1. Nuclear Energy

How does a nuclear reactor work?

Nuclear reactors are, fundamentally, large kettles, which are used to heat water to produce enormous amounts of low-carbon electricity. They come in different sizes and shapes, and can be powered by a variety of different fuels.

A nuclear reactor is driven by the splitting of atoms, a process called fission, where a particle (a ‘neutron’) is fired at an atom, which then fissions into two smaller atoms and some additional neutrons. Some of the neutrons that are released then hit other atoms, causing them to fission too and release more neutrons. This is called a chain reaction.

The fissioning of atoms in the chain reaction also releases a large amount of energy as heat. The generated heat is removed from the reactor by a circulating fluid, typically water. This heat can then be used to generate steam, which drives turbines for electricity production. 

In order to ensure the nuclear reaction takes place at the right speed, reactors have systems that accelerate, slow or shut down the nuclear reaction, and the heat it produces. This is normally done with control rods, which typically are made out of neutron-absorbing materials such as silver and boron.

Two examples of nuclear fissioning of uranium-235, the most commonly used fuel in nuclear reactors.

Nuclear reactors come in many different shapes and sizes – some use water to cool their cores, whilst others use gas or liquid metal. The most common power reactor types use water, with more than 90% of the world’s reactors being water-based. Further information on the many different types of reactor around the world can be found in the Nuclear Power Reactors section of the Information Library.

Nuclear reactors are very reliable at generating electricity, capable of running for 24 hours a day for many months, if not years, without interruption, whatever the weather or season. Additionally, most nuclear reactors can operate for very long periods of time – over 60 years in many cases. In 2019, units 3&4 at the Turkey Point plant in Florida were the first reactors in the world to be licensed for 80 years of operation.  

What fuels a reactor?

A number of different materials can be used to fuel a reactor, but most commonly uranium is used. Uranium is abundant, and can be found in many places around the world, including in the oceans. Other fuels, such as plutonium and thorium, can also be used. 

Most of today’s reactors contain several hundred fuel assemblies, each having thousands of small pellets of uranium fuel. A single pellet contains as much energy as there is in one tonne of coal. A typical reactor requires about 27 tonnes of fresh fuel each year. In contrast, a coal power station of a similar size would require more than two-and-a-half million tonnes of coal to produce as much electricity.

Nuclear fuel pellets are not much larger than a sugar cube

How about the waste?

Like any industry, the nuclear industry generates waste. However, unlike many industries, nuclear power generates very little of it – and fully contains and manages what it does produce. The vast majority of the waste from nuclear power plants is not very radioactive and for many decades has been responsibly managed and disposed of. If nuclear power was used to supply a person’s electricity needs for an entire year, only about 5 grams of highly-radioactive waste would be produced, which is the same weight as a sheet of paper. 

The used fuel which comes out of the reactor can be managed in different ways, including recycling for energy production or direct disposal. As a matter of fact, many countries have been using recycled fuel for decades to partially fuel their reactors.  

Used nuclear fuel awaiting recycling

1. Nuclear Energy

Worldwide facts

For more than 60 years, nuclear energy has provided the world with reliable electricity.  Today, more than 400 reactors are operating in more than 30 countries. 

These plants generate around 10 percent of the world’s electricity without emitting greenhouse gases.

More nations are exploring the use of nuclear energy, particularly as electricity demand increases and concerns about climate change rise.

1. Nuclear Energy

Nuclear Fission

Fission is the process of splitting a nucleus in two.

Inside each uranium fuel pellet, there are millions of uranium nuclei. When these nuclei are split, a huge amount of energy is released. Some of this energy is from radiation, but the biggest source is kinetic energy. This is the energy that produces heat inside a reactor, which in turn is used to generate steam, and ultimately creates electricity.

1. Nuclear Energy


Enriched uranium is the fuel for nuclear reactors. Uranium is an abundant, naturally radioactive element found in most rocks. As uranium breaks down or decays, it produces heat inside the Earth’s crust. A similar process generates heat inside a nuclear reactor.

1. Nuclear Energy

How does it work?

A nuclear reactor produces electricity in much the same way other power plants do. The chain reaction produces the energy, which turns water into steam. The pressure of the steam turns a generator, which produces electricity.

The difference is in how the heat is created. Power plants that run on fossil fuels burn coal, oil or natural gas to generate heat. In a nuclear energy plant, heat is produced from splitting atoms – a process called nuclear fission.

  • Nuclear reactor creates heat that is used to make steam
  • The steam turns a turbine connected to an electromagnet, called a generator
  • The generator produces electricity

In a Pressurized Water Reactor (PWR) – the type of reactor being built in the UAE – high pressure prevents water in the reactor vessel from boiling. The super-heated water is carried to a steam generator, which is made up of many small pipes. The heat in these pipes is used to turn a second, isolated, supply of water to steam, which is in turn used to drive the turbine. The water from the reactor is pumped back into the reactor vessel and reheated. The steam from the turbine is cooled in a condenser and the resulting water is sent back to the steam generator.

1. Nuclear Energy

Nuclear Energy in the UAE

In the UAE, the Barakah Nuclear Energy Plant, located in the Al Dhafra Region of the Emirate of Abu Dhabi, is home to four reactors. Each reactor is designed to produce 1,400 megawatts (MW) of electricity with nearly zero carbon emissions.

Built to operate for 60 years or more, these reactors will provide efficient and reliable low-carbon electricity to the nation for generations to come. Once fully operational, the plant will prevent the release of more than 21 million tonnes of greenhouse gas emissions per year. This is equivalent to removing 3.2 million sedan cars from the UAE’s roads.

In 2016, ENEC established Nawah Energy Company, which is responsible for operating and maintaining the four reactors at Barakah. As the teams at both ENEC and Nawah prepare for the plant to transition from a construction project to an operating facility, they work to ensure that it meets the highest national and international standards of quality, and benefit from global operating experience.

1. Nuclear Energy

What is nuclear energy?

Nuclear energy provides efficient and reliable electricity around the world. Today, more than 400 commercial reactors operate in more than 30 countries.

The common definition for nuclear energy is the energy released by a chain reaction, especially by fission or fusion. Practically speaking, nuclear energy uses fuel made from mined and processed uranium to make steam and generate electricity.

Nuclear generation is the only source of electricity that can produce a constant supply of power – known as baseload power—reliably without emitting greenhouse gases.

Nuclear energy has one of the lowest environmental impacts on land and natural resources of any electricity source.

1. Nuclear Energy

What is Nuclear Energy?

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 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.

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.

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.

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.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.