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Turbine of a nuclear plant

Cattenon Nuclear Power Station,
France

How Does A Nuclear Power Plant Work?

The operation of a nuclear power plant is similar to that of any other thermal power plant. A nuclear power plant is a type of thermal power plant. Its function is to generate electrical energy.

How does a nuclear power plant work?

There are several types of exchanges, but at the base they work the same:

  1. Generate nuclear reactions. Thermal energy is obtained.
  2. Generate water vapor with thermal energy.
  3. Activate a steam turbine. Mechanical energy (kinetic energy) is obtained.
  4. Actuate an electric generator. Electricity is obtained.

A nuclear power plant is a facility in which the entire process is carried out. The most important difference with other thermal power plants is the way of obtaining thermal energy. In a nuclear plant it is carried out in the nuclear reactor.

The other types of thermal power plants are mainly those that use fossil fuels. Coal or natural gas mainly. There are also solar thermal plants that use the sun to generate steam.

What is a nuclear reaction?

A nuclear reaction is an alteration in the nucleus of an atom.

Atoms are made of a combination of subparticles. Protons and neutrons. These subparticles are linked by force bonds that have a large amount of energy. 

The concept of nuclear energy refers to the energy of the nucleus. The concept of atomic energy refers to the atom. However, in both cases we mean the same thing.

If this atomic structure is altered, two things can happen:

In both cases, a large amount of thermal energy is released.

Today, all nuclear power plants use fission reactors. Nuclear fusion is not yet viable.

How many types of nuclear power plants are there?

Worldwide 90% of the plants use light water reactors. Light water is running water; in nuclear engineering it is called that. Two types of light water reactors are distinguished:

Between these two types of reactor, the pressurized water reactor is the most widely used in the world.

How does a pressurized water nuclear power plant work?

 

The basic operation of a nuclear power plant with a pressurized water reactor can be simplified in 4 steps:

  1. Obtaining thermal energy by nuclear fission of the nucleus of the atoms (atomic nucleus) of the nuclear fuel.
  2. Generate water vapor using the thermal energy previously obtained from the heat generator.
  3. Actuate a set of turbines using the water vapor obtained.
  4. Take advantage of the mechanical energy of the turbines to drive an electric generator. This electric generator will generate electricity.

From a physical point of view, several energy changes are observed:

Initially we have nuclear energy (the one that keeps the nuclei of the atoms cohesive). Later, when it breaks, it is converted into thermal energy. With the help of thermodynamics, part of the thermal energy is converted into steam.

Thermal energy becomes internal energy of water (now steam). The internal energy and the heat energy of the water are transformed into kinetic energy when driving the turbine.

Finally, the generator converts kinetic energy into electrical energy.

Water circuits

Nuclear power plants that operate with a pressurized water reactor have two water circuits:

  • Primary circuit. It goes through the reactor.
  • Secondary circuit. It goes through the steam turbines.

In the primary circuit the water is subjected to high pressure. When passing through the reactor, the water acquires a very high temperature and the pressure prevents it from being gasified. It cannot be converted to steam. This is the objective.

The secondary circuit is also closed. Some of the water is converted to steam. It is heated because it is in contact with the primary circuit. Steam passes through the turbine.

Finally, it is cooled by being in thermal contact with an external water source.

What happens in the nuclear reactor?

The nuclear reactor is the most sensitive and most important part of the plant.

The reactor is in charge of converting nuclear energy into thermal energy. Inside it are placed the nuclear fuel rods. Generally uranium. Uranium is very unstable.

If a neutron collides with a uranium atom, it is highly likely to break. This break is a nuclear fission reaction. Chunks of the atom and one or two more neutrons are released in a nuclear fission. These neutrons can collide with atoms and generate chain reactions.

If these reactions were not controlled more and more reactions per second would take place. The heat generated would be so high that it could not be contained and the reactor would melt (as in Chernobyl and Fukushima).

To prevent this from happening, there are control bars. Control bars have the ability to attract neutrons. Without neutrons there are no more reactions.

Containment building

The containment building is the building where the nuclear power plant and the primary circuit are located. The most sensitive parts of the nuclear power plant.

The containment building is designed to:

  1. Contain possible explosions.

  2. Avoid the possible escape of nuclear radiation to the outside.

How is the electricity generated?

When the steam has hit the turbine it has transferred a large part of its thermal energy to the turbine. Now the turbine has mechanical energy, it spins.

This turbine is connected to an electric generator. the generator transforms kinetic energy into electrical energy.

 

The water vapor leaving the turbine has lost a lot of heat energy but it is still very hot steam. It must be refrigerated before putting it back into the circuit. 

When leaving the turbine, the steam goes to a condensation tank. The water will be in thermal contact with some cold water pipes outside. The water vapor becomes liquid. Through a pump the water is directed back to the reactor.

The cycle repeats.

What is the smoke coming out of the chimneys of nuclear power plants?

The white smoke that comes out of the chimneys of nuclear plants is water vapor.

When the cold water comes into thermal contact with the steam that comes out of the turbines, it quickly heats up. Heat is transferred. Due to heat, some of this external water is converted to steam.

For this reason, nuclear power plants are always installed near an abundant source of cold water. It can be the sea, a river, or a lake. Water is needed for cooling in the condensation tank.

Summary

A nuclear power plant aims to extract energy from an atom and convert it into electricity.

This process is carried out in 4 stages.

  1. Convert the energy of the atom into thermal energy through nuclear reactions.
  2. Generate steam using this thermal energy.
  3. Drive a steam turbine.
  4. Convert the kinetic energy of the turbine into electricity. Electric generator.

-----------------

The operation of a nuclear power plant is similar to that of any other thermal power plant. A nuclear power plant is a type of thermal power plant. Its function is to generate electrical energy.

