Difference Between Nuclear Fission and Nuclear Fusion

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The process of nuclear fusion is just the opposite of that of nuclear fission. We can distinguish between nuclear fission and nuclear fusion by considering the following scenario:

Two highly active atoms are approaching each other and after the collision, because of the strong inter-atomic force of attraction, they fuse to form a bigger atom, we can say this is similar to nuclear fusion, and similarly, if a source of energy (light) splits into quanta or photons, we say it the nuclear fission process.

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Difference Between Nuclear Fission and Nuclear Fusion

Nuclear Fission:

The word ‘fission’ clearly signifies splitting or breaking of something into smaller pieces. Here, nuclear fission means breaking or splitting of a big or a parent atom into smaller ones or two or more daughter atoms. Technically, these small atoms are light in their weights.

When the breaking occurs, a large amount of energy is released, which signifies that the nuclear fission process is exothermic.

Nuclear Fusion:

The word ‘fuse’ means combining two or more objects together. Here, the word ‘nuclear fusion’ means two or more atoms combine to form a big atom. Since it requires absorbing energy to fuse two atoms, the nuclear fusion process is endothermic. We can think of two bogies of trains joining or fusing through a magnet.

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Difference Between Nuclear Fission and Nuclear Fusion in Tabular Form 


Nuclear Fission

Nuclear Fusion 

Definition to distinguish between nuclear fission and nuclear fusion

Splitting of one atom into two or more daughter atoms (lighter ones).

Combination of two or more lighter atoms to form a large one.

Process of natural occurrence

Fission cannot be observed in nature as this reaction doesn’t occur naturally. 

Fusion processes can be observed in stars such as the Sun.

By-products formed after reaction

After fission, a lot many highly radioactive particles are generated.

In the process of nuclear fusion, a very few radioactive particles are produced; however, on using fission "trigger" is used, radioactive particles formation takes place.

Critical conditions 

For a nuclear fission process to occur, it is necessary to have a critical mass of the substance with high-speed neutrons.

For a nuclear fusion process to occur, a higher density with an environment of high temperature is necessary.

Requirement of Energy

It takes a little energy to split an atom in a fission reaction.

Extremely high energy is required to bring two or more protons in close approach with each other so that nuclear forces overcome their electrostatic repulsion.

The release of an energy

In the process of nuclear fission, the energy released by fission is a million times greater than that released in chemical reactions; this means that the process is exothermic.

Also, this energy is comparatively lower than the energy released by nuclear fusion.

The energy released by fusion is three to four times greater than the energy released by fission; also, the process of nuclear fusion is endothermic. 

Nuclear bomb formation

One class of nuclear weapon is a fission bomb to which we call an atomic bomb or atom bomb.

One class of nuclear weapon is the H2 bomb that uses a fission reaction to activate a fusion reaction.

The production of energy

Nuclear fission has an application in nuclear power plants. 

Fusion is  the technology for experimentation that is utilised for generating energy. 

Usage of the fuel

Uranium is the significant fuel used in nuclear power plants primarily. 

Hydrogen isotopes, viz: Deuterium and Tritium are the primary fuels, which are used in experimental fusion power plants.

Nuclear Fusion & Nuclear Fission in Physics

Atoms are held together by two fundamental forces of nature viz: the weak and strong nuclear bonds. The total amount of energy held within the atomic bonds is the binding energy. The more binding energy held within the bonds, the more stable the atom is. Moreover, atoms try to become more stable by incrementing their binding energy.

Nuclear Fission vs Nuclear Fusion                 

Both nuclear fission and nuclear fusion reactions are chain reactions, which means that one nuclear event causes at least one another nuclear reaction, and typically continues. The result obtained is an increasing cycle of reactions that can quickly become uncontrollable. Such a type of nuclear reaction can have multiple splits of heavy isotopes such as Uranium 235U or the combining of light isotopes viz:. 2H and 3H).

Fission chain reactions occur only when neutrons break unstable isotopes. This type of impact and scatter process is difficult to control/bear; however, the initial conditions are comparatively simple to achieve. 

However, the fusion chain reaction develops or occurs only under extreme pressure and temperature conditions that remain stable by the energy released in the process of fusion. We also find that the initial conditions and stabilizing fields are very hard to execute with our current technology, so Physics requires really advanced technology to carry out this extreme process.

FAQ (Frequently Asked Questions)

Question 1: Differentiate Nuclear Fission from Nuclear Fusion.


Below are the points to differentiate nuclear fission from nuclear fusion:

  • The process of nuclear fusion is more expensive than the process of nuclear fission.

  • Nuclear fission confines to reside in a lighter nuclei, while nuclear fusion tends to confine in a large nuclei.

Question 2: What is the Difference Between Nuclear Fusion and Fusion?

Answer: Nuclear fusion and nuclear fission are two different types of reactions that release energy because of the presence of high-powered atomic bonds between particles residing in the nucleus. In fission, an atom splits into two or more tiny, lighter atoms. Fusion, on the other hand, occurs when two or more light-weighted atoms fuse together, produce a larger, heavier atom.

Question 3: Can Nuclear Fission be Controlled by Fusion?

Answer: During the process of nuclear fission an enormous amount of energy is liberated during the ongoing reaction. However, this liberation or release is 3-to-4 times lesser than the energy liberated during the nuclear fusion process. 

Nuclear fission can be controlled via varying scientific processes while nuclear fusion is impossible to control.

Question 4: Is Nuclear Fusion Possible Naturally?

Answer: Yes. We can see this process in the star like the Sun but this is possible only when there is extremely high temperature, pressure, and density.