred by water circulating under pressure created by MCP 2. The VVER-1000 reactor has four main circulation circuits (one circuit is conventionally shown in Fig. 2) and the same number of MCPs.


Rice. 2. Simplified process flow diagram of a nuclear power plant with a water-cooled power reactor:
1 - steam generator; 2 - main circulation pump (MCP); 3 - volume compensator; 4 - hydraulic accumulator of the emergency cooling system; 5 - reactor; 6 - installation of special water treatment; 7 - pump for normal make-up and boron regulation; 8 - heat exchanger and pump for cooling the pool of fuel elements (fuel rods); 9 - emergency supply tanks of boron solution of the ECCS system of normal and high concentration; 10 - reactor cooldown heat exchanger; 11 - sprinkler pumps; 12 - pumps for emergency cooling of low and high pressure; 13, 15 - emergency and working pumps for pumping boron concentrate; 14 - tank of boron concentrate; 16 - steam turbine; 17 - separator-superheater; 18 - high-speed reduction units (BRU) for steam release; 19 - generator; 20 - oil cooler; 21, 22 - gas cooler and its pump; 23 - process water pump; 24 - turbine circulation pump; 25 - capacitor; 26, 28 - condensate pumps of the first and second stages; 27- condensate cleaning; 29 - low pressure heater; 30 - nutrient turbopump; 31 - sand reserve feed electric pump; 32 - cooling pump; 33 - deaerator; 34 - high pressure heater; 35 - feed water storage tank; 36 - emergency feed pump; 37 - pumps for draining the coolant of the I circuit

To maintain a certain steam pressure above the water level, a volume compensator 3 with electric heating is installed in the reactor circuit, which ensures the evaporation of water in the volume compensator.
NPP safety is ensured by normal operation systems, containment systems and the reactor core emergency cooling system (ECCS). The containment system and the ECCS must ensure the non-proliferation of radioactivity outside the hermetically sealed rooms of the NPP under all normal and emergency modes. Emergency cooling of the reactor is provided by three independent systems. One of these systems consists of emergency boron solution tanks 9, cooldown heat exchanger 10, sprinkler pump 11, low and high pressure emergency cooldown pumps 12. In the event of depressurization of the reactor circuit and a small leak, pumps 12 are switched on, supplying the borated solution to the circuit. At the maximum design basis accident (MPA) - a rupture of the main circulation circuit and a pressure drop in the reactor, water is supplied to the volume above the core and below it from the pumped storage tanks 4. This should prevent boiling of water in the reactor. At the same time, borated water is supplied to sprinkler installations and to the reactor circuit. In the water jets of the sprinkler system, the steam condenses and pressure build-up in the containment is prevented. The water flowing into the pits is cooled in heat exchangers 10 and re-injected into the circuit and sprinkler installations until the reactor is completely cooled.
The feed of the primary circuit in normal mode is carried out by pumps 7 from the deaerator of the primary circuit. At low flow rates, boron-containing water is supplied by pumps 13 and 15.
There is a heat exchanger and a pump 8 to cool the water in the pool for reloading and holding fuel elements (fuel elements). Pumps 37 are necessary to ensure the circulation of the coolant through the heat exchanger and special water treatment.
With the help of the reactor control and protection system (CPS), the reactor is started and shut down, the output and automatic maintenance of power and the alignment of the energy release fields over the volume of the core are carried out. The reactor is controlled and protected by moving neutron absorbers in the reactor core using the controls.
The technological scheme of the second non-radioactive circuit of the NPP is in many respects similar to the scheme of the CES.
Structurally, the reactor compartment with the VVER-1000 reactor consists of a sealed part - the shell and a non-pressurized part - the lining. The main equipment is located in the sealed part: a reactor, a steam generator, an MCP, a volume compensator, main circulation pipelines, ECCS tanks, etc. To ensure the necessary degree of safety, equipment and communications with a high-pressure radioactive coolant, which, when the circuit is decompressed, releases radioactive fission fragments to the outside, enclosed in a sealed envelope. The shell retains the radioactive products of the accident inside the room without worsening the over-permissible limit of the radiation situation outside the reactor shell.
The layout of NPP power units with VVER-1000 reactors is based on the principle of modular layout, i.e. Each power unit provides for all systems that ensure the radiation and nuclear safety of the power unit, as well as emergency shutdown, cooldown, residual heat removal and a set of post-accident measures, regardless of the operating mode of the other power units. General plant systems required to ensure the operation of power units in normal operation modes are separated into separate NPP facilities.
The sealed part has a cylindrical shape and consists of two volumes - upper and lower, which are connected by air. The upper part is covered with a spherical dome. In the upper part of the shell, equipment of the reactor plant, primary coolant purification systems, transport and technological equipment and ventilation systems are installed.
The lower cylindrical part of the shell is coaxial with the upper cylinder and rests on the foundation plate of the reactor compartment. In this part, the ventilation chambers of the pipelines of the emergency cooling system of the reactor, the cooling system of the reactor shaft, etc. were installed.
The non-pressurized part of the reactor compartment has the shape of a square in plan, which encloses the circumference of the shell. The premises are equipped with block technological systems, which, according to the functional purpose of the technological processes, should be located in the strict regime zone. The reactor compartment is a strict regime zone. In the premises of the reactor compartment, personnel may be exposed to external 0- and -7 radiation, air pollution with radioactive gases and aerosols, surface contamination building structures and equipment with radionuclides or radioactive substances.
At NPPs with VVER-1000 reactors, the premises of the free regime zone include: the machine room, where the K-1030-60/1500 or K-1000-60/1500 turbine and the TVV-1000-4UZ turbine generator are installed, the supply 42 ventilation center, block shields controls and other equipment, i.e. premises in which personnel are not directly involved in work with sources of ionizing radiation. In the free regime zone, the impact on personnel of ionizing radiation is practically excluded.
When assessing the level of radiation in NPP premises, the main factor of radiation exposure is the flux of ionizing radiation penetrating the biological protection, mainly the flux of 7-radiation. In all areas of the NPP, ventilation systems ensure acceptable concentrations of radioactive substances in the inhaled air.