There are several types of thermal power plants, but basically, they work identically:

  1. Generate heat. In our case, the nuclear reactor produces heat.
  2. Generate water vapor with thermal energy.
  3. Activate a steam turbine. Mechanical energy (kinetic energy) is obtained.
  4. Actuate an electric generator. Electricity is obtained.

A nuclear power plant is a facility in which the entire process is carried out. The most important difference with other thermal power plants is the way of obtaining thermal energy. In a nuclear plant it is carried out in the nuclear reactor.

The other types of thermal power plants are mainly those that use fossil fuels. Coal or natural gas mainly. There are also solar thermal plants that use the sun to heats water and generate steam.

What is a nuclear reaction?

A nuclear reaction is an alteration in the nucleus of an atom.

Atoms are made of a combination of sub-particles. Protons and neutrons. These sub-particles are linked by force bonds that have a large amount of energy. 

The concept of nuclear energy refers to the energy of the nucleus. The concept of atomic energy refers to the atom. However, in both cases we mean the same thing.

If this atomic structure is altered, two things can happen:

In both cases, a large amount of thermal energy is released.

Today, all nuclear power plants use fission reactors. Nuclear fusion is not yet viable.

How many types of nuclear power plants are there?

Worldwide 90% of the plants use light water reactors. Light water is running water; in nuclear engineering it is called that. Two types of light water reactors are distinguished:

  • Pressurized water nuclear reactor (PWR).
  • Boiling Water Nuclear Reactor (BWR). 

Between these two types of reactors, the pressurized water reactor is the most widely used in the world.

How does a pressurized water nuclear power plant work?

How does a nuclear power plant work?

The basic operation of a nuclear power plant with a pressurized water reactor can be simplified in 4 steps:

  1. Obtaining thermal energy by nuclear fission of the nucleus of the atoms (atomic nucleus) of the nuclear fuel.
  2. Generate water vapor using the thermal energy previously obtained from the heat generator.
  3. Actuate a set of turbines using the water vapor obtained.
  4. Take advantage of the mechanical energy of the turbines to drive an electric generator. This electric generator will generate electricity.

From a physical point of view, several energy changes are observed:

Initially we have nuclear energy (the one that keeps the nuclei of the atoms cohesive). Later, when it breaks, it is converted into thermal energy. With the help of thermodynamics, part of the thermal energy is converted into steam.

Thermal energy becomes the internal energy of water (now steam). The internal energy and the heat energy of the water are transformed into kinetic energy when driving the turbine.

Finally, the generator converts kinetic energy into electrical energy.

Water circuits

Nuclear power plants that operate with a pressurized water reactor have two water circuits:

  • Primary circuit. It goes through the reactor.
  • Secondary circuit. It goes through the steam turbine generator.

In the primary circuit the water is subjected to high pressure. When passing through the reactor, the water acquires a very high temperature and the pressure prevents it from being gasified. It cannot be converted to steam. This is the objective.

The secondary circuit is also closed. Some of the water is converted to steam. It is heated because it is in contact with the primary circuit. Steam passes through the turbine.

Finally, it is cooled by being in thermal contact with an external water source.

What happens in the nuclear reactor?

The nuclear reactor is the most sensitive and most important part of the plant.

Reactor operation converts nuclear energy into thermal energy. Inside it are placed the nuclear fuel rods. Generally uranium fuel. Uranium is very unstable.

If a neutron collides with a uranium atom, it is highly likely to break. This break is a nuclear fission reaction. Chunks of the atom and one or two more neutrons are released in a nuclear fission. These neutrons can collide with atoms and generate chain reactions.

If these reactions were not controlled more and more reactions per second would take place. The heat generated would be so high that it could not be contained and the reactor would melt (as in Chernobyl and Fukushima).

To prevent this from happening, there are control bars. Control bars have the ability to attract neutrons. Without neutrons there are no more reactions.

In fact, control rods aren't only a security system. They allow to regulate the power of the reactor depending on electricity demand.

Containment building

The containment building is the building where the nuclear power plant and the primary circuit are located. The most sensitive parts of the nuclear power plant.

The containment building is designed to:

  1. Contain possible explosions.
  2. Avoid the possible escape of nuclear radiation to the outside.

How is the electricity generated?

When the steam has hit the turbine it has transferred a large part of its thermal energy to the turbine. Now the turbine has mechanical energy, it spins.

This turbine is connected to an electric generator producing electricity.

How does a nuclear power plant work?

The water vapor leaving the turbine has lost a lot of heat energy but it is still very hot steam. It must be refrigerated before putting it back into the circuit. 

When leaving the turbine, the steam goes to a condensation tank. The water will be in thermal contact with some cold water pipes outside. The water vapor becomes liquid. Through a pump the water is directed back to the reactor.

The cycle repeats.

What is the smoke coming out of the chimneys of nuclear power plants?

The white smoke that comes out of the chimneys of nuclear plants is water vapor.

When the cold water comes into thermal contact with the steam that comes out of the turbines, it quickly heats up. Heat is transferred. Due to heat, some of this external water is converted to steam.

For this reason, nuclear power plants are always installed near an abundant source of cold water. It can be the sea, a river, or a lake. Water is needed for cooling in the condensation tank.

Summary

How does a nuclear power plant works in a few words?

A nuclear power plant aims to extract energy from an atom and convert it into electricity.

This process is carried out in 4 stages.

  1. To convert the energy of the atom into thermal energy through nuclear reactions.
  2. To generate steam using this thermal energy.
  3. To drive a steam turbine.
  4. To convert the kinetic energy of the turbine into electricity. Electric generator.

    References

    Author:

    Published: December 10, 2009
    Last review: May 11, 2020