Nuclear Energy

How Does Nuclear Energy Work?

By April 22, 2021No Comments
how does nuclear energy work

How Does Nuclear Energy Work?

Nuclear energy is one of the leading sources of energy for generating electricity, with over 30 countries running 400 commercial reactors. On average, it is responsible for around 20% of all energy production depending on what country you are from. However, among green energy sources, it takes up around 55% of all carbon-free energy production. Perhaps everybody knows that nuclear power plants work with radioactive material. But how exactly does nuclear energy work?

If you have been nursing this question and want to know more about what powers the system and how it generates electricity, here is your explanation. We will also elaborate on what nuclear fission is and what the different types of nuclear power plants are.

How Does Nuclear Energy Work To Generate Electricity?

There is not much difference in how a nuclear reactor works to how other power plants work. Like other power generating systems, be it geothermal or coal-burning power plants, a nuclear reactor produces electricity by a generator propelled by steam. The only difference between the various power plants is how they generate heat to boil water and produce steam. In other words, it comes down to what type of fuel is used.

As the name suggests coal power plants burn coal. However, nuclear plants use mostly radioactive uranium as their fuel. A nuclear energy power plant uses a chain reaction process to generate energy and create steam that eventually turns the turbine.

The nuclear reactor creates heat by splitting a radioactive element, known as the fuel. The generated heat boils the water to create steam, and the steam pressure turns the turbine connected to a generator. The generator then produces electricity.

Nuclear Reactors Types

There are different nuclear reactors, with pressurized water reactors and boiling-water nuclear reactors being the most commonly used. The main distinction between them is the number of water supply loops they have.

Pressurized Water Reactor (PWR)

Pressurized water reactor is a common type of reactor that uses two loops of water supply. However, the high pressure does not allow the water in the reactor vessel to boil. The supper-heated water is directed to the steam generator, which contains several small pipes.

The heat in the pipes interacts with another water supply, turning it to steam. Subsequently, the steam turns the turbine.

In this nuclear energy power plant, there are two sections (loops) of water supply: one in the reactor and the other one in the turbine. The water in the reactor section goes back to the reactor vessel, while the steam in the turbine is condensed to water and directed back to the steam generator.

diagram of how pressurized water nuclear reactor works

Diagram of how pressurized water nuclear reactor works.

Boiling Water Nuclear Reactors (BWR)

Unlike the pressurized water reactor, the boiling-water reactor has only one water supply section. This means that the system heats water by the energy escape from fission to produce steam that turns the turbine. What is fission? Read on to find out.

Other nuclear reactor types include:

  • Advanced gas-cooled reactor (AGR)
  • Light water graphite-moderated reactor (LWGR)
  • Fast neutron reactor (FNR)

Are There Other Fuels Other Than Uranium?

There are different fuels to power nuclear reactors, with uranium being the most common. Uranium, a naturally radioactive element, is widely used for fuelling nuclear power plants, thanks to its abundance and availability in several sources. Uranium is a radioactive isotope, which means it is an unstable element.

Because of its instability, it naturally generates heat when broken down naturally under the earth. The natural breaking down of elements is called radioactive decay. Moreover, the nuclear energy system takes advantage of this, “mechanically” breaking down uranium to produce heat for powering its turbine to ultimately generate electricity.

Other fuels for nuclear reactors include thorium and plutonium.

Nuclear Fission

To answer the question of how does nuclear energy work, the term “fission” needs to be understood. The reason is, nuclear reactors depend on fission for heat to boil the water into steam. The fission occurs at the atomic level. It is also worth pointing out that fission can only occur in unstable elements called radioactive isotopes.

Fission (also known as nuclear fission) is the process of dividing (or splitting) atoms into smaller atoms. This nuclear reaction is initiated by a neutron. As more atoms are being split into smaller particles, new neutrons are released as a result. The newly released neutrons have the freedom to react with other atoms, causing a nuclear reaction.

While nuclear fission is taking place and atoms are being split, vast amounts of energy in the form of heat are released along with radiation. The released energy is essential for powering the reactor, turning water into steam.

The nuclear fuel comes in small pellets  and each of them houses millions of nuclei (atoms). Each pellet contains an enormous amount of energy. In comparison, one pellet contains as much energy as 1000 kg of coal.

When atoms are split, producing more neutrons to interact with more atoms, there needs to be a way to control the reaction. It needs to be slowed down if needed, accelerated, or stopped completely.  In other words, the nuclear reactor operators have to be able to control the number of neutrons inside the core. If they did not have such a mechanism in place, there would run the risk of everything spiraling out of control. This is where control rods come in. Read on!

Also Read: What are the Advantages of Wind Energy?

How Does Nuclear Energy Work: Different Components

To understand how a nuclear reactor works to generate electricity, it is important to talk about its different components and their functions:


Fuel is necessarily needed to generate heat, and, as mentioned earlier, uranium is the most commonly used fuel to power nuclear reactors. For a new reactor with new fuel to start operation, a neutron source is required. This source can be radium, beryllium, polonium, or any other alpha-emitter.

However, this is not necessary when restarting a reactor with used fuel.


In a nuclear reactor, a material is needed to slow down the speed of neutrons in nuclear fission. It is not to absorb or eliminate them. The ultimate purpose of this material is to ensure neutrons are more effective in interacting with the atoms and continued fission can be sustained. Common materials used as a moderator are water, heavy water, and graphite.

If you have watched the HBO series Chernobyl about the tragedy that happened more than 30 years ago, you would see graphite lying on the ground. The graphite was used to moderate the neutrons in the reactor.

Control Rods or Blades

As the name suggested, control rods are used to control the reaction rate in the nuclear reactor. The rods, typically made of hafnium, boron, or cadmium, are neutron-absorbing material. This means, as opposed to the moderator, their primary task is to slow down, accelerate, or completely stop the nuclear reaction. They are inserted or withdrawn from the core as appropriate.

the shape of cooling towers is specifically designed to effectively cool the fluid in the system

The shape of cooling towers is specifically designed to effectively cool the fluid in the system.


Coolant is the liquid needed to transfer heat from fission to the turbine. Most systems, except BWR, use two loops of fluids to transfer heat to the turbine. Two loops are used mainly to eliminate the partial radioactivity of the primary fluid. Both fluids are continuously recycled back to the system.

Steam generator

This part collects high-pressure primary coolant that transfers heat from the reactor and uses it to heat another liquid into steam. Steam generators are only used in pressurized water reactors (PWR). Due to its high pressure, the primary coolant is unable to reach its boiling point. Reactors have up to six loops with an individual steam generator.


This is like housing for all the components in a nuclear reactor. The purpose of the containment is to protect the components from outside intrusion. The containment also ensures that those outside are protected from the effects of the system should anything go wrong.

Because nuclear energy power plants work with radioactive material, safety measures are built in to contain radiation in the unlikely event of it escaping. It is generally a concrete or steel structure with a meter-thick shell.

Other components include the turbine that transfers the rotational movement to the generator. Moreover, there is a condenser(s). Its main task is to turn hot steam back into water to be then recycled back to the system. Cooling towers, as the name suggests,  cool and recycle the water.