Pointers on fusion/binding energy

[Stevie D]

Hi there.

 

Writing a short piece in which I'm weighing up the viability of fusion power in the future compared with other, non-fossil fuel technologies.

 

I've not dipped into fusion before, so I'm doing my best to get my head around it.

 

I'm stuck on binding energy. My understanding is that mass gets converted into energy when nucleons combine to form a nucleus, as the result of the drop in mass. That's fine; here's where I get confused:

 

1. An element like iron has a binding energy per nucleon which is higher than that of a much lighter atom, like helium. Since the binding energy in iron is relatively high, would that not mean there would be a greater disparity between the mass of an iron atom and the mass of its component nucleons in isolation?
    
   
2. If that is the case, would there not be more energy release per nucleon when they combined to form the iron nuclide?
    
   
3. If so, why is the focus on fusing the lightest elements in order to derive energy?
   

Hope I explained it well enough. Thanks for your time.

 

Steve

[swansont]

 

 

An element like iron has a binding energy per nucleon which is higher than that of a much lighter atom, like helium. Since the binding energy in iron is relatively high, would that not mean there would be a greater disparity between the mass of an iron atom and the mass of its component nucleons in isolation?

 

Yes

 

If that is the case, would there not be more energy release per nucleon when they combined to form the iron nuclide?

 

Yes

 

If so, why is the focus on fusing the lightest elements in order to derive energy?

 

Forming a heavy nucleus from its constituents is increasing difficult if you try and do it all at once, because all of the components have to interact in a short period of time. That's basically a non-starter.

 

Because nuclei also repel due to the electrostatic force, and this scales with the charge, it's more difficult to fuse two moderate-mass nuclei to form iron. If we can't fuse Hydrogen in a sustainable fashion, we have no hope of fusing e.g. Carbon.

[Stevie D]

That's the missing piece. Thanks for the reply.