Why not more fusion with a net release of energy?

In summary: So the Strong Force is the reason that we don't see more massive elements being formed in stars, as it has a limited range and can only hold the nucleus together up to a certain size. In summary, the fusion process in stars ends with the formation of iron due to the limited range of the strong force, which is unable to hold together nuclei larger than iron, making it the most stable element.
  • #1
pivoxa15
2,255
1
why does the energy-liberating fusion process ends with the formation of iron and not heavier elements such as uranium?
 
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  • #2
I believe you mean fission?
 
  • #3
I don't think so. I was thinking how stars can fuse 3 helium nuclei to form a carbon-12 and get a net release of energy. And combine some carbon-12 to form an iron and get a net release of energy. But it is not possible to fuse some irons to form Uranium and get a net release of energy. To do the latter, the star must put energy in. Why is that? I am guess it is because atoms with more protons and neutrons than iron are unstable because the nuclei is too large for the strong force to be effective, so the coulomb repulsion force comes into play. But there must be a better explanation.
 
  • #4
Look at the nuclear binding energy. There's a maximum around iron.

Zz.
 
  • #5
Look at the nuclear binding energy. There's a maximum around iron.

I think he understands that, he wants to know why. I personally don't know enough about nuclear physics to answer your question. I'm not even sure if nuclear physicists know.
 
  • #6
According to the the 'hyperphysics' site, Nickel-62 is actually the most tightly bound nucleus, but it's a close race with Fe-56. :tongue2: Great site, I learn something new every time I visit.
Entropy said:
I think he understands that, he wants to know why. I personally don't know enough about nuclear physics to answer your question. I'm not even sure if nuclear physicists know.
The answer seems to lie in the difference between the Electromagnetic force and the Strong Force. The EM force has an infinite range and works to push all of the protrons in the nucleus apart. The Strong Force is ~20 times stronger and tries to pull all of the protons and neutrons together, but it's range is extremely short, ~10-15 meters.
In small nuclei, the nucleus is smaller than the range of the Strong Force and every nucleon (proton or neutron) interacts with every other nucleon in the nucleus. In large nuclei, the nucleus is actually larger than the range of the Strong Force, so not every nucleon reacts with every other one, but every proton is still interacting (via EM) with every other proton, resulting in a less tightly bound (on a per-nucleon basis) nucleus.
 

Why is it so difficult to achieve fusion with a net release of energy?

The main challenge with achieving fusion with a net release of energy is the high temperatures and pressures required to initiate and sustain the fusion reactions. These conditions are difficult to create and maintain.

What are the primary obstacles to achieving fusion with a net release of energy?

The two primary obstacles to achieving fusion with a net release of energy are the need for high temperatures and pressures, and the issue of plasma instabilities that can disrupt the fusion process.

Why is fusion with a net release of energy considered a potential source of clean and sustainable energy?

Fusion reactions produce energy by fusing together light nuclei, such as hydrogen isotopes, which are abundant and can be obtained from seawater. This process does not produce greenhouse gases or long-lived radioactive waste, making it a potential source of clean and sustainable energy.

What are the current advancements in fusion research?

There are several fusion research projects currently underway, such as the International Thermonuclear Experimental Reactor (ITER) in France, which aims to demonstrate the feasibility of fusion power, and the Wendelstein 7-X stellarator in Germany, which is exploring a different approach to confining plasma. These projects are expected to provide valuable insights and advancements in fusion research.

What challenges need to be overcome for fusion with a net release of energy to be a viable energy source?

In addition to the technical challenges of achieving and sustaining fusion reactions, there are also economic and societal challenges that need to be addressed for fusion with a net release of energy to become a viable energy source. These include the high cost of building and operating fusion reactors, as well as public acceptance and support for this technology.

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