A nuclear process in which two or more light weight nuclei combine to form a heavier nucleus is called fusion Reaction During this reaction a large quantity of energy is liberated which is more than the fission reaction, another form of nuclear reaction. In fusion reactions, conversion of mass into energy occurs.

This fusion reaction occurs at a very high temperature and it is also known as thermo nuclear reaction. Such types of fusion processes are going on in the sun and other stars of the Universe. It is quite difficult on earth to produce such high temperatures by ordinary means. But the possibility of fusion process has been practically demonstrated by exploding hydrogen bombs where high temperature is first created by fission reactions for the initiation of fusion reaction. There may be two type of fusion reaction

(i) Controlled fusion reaction.

(ii) Uncontrolled fusion reaction.


The fusion reactions involve the use of Deuterium and Tritium (T) as fuel. These reactions can be started at suitably high temperature at sufficiently high temperature the gases are completely ionized to form the “plasma” which is a mixture of positive ions and electrons.

When plasma is heated, it produces increasing amount of energy. If the fusion process and the liberations of energy are to be continued, the rate of energy generation must exceed the rate of loss due to radiation. Where as in uncontrolled fusion reaction, there unlimited liberation of energy for e.g. – in the production of hydrogen bomb a mixture of deuterium and tritium oxide is used and this mixture is detonated at a very high temperature.

Scientists all over the world have claimed that the use of this fusion reaction could be in production of high amount of energy in nuclear power plant. For conducting more research and its feasibility in nuclear energy production International Thermometer Experimental Reactor at the base cost of 2500 crore has been situated.

India has also joined this experimental project. On November 21, 2006, the seven participants i.e. European Union, India, Japan, China, Russia, South Korea and the USA formally agreed to fund the project.