What is nuclear energy used for

What is Nuclear Energy? The Science of Nuclear Power

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Nuclear energy is a form of energy released from the nucleus, the core of atoms, made up of protons and neutrons. This source of energy can be produced in two ways: fission – when nuclei of atoms split into several parts – or fusion – when nuclei fuse together.

The nuclear energy harnessed around the world today to produce electricity is through nuclear fission, while technology to generate electricity from fusion is at the R&D phase. This article will explore nuclear fission. To learn more about nuclear fusion, click here.

What is nuclear fission?

Nuclear fission is a reaction where the nucleus of an atom splits into two or more smaller nuclei, while releasing energy.

For instance, when hit by a neutron, the nucleus of an atom of uranium-235 splits into two smaller nuclei, for example a barium nucleus and a krypton nucleus and two or three neutrons. These extra neutrons will hit other surrounding uranium-235 atoms, which will also split and generate additional neutrons in a multiplying effect, thus generating a chain reaction in a fraction of a second.

Each time the reaction occurs, there is a release of energy in the form of heat and radiation. The heat can be converted into electricity in a nuclear power plant, similarly to how heat from fossil fuels such as coal, gas and oil is used to generate electricity.

Nuclear fission (Graphic: A. Vargas/IAEA)

How does a nuclear power plant work?

Inside nuclear power plants, nuclear reactors and their equipment contain and control the chain reactions, most commonly fuelled by uranium-235, to produce heat through fission. The heat warms the reactor’s cooling agent, typically water, to produce steam. The steam is then channelled to spin turbines, activating an electric generator to create low-carbon electricity.

Find more details about the different types of nuclear power reactors on this page.

Pressurized water reactors are the most used in the world. (Graphic: A. Vargas/IAEA)

Mining, enrichment and disposal of uranium

Uranium is a metal that can be found in rocks all over the world. Uranium has several naturally occurring isotopes, which are forms of an element differing in mass and physical properties but with the same chemical properties. Uranium has two primordial isotopes: uranium-238 and uranium-235. Uranium-238 makes up the majority of the uranium in the world but cannot produce a fission chain reaction, while uranium-235 can be used to produce energy by fission but constitutes less than 1 per cent of the world’s uranium.

To make natural uranium more likely to undergo fission, it is necessary to increase the amount of uranium-235 in a given sample through a process called uranium enrichment. Once the uranium is enriched, it can be used effectively as nuclear fuel in power plants for three to five years, after which it is still radioactive and has to be disposed of following stringent guidelines to protect people and the environment. Used fuel, also referred to as spent fuel, can also be recycled into other types of fuel for use as new fuel in special nuclear power plants.

What is the Nuclear Fuel Cycle?

The nuclear fuel cycle is an industrial process involving various steps to produce electricity from uranium in nuclear power reactors. The cycle starts with the mining of uranium and ends with the disposal of nuclear waste.

Nuclear waste

The operation of nuclear power plants produces waste with varying levels of radioactivity. These are managed differently depending on their level of radioactivity and purpose. See the animation below to learn more about this topic.

Radioactive Waste Management

Radioactive waste makes up a small portion of all waste. It is the by-product of millions of medical procedures each year, industrial and agricultural applications that use radiation and nuclear reactors that generate around 11 % of global electricity. This animation explains how radioactive waste is managed to protect people and the environment from radiation now and in the future.

The next generation of nuclear power plants, also called innovative advanced reactors, will generate much less nuclear waste than today’s reactors. It is expected that they could be under construction by 2030.

Nuclear power and climate change

Nuclear power is a low-carbon source of energy, because unlike coal, oil or gas power plants, nuclear power plants practically do not produce CO₂ during their operation. Nuclear reactors generate close to one-third of the world’s carbon free electricity and are crucial in meeting climate change goals.

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What Is the Nuclear Energy? Nuclear Definition

Nuclear definition: it is something that comes from the nucleus. Nuclear physics is a branch of physics that studies the properties and behavior of atomic nuclei. Thus, nuclear energy is a source of energy that takes advantage of the energy inside the atom’s nuclei.

