Difference Between Nuclear Fission and Nuclear Fusion

Edited by Diffzy | Updated on: July 12, 2023


Difference Between Nuclear Fission and Nuclear Fusion

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Most of the energy produced around us is by some or the other chemical processes. And if you are a chemistry lover, then my reader, this article is just for you! Today we live in an "Atomic" era. In this era, we can produce energy by breaking the bond of the form of matter, an atom. The potential of this atomic era can turn out to be huge if used wisely and ethically.

Chemical reactions used to generate a very high amount of energy are known as nuclear reactions. Today nuclear energy is the world's second-largest source of low-carbon electricity behind hydropower. Generally, the process of nuclear fission generates energy in nuclear power plants. Energy generation by nuclear fusion on the earth is still under research, but in nature, many stars and celestial bodies use nuclear fusion to release energy. In recent times, nuclear energy has proved to be extremely useful for power generation. Conventional fuels like oil and coal are becoming outdated because of their pollutant properties and declining sources of oil wells and coal mines.

Nuclear Fission vs Nuclear Fusion

Now you would wonder what the difference between nuclear fission and fusion is when both reactions produce energy. Nuclear fission is a process in which the nucleus of a heavy atom splits into two or more daughter nuclei, usually into equal masses. In a nuclear fusion reaction, two lightweight nuclei combine to form a single heavier-mass nucleus. Usually, nuclear fission occurs when a highly energized particle bombards the heavy-mass nucleus. Nuclear fusion occurs when an atom is accelerated close to the speed of light or heated to extremely high temperatures and pressure.

Difference Between Nuclear Fission and Nuclear Fusion in Tabular Form

Parameters of comparisonNuclear FissionNuclear fusion
DefinitionIt is a reaction in which one nucleus splits into two or more number nuclei, and this causes the release of energy, which balances the energy equation.It is a reaction in which two light nuclei join to form one whole nucleus, and the extra energy is released to balance the energy equation.
ProcedureNuclear fission can be achieved, by bombarding a variety of accelerated particles like protons, neutrons, alpha particles, or gamma rays radiation.Nuclear fusion can be achieved, in a state of matter called plasma.
Energy releasedThe energy released in this reaction is extremely high.The energy released in this reaction is relatively higher than nuclear fission.
Fuels used for the reactionsUraniumA mixture of deuterium and tritium
Use in power generationThis reaction can produce clean, safe, and sustainable energy. There are well-developed technologies existing today for harnessing this energy by nuclear fission.This reaction can produce four times more energy than produced by nuclear fission. Technology for power generation by fusion is still under research.
The energy required to induce the reactionHighExtremely high. Higher than a fission reaction.
Natural occurrenceNoneOccurs naturally in stars, the sun, and some other celestial bodies.

What is Nuclear Fission?

Nuclear fission was discovered just before the second world war. The atom bomb essentially works on the principle of nuclear fission. It was first discovered by German radiochemists Otto Hahn and Fritz, accompanied by Lise Meitner. They found out that when a nucleus of a heavy element bombards with highly energized neutrons, the core nucleus of a heavy element disintegrates into two or more number nuclei and releases energy. The energy released is equal to the mass lost in the process of nuclear fission, which converts into kinetic and heat energy.

This discovery created the most incredible history in the technological era.


The fission process works on the fundamental of energy conservation.

The particles bombarded on heavy element provides enough energy to the neutrons in the nucleus of the atom that the neutron breaks the nuclear forces and disintegrates from the nucleus.

The energy released is enormous and can start a chain reaction.

The chain reaction is explained further as follows. In the fission process, a large quantity of energy is released, radioactive products are formed, and several neutrons are emitted. These neutrons can induce fission in a nearby nucleus of fissionable material and release more neutrons that can repeat the sequence, causing a chain. This chain reaction continues until all the original nuclear fuel is exhausted.

A controlled chain reaction can benefit society but uncontrolled reaction results in nothing but unimaginable destruction.


The nucleus is struck by a neutron (gamma rays), and this neutron gets absorbed by the nucleus.

Due to an imbalance of mass, the nucleus deforms.

Disintegration takes place rapidly, and the nuclear forces are overpowered.

The disintegrated nuclei release two or more neutrons in the form of heat energy.

Fission products are formed.

Radioactive decay occurs wherein fission products lose their excess energy, and the emission of particles takes place.

Nuclear Reactor

All the above process occurs in a nuclear fission reactor. A nuclear reactor is the most important part of a nuclear power plant. It is where nuclear-chain reactions occur that produce energy by fission. The heat produced can be used to produce electricity.

A significant purpose of a reactor is to contain and control the energy released. The preferred nuclear fuel is sealed inside metal tubes. These tubes are called fuel rods. Generally, about 200 such rods are assembled to form a fuel assembly. A collection of such assemblies is called a core.

The fuel rods are dipped in water in the reactor, which functions as both a coolant and moderator. The job of the moderator is to slow down the neutrons produced by fission to control the chain reaction. Control rods may be immersed in the reactor core to reduce the reaction rate or pulled out to increase the same. The heat produced by such reactions converts the water into steam, which is further converted into carbon-free electricity with the help of turbines.


The two major uses of nuclear fission reactions are energy generation in power plants and the development of atomic weapons.

So how is power generation from nuclear reaction beneficial to society? Let's look into its advantages over other power-generating sources.

Clean Source For Power Generation

Unlike other energy sources which are harmful to the environment or are depleting, nuclear energy is cleaner and creates zero carbon waste. In contrast to fossil fuels, which cause serious damage to the environment, nuclear fission produces energy without releasing greenhouse gases into the atmosphere, which reduces the effects of global warming and even helps fight pollution. With more research and developments in nuclear fission reactions, this energy source is becoming easier to harness.

