The binding energy per nucleon of deuterium and helium atom  is 1.1 MeV and 7.0 MeV. If two deuterium nuclei fuse to form helium atom, the energy released is

H 2 1 +H 2 1 →He 4 2 +energyBinding energy of a (H 2 1 ) deuterium nuclei = 2 x 1.1 = 2.2MeV Total binding energy of two deuterium nuclei = 2.2 x 2 = 4.4MeVBinding energy of a (He 4 2 ) nuclei = 4 x 7 = 28MeV So, energy released in fusion = 28 - 4.4 = 23.6 MeV