A Nuclear Power Plant is a specialized facility designed to generate electricity by harnessing energy produced from nuclear reactions, specifically nuclear fission. In this process, atoms of radioactive materials such as uranium or plutonium split apart, releasing a substantial amount of heat energy. This heat is then utilized to produce steam, which drives turbines connected to electrical generators, converting mechanical energy into electrical energy. Nuclear power plants are characterized by their ability to deliver large-scale, stable, and continuous power output with significantly lower greenhouse gas emissions compared to fossil fuel-based power generation, making them a crucial component in modern energy infrastructure.

Everyday the demand for electrical power is increasing. To meet this increasing demand for electrical power is not enough with the utilization of available fossil fuels Because the availability of fossil fuels is limited and causes depletion by its usage. In India, the availability of fossil fuels is very limited and hence we must depend on nuclear fuels for the generation of electrical power. Thus, it is very important to use nuclear energy for the generation of power in India and also it is economical to generate power from Nuclear energy.

This article focuses on Nuclear power plants. We will discuss its working, Nuclear fuels, reactors, etc. The information in this article helps you extensively in your SSC JE Electrical and GATE Electrical preparation journey.

Nuclear Power Plant

The energy needed by a country cannot be met from a single source. Hydroelectric power stations produce cheap power but need the backing of thermal power plants. But the reserves of fossil fuels like Coal. Oil and Gas are fast depleting. Hence, there is a need to seek alternate sources of energy. Nuclear Power is the only source that can supply the future energy demand of the world. One of the main attractions is that a huge amount of energy can be released from a small quantity of active material (fuel) i.e., by completely burning 1 kg of Uranium (2 would give energy equivalent to 3,000 tonnes of high-grade coal.

Fig : Nuclear power plant diagram

A Generating Station which utilizes Nuclear Energy for generating Electricity is known as a "Nuclear Power Station"

The below table categories the Nuclear power plants in India and their capacity

The largest nuclear power plant in India is in Kudankulam in Tamil Nadu with 2000MW

How can Nuclear Energy be Harnessed?

Nuclear power can be harnessed through Nuclear Fission, and chain reaction this entire process continues and repeats. From this, the Nuclear Energy is obtained. 

Nuclear Fission 

The splitting of a heavy nucleus into two or smaller nuclei is called Nuclear Fission. The fission of a heavy atom can be caused by bombarding it with a neutron. The main advantage of neutrons compared to other particles (such as protons, x-rays, etc) is that they are neutral (have no charge) and therefore they can make their journey through the orbits of electrons and then through the nuclear at low energy.

You can study about Nuclear Fusion 

Chain Reaction

It may be defined as a fission reaction in which the neutrons from a previous step continue to propagate and repeat the reaction. 

Fig : Chain reaction

For example, when \( U^{235}\) →nucleus is hit by a neutron the reaction is as follows. 

• \( U^{235}+n^1 →La ^{148}+Br^{85}+3 \ neutrons\)

Each of the three neutrons produced in this reaction strikes another \( U^{235}\) nucleus, which further causes the production of nine subsequent reactions. These nine reactions in turn further give rise to twenty-seven reactions and so on. The process of reaction by multiplication in threes at each fission is shown above.

Nuclear Fiission

Nuclear Fission: The splitting of a heavy nucleus into two or smaller nuclei is called "Nuclear Fission”

The fission of a heavy atom can be caused by bombarding it with a neutron. The main advantage of neutrons compared to other particles (such as protons, x-rays, etc) is that they are neutral (have no charge) and therefore they can make their journey through the orbits of electrons and then through the nuclear at low energy.

Fig: Nuclear fission and nuclear fusion reactions

Nuclear Fusion

If the elements having higher as well as lower mass numbers could be transferred into elements near the center, then a huge amount of energy is released. For transforming light elements, they must be fused by the applications of very strong electrical discharge in a vapor of light element, and such an action is called "Fusion".

Chain Reaction

It may be defined as a fission reaction in which the neutrons from a previous step continue to propagate and repeat the reaction. We know that in nuclear fission a heavy nucleus (Uranium) splits into two or more similar nuclei when it is bombarded by slow-moving neutrons. This causes the emission of neutrons (fission neutrons) with the release of huge amounts of energy. These fission neutrons cause further fission. If this process is repeated, then in a short time a huge amount of energy will be released which may cause an explosion. This is known as an explosive chain reaction. Actually, in a reactor, a controlled chain reaction is taking place which can be done by systematically removing fission neutrons from the reactor.

What is a Nuclear Reactor?