Nuclear energy is the internal energy possessed by the nuclei of atoms. In general, folks use this concept to refer to harnessing this energy.

Atoms are the smallest particles in a material. They are composed of a nucleus and a cloud of electrons. The atomic nucleus comprises two sub-particles (neutrons and protons) that are held together by energy bonds. The critical element is that the creation or destruction of these bonds releases heat energy.

Nuclear technology deals with harnessing this internal energy for a wide range of uses. The best-known application of atomic energy is generating electrical energy in nuclear power plants.

Nuclear power plants are facilities where thermal energy is generated by causing atomic reactions in the nuclear reactor releasing energy. Subsequently, the thermal energy is converted into electrical energy through heat exchange and mechanical processes.

The main advantage of nuclear energy is that it is an alternative to fossil fuels. But, on the other hand, the waste generated takes millions of years to disappear.

This kind of energy does not release greenhouse gases, but it is not considered clean energy because it generates radioactive waste.

How Is Nuclear Energy Obtained?

We get nuclear energy inside the nucleus of atoms using two techniques:

Splitting the nucleus of an atom: nuclear fission

When one of these two physical reactions occurs, the atoms experience a slight loss of mass. This lost mass is converted into a large amount of heat energy as Albert Einstein discovered with his famous equation E=m·c2.

Technique 1: Nuclear Fission

Nuclear fission is a way of getting the energy contained in a uranium atom by splitting the atomic nucleus into different smaller particles. This type of reaction generates a large amount of heat energy that can be used later in different ways.

One of the crucial features of nuclear fission is that it is generated by bombarding an unstable atom with a neutron. Once the nucleus has fissioned, one or two more neutrons are left free to collide with other atoms, generating a chain reaction.

The resulting particles are spent fuel (nuclear waste) that must be replaced when the ratio is too high and prevents free neutrons from finding atoms to fission.

Nuclear fission is currently the type of nuclear reaction used in all nuclear plants to produce electricity.

The first nuclear reactor was built in the United States, part of the Manhattan Project.

Technique 2: Nuclear Fusion

Nuclear fusion is the reverse process: the fusion of the nucleus of two atoms. The nuclei of atoms must be subjected to very high pressure and temperature conditions. A large amount of energy is also obtained through this type of reaction.

However, technically it has not yet been possible to build viable nuclear power reactors to produce electricity.

Nuclear physicists claim that this technique has multiple advantages compared to fission:

It is more sustainable for the environment

An example of nuclear fusion energy is the energy produced by the Sun. Nuclear fusion reactions are generated in the core of the star in our Solar System.

For What Is Nuclear Energy?

Once we know the definition of nuclear energy, we can better understand what applications it can be given. Atomic energy has a wide variety of applications. The best-known uses of nuclear energy are the generation of electricity in nuclear power plants and the military field.

In any case, some nuclear reactors have the function of generating radioisotopes for use in medicine, treatment of plagues, etc. For example, in medicine, nuclear radiation is used to perform x-rays or specific radiological treatments.

In the military field, it is used to create weapons and propulsion of vehicles. The effects that nuclear weapons can have on the population are devastating. To date, the atomic bomb has only been dropped twice (on the cities of Nagasaki and Hiroshima during World War II). Despite this, there are many treaties and agreements to regulate these activities.

Nuclear technology is also used to propel vehicles and missiles in the military because it allows excellent autonomy with very little fuel.

What Is Nuclear Fuel?

When we talk about nuclear fuel, we refer to the radioactive material used to generate nuclear reactions. Fission reactors need unstable atoms that can be easily broken.

Uranium is a chemical element found in nature and meets these conditions. However, for natural uranium to be used as nuclear fuel, it must undergo enrichment. This process makes it even more unstable and more efficient for atomic power plants.

The planet’s uranium reserves are not considered unlimited, so nuclear energy is not renewable energy such as solar or wind energy.

