Nuclear Reaction : Basics

  Nuclear Reactions

Nuclear Reaction

Nuclear reaction is the process in which two nuclei, or else a nucleus of an atom and a subatomic particle (such as a proton, neutron, or high energy electron) from outside the atom, collide to produce one or more nuclides that are different from the nuclide(s) that began the process.

Nuclear Scattering

Thus, a nuclear reaction must cause a transformation of at least one nuclide to another. If a nucleus interacts with another nucleus or particle and they then separate without changing the nature of any nuclide, the process is simply referred to as a type of nuclear scattering, rather than a nuclear reaction

"Nuclear reaction" is a term implying an induced change in a nuclide, and thus it does not apply to any type of radioactive decay (which by definition is a spontaneous process)

  Nuclear Energy

Nuclear energy is the energy released when the nuclei of atoms split or are fused

Branch of science that deal with nuclear reaction is known as Nuclear Physics/ Nuclear Chemistry

It deals with two phenomenon:

  • Nuclear Fusion
  • Nuclear Fission

Matter and Energy

  Nuclear Fusion

Fusion is a nuclear reaction whereby two light atomic nuclei fuse or combine to form a single larger, heavier nucleus

The fusion process generates tremendous amounts of energy; or for fusion to occur, a large amount of energy is needed to overcome the electrical charges of the nuclei and fuse them together

  • It is accompanied by the release or absorption of energy depending on the masses of the nuclei involved.
  • Iron and nickel nuclei have the largest binding energies per nucleon of all nuclei and therefore are the most stable
  • The fusion of two nuclei lighter than iron or nickel generally releases energy
  • The fusion of nuclei heavier than them absorbs energy

Fusion reactions do not occur naturally on our planet but are the principal type of reaction found in stars. The large masses, densities, and high temperatures of stars provide the initial energies needed to fuel fusion reactions. The sun fuses hydrogen atoms to produce helium, subatomic particles, and vast amounts of energy. Nuclear fusion reactions are also called thermonuclear reactions.

Nuclear fusion produces less nuclear waste than nuclear fission and the materials are easier to obtain.


Every second, the sun converts 500 million metric tons of hydrogen to helium. Due to the process of fusion, 5 million metric tons of excess material is converted into energy in each second. This means that every year, 157,680,000,000,000 metric tons are converted into energy.


  Nuclear Fission

Nuclear fission is the process of splitting a nucleus into two nuclei with smaller masses; Fission means “to divide”.

Only large nuclei with atomic numbers above 90 can undergo fission

Products of fission reaction usually include two or three individual neutrons, the total mass of the product is somewhat less than the mass of Uranium-235

Fate of Neutron

1 - Cause another fission by colliding with a U235 nucleus

Creates two smaller nuclides and free neutrons, The free neutrons potentially collide with nearby U235 nuclei, May cause the nuclide to split as well. Each split (fission) is accompanied by a  large quantity of  E-N-E-R-G-Y.

2 - Be absorbed in other material

3 - Lost in the system

If sufficient neutrons are present, we may achieve a chain reaction

Chain Reaction

A chain reaction is an ongoing series of fission reactions. Billions of reactions occur each second in a chain reaction

Controlled Chain Reaction

On earth, nuclear fission reactions take place in nuclear reactors, which use controlled chain reactions to generate electricity.

Un-Controlled Chain Reaction

Uncontrolled chain reactions take place during the explosion of an atomic bomb