A nuclear power plant is an industrial facility that produces electricity by harnessing nuclear energy, which is released in the form of thermal energy during a nuclear fission chain reaction inside a reactor vessel. Many people do not know how a nuclear power plant works.
For this reason, we are going to tell you in detail How a nuclear power plant works from the inside.
Main elements of a nuclear power plant
The nuclear reactor is the main element of a power plant, as it contains the nuclear fuel (usually uranium) and is equipped with systems that allow the start, maintenance and controlled cessation of the nuclear reaction. The operation of a nuclear power plant is similar to that of a traditional thermal power plant, in which thermal energy is generated by the combustion of fossil fuels. In contrast, a nuclear reactor obtains thermal energy from nuclear fission chain reactions that occur within the uranium atoms present in nuclear fuel.
The thermal energy generated is used to heat water until it reaches the vaporization point, turning into steam at high pressure and temperature. This steam It drives a turbine connected to a generator, which converts the mechanical energy produced by the rotation of the turbine into electrical energy.
While there are several types of nuclear reactors, two specific designs stand out, together accounting for more than 80% of the nearly 450 operating units worldwide: the pressurized water reactor (PWR) and the boiling water reactor (BWR).
Operation of a pressurized water reactor (PWR)
It is essential to note that during nuclear fission, the nuclei of heavy atoms, which are hit by neutrons, break down into smaller, lighter nuclei. This process releases the energy that binds protons and neutrons together and results in the emission of two or three neutrons. These emitted neutrons They are capable of inducing additional fissions by interacting with other heavy nuclei, which in turn will release more neutrons, perpetuating the cycle. This cascading effect is known as a nuclear fission chain reaction.
The operation of a nuclear power plant can be summarized in the following phases:
- In the nuclear reactor, The uranium undergoes fission, generating a substantial amount of energy that heats the high-pressure cooling water circulating through the system. This heated water is then transported through the primary circuit to a heat exchanger, known as a steam generator, where it facilitates the production of steam.
- The turbine-generator assembly receives steam through a secondary circuit. Upon arrival, the steam causes the turbine blades to rotate. This rotation of the turbine shaft subsequently drives the alternator, converting mechanical energy into electricity.
- Once the water vapor has passed through the turbine, it goes to a condenser, where it is cooled and transformed back into liquid water.
- The water is then returned to the steam generator to generate steam once again, operating within a closed circuit.
Key components of a nuclear power plant
We have said before that a nuclear reactor is a facility designed to start, maintain and terminate fission chain reactions in a controlled manner, equipped with the necessary mechanisms to extract the heat produced. The reactor is the main element of a power plant and functions as the place where nuclear fuel is stored.
The main elements of a nuclear power plant are:
- Fuel type: It is the material in which fission reactions take place, which normally use enriched uranium dioxide. This substance has a dual function: it acts as a source of energy and as a supplier of neutrons necessary to maintain the chain reaction. It is supplied in solid form, consisting of cylindrical pellets wrapped in metal rods approximately four metres long.
- Moderator: A substance that reduces the speed of fast neutrons produced during fission, thus facilitating additional fissions and maintaining the chain reaction.
- Refrigerant: It is the same water that acts as a moderator and is used to eliminate the heat produced by the fission reaction that occurs in the uranium fuel.
- Control bars: These are the reactor's control components and function as neutron absorbers. Made of boron carbide or indium-cadmium, these rods allow for continuous management of the neutron population, ensuring the reactor's stability and facilitating its shutdown when necessary.
- Armor: It is used to inhibit the escape of radiation and neutrons from the reactor into the external environment. Materials such as concrete, steel or lead are typically used for this purpose.
- Safety features: Every nuclear facility is equipped with numerous safety systems designed to prevent the release of radioactivity into the environment, including the containment structure.
- Pressure regulator: is a critical component of the primary cooling circuit. This regulator maintains the equilibrium between the liquid and vapor phases under saturation conditions to effectively manage the pressure within the reactor.
- Reactor vessel: It contains the nuclear reactor where the fission chain reaction takes place. The core of this vessel is made up of fuel elements.
- Steam generators: They function as heat exchangers, in which the cooling water from the primary circuit flows through inverted U-shaped tubes and transfers its thermal energy to the water in the secondary circuit, thus converting it into water vapour.
- Containment building: It is the enclosure that contains the reactor cooling system along with various auxiliary systems and acts as a protective barrier during normal operations, effectively preventing the escape of contaminating substances into the outside environment. In conjunction with other safety systems, it has the critical responsibility of preventing the possible release of fission products into the atmosphere in the event of an accident.
- Turbine: The installation is designed to capture steam from steam generators, converting its energy into rotational mechanical energy through the blades. Several sections are intended for steam expansion. The shaft is securely attached to the alternator shaft.
- Alternator: Device that generates electricity by transforming the rotational mechanical energy of the turbine into medium voltage and high intensity electrical energy.
- Transformer: Device designed to increase the voltage of the electricity generated by the alternator in order to reduce losses during its transmission to consumption points.
- Cooling water: Water from a river, reservoir or sea is used to condense water vapour inside the condenser. This water can be returned directly to its original source, which is known as an open cycle, or recycled through a cooling tower in a closed cycle system.
- Cooling towers: They facilitate the dissipation of part of the residual heat generated during the production of electricity into the atmosphere, serving as a source of cold. This system is used to cool the water circulating through the condenser, which is an integral component of the plant's auxiliary cooling circuit.
- Condenser: A heat exchanger consists of a series of tubes that facilitate the circulation of cooling water. The vaporized water that enters the condenser from the turbine undergoes a liquefaction process, passing into the liquid phase. This process generates a vacuum that improves the operational efficiency of the turbine.
I hope that with this information you can learn more about how a nuclear power plant works from the inside.