In the case of nuclear fusion, the most optimal material is the one with the simplest atomic structure, that is, the fewest number of protons. For now, we are working mainly with two isotopes of hydrogen: tritium and deuterium, the first element in the periodic table.

Published: December 10, 2009
Last review: January 17, 2022

What is nuclear energy and is it a viable resource?

Nuclear energy’s future as an electricity source may depend on scientists’ ability to make it cheaper and safer.

What is Nuclear Energy?

Nuclear power is generated by splitting atoms to release the energy held at the core, or nucleus, of those atoms. This process, nuclear fission, generates heat that is directed to a cooling agent—usually water. The resulting steam spins a turbine connected to a generator, producing electricity.

About 450 nuclear reactors provide about 11 percent of the world’s electricity. The countries generating the most nuclear power are, in order, the United States, France, China, Russia, and South Korea.

The most common fuel for nuclear power is uranium, an abundant metal found throughout the world. Mined uranium is processed into U-235, an enriched version used as fuel in nuclear reactors because its atoms can be split apart easily.

In a nuclear reactor, neutrons—subatomic particles that have no electric charge—collide with atoms, causing them to split. That collision—called nuclear fission—releases more neutrons that react with more atoms, creating a chain reaction. A byproduct of nuclear reactions, plutonium, can also be used as nuclear fuel.

Types of nuclear reactors

In the U.S. most nuclear reactors are either boiling water reactors, in which the water is heated to the boiling point to release steam, or pressurized water reactors, in which the pressurized water does not boil but funnels heat to a secondary water supply for steam generation. Other types of nuclear power reactors include gas-cooled reactors, which use carbon dioxide as the cooling agent and are used in the U.K., and fast neutron reactors, which are cooled by liquid sodium.

Nuclear energy history

The idea of nuclear power began in the 1930s, when physicist Enrico Fermi first showed that neutrons could split atoms. Fermi led a team that in 1942 achieved the first nuclear chain reaction, under a stadium at the University of Chicago. This was followed by a series of milestones in the 1950s: the first electricity produced from atomic energy at Idaho’s Experimental Breeder Reactor I in 1951; the first nuclear power plant in the city of Obninsk in the former Soviet Union in 1954; and the first commercial nuclear power plant in Shippingport, Pennsylvania, in 1957. (Take our quizzes about nuclear power and see how much you’ve learned: for Part I, go here; for Part II, go here.)

Nuclear power, climate change, and future designs

Nuclear power isn’t considered renewable energy, given its dependence on a mined, finite resource, but because operating reactors do not emit any of the greenhouse gases that contribute to global warming, proponents say it should be considered a climate change solution. National Geographic emerging explorer Leslie Dewan, for example, wants to resurrect the molten salt reactor, which uses liquid uranium dissolved in molten salt as fuel, arguing it could be safer and less costly than reactors in use today.

Others are working on small modular reactors that could be portable and easier to build. Innovations like those are aimed at saving an industry in crisis as current nuclear plants continue to age and new ones fail to compete on price with natural gas and renewable sources such as wind and solar.

The holy grail for the future of nuclear power involves nuclear fusion, which generates energy when two light nuclei smash together to form a single, heavier nucleus. Fusion could deliver more energy more safely and with far less harmful radioactive waste than fission, but just a small number of people—including a 14-year-old from Arkansas—have managed to build working nuclear fusion reactors. Organizations such as ITER in France and Max Planck Institute of Plasma Physics are working on commercially viable versions, which so far remain elusive.

Nuclear power risks

When arguing against nuclear power, opponents point to the problems of long-lived nuclear waste and the specter of rare but devastating nuclear accidents such as those at Chernobyl in 1986 and Fukushima Daiichi in 2011. The deadly Chernobyl disaster in Ukraine happened when flawed reactor design and human error caused a power surge and explosion at one of the reactors. Large amounts of radioactivity were released into the air, and hundreds of thousands of people were forced from their homes. Today, the area surrounding the plant—known as the Exclusion Zone—is open to tourists but inhabited only by the various wildlife species, such as gray wolves, that have since taken over.

