Radioactivity — Question 9

(a) Nuclear fusion is the process in which two light nuclei combine to form a heavy nucleus. In this process, huge amount of energy is released.

Example —

When two deuterium nuclei ($_{1}^{2}\text{H}$) fuse, 3.3 MeV energy is released and the nucleus of helium isotope ($_{2}^{3}\text{He}$) is formed. This helium isotope again gets fused with one deuterium nucleus to form a helium nucleus ($_{2}^{4}\text{He}$) and 18.3 MeV energy is released in this process. The nuclear reaction are —

$_{1}^{2}\text{H} + \space _{1}^{2}\text{H} \longrightarrow \space _{2}^{3}\text{He} + \space _{0}^{1}\text{n} + 3.3 \text{ MeV}$

$_{2}^{3}\text{He} + \space _{1}^{2}\text{H} \longrightarrow \space _{2}^{4}\text{He} + \space _{1}^{1}\text{H} + 18.3 \text{ MeV}$

Thus in all, three deuterium nuclei fuse to form a helium nucleus with a release of 21.6 MeV energy.

(b) Nuclear fusion is also called as thermo-nuclear reaction because nuclear fusion takes place at very high temperature.