How does a hydroelectric power plant, for example, work? Everything is simple here. A dam is being built, a large body of water is created, and pressurized water flows turn the shaft of a generator that generates electricity. How are wind farms arranged? Everything is much easier here! The wind turns large blades that rotate the generator shaft, electricity is produced. And what is the principle of operation of a nuclear power plant? It turns out that most people do not understand at all how they get electricity using nuclear reactors. For many, it's like some kind of magic, something like this happens in a nuclear reactor, from where an electric current is obtained.

I think that this is unfair, people should know how nuclear power plants work, because everything is much simpler and clearer than it might seem. I will tell you about the principles of operation of nuclear energy using the example of the Novovoronezh NPP.

So, the nuclear power plant from the outside looks like many industrial enterprises with technical buildings, taps and pipes. A notable difference lies in the large cooling towers, from which large puffs of steam emerge. Although there are cooling towers at conventional thermal power plants, so nuclear power plants can easily be overlooked.

We turn to the most famous part of the nuclear power plant from films and photographs - the control panel.
This is a block control panel of the 4th power unit of the Novovoronezh nuclear power plant, launched in 1972. It uses a VVER-440 reactor with a capacity of 400 MW.

Novovoronezh NPP is one of the first nuclear power plants in the USSR and the world's first nuclear power plant with a water-cooled power reactor. The nuclear power plant supplies about 20 enterprises and more than 2 million inhabitants of the Central Black Earth region, and also provides 85% of the Voronezh region with electricity.

The well-known "round thing with diamonds" is a section of the reactor core. Control rods are shown in red, fuel assemblies are shown in white. In short and roughly, a nuclear reactor is a large vertical cylinder, inside which are nuclear fuel rods and control rods.

Units 3 and 4 were built in the early 1970s and were supposed to be completed in the early 2000s, but later their service life was extended. Since last year, active modernization has been carried out.

In total, there were 6 power units in the history of the Novovoronezh station, the first of which was launched in 1964, and the sixth in 2016. The seventh power unit is currently under construction, and the first and second have already been decommissioned.

The topmost part of the reactor, the lid resembles a large bell, and the rods themselves are deep below. This is the reactor compartment of the 3rd and 4th power units, and such an observation deck exists only at the Novovoronezh NPP. Yes, this is exactly what a nuclear reactor looks like from the outside.
Slightly behind the lid is a core changer that drives up from above when the lid is opened and does the work inside.