In the case of Japan’s Fukushima Daiichi, the aftermath of the Tohoku earthquake and tsunami caused the plant’s catastrophic failures. Several years on, the surrounding towns struggle to recover, evacuees remain afraid to return, and public mistrust has dogged the recovery effort, despite government assurances that most areas are safe.

Other accidents, such as the partial meltdown at Pennsylvania’s Three Mile Island in 1979, linger as terrifying examples of nuclear power’s radioactive risks. The Fukushima disaster in particular raised questions about safety of power plants in seismic zones, such as Armenia’s Metsamor power station.

Other issues related to nuclear power include where and how to store the spent fuel, or nuclear waste, which remains dangerously radioactive for thousands of years. Nuclear power plants, many of which are located on or near coasts because of the proximity to water for cooling, also face rising sea levels and the risk of more extreme storms due to climate change.

What is nuclear energy used for

Everything around you is made up of tiny objects called atoms. Most of the mass of each atom is concentrated in the center (which is called the nucleus), and the rest of the mass is in the cloud of electrons surrounding the nucleus. Protons and neutrons are subatomic particles that comprise the nucleus.

Nuclear Energy Today

Nuclear reactors produce just under 20% of the electricity in the USA. There are over 400 power reactors in the world (about 100 of these are in the USA). They produce base-load electricity 24/7 without emitting pollutants (including CO₂) into the atmosphere. They do, however, create radioactive nuclear waste which must be stored carefully.

Fission and Fusion

There are two fundamental nuclear processes considered for energy production: fission and fusion.

Click here to see animations of fission and fusion reactions.

Energy density of various fuel sources

The amount of energy released in nuclear reactions is astounding. Table 1 shows how long a 100 Watt light bulb could run from using 1 kg of various fuels. The natural uranium undergoes nuclear fission and thus attains very high energy density (energy stored in a unit of mass).

Table 1 Energy densities of various energy sources in MJ/kg and in length of time that 1 kg of each material could run a 100W load. Natural uranium has undergone no enrichment (0.7% U-235), reactor-grade uranium has 5% U-235. By the way, 1 kg of weapons grade uranium (95% U-235) could power the entire USA for 177 seconds. All numbers assume 100% thermal-to-electrical conversion. See our energy density of nuclear fuel page for details.

Capabilities of Nuclear Power

Sustainable

Table 1 sums the sustainability of nuclear power up quite well. However, there is quite a bit of talk about nuclear fuel (Uranium) running low just like oil. Technically, this is a non-issue, as nuclear waste is recyclable. Economically, it could become a major issue. Today’s commercial nuclear reactors burn less than 1% of the fuel that is mined for them and the rest of it or so is thrown away (as depleted uranium and nuclear waste). The US recycling program shut down in the ’70s due to proliferation and economic concerns. Today, France and Japan are recycling fuel with great success. New technology exists that can greatly reduce proliferation concerns. Without recycling, the 2005 Uranium Reserves “Red Book” published by the U.N. IAEA suggests that there are over 200 years of Uranium reserves at current demand. There is also a very large supply of uranium dissolved in seawater at very low concentration. No one has found a cheap-enough way to extract it yet, though people have come close. Nuclear reactors can also run on Thorium fuel.

Ecological

In operation, nuclear power plants emit nothing into the environment except hot water. The classic cooling tower icon of nuclear reactors is just that, a cooling tower. Clean water vapor is all that comes out. Very little CO₂ or other climate-changing gases come out of nuclear power generation (certainly some CO₂ is produced during mining, construction, etc., but the amount is about 50 times less than coal and 25 times less than natural gas plants. Details coming soon). The spent nuclear fuel (nuclear waste) can be handled properly and disposed of geologically without affecting the environment in any way.

