What Is the Role of Binding Energy in Fusion and Fission?

[logearav]

Homework Statement

the lesser amount of binding energy for lighter and heavier nuclei explains fusion and fission. It has been mentioned large amount of energy is released during fusion and fission due to this low binding energy.
i can't understand the concept. binding energy is the the energy due to mass defect. how much energy is released during fusing two lighter Hydrogen nuclei into a heavier helium

Homework Equations

The Attempt at a Solution

 

[hikaru1221]

Have a look at this: http://en.wikipedia.org/wiki/File:Binding_energy_curve_-_common_isotopes.svg
You can see that the peak is around the element of medium number of nucleons (or protons; anyway, the ratio Z/N is almost the same for stable isotopes). So in order to obtain some amount of energy from nuclear reaction, people have 2 ways: fusion (light element -> medium/larger one) and fission (heavy -> medium). The reverse way is meaningless: there is no such reaction from medium element to heavy / light one that benefits people.

A typical fusion reaction: Hydrogen H1 + neutron -> Deuterium D2, the energy released is just around 2 MeV, far inferior to fission reaction whose released energy is around 200 MeV. However, the best thing about fusion reaction is that, given the same mass of input fuel, you obtain way larger amount of output energy. Do some simple math and you will see Besides, one prospect of nuclear fusion is that light element is easier to find in the nature. If we had uranium mine everywhere around our houses, geneticists wouldn't have to spend much time of their life on their research, don't you think so?