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On the left side of the image is a part of the complex installation of a nuclear power plant, which generates electricity.

This part, the containment structure is composed of a container for the reactor, represented on the left edge in the form of a vertical rectangle, with a domed lid.

Inside the rector container are connected the following components:

  • control rods, marked as three vertical and parallel lines,on the left side of the container, located between the fuel rods, marked as three wavy and parallel lines in the left lower side of the reactor vessel, which is highlighted as a large circle elongated vertically, on the left edge.
  • the pressurizer, rendered in the form of a small circle elongated vertically, next to the reactor, top center;
  • the pumps located in the bottom center, one below the pressurizer, next to the reactor, and the second one outside the reactor container, bottom center of the image, both marked with a small circle inside of which is a dot surrounded by four lines;
  • the heat exchanger, also called steam generator, parallel to the reactor, rendered by a vertically elongated circle, half filled with dotted texture;
  • the cold water used for cooling the hot water boiled from the reactor’s heat, rendered by dotted texture;

From the steam generator starts a steam pipe to the top right, which connects it with the turbine, shown in the center of the image, above, in the form of a square with the upper side domed and then with the generator, represented in the upper right edge, as a horizontal and embossed rectangle.

In the lower right, the condenser is represented, by a vertical rectangle, half filled by dotted texture, connected upwards to the turbine from where retrieves the steam and converts it in liquid water, and pumping it back to the steam generator, in order to cool the boiling water next to the reactor.

The energy thus obtained from the nuclear reactions is distributed to the high voltage power lines.

General information

After the discovery of the utility of the electric current, interest in its generation methods increased. At first, electricity was only available in places where there were individual power generators. For this reason, it was necessary to create an electricity generation and distribution infrastructure to ensure the supply of electricity to a wider area. The infrastructure has been created and so we have electricity in almost all populated areas of the Earth. This infrastructure is called an electricity grid. The main components of the electricity grid are the power plants in which the current is produced, the transformer stations that adjust the voltage according to the needs of the consumers, and the cables through which all elements of the grid are interconnected. The electricity reaches the consumers through the cables as well.

Power plants are of many kinds, depending on the energy they use to produce electricity. All power plants have as their main component electric generators, which convert mechanical energy into electricity.

A category of power plants is represented by nuclear or atomic power plants. As a mode of operation, it resembles thermal power plants, in that even in the case of nuclear power plants, steam force is used. The major difference is that heat is obtained not by burning fuels, but by nuclear reaction. The reactor is the site where the fission of the nuclei takes place, a process that produces heat. This energy is used for heating water, which turns to steam, and pressure steam activates the turbines of electricity generators. The only nuclear power plant in Romania is at Cernavoda. The great disadvantage of nuclear power plants is pollution by radioactive waste, which is very harmful to human, animal and plant health.

The nuclear power plant (or atomo-electric power plant) is a modern power generation plant based on nuclear reactions. The nuclear reactor is a complex installation in which the fission of the nuclei of heavy elements is carried out, by a controlled chain reaction, in order to allow the use of the energy released.

The active area of such an installation shall consist of nuclear fuel, moderator, control bars and coolant. In the heat exchanger, the water evaporates and becomes the mechanical working agent, putting the turbine into operation. It is the electric generator that converts the kinetic energy of the turbine into electricity.

Nuclear power plants are classified according to the type of reactors used:

  • thermalized neutron reactor:
    • pressurized water reactor
    • hot water reactor
    • heavy water reactor under pressure
    • gas-cooled reactor
    • graphite-water nuclear reactor
  • fast neutron reactor

By the type of energy released, nuclear power plants may be divided into:

  • Nuclear power plants (NPP) designed to generate electricity. At the same time, many nuclear power plants have thermal power plants and power plants designed to heat the water in the grid using heat loss from the plant.
  • Thermopower plants and atomic power plants (TAPP), which produce both electricity and heat.

The figure shows the operation of a nuclear power plant with a power reactor cooled with double-circuit water. The energy released into the reactor core is transferred to the primary coolant. The coolant then penetrates the heat exchanger (steam generator), where it heats the waters of the second circuit to the boil. The resulting steam enters the turbine by rotating the electric generators. When exiting the turbines, the steam enters the capacitor, where it is cooled by a large amount of water coming from the tank.

The pressure compensator is a rather complicated and cumbersome design, which serves to equalize pressure fluctuations in the circuit during the operation of the reactor, due to the thermal dilation of the coolant. The pressure in circuit 1 can reach up to one hundred sixty atmospheres (VVER-1000).

In addition to water, in different reactors, metal melts can also be used as a coolant: sodium, lead, eutectic bismuth lead, etc. The use of liquid metal cooling liquids allows us to simplify the design of the reactor core housing (unlike the water circuit, the pressure in the liquid metal circuit does not exceed atmospheric pressure) and to relieve the pressure compensator.

If it is impossible to use large amounts of water to condense steam instead of using a tank, the water can be cooled in special cooling towers (cooling towers) which, due to their size, are usually the most visible part of a nuclear power plant.

Any operational nuclear power plant has an environmental impact in three areas:

  • gaseous (including radioactive) emissions into the atmosphere;
  • emission of large amounts of heat;
  • distribution of liquid radioactive waste around nuclear power plants.

During the operation of a nuclear reactor, total activity in the reactor core increases millions of times. The number and composition of radioactive gaseous emissions and aerosols in the atmosphere depends on the type of reactor, the duration of operation, the strength of the reactor, the efficiency of the purification of gas and water. Gas and aerosol emissions undergo a complex purification system, which is necessary to reduce its activity and then is emitted into the atmosphere through a ventilation duct.

Did you know that? The largest atomic catastrophe in Europe occurred on twenty six April 1986 at the Chernobyl nuclear power plant, when the plant’s reactor four exploded. The consequences of this accident are still being felt today and will still be present for a long time.

Bibliography

  1. https://ro.wikipedia.org/wiki/Central%C4%83_nuclear%C4%83
  2. https://ro.wikipedia.org/wiki/Accidentul_nuclear_de_la_Cernob%C3%AEl#%C3%
  3. https://ro.wikipedia.org/wiki/Energia_nuclear%C4%83_%C3%AEn_Rom%C3%A2
  4. https://ro.wikipedia.org/wiki/Central%C4%83_nuclear%C4%83

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