Grade 7 – Nuclear Energy

Nuclear Explained by Andrea Galindo, IAEA Office of Public Information and Communication

Adapted from:

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.

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 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.

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.

Other Uses of Nuclear Technology

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There are a number of other beneficial uses for nuclear technology in addition to creating electricity. These range from agriculture to medical, and space exploration to water desalination.

Agriculture and Food

In many parts of the world, agricultural workers use radiation to prevent harmful insects from reproducing. When insects cannot have offspring, there are fewer of them. Reducing the numbers of pests and bugs protects crops, providing the world with more food.

Irradiation also kills bacteria and other harmful organisms in food. This type of sterilization occurs without making food radioactive or significantly affecting the nutritional value. In fact, irradiation is the only way to kill bacteria in raw and frozen foods effectively.


Nuclear technologies provide images inside the human body and can help to treat disease. For example, nuclear research has allowed doctors to predict precisely the amount of radiation required to kill cancer tumors without damaging healthy cells.

Hospitals sterilize medical equipment with gamma rays safely and inexpensively. Items sterilized by radiation include syringes, burn dressings, surgical gloves and heart valves.

Space Exploration

Nuclear technology makes deep space exploration possible. The generators in unmanned spacecraft use the heat from plutonium to generate electricity and can operate unattended for years. This reliable, long-term source of electricity powers these spacecraft, even as they venture deep into space.

The Nuclear Energy Institute notes that Voyager 1, which was launched in 1977 to study the outer solar system, is still transmitting data today.

Water Desalination

The World Nuclear Association notes that one-fifth of the world’s population does not have access to safe drinking water and that number is expected to grow. Nuclear technology can play an important role in overcoming this challenge.

Water desalination is the process of removing salt from saltwater to make the water drinkable. However, this process requires a lot of energy. Nuclear energy facilities can provide the large amount of energy that desalination plants need to provide fresh drinking water.

Criminal Investigation

Criminal investigators frequently rely on radioisotopes to obtain physical evidence linking a suspect to a specific crime. They can be used to identify trace chemicals in materials such as paint, glass, tape, gunpowder, lead, and poisons.


Hospitals use gamma radiation to sterilise medical products and supplies such as syringes, gloves, clothing, and instruments that would otherwise be damaged by heat sterilisation.

Many medical products today are sterilised by gamma rays from a cobalt-60 source, a technique which generally is much cheaper and more effective than steam heat sterilisation. The disposable syringe is an example of a product sterilised by gamma rays. Because it is a ‘cold’ process, radiation can be used to sterilise a range of heat-sensitive items such as powders, ointments, and solutions, as well as biological preparations such as bone, nerve, skin, etc, used in tissue grafts.

The benefit to humanity of sterilisation by radiation is tremendous. It is safer and cheaper because it can be done after the item is packaged. The sterile shelf life of the item is then practically indefinite provided the package is not broken open. Apart from syringes, medical products sterilised by radiation include cotton wool, burn dressings, surgical gloves, heart valves, bandages, plastic and rubber sheets, and surgical instruments.

Insect control

In addition to agricultural pest control (see Agriculture section above), SIT has found important applications in the fight against disease-carrying insects. The most recent high-profile application of SIT has been in the fight against the deadly Zika virus in Brazil and the broader Latin America and Caribbean region. Following its outbreak, impacted countries requested urgent support from the IAEA to help develop the established technique to suppress populations of disease-carrying mosquitoes. The IAEA responded by providing expert guidance, extensive training, and by facilitating the transfer of gamma cell irradiators to Brazil.