Block control panel of the 5th power unit, built in 1980. It uses a VVER-1000 reactor with a capacity of 1000 MW.

The power unit was supposed to be decommissioned in 2010, but later the deadline was extended.
Since 1995, Novovoronezh NPP has been modernizing power units to bring them in line with modern standards security.

Since the power unit and control panel are newer, the section of the reactor core is also displayed not in analog form, but on a computer monitor in real time. Temperature and many other parameters can be observed.

The most important button that completely turns off the reactor when the most terrible emergencies. We wish the NPP employees that such accidents never happen, and that this button always remains sealed.

In many places and premises of the station there are special devices that measure the level of radiation - Geiger counters or dosimeters.

The fifth power unit of the Novovoronezh NPP looks like a cylinder from the outside. Inside the unusual building is the nuclear reactor itself, surrounded by a special protective cylindrical shell of reinforced concrete. After repair and modernization in 2011, it was put into operation again, its capacity is 1000 MW.

And now the main question: why do we need a reactor at all, how does electricity come from all this?
In reality, everything turns out to be not as “magical” as one would probably like. A nuclear reactor is actually a large boiler that heats water.

After heating, the water is sent to another closed circuit with water, which is already turning into steam. This steam turns a large turbine that drives a generator that generates electricity.

In general, everything is simple: the reactor heats up, water / steam turns the generator, electricity is obtained.
Machine room of the 5th power unit.

The heated water must be further directed and cooled somewhere, for this they came up with entire cooling towers - cooling towers. Water is pumped up by the pump, and then falls down, breaking up into small droplets in the sprinkler. A stream of air is supplied from below, which evaporates part of the water, and part simply cools and falls down.
These are the cooling towers of the 3rd and 4th power units with a height of 95 meters.

The complete switchgear is designed for receiving, distributing and transmitting electricity. Roughly speaking, a large transformer. Power lines are located inside special pipes, everything is reliable and safe.
This is the switchgear of the sixth power unit of the Novovoronezh NPP.

The central control panel of the 6th power unit, which is this moment is the most powerful nuclear power industry in Russia - 1200 MW. Built on safety technologies that have become relevant after the Fukushima accident. Type of nuclear reactor VVER-1200.

The sixth power unit from the street does not look as infernal as the fifth cylinder, but you can recognize it by the upper part with pipes. In August 2016, the power unit was connected to the grid and delivered the first 240 MW to the power system. At the moment, this is the most high-tech power unit in Russia that meets the most modern requirements for reliability and safety.

Spray pools of the 6th unit, which are needed to cool the reactor consumption systems. In the background is the building of the sixth power unit, cooling towers of the 6th and the 7th power unit under construction, and the construction itself.

The seventh power unit will be the twin of the sixth, the completion of construction is scheduled for 2018. The power unit will be resistant to earthquakes, hurricanes, floods, explosions, even aircraft crashes. Type of reactor VVER-1200.

Turbine hall of the 6th power unit.

The service life of the unit's main equipment is now 60 years, and not 30 years, as it was at the old power units.

The cooling towers of the 6th and 7th power units are much larger and higher than the old ones, their height is 171 meters.

Now, instead of two cooling towers per power unit, one is used, but larger. This made it possible to reduce the area of ​​the nuclear power plant itself and reduce the cost of materials and funds.

Control point of the 6th power unit. The power unit is scheduled to be put into full commercial operation at the end of 2016 after various tests.

Many thanks in person

One of the most global problems humanity is energy. Civilian infrastructure, industry, the armed forces - all this requires a huge amount of electricity, and a lot of minerals are allocated annually to generate it. The problem is that these resources are not endless, and now, while the situation is more or less stable, we need to think about the future. Great hopes were placed on alternative, clean electricity, however, as practice shows, the end result is far from desired. The costs of solar or wind power plants are huge, and the amount of energy is minimal. And that is why now nuclear power plants are considered the most promising option for further development.