Nuclear reactor is the heart of the nuclear power station, where a tremendous amount of heat energy is released as a result of the nuclear fission of radioactive materials. This heat is utilized to heat the coolant which in turn generates steam. The working of a nuclear reactor can be explained from the following basic components of a nuclear reactor: 

Fig : Construction and working of nuclear reactor Diagram

• Fuel: The fuels generally used in the reactor are\(_{92}U^{235},\ _{94}U^{239},\ and\ _{92}U^{233},_{92}U^{238} ,_{90}Th^{232}\) etc . Fuel should be shaped and located in the reactor such that uniform heat should be produced.
• Reactor Core: It is built of graphite bricks, having channels machined through them. The core is cylindrical in shape and is placed on a large pressure vessel totally enclosed in a thick-walled shielding structure of concrete about 2-3 meters thick. The size of the core is just sufficient to maintain a chain reaction.
• Moderator: The purpose of the moderator is to moderate or slow down neutron speed to a value that increases the probability of the fission process. Graphite, Heavy water an most commonly used as moderators. Beryllium and ordinary water can also be used as moderators with natural uranium and enriched uranium respectively. It is the central part of the core. 
• Shielding: The purpose of shielding is to prevent the escape or leak of neutrons (fast and slow), \(\alpha, \beta\ particles\ and\ \gamma-rays\) from the reactor as these radiations are harmful to a human being. Lead iron or concrete shields are used for this purpose.
• Control rods: The control of the chain reaction inside the reactor is obtained by inserting control rods into the reactor core. The control rods are made with cadmium (or boron because cadmium is a strong neutron absorber. When control rods are pushed into the core they absorb some of the neutrons and hence few neutrons are available for a chain reaction. However, when they are pulled out from the reactor core more neutrons are available for the fission process. 

Therefore pulling out and pushing them into the supply of neutrons for fission purposes can be regulated. These rods are in practice suspended from the top of the reactor in the channel of the core and are lowered or raised by a special mechanism according to the load requirements.

• Reflector: To avoid the leakage or escape of neutrons from the reactor it is essential to surround the reactor with material acting as a Reflector. As the name indicates, the function of the reflector is to reflect as many leakage neutrons as possible back into the reactor. The reflector gets heated due to the collision of neutrons with its atoms, hence cooling is essential. The materials used for the reflector are the same as the materials used for the moderator i.e. Graphite, Heavy water.
• Coolant: A coolant is a medium through which heat produced in the reactor is transferred to the heat exchanger for further utilization in power generation. Liquid sodium is generally used as a coolant. When water is used as a coolant it takes up heat and gets converted into steam in the reactor itself, which is directly used to drive the turbine. The commonly used coolants are gas (\( CO_2\), air, hydrogen, helium), and some organic liquids.
• Reactor Vessel: The Reactor vessel encloses the reactor core, reflector, and shield. It

is a strong-walled container generally cylindrical in shape and provides the exit for the passage of coolant. It should withstand high pressures. The holes are provided at the top of the vessel to insert the control rods.

Types of Nuclear Reactors

The nuclear reactors can be classified as follows:

On the Basis of Fission

• Fast Reactors: In the fast reactor the fission is affected by fast neutrons without the use of moderators. In fast reactors most of the neutrons have energies of about 1000 eV
• Thermal Reactors: In a thermal reactor, most of the neutrons have energies of about 0.03 eV.
• Intermediate Reactors: In the Intermediate reactor fission takes place by neutrons In course of slowing down.

Depending on the Type of Fuel Used

The main fuels used in the reactor are natural uranium (99.28% \( U^{238}\) and 0.714% \( U^{235}\)), enriched uranium (containing a higher percentage of \( U^{235}\)) and two more possible fuels\( Pu^{239}\) (obtained from \( U^{238}\)) and \( U^{233}\) (obtained from \( Th^{232}\) ) are produced artificially from fertile materials by neutron reactions. 

The following reactors are designed to work on the above fuels.

1.  Burner reactor.
2. Converter or breeder reactor.

Fissile materials (\( U^{235}, Pu^{239} \ and \ U^{233}\)) are used in burner reactor. In a converter or breeder reactor, the fertile materials are converted into fissile materials. For instance, the absorption of neutrons by \( U^{238}\)converts it to \( Pu^{239}\) which can be used for further fission. In most thermal reactors, the conversion ratio is less than unity. However, under proper conditions this ratio exceeds unity and the reaction produces more fissile material. A reactor in which the conversion ratio (the ratio of fissile nuclei formed to fissile nuclei consumed) is greater than unity is called a breeder reactor.

