I Some confusion with the Binding Energy graph of atoms

[JohnnyGui]

TL;DR

Fusing atoms up to Fe-56 releases binding energy but also requires energy to overcome the charges of protons. Where does that energy go after fusion?

My question is about the following graph:

I keep on reading that fusing atoms up until Fe-56 doesn’t cost energy and only releases binding energy. However, I understood that fusing atoms also require energy to overcome the positive charges of the protons. Where does that energy go after fusion? Does it go into the mass of the newly fused atom, escape as heat or is the released binding energy shown in the graph actually the net energy after subtracting the required fusion energy?

I secretly want it to be the latter; that the binding energy shown in the graph for each atom is the net energy after subtracting the fusion energy that is needed to overcome the charges.

If not, it gives me another issue of confusion which I find best to explain after I first know the answer to my initial question.

 

[QuarkyMeson]

The graph represents what is on the axes- mass number against the average binding energy per nucleon. The average binding energy per nucleon represents how much energy you need to supply to unbind that nucleus completely. It's an intrinsic property of the nucleus in the ground state. It doesn't include the energy you need to put in to overcome the Coulomb barrier to fuse the lighter elements together.

So when you fuse the products up to around FE-56 you have more binding energy per nucleon, That difference in total binding energy is released to the outside as kinetic energy and radiation. This is why it's possible for fusion of lighter elements (than FE-56) and fission of heavier elements to release net energy.

Whether or not you get net energy out is the total difference in all the outputs minus the inputs.

Also I think I missed this but it's important- any kinetic energy you put in to get your nuclei over the Coulomb barrier for fusion isn't lost. After fusion, essentially all energy is still accounted for in the final particles. The Coulomb barrier mainly affects how likely the reaction is, not whether it’s exothermic once it happens.

Now that said, a real fusion reactor isn't one fusion event or an isolated system in practice. You need to be able to keep your plasma in a fusion favorable state for long enough to both reclaim and exceed the input energy you've spent in creating and maintaining that state to create useful power - all while dealing with the several loss channels that exist that carry away energy you can't harness to spin a turbine. Anyway. Hope that helps.