NPP history

The first ideas regarding the use of the atom to generate electricity appeared in the USSR around the 40s of the XX century, almost 10 years before the creation of their own weapons of mass destruction on this basis. In 1948, the principle of operation of nuclear power plants was developed and at the same time it was possible for the first time in the world to power devices from atomic energy. In 1950, the United States completes the construction of a small nuclear reactor, which at that time can be considered the only power plant of this type on the planet. True, it was experimental and produced only 800 watts of power. At the same time, the foundation was being laid in the USSR for the world's first full-fledged nuclear power plant, although after commissioning it still did not produce electricity on an industrial scale. This reactor was used more to hone the technology.

From that moment began the mass construction of nuclear power plants around the world. In addition to the traditional leaders in this "race", the USA and the USSR, the first reactors appeared in:

• 1956 - UK.
• 1959 - France.
• 1961 - Germany.
• 1962 - Canada.
• 1964 - Sweden.
• 1966 - Japan.

The number of nuclear power plants being built was constantly increasing, until the Chernobyl disaster, after which construction began to freeze and gradually many countries began to abandon nuclear energy. At the moment, new such power plants appear mainly in Russia and China. Some countries that previously planned to switch to another type of energy are gradually returning to the program, and another jump in the construction of nuclear power plants is possible in the near future. This is an obligatory stage in the development of mankind, at least until other efficient options for energy production are found.

Features of nuclear energy

The main plus is the generation of a huge amount of energy with minimal cost fuel with virtually no contamination. The principle of operation of a nuclear reactor at a nuclear power plant is based on a simple steam engine and uses water as the main element (not counting the fuel itself), therefore, from an environmental point of view, the harm is minimal. The potential danger of power plants of this type is greatly exaggerated. The causes of the Chernobyl disaster have not yet been reliably established (more on that below), and moreover, all the information collected as part of the investigation made it possible to modernize the existing stations, eliminating even the unlikely options for radiation emissions. Ecologists sometimes say that such stations are a powerful source of thermal pollution, but this is also not entirely true. Indeed, hot water from the secondary circuit enters water bodies, but most often their artificial versions are used, created specifically for this, and in other cases, the share of such a temperature increase cannot be compared with pollution from other energy sources.

Fuel problem

Not the last role in the popularity of nuclear power plants is played by fuel - uranium-235. It requires much less than any other species with a simultaneous huge release of energy. The principle of operation of a nuclear power plant reactor implies the use of this fuel in the form of special “pills” placed in rods. In fact, the only difficulty in this case is to create just such a form. However, in Lately information begins to appear that the current world reserves will also not be enough for a long time. But this is already provided. The newest three-loop reactors run on uranium-238, which is very plentiful, and the fuel shortage problem will disappear for a long time.

The principle of operation of a double-circuit nuclear power plant

As mentioned above, it is based on a conventional steam engine. In short, the principle of operation of a nuclear power plant is to heat water from the primary circuit, which in turn heats the water of the secondary circuit to a state of steam. It protrudes into the turbine, rotating the blades, causing the generator to generate electricity. The “waste” steam enters the condenser and turns back into water. Thus, a practically closed cycle is obtained. In theory, all this could work even easier, using only one circuit, but this is already really unsafe, since the water in it, in theory, can be contaminated, which is excluded when using the system standard for most nuclear power plants with two water cycles isolated from each other.

The principle of operation of a three-loop nuclear power plant

These are already more modern power plants that operate on uranium-238. Its reserves make up more than 99% of all radioactive elements in the world (hence the huge prospects for use). The principle of operation and design of a nuclear power plant of this type is already in the presence of as many as three circuits and the active use of liquid sodium. In general, everything remains about the same, but with minor additions. In the primary circuit, heated directly from the reactor, this liquid sodium circulates at a high temperature. The second circle is heated from the first and also uses the same liquid, but not as hot. And only then, already in the third circuit, water is used, which is heated from the second to the state of steam and rotates the turbine. The system turns out to be more complex technologically, but it is necessary to build such a nuclear power plant only once, and then it remains only to enjoy the fruits of labor.