Independent

With nuclear power, many countries can approach energy independence. Being «addicted to oil» is a major national and global security concern for various reasons. Using electric or plug-in hybrid electric vehicles (PHEVs) powered by nuclear reactors, we could reduce our oil demands by orders of magnitude. Additionally, many nuclear reactor designs can provide high-quality process heat in addition to electricity, which can in turn be used to desalinate water, prepare hydrogen for fuel cells, or to heat neighborhoods, among many other industrial processes.

Problems with Nuclear Power

Nuclear Waste

When atoms split to release energy, the smaller atoms that are left behind are often left in excited states, emitting energetic particles that can cause biological damage. Some of the longest lived atoms don’t decay to stability for hundreds of thousands of years. This nuclear waste must be controlled and kept out of the environment for at least that long. Designing systems to last that long is a daunting task — one that been a major selling point of anti-nuclear groups.

Dramatic accidents

Three major accidents have occurred in commercial power plants: Chernobyl, Three Mile Island, and Fukushima. Chernobyl was an uncontrolled steam explosion which released a large amount of radiation into the environment, killing over 50 people, requiring a mass evacuation of hundreds of thousands of people, and causing up to 4000 cancer cases. Three Mile Island was a partial-core meltdown, where coolant levels dropped below the fuel and allowed some of it to melt. No one was hurt and very little radiation was released, but the plant had to close, causing the operating company and its investors to lose a lot of money. Fukushima was a station black-out caused by a huge Tsunami. Four neighboring plants lost cooling and the decay heat melted the cores. Radiation was released and the public was evacuated. These three accidents are very scary and keep many people from being comfortable with nuclear power.

Nuclear power plants are larger and more complicated than other power plants. Many redundant safety systems are built to keep the plant operating safely. This complexity causes the up-front cost of a nuclear power plant to be much higher than for a comparable coal plant. Once the plant is built, the fuel costs are much less than fossil fuel costs. In general, the older a nuclear plant gets, the more money its operators make. The large capital cost keeps many investors from agreeing to finance nuclear power plants.

What Are the Peaceful Uses of Nuclear Energy?

The primary use of nuclear energy is the generation of electrical power. However, there are many other peaceful uses of nuclear energy.

If we work with different isotopes of the same element, we can use nuclear technology for other uses in various fields.

Nuclear energy does not only manifest itself in fission and fusion processes but is also present in radioactive materials, whether natural or artificial.

These radioactive materials have had various applications in different fields, for several decades, for the benefit of humanity.

Its uses in agriculture include its use as tracers to know the use of nutrients and thus the improvement of crops. Also, they have been used to control pests without harming food products in this field.

In medicine, they use nuclear energy to diagnose and treat some kind of tumor, among other uses.

In industry, its uses range from the thickness and density control to component failure detection due to internal defects. They have also been used as energy sources to operate maritime buoys, and some projects allow their use as energy sources for emergency lighting at home.

The International Atomic Energy Agency (IAEA) promotes a solid and sustainable global nuclear safety and security framework along the nuclear fuel cycle in the Member States

The main uses of atomic energy are as follows:

1. Electricity Generation

The most important and well-known use of nuclear energy is the generation of electricity in nuclear power plants.

During the Second World War, the United States dropped two atomic bombs on Japan. At that moment, the world realized how harmful nuclear technology could be. As a result, there were international efforts to encourage the countries to leave atomic weapons aside and rethink nuclear activities to civil and peaceful use.

In this sense, nuclear reactors were given a new use: to generate electricity from the nuclear fission of uranium atoms.

A nuclear power plant is a facility capable of turning out the atomic energy contained in uranium atoms to generate electricity. The process to obtain this conversion is the result of heat exchange and mechanical operation. Uranium is one of the elements on the periodic table of the most unstable elements, making it ideal for this purpose.

At first, the nuclear reactor generates fission reactions of the atomic nuclei of uranium, emitting a large amount of thermal energy. Then, with all this heat energy, high-pressure steam is obtained to drive the plant’s steam turbines. In this way, mechanical energy is conveyed to power the electrical generator and convert the kinetic energy of the shaft into electrical energy.

2. Industrial Processes

Nuclear energy plays a vital role in modern industry, improving measurement and automation processes for product quality control. In particular, it is used in:

Development and improvement of processes.