Depending on the Moderator Used

According to the moderator used, reactors can be classified as

• Ordinary water (\( H_2O\)) moderated.
• Heavy water (\( D_2O\)) moderated

Graphite moderated reactors.​

Depending on the Type of Coolant Used

According to the type of coolant used, reactors are classified as

• Water (\( H_2O\) and \( D_2O\)) cooled reactor
• Gas (air, \( CO_2\), He) cooled reactor.
• Liquid metal (sodium and potassium) cooled reactor.
• Organic liquid (polyphenyl) cooled reactor.

Working Principle of Nuclear Power Plant

The block diagram of the Nuclear Power plant is shown below. The concept of nuclear power generation is much similar to that of conventional steam power generation. Nuclear power plant working is similar to the boiler of the steam power plant is replaced by a Nuclear reactor and Heat exchanger

The essential components of a Nuclear Power Plant are :

1. Nuclear reactor
2. Heat exchanger
3. Steam turbine
4. Alternator
5. Condenser etc.

Fig: construction and working of nuclear power plant 

The Nuclear reactor is the heart of the nuclear power plant. A tremendous amount of heat energy is produced in the reactor in the breaking of atoms of Uranium or other fission materials by the fission process. This heat is extracted by pumping coolant (molten metal) generally a Sodium metal or gas: The coolant carries heat to the heat exchanger. The heat exchanger converts water into steam by utilizing the heat of the coolant.

After giving up heat, the coolant is again pumped into the reactor. The steam produced in the heat exchanger is fed to the steam turbine through a steam valve. After doing used work in the turbine the steam is allowed to condenser. The condenser condenses the steam and is pumped to the heat exchange by a feed water pump. The steam drives the turbine coupled to an Alternator which converts the mechanical energy of the turbine to electrical energy. The output of the alternator is stepped-up and fed to the bus bars through isolators and circuit breakers.

Nuclear Fuels

The fuel used in Nuclear power stations are called nuclear fuel, as like all radioactive elements there are only specific uses for nuclear fuels. Elements or isotopes whose nuclei can be used to undergo nuclear fission by nuclear bombardment and sustain the chain reaction is called “Nuclear fuel” The main fuels used in nuclear reactors are uranium, thorium, and plutonium. The most commonly used are natural uranium, uranium oxide, and uranium carbide. Radioactive materials, mainly rare earth elements can be easily transmuted. The fuels generally used in Nuclear Power Generation are

1. Uranium \(U^{235}\ U^{238}\ U^{234}\)
2. Thorium \(Th^{232}\)
3. Plutonium \(Pu^{239}\)

The following are the properties of fuel elements

Properties of Uranium

It occurs in nature in small quantities about 1 in 140 parts of the ore. The uranium deposits are in Canada, Belgium, Czechoslovakia, and the USA. The natural uranium \(_{92}U^{238}\) contains only 0.7% of fission. The present reactor use enriched uranium \(_{92}U^{235}\) and diluted along with aluminum or zirconium.

The physical properties of uranium are:

• Density: \(19.14 gm/cm^3\)
•  Melting point:\( (1150\pm1degree C)\)
•  Boiling point: about \((4000degree C)\)
•  Electrical resistivity:\( (2\ to \ 5\times10^4 μΩ-cm)\)
• Thermal conductivity: \((0.063 \ at \ 75degree C)\)

\((0.078 \ at \ 400degree C)\)

Properties of Thorium

It occurs mainly in Monazite sands near sea coasts. Particularly, India has large reserves of monazite sands on the Kerala coasts. It is of low strength and has poor corrosion resistance. Because of the high cost, it has not been very popular. When the nucleus of Thorium \(_{90}Th^{232}\) is bombarded with a neutron it undergoes a reaction to form \(_{90}Th^{233}\) which can be caused to fission useful at atomic fuel.

The physical properties of Thorium are

• Density: 11.72 gm/cm^3
•  Melting point: \((1700\pm10° C)\)
•  Boiling point: about \((3000° C)\)
•  Electrical resistivity: \((18.5 μΩ-cm\ at 20°C)\)
• Thermal conductivity: \((0.091 \ at \ 800° C)\)

\((0.109\ at \ 65° C)\)

Properties of Plutonium

It is even rare in nature, but can be made in a nuclear reactor by the disintegration of Uranium \(U^{235}\) in presence of a Moderator, generally graphite or heavy water. The nuclear reactor produces \(U^{239}\), which disintegrates into plutonium, a fissile material.

The physical properties of Plutonium are:

• Density: \(19.84 gm/cm^3\)
• Melting point: \((64 ° C)\)
• Boiling point: \((3232° C)\)

General Properties of Nuclear Fuel

The nuclear fuel elements must have the following properties

• It must be very strong at any condition of temperature and external loading 
• It must be able to resist the corrosion caused by coolant, and any other neighboring materials. 
• It must be stable under high operating temperature conditions
• It should not capture neutrons.
• It should have better heat transfer properties.
• The removal of fuel elements should be easy whenever required.
• It should not be expensive. 
• It should be resistant to radiation damage.