Chernobyl

The principle of operation of the Chernobyl nuclear power plant is believed to have become the main cause of the disaster. Officially, there are two versions of what happened. One by one, the problem arose due to the incorrect actions of the reactor operators. According to the second - because of the unsuccessful design of the power plant. However, the principle of operation of the Chernobyl nuclear power plant was also used in other plants of this type, which function properly to this day. There is an opinion that there was a chain of accidents, which is almost impossible to repeat. This is a small earthquake in that area, an experiment with a reactor, minor problems in the design itself, and so on. Together, this caused the explosion. Nevertheless, the reason that caused a sharp increase in the power of the reactor when it should not have been is still unknown. There was even an opinion about a possible sabotage, but to this day it has not been possible to prove anything.

Fukushima

This is another example of a global catastrophe involving a nuclear power plant. And in this case, too, the cause was a chain of accidents. The station was reliably protected from earthquakes and tsunamis, which are not uncommon on the Japanese coast. Few could have imagined that both of these events would occur simultaneously. The principle of operation of the Fukushima nuclear power plant generator involved the use of external sources energy to keep the entire security complex operational. This is a reasonable measure, since it would be difficult to obtain energy from the station itself during the accident. Due to the earthquake and tsunami, all these sources went out of order, which caused the reactors to melt and a catastrophe occurred. Measures are now being taken to repair the damage. According to experts, it will take another 40 years.

Despite all its effectiveness, atomic Energy still remains quite expensive, because the principles of operation of the nuclear power plant steam generator and its other components imply huge construction costs that need to be recouped. Now electricity from coal and oil is still cheaper, but these resources will run out in the coming decades, and over the next few years, nuclear energy will be cheaper than anything. At the moment, clean electricity from alternative energy sources (wind and solar power plants) costs about 20 times more.

It is believed that the principle of operation of nuclear power plants does not allow building such plants quickly. It is not true. The construction of an average object of this type takes about 5 years.

The stations are perfectly protected not only from potential radiation releases, but also from most external factors. For example, if the terrorists chose any nuclear power plant instead of the twin towers, they would be able to cause only minimal damage to the surrounding infrastructure, which would not affect the operation of the reactor in any way.

Results

The principle of operation of nuclear power plants is practically the same as the principles of operation of most other traditional power plants. Steam energy is used everywhere. Hydroelectric power plants use the pressure of flowing water, and even those models that are powered by solar energy also use liquid that is heated to a boil and rotates turbines. The only exception to this rule is wind farms, in which the blades spin due to the movement of air masses.

Nuclear power plant and its device:

Nuclear power plant (NPP) is a nuclear installation, the purpose of which is to generate electrical energy.

- reloading machine fuel(loading machine).

The operation of this equipment is controlled by personnel - operators using a block control panel for this purpose.

The key element of the reactor is a zone located in a concrete shaft. It also provides a system that provides control and protective functions; with its help, you can choose the mode in which the controlled fission chain reaction should take place. The system also provides emergency protection, which allows you to quickly stop the reaction in the event of an emergency.

In the second building nuclear plant there is a turbine hall in which the turbine and steam generators are located. In addition, there is a building in which nuclear fuel is reloaded and spent nuclear fuel is stored in specially designed pools.

Within the territory of nuclear power plant are located capacitors, as well as cooling towers, a cooling pond and a spray pond, which are components of a circulating cooling system. Cooling towers are towers made of concrete and shaped like a truncated cone; a natural or artificial reservoir can serve as a pond. nuclear plant equipped with high-voltage power lines extending beyond the borders of its territory.

Building the world's first nuclear power plant was started in 1950 in Russia and completed four years later. For the implementation of the project, an area was chosen near the village. Obninsky (Kaluga region).

However, electricity was first generated in the United States of America in 1951; the first successful case of its receipt was recorded in the state of Idaho.

In the field of production electricity The United States leads the way with more than 788 billion kWh of electricity produced annually. The list of leaders in terms of output also includes France, Japan, Germany and Russia.

The principle of operation of a nuclear power plant:

Energy is generated using reactor where nuclear fission takes place. In this case, the heavy nucleus decays into two fragments, which, being in a very excited state, emit neutrons (and other particles). The neutrons, in turn, cause new fission processes, as a result of which more large quantity neutrons. This continuous decay process is called a nuclear chain reaction, the characteristic feature of which is the release of a large amount of energy. The production of this energy is the goal of the work. nuclear power plant(NUCLEAR PLANT).

The production process includes the following steps:

1. 1. transformation nuclear energy in thermal;
2. 2. conversion of thermal energy into mechanical;
3. 3. transformation mechanical energy into electrical.