Sustainable Energy Source

An enormous amount of energy is produced by the process of nuclear fission, which can be utilized to satisfy the needs of next-generation high-tech cities and industries. As this is a very rapid reaction, energy can be produced depending on the requirement with greater reliability.

Economic Source Of Energy

The cost of operation is little once the nuclear power plant is commissioned. The cost of operating the plant is only the payment of workers to run the plant and the cost of the raw materials required.

Hazards And Tragedies In The Past

Just like every coin has two sides, this incredible source of energy has a few cons. The trade-off to high energy generation is:

Very High Risk Of Radiation Exposure

The radiation emitted during the fission reaction is extremely harmful to humans and animals. The workers who are exposed while working at nuclear power plants are at great risk of radiation poisoning, cancer, and other diseases associated with radiation.

High Vulnerability

No matter how advanced technology encases nuclear reactions, there remains a high risk of explosion and uncontrolled nuclear reactions. Any minute accident at a nuclear plant can cause enormous damage, affecting the lives of millions.

Radioactive Contamination Risk

The waste released from the nuclear power plant is highly radioactive and harmful to all living beings. There are high chances of water contamination from these plants which can cause diseases and death in living beings.

High Cost Of Plant Construction And Approval

Building a nuclear power plant requires a mighty investment, and this is due to the latest technologies and safety measures necessary to run it properly.

What is nuclear fusion?

Have you ever wondered how the sun constantly generates energy? The answer is nuclear fusion. The atmospheric condition of the sun is favorable for nuclear fusion. Due to the very high density, temperature, and pressure on the surface of the sun, light elements like hydrogen, helium, and isotopes of hydrogen keep fusing, and energy is released in the form of heat. This same heat is radiated to the earth. The energy released because of fusion is called binding energy. To understand fusion even better let's dive into detail.


  • Nuclear fusion is essentially the antithesis of the fission process. Light nuclei are combined to release excess binding energy and they form a heavier nucleus.
  • It works on the principle of conservation of energy.
  • Since the fusion products are more stable than the parent nuclei more energy is released in this reaction.
  • The net energy output is greater here than in fission, but so is the energy input required to start the reaction.
  • The condition for fusion is high temperature, density, and pressure.


  • The nuclear reaction fuel (usually isotopes of hydrogen) is first compressed and heated to a very high temperature.
  • After the conditions are suitable for the fusion reaction, the repulsive forces are overpowered, and the nuclei of atoms start merging.
  • After the initiation of the reaction, there is an increase in the collision of atoms and more energy is released.
  • The chain reaction continues until all the nuclear fuel is exhausted.

Fusion Reactors

The major function of a fusion reactor is to create conditions suitable for the fusion reaction to take place and then to contain the reaction. Since the conditions for fusion are as good as creating the conditions on the surface of the sun, it is still a challenge to build a fusion reactor for energy production purposes.

Some of the challenges to building a commercial fusion reactor are –

  •  Difficulty in achieving the heating of the reacting mixture to a very high temperature, to overcome the repulsive forces of positively charged nuclei.
  • Compressing the mixture to a high density so that the probability of collision (and thus reaction) among the nuclei can be high, and keeping the reacting mixture together long enough for the fusion reaction to produce energy at a rate that is greater than the rate of energy input (as heat and compression).
  • The biggest challenge is that of providing a huge amount of energy to the reactants. This is why fusion is called a thermonuclear reaction.

Advantages Of Nuclear Fusion Over Fission

  • Fusion offers several advantages over fission. One advantage is that the reserves of fusionable isotopes are much larger than those of fissionable isotopes; in fact, they are essentially unlimited.
  • Another advantage is that the products of fusion reactions are less radioactive than the products of fission reactions. Among the products of the fusion reactions listed above, only tritium and neutrons are radioactive.
  • The last advantage of fusion lies in its inherent safety. There would be very little fusionable material at any given time in the reactor and the likelihood of a runaway reaction would thus be very small. Furthermore, the reaction is so hard to achieve in the first place that small perturbations in reactor conditions would probably terminate it.

Main Differences Between Nuclear Fission and Fusion In Points

  • Nuclear fission means the splitting of the nucleus into two or more nuclei whereas nuclear fusion means the merging of two nuclei to form one heavier nucleus.
  • Nuclear fission does not occur naturally in nature whereas nuclear fission occurs naturally in the sun and stars.
  • Fission occurs when highly energized neutrons or radiations are bombarded on a heavy nucleus. This extra energy provided overpowers the nuclear forces in an atom and thus disintegrates the atom into two or more nuclei. Whereas nuclear fusion occurs when the nuclear fuel is subjected to high density, temperature, and pressure conditions, also called the plasma state.
  • The energy released in fusion is much larger than in fission.
  • Fission is more dangerous while fusion reactions create less radioactive products and thus are safer than nuclear fission.
  • Technology to harness power from nuclear fission is much more developed than that of nuclear fusion. There is still much research on going to use of nuclear fusion on a commercial level for power generation.


Nuclear energy is by far the most advanced method of power generation. It can achieve heights in technological developments like never before. Fission is a much more developed concept than fusion and both nuclear reactions have changed the ideas of power generation. Ammunition technology has become advanced but at the same time extremely dangerous.

Any energy resource if used ethically and morally can turn out to be beneficial to society and the scientific community. Nuclear energy can be a boon or a bane to humanity. It is up to us how we choose to use it.


  • https://www.iaea.org/newscenter/news/what-is-nuclear-fusion
  • https://personal.ems.psu.edu/~radovic/Chapter14.pdf


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"Difference Between Nuclear Fission and Nuclear Fusion." Diffzy.com, 2024. Mon. 17 Jun. 2024. <https://www.diffzy.com/article/difference-between-nuclear-fission-and-nuclear-fusion>.

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