It is used as a prerequisite for the complete automation of high-speed production lines. In addition, this technology is applied to the research of processes, mixing, maintenance, and the study of wear and corrosion of facilities and machinery.

Nuclear technology is also used in the manufacture of plastics and the sterilization of single-use products.

Nuclear radiation is currently used in a wide field of activities such as quality control in raw materials, industrial processes of cement plants, thermal power plants, or oil refineries.

Some of the branches that we can highlight in the use of nuclear energy are:

Tracings

Radioactive substances are introduced into a specific industrial process to detect the trajectory of said substances thanks to their emission. Thanks to this layout, information is obtained to prolong the life of industrial equipment.

X-rays of Internal Structure in the Pieces

It is a quality control application that is a non-destructive method that allows checking the quality of welds, metal, or ceramic parts without damaging or altering the composition of the material.

Improve Product Quality

An example of this use can be radiation used to create plastics and sterilize «single-use» products.

Zinc Injection

Reduces the radioactive dose rate and mitigates the initiation of stress corrosion cracking.

Mining

Using nuclear probes, the physics and chemistry of soils can be determined, which allows identifying if a stratum contains enough minerals or fuels.

4. Nuclear Medicine

One of the most important applications of nuclear energy after generating electricity is its use to treat and diagnose diseases: nuclear medicine.

Ionizing radiation allows images of the interior of patients to be obtained, helping to diagnose diseases. In addition, this nuclear material is also used to treat diseases such as cancer as it can destroy tumor cells.

One in three patients who go to a hospital in a country in the first world receives the benefits of some nuclear medicine procedure.

Some examples of the use of nuclear medicine are:

Techniques such as radiation therapy to treat malignant tumors

Use of teletherapy for cancer treatment

Radiological biology makes it possible to sterilize medical products.

5. Agriculture and Pest Control

The application of isotopes to agriculture has increased agricultural production in less developed countries.

The agricultural sector uses nuclear and related technologies to adapt to climate change, increasing resource use efficiency and productivity sustainably.

Nuclear technology is beneficial in:

Insect pest control

Maximum use of water resources

Improvement of crop varieties

Establishment of the necessary conditions to optimize the effectiveness of fertilizers and water.

6. Pest Management

The sterile insect technique (SIT) involves mass rearing and sterilizing male insects before releasing them onto pest-infested areas. The method suppresses and gradually eliminates established pests or prevents invasive species and is safer for the environment and human health than conventional pesticides.

Guatemala, Mexico, and the United States of America have been using SIT for decades to prevent the northward spread ( Mexico and the United States) of the Mediterranean fruit fly.

In Latin America, Guatemala sends hundreds of millions of sterile male mosquitoes each week to California and Florida to protect valuable crops, such as citrus. With sterile males unable to reproduce, it is the perfect birth control for insects.

7. Food Security

Nuclear techniques play a crucial role in treating food safely.

Nuclear techniques help national authorities in more than 50 countries improve food safety by addressing harmful residues and contaminants in food products and enhancing their systems with stable isotope analysis.

The application of isotopes makes it possible to increase the preservation of food considerably. Currently, more than 35 countries allow irradiation of some foods.

8. Environment

The application of isotopes makes it possible to determine the exact amounts of pollutants and places where they occur and their causes.

Furthermore, electron beam treatment reduces the environmental and health consequences of the large-scale use of fossil fuels.

Nuclear energy contributes more effectively than other techniques to solve problems such as the greenhouse effect and acid rain.

9. Other Uses of Nuclear Energy

Nuclear energy is also used in the dating of archeological elements. This process is possible thanks to the binding properties of the carbon-14 isotope to bones, wood, or organic waste.

It is also used in Geophysics and Geochemistry. These sciences harness natural radioactive materials to date rock, coal, or oil deposits.

Other uses of nuclear technology occur in disciplines such as hydrology, mining, or the space industry.

Published: May 19, 2010
Last review: September 2, 2021