At the first stage in reactor nuclear is being loaded fuel(uranium-235) to start a controlled chain reaction. The fuel releases thermal or slow neutrons, which leads to the release of a significant amount of heat. To remove heat from the reactor core, a coolant is used, which is passed through the entire volume of the core. It may be in liquid or gaseous form. The emerging thermal energy further serves to generate steam in the steam generator (heat exchanger).

At the second stage, steam is supplied to the turbogenerator. Here, the thermal energy of the steam is converted into mechanical energy - the energy of rotation of the turbine.

At the third stage, with the help of a generator, the mechanical energy of the turbine rotation is converted into electrical energy, which is then sent to consumers.

Classification of nuclear power plants:

Nuclear power plants classified according to the type of reactors operating in them. There are two main types of nuclear power plants:

- with reactors using thermal neutrons (pressure-water nuclear reactor, boiling water reactor, heavy-water nuclear reactor, graphite-gas nuclear reactor, graphite-water nuclear reactor, etc. thermal neutron reactors);

– with reactors using fast neutrons (fast neutron reactors).

According to the type of energy produced, there are two types nuclear power plants :

– nuclear plant for the production of electricity;

- ATES - nuclear combined heat and power plants, the purpose of which is to generate not only electrical, but also thermal energy.

One-, two- and three-loop reactors of a nuclear power plant:

Reactor nuclear power plant it can be one-, two- or three-circuit, which is reflected in the scheme of operation of the coolant - it can have, respectively, one, two or three circuits. In our country, the most common are stations equipped with double-circuit water-cooled power reactors (VVER). According to Rosstat, there are currently 4 nuclear plant with 1-loop reactors, 5 with 2-loop reactors and one with a 3-loop reactor.

Nuclear power plants with a single-loop reactor:

Nuclear power plants of this type - with a single-loop reactor are equipped with reactors of the RBMK-1000 type. The unit houses a reactor, two condensing turbines and two generators. The high operating temperatures of the reactor allow it to simultaneously perform the function of a steam generator, which makes it possible to use a single-loop scheme. The advantage of the latter is a relatively simple principle of operation, however, due to its features, it is quite difficult to provide protection against radiation. This is due to the fact that when applying this scheme, all elements of the block are exposed to radioactive radiation.

Nuclear power plants with a bypass reactor:

The two-circuit scheme is used on nuclear plant with reactors of the VVER type. The principle of operation of these stations is as follows: a coolant, which is water, is supplied to the reactor core under pressure. It is heated, after which it enters the heat exchanger (steam generator), where it heats the secondary circuit water to boiling. Radiation is emitted only by the first circuit, the second has no radioactive properties. The block device includes a generator, as well as one or two condensing turbines (in the first case, the power turbines is 1000 megawatts, in the second - 2 x 500 megawatts).

The advanced development in the field of bypass reactors is the VVER-1200 model proposed by the Rosenergoatom concern. It was developed on the basis of modifications of the VVER-1000 reactor, which were manufactured on orders from abroad in the 1990s. and in the first years of the current millennium. The new model improves all the parameters of the predecessor and provides for additional safety systems to reduce the risk of radioactive radiation escaping from the pressurized compartment of the reactor. New development has a number of advantages - its power is 20% higher compared to the previous model, the capacity factor reaches 90%, it is able to work for a year and a half without overload fuel(usual terms are 1 year), its operational period is 60 years.

Nuclear power plants with a three-loop reactor:

The three-circuit scheme is used on nuclear power plants with reactors of the BN type ("fast sodium"). The operation of such reactors is based on fast neutrons, radioactive liquid sodium is used as a coolant. To exclude its contact with water, the design of the reactor provides for an additional circuit, which uses sodium without radioactive properties; this provides a three-circuit type of circuit.

The modern 3-loop reactor BN-800, developed in the 80s-90s of the last century, provided Russia with a leading position in the production of fast reactors. Its key feature is protection from influences arising from inside or outside. This model minimizes the risk of an accident in which the core melts and plutonium is released during the reprocessing of irradiated nuclear fuel.

In the reactor under consideration, different kinds fuel - conventional with uranium oxide or MOX fuel based on uranium and