What Is a Nuclear Reactor?

A nuclear reactor (or atomic reactor) is a facility capable of converting nuclear energy into thermal energy. The reactors have the ability to start, control and maintain the nuclear chain reactions that occur in the core of this facility.

What is a nuclear reactor?

In a common nuclear power plant, nuclear reactors are used for the production of thermal energy and to generate steam to drive the steam turbines with which it is obtained.

Uses and Applicactions of Nuclear Reactors

A nuclear reactor is primarily used to generate electrical power through a process called controlled nuclear fission. Nuclear power plants are facilities designed to use nuclear reactors for this purpose.

However, there are atomic reactors to fulfill other objectives. Here are some uses and benefits of nuclear reactors:

Electric Power Generation

Nuclear reactors are a continuous source of electrical power. Nuclear fission produces a large amount of heat, which is used to generate steam and drive turbines that, in turn, generate electricity.

One of the main advantages that atomic reactors provide is that they can operate for long periods without interruption. In this way, they can provide a constant base power source to meet electrical demand.

Radioisotope Production

Nuclear reactors are also used for the production of radioisotopes used in medicine, research, and industrial applications.

Some radioisotopes have unique properties that are used in medical diagnosis and treatment, such as imaging and radiation therapy.

Scientific and Technological Research

Nuclear reactors play a crucial role in scientific research and technological development.

Research reactors are used for:

  • Study the physics of atomic nuclei.

  • Conduct research on nuclear materials.

  • Simulate extreme conditions.

  • Analyze security.

  • Improve and develop new reactor designs.

What Are the Parts of a Nuclear Reactor?

A nuclear reactor is made up of the following components:

Nuclear Reactor Core

The reactor core is made up of fuel rods with a characteristic geometric shape. It is cooled by a fluid, usually water.

In some nuclear reactors, the core is located inside a water pool, about 10 to 12 meters deep, or inside a pressure vessel made of steel.

A reactor vessel is the pressure vessel containing the nuclear reactor coolant, core shroud, and reactor core.

Nuclear Fuel Rods

What is a nuclear reactor?

They are the physical place where nuclear fuel is confined. Some fuel rods contain uranium mixed in aluminum in the form of flat sheets. These sheets are separated by a certain distance that allows the circulation of heat sink fluid.

The sheets are located in a kind of box that serves as a support.

Nuclear Fuel

Nuclear fuel is a material with the ability to fission sufficiently to reach critical mass. That is, to maintain a nuclear chain reaction. It is positioned so that the thermal energy that produces this atomic reaction can be quickly extracted.

What is a nuclear reactor?Solid nuclear fuel is used in nuclear power plants. Nuclear fuels vary depending on the type of reactor, but generally, uranium fuel derivatives or plutonium are used.

Natural uranium is mined from uranium mines, but it is not radioactive enough to be used directly in a reactor. Natural uranium undergoes an enrichment process to obtain more unstable isotopes to increase the coefficient of reactivity.

Control Rods

Control rod bundles provide a quick means of monitoring chain reactions. These bars allow rapid changes in reactor power and its eventual shutdown in case of emergency.

The control rods are made of neutron-absorbing materials and are usually the same dimensions as the fuel elements. 

The fuel assemblies in the core are arranged in rows of 10 aligned along with linear support structures.

The core reactivity coefficient is increased or decreased by raising or lowering the control rods. By submitting or reducing them, the presence of neutron absorbing material in the nucleus is modified.

What is a nuclear reactor?

In typical operation, a nuclear reactor has the control rods fully or partially removed from the core.

The design of nuclear power plants is such that in the event of a failure in a reactor safety or control system, it always acts in the sense of maximum safety, fully inserting all the control rods into the reactor core.

This action brings the nuclear reactor to a safe shutdown in a few seconds.

Nuclear Moderator

The neutrons resulting from a nuclear fission reaction have high kinetic energy. The higher their speed, the less likely they are to fission other atoms, so it is convenient to reduce this speed to encourage new chain reactions.

The moderator's function is to reduce the neutrons' kinetic energy through the neutrons' elastic collisions with the moderator's nuclei.

Reactor Coolant

The reactor uses a coolant to take advantage of the thermal energy given off by nuclear fission reactions. The coolant's function is to absorb this heat energy and transport it to other plant elements and generate electricity.

The coolant must be anti-corrosive, with a high heat capacity, and must not absorb neutrons.

Neutron Reflector

A certain number of neutrons tend to escape from the region where they are produced in a nuclear chain reaction. This leakage of neutrons can be minimized with a reflector medium that redirects them within the reaction region.

The reflective medium that surrounds the nucleus must have a low effective capture section to reduce the number of neutrons and that as many as possible of them are reflected.

Nuclear Reactor Shield

When the reactor is in operation, a large amount of radiation is generated. Shielding is used to protect and isolate facility workers from radioactivity caused by fission products.


Published: July 18, 2012
Last review: May 22, 2023