Nuclear Reactions. Types and Applications

28/03/2026

The online nuclear reaction simulations on this page enlighten us on the basic principles of these reactions, which are the foundation of nuclear weapons and nuclear reactors for power generation. We will discover what nuclear fission and nuclear fusion are and why they are sources of energy.

What are nuclear reactions

Nuclear reactions are processes in which atomic nuclei interact and undergo changes, which can result in the release of energy. These reactions are fundamental in nuclear physics and in the production of energy in the form of nuclear power.

Types of nuclear reactions

There are two main types of nuclear reactions: fission reactions and fusion reactions.

Nuclear fission reactions

In nuclear fission reactions, a heavy nucleus splits into two or more smaller nuclei, releasing a large amount of energy in the process. This type of reaction is the basis of early nuclear weapons and of energy production in nuclear fission reactors.

Nuclear fusion reactions

In nuclear fusion reactions, two light nuclei join together to form a heavier nucleus, also releasing a large amount of energy. Nuclear fusion is the process that occurs inside the Sun and is also used in the most modern and powerful nuclear weapons.

Nuclear power plants

Nuclear fission reactions are the basis for energy production in nuclear power plants, one of the most powerful sources of electricity in existence. In these nuclear power plants, the nuclei of heavy atoms, such as uranium-235 or plutonium-239, are split into smaller fragments. This process releases an enormous amount of energy in the form of heat, which is used to drive electricity-generating turbines.

Nuclear fusion power plants remain a pipe dream today. Although much progress has been made in recent years, there is still no viable and operational solution for this type of power plant. The technical difficulties are enormous; for example, it is necessary to reach temperatures of hundreds of millions of degrees and extreme pressures to keep the plasma confined long enough for the reaction to produce more energy than it consumes. Eventually, they would be a virtually inexhaustible source of energy with enormous implications. Unfortunately, however, there are no plans to build such a plant in the short or medium term.

Atomic weapons

The same nuclear reactions that generate electricity can also be used for destructive purposes in nuclear weapons. There are two main types: fission bombs (such as those dropped on Hiroshima and Nagasaki in 1945) and fusion or thermonuclear bombs, which are much more powerful and use the fusion of light nuclei such as hydrogen. The devastating power of these weapons comes from the sudden release of an immense amount of energy in the form of explosion, radiation, and heat. Their use has had a strong impact on contemporary history and continues to be a subject of international debate, both because of the humanitarian consequences and the need to control their proliferation and prevent their use in armed conflicts.

Other applications of nuclear reactions

In addition to energy production and atomic weapons, nuclear reactions also have applications in medicine, research and materials production. Radiotherapy uses radioactive isotopes to treat cancer, while research reactors are used to generate neutrons for scientific experiments.

Explore the exciting STEM world with our free, online, simulations and accompanying companion courses! With them you’ll be able to experience and learn hands-on. Take this opportunity to immerse yourself in virtual experiences while advancing your education – awaken your scientific curiosity and discover all that the STEM world has to offer!

Nuclear reaction simulations

Alpha
Beta
Fission
Reaction

Alpha

Alpha decay is a variant of radioactive decay whereby an atomic nucleus emits an alpha particle and becomes a nucleus with four units fewer mass number and two units fewer atomic number.

Beta decay

Beta decay or beta emission is a process by which an unstable nucleus emits a beta particle (an electron or positron) to compensate for the ratio of neutrons to protons in the atomic nucleus. This disintegration violates parity.

Nuclear fission

Nuclear fission is the splitting of a nucleus into lighter nuclei, plus some by-products such as free neutrons, photons (usually gamma rays) and other fragments of the nucleus such as alpha (helium nuclei) and beta (high-energy electrons and positrons) particles plus a large amount of energy.

Nuclear reaction

This simulation is intended to show the principle of a nuclear fission reaction. See what happens when bombarding uranium atoms, depending on the concentration. When considering this simulation, note that the proportions of the model presented may not match reality, that the nucleus has been exaggerated and drawn large, and that the electrons around the nucleus are not shown.

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–

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1627

–

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1875

–

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1620

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Test your knowledge

What are nuclear reactions, and what processes do they involve?

Nuclear reactions are processes in which atomic nuclei undergo transformations that can release or absorb large amounts of energy. Unlike chemical reactions, which involve electrons, nuclear reactions directly modify the structure of the nucleus, changing the number of protons, neutrons or both. There are two main types: fission, in which a heavy nucleus splits into smaller nuclei, and fusion, where light nuclei combine to form a heavier one. Both processes release energy due to differences in nuclear binding energy. Nuclear reactions are fundamental in nuclear physics, in the production of energy in fission reactors and in the processes that power stars like the Sun. They also have applications in medicine, research and materials generation.

How do fission and fusion differ, and why do both release so much energy?

Nuclear fission consists of splitting a heavy nucleus, such as uranium‑235 or plutonium‑239, into smaller fragments. This process releases energy because the fission products are more stable and have a lower binding energy per nucleon. Nuclear fusion, on the other hand, joins light nuclei such as hydrogen isotopes to form a heavier nucleus. It also releases energy because the resulting nucleus has a higher binding energy. Fission is currently used in nuclear power plants, while fusion is the process that powers the Sun and thermonuclear weapons. Although fusion could provide almost unlimited energy, it requires extreme temperatures and pressures that have not yet been maintained in a stable way in terrestrial reactors.

Why do nuclear reactions release so much energy?

The energy released in a nuclear reaction comes from the atom’s nucleus itself, where the forces that hold protons and neutrons together are much stronger than chemical forces. When a nucleus splits or fuses, its binding energy changes, and that difference is released as heat, radiation or particle motion. Although the amount of matter that changes is very small, the famous relation shows that even a tiny variation in mass produces an enormous amount of energy. That is why nuclear reactions are so powerful.

How do fission nuclear power plants produce electricity?

In a fission nuclear power plant, heavy nuclei such as uranium‑235 split into smaller fragments. This reaction releases a large amount of heat, which is used to heat water and produce steam. The steam drives turbines connected to generators, which transform mechanical energy into electricity. Although the nuclear process takes place inside the reactor, the final part—turbines and generators—works just like in a conventional thermal power plant. The difference is that the heat comes from nuclear reactions instead of fossil fuels.

What other applications do nuclear reactions have besides producing energy?

Nuclear reactions are used in many fields. In medicine, radiotherapy uses radioactive isotopes to destroy cancer cells. In research, experimental reactors generate neutrons that make it possible to study materials and carry out scientific experiments. They are also used to produce isotopes employed in medical diagnosis, food preservation and the analysis of works of art. Even in industry they are used to improve materials or detect flaws in structures through radiation‑based techniques.