# Explain : Nuclear Fusion.

ANS:


* The process in which two nuclei combine to form a heavy nucleus is called Nuclear Fusion.

* For example, two nuclei of heavy hydrogen (deuterium), 1H2 fuse to form one nucleus of helium, 2He3.

* During nuclear fusion, the mass of the products formed is slightly less than the mass of the reactants. This is called 'Mass Defect' and the 'missing mass' is converted into energy according to the Einstein's mass-energy equation, E = mc2.

* When two deuterium nuclei combine, following two reactions are possible:

1H2 + 1H2 → 2He3 + 0H1 + 3.3 MeV

1H2 + 1H2 → 1H3 + 1H1 + 4.0 MeV


* The main advantage of the above reaction is that we obtain about 33 g of deuterium from 1 cubic meter (1000 lit) of seawater. Thus, seawater contains about 1015 tons of deuterium.

* 1 gallon of deuterium releases energy equivalent to that released by 600 gallons of petrol.

* The following reaction involving tritium is possible at low temperature and it gives more energy.

1H3 + 1H2 → 2He4 + 0n1 + 17.6 MeV


* The proportion of tritium in seawater is less but we can obtain it by bombarding lithium isotope with a neutron.

3Li6 + 0n1 → 1H3 + 2He4

3Li7 + 0n1 → 1H3 + 2He4 + 0n1


* In thermonuclear fusion process, a fusion fuel is heated to 106 K when ionization takes place to form plasma.

* Plasma is a mixture of moving charged particles with equal number of negative and positive charges.

* It is difficult to control thermonuclear fusion. However, attempta are going on to develop a process of controlled fusion to obtain energy.

* Uncontrolled nuclear fusion is used to prepare weapons of mass destruction like hydrogen bomb.

* As compared to nuclear fission, the nuclear fusion has following advantages:

1. Fuel for nuclear fusion is cheap and easily available.

2. There is no requirement of disposing off of nuclear wastes.

3. It is pollution free.