Nuclear energy

05 Sources of energy


    • The energy released during a nuclear reaction is called nuclear energy.
    • Nuclear energy can be obtained by two types of nuclear reactions:
      • Nuclear fission, and
      • Nuclear fusion.



  • In a process called nuclear fission, the nucleus of a heavy atom, when bombarded with low energy neutrons, gets split into lighter atoms with the release of tremendous amount of energy.
  • This can be harnessed to generate electricity. This is called nuclear energy.
  • The process in which the heavy nucleus of a radioactive atom (such as uranium, plutonium or thorium) splits up into smaller nuclei when bombarded with low energy neutrons, is called nuclear fission.
  • A tremendous amount of energy is produced in the nuclear fission process.
  • When uranium-235 atoms are bombarded with slow moving neutrons, the heavy uranium nucleus breaks up to produce two medium –weight atoms, barium-139 and krypton-94, with the emission of 3 neutrons. A tremendous amount of energy is produced during the fission of uranium.
  • This fission reaction can be represented in the form of a nuclear equation as:
  • U92235 +  n01 Fusion B56139a + K3694r + 301n + tremendous amount of energy
  • The energy produced during nuclear fission reactions is used for generating electricity at nuclear power plants.
  • When all the neutrons produced during fission of uranium-235 are allowed to cause further fission, then so much energy is produced in a very short time that it cannot be controlled and leads to an explosion called atom bomb.
  • We can, however, control a nuclear fission reaction by using control rods made of boron.
  • Boron has a property that it can absorb neutrons.
  • So, when a nuclear fission reaction is carried out in the presence of boron rods, the excess neutrons produced during successive fissions of uranium-235 atoms are absorbed by boron rods and hence not available to cause further fission.
  • Due to this a controlled fission reaction of uranium-235 takes place liberating heat energy at a slow, steady and manageable rate which can be used for generating electricity at a nuclear power plant.
  • Nuclear fusion reactions of hydrogen are the source of sun’s energy. Other stars also obtain their energy from the nuclear fusion reactions of hydrogen.
  • An advantage of nuclear fusion reactions over nuclear fission for producing electricity is that the amount of energy released in a fusion reaction is much more than that liberated in a fission reaction.


  • It produces a large amount of useful energy from a very small amount of a nuclear fuel (like uranium-235).
  • Once the nuclear fuel (like uranium-235) is loaded into the reactor, the nuclear power plant can go on producing electricity for two to three years at a stretch. Thus, no need for putting in nuclear fuel again and again.
  • It does not produce gases like carbon dioxide which contribute to greenhouse effect or sulphur dioxide which causes acid rain.


  • The waste products of nuclear fission reaction (produced at nuclear power plants) are radioactive which keep on emitting harmful nuclear radiations for thousands of years.
  • So, it is very difficult to store or dispose of nuclear wastes safely.
  • Improper nuclear waste storage or disposal can pollute the environment.
  • There is the risk of accidents in nuclear reactors (especially the old nuclear reactors).
  • Such accidents lead to the leakage of radioactive materials which can cause serious damage to the plants, animals (including human beings) and the environment.
  • The high cost of installation of nuclear power plants and the limited availability of uranium fuel make the large scale use of nuclear energy prohibitive.

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