Nuclear Power Plant Working
The main use currently given to nuclear energy is that of electric power generation. Nuclear power plants are the facilities responsible for this process.
From the outset, we wonder what is nuclear energy? According to its definition, nuclear energy is the internal energy contained in the nucleus of an atom. This energy can be released in the form of heat energy through fission or fusion reactions. Virtually all nuclear power plants in production use nuclear fission since nuclear fusion is currently unfeasible despite being in the process of development.
The operation of a nuclear power plant is identical to the operation of a thermoelectric power plant working with fossil fuels like coal, oil or gas, except in the way of providing heat to the water for converting this one into steam. In nuclear reactors this process of producing heat is made by the fission reactions of the fuel atoms.
A variety of types of nuclear reactors are available to operate in a nuclear power plant. However, all types of nuclear reactors have the same goal: to use the heat from nuclear fission reactions to drive the turbines that are going to generate electricity.
From all types of nuclear reactors, two stand out: the nuclear pressurized water reactor (PWT) and the boiling water nuclear reactor (BWR). The pressurized water reactor is the most used in the world and the one that we will explain in a simplified way next.
Working of a light water nuclear power plant
- Obtaining thermal energy by nuclear fission of the nucleus of atoms of nuclear fuel.
- Generate steam in the heat generator by means of the thermal energy obtained previously.
- Operate a set of turbines using the steam obtained.
- 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 changes of energy are observed: initially we have nuclear energy (that keeps the nuclei of the atoms cohesion), later, when it is broken, it becomes thermal energy. Part of the thermal energy is converted into internal energy of water by becoming steam according to the principles of thermodynamics. The internal energy and the heat energy of the water are transformed into kinetic energy when the turbine is actuated. Finally, the generator converts the kinetic energy into electrical energy.
The basic principle of the performance of a nuclear power plant is based on obtaining heat energy through the nuclear fission of the atoms´ nucleus from the fuel. This heat energy, already being steam, will be converted into mechanical energy by a turbine, and in the end this mechanical energy will be converted into electrical energy by a generator.
Generation of electricity
The steam exits the containment building due to the high pressure that it is subjected to, until it reaches the turbine and the steam makes the turbine rotate. At this moment, part of the heat energy of the steam is being transformed into kinetic energy. This turbine is connected to an electric generator whereby the kinetic energy is transformed into electric energy.
On the other hand, the water vapour that has gone out of the turbine, although it has lost calorific energy, it continues being in gas state and very warm. To re-use water contained in the mentioned water steam, it is necessary to refrigerate it before introducing the water back to the circuit. Once out of the turbine, the steam goes to a condensation chamber where it cools down by being in contact with pipelines of cold water. The water steam becomes liquid and using a pump, water is sent back again to the nuclear reactor so that the cycle can start again.
That is why nuclear plants are always installed near of an abundant supply of cold water (sea, river, lake) to take this water to the condensation chamber. The column of white smoke that can be seen emerging from some plants is the steam raised when this heat exchanges.
- United States Nuclear Regulatory Comission
- How Nuclear Power Works -The Union of Concerned Scientists - At a basic level, nuclear power is the practice of splitting atoms to boil water, turn turbines, and generate electricity.
Last review: June 28, 2017