Components of Nuclear Power Plant

The following component are important for the working of nuclear power 

Coolant

In a reactor due to the fission reaction heat will be generated continuously. If this heat is not transferred to a heat exchanger then it may lead to damage to the vessel and hence a special material is needed to transfer the heat from a nuclear reactor to a heat exchanger. This material is called Coolant in nuclear reactors. The materials used as coolants are Heavy water, light water, gases (air, CO2, Hydrogen, helium), Liquid metal coolants (sodium, lithium, bismuth, lead), and organic liquids (Benzene, diphenyl, and terphenyl)

Reflector

In a nuclear reactor there may be every possibility of leakage of neutrons from the reactor. To avoid the leakage (or) escape of neutrons from the reactor a special material is needed which reflects the neutrons into the reactors. This material is called a “Reflector” Reflectors of a nuclear reactor are made of Graphite, Beryllium, Heavy water, and Ordinary water

Control rods

In a nuclear reactor, for every nuclear fission action it releases three number of electrons. If it continues a larger number of neutrons are generated which leads to damage to the reactor by participating in further fission. Hence, in order to have controlled nuclear fission reactions at every stage the excess neutrons must be absorbed. In order to absorb the neutrons from the nuclear reactor it needs a special device called as Nuclear reactor Control rod Which absorbs its position inside the nuclear reactor. Control rods are made of Cadmium, Boran, Silver, Indium, and Hafnium.

Advantages of Nuclear Power Plants

• High Efficiency & Energy Density: Produces substantial amounts of energy from minimal fuel, significantly exceeding the fuel efficiency of traditional fossil fuel power plants.
• Stable Base-load Supply: Provides consistent and reliable electricity essential for maintaining grid stability and energy distribution.
• Low Operating Costs: After initial construction, nuclear plants benefit from inexpensive uranium fuel and relatively low operational expenses.
• Reduced Logistical Complexity: Minimal fuel volume simplifies fuel transportation, storage, and management.
• Minimal Emissions: Nuclear plants emit negligible direct greenhouse gases, reducing air pollution and addressing climate change concerns effectively.

Disadvantages of Nuclear Power Plants

• High Initial Investment: Significant upfront costs for construction and commissioning exceed those of traditional power plants.
• Radioactive Waste Management: Produces hazardous radioactive waste, necessitating secure long-term storage and disposal methods.
• Risk of Accidents: Although rare, potential catastrophic outcomes require meticulous safety measures and continuous monitoring systems.
• Operational Complexity: Advanced reactor controls, stringent regulations, periodic maintenance, and downtime increase operational challenges.
• Grid Integration Issues: Complex electrical considerations like voltage stability and reactive power management demand specialized electrical engineering expertise.

Applications of Nuclear Energy

• Electricity Generation: Primary use in large-scale, stable, continuous base-load power generation for national and regional electrical grids.
• Naval Propulsion: Powers submarines and aircraft carriers with exceptional energy density and long operational durations without frequent refueling.
• Medical Field: Utilized for radiation therapy in cancer treatments and production of medical radioisotopes for diagnostics.
• Industrial Applications: Includes food preservation through irradiation and sterilization of medical instruments.
• Space and Remote Exploration: Radioisotope thermoelectric generators (RTGs) provide reliable electricity for spacecraft and remote research installations.

Safety Measures in Nuclear Power Plants

• Redundant Safety Systems: Multiple backup systems, including emergency cooling, containment structures, and control rods, ensure swift response in emergencies.
• Advanced Monitoring Systems: Continuous real-time tracking of reactor conditions (temperature, pressure, radiation, neutron flux) through digital instrumentation.
• Automated Protection and Controls: Automated relays and digitally controlled shutdown mechanisms swiftly activate safety protocols.
• Backup Power Supply: Emergency diesel generators and battery systems provide power for essential safety systems during outages.
• Regular Drills and Simulations: Routine safety practices, drills, and stringent regulatory compliance ensure preparedness and risk mitigation.

Comparison with Other Power Generation Methods

Comparisons among nuclear power and alternative methods, such as thermal (coal, gas), hydroelectric, solar, and wind power highlight unique benefits and challenges.

This article summarizes all the information related to the Nuclear Power Plant, which helps to propel your preparation for various AE/JE examinations. To boost your preparation, you can also test yourself through numerous Mock Tests for Electrical Engineering Exams. You can check the syllabus for the AE/JE exam. You can visit the Testbook app to keep yourself updated with all the exam-oriented information related to the upcoming examinations, including GATE Electrical and AE/JE Electrical exam