Can Neutron-X Fusion Reactions Overcome the Repulsion Problem in Fusion Energy?

In summary, the conversation discusses the possibility of using neutron-proton fusion as an alternative to traditional fusion reactions. However, it is pointed out that the energy gain from this method would be minimal compared to traditional fission reactions. Additionally, the issue of neutron balance in fission reactors is also addressed.
  • #1
benswitala
18
2
Hi,

I was reading about fusion reactions recently, and it was pointed out that the problem seems to be that positively charged nuclei repel each other. If that is the problem, why don't scientists try to go with another fusion reaction? Would it be possible to have fusion if neutrons fuse with something else, say normal hydrogen? You have a bunch of hydrogen (1 proton in nucleus), you have some neutron source, and you bombard the hydrogen with the neutrons. Some of the neutrons fuse with the hydrogen and produces some fusion energy. This way, the positive-positive repulsion is avoided. If I'm not mistaken, ordinary fission reactors produce a lot of neutrons, so maybe that could be the neutron source to produce neutrons in the neutron-proton fusion. Thanks.

Ben

(I selected the I for Intermediate prefix although I am not currently an undergrad. I have an undergrad degree in computer science (and soon a master's), and studied physics for two semester (Newton and Maxwell)).
 
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  • #2
And how do you move the neutrons from where you make them to where you want to use them?
 
  • #3
benswitala said:
(I selected the I for Intermediate prefix although I am not currently an undergrad. I have an undergrad degree in computer science (and soon a master's), and studied physics for two semester (Newton and Maxwell)).
I can tell your degree is in CS because your parens match. :smile:
 
  • #4
Fusion is useful if the reaction nets energy. Where is energy here?
 
  • #5
Vanadium 50 said:
And how do you move the neutrons from where you make them to where you want to use them?
Since the neutrons just spray around and the direction can't be guided, could you surround the neutron source with the other reactant?
 
  • #6
berkeman said:
I can tell your degree is in CS because your parens match. :smile:
That's not a good way to identify a computer scientist. Anyone can write balanced parentheses.
 
  • #7
mathman said:
Fusion is useful if the reaction nets energy. Where is energy here?
I really don't know, where is it?
 
  • #8
benswitala said:
That's not a good way to identify a computer scientist. Anyone can write balanced parentheses.
Apparently not me... :smile:

[/thread hijack]
 
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  • #9
Honestly, I don't think you have thought this through. And you should have, it would let you post a better question.

pn fusion produces 2.2 MeV per fusion. You could look this up.
A typical uranium fission releases 200 MeV per fission. You could look this up.
A typical uranium fission releases 2.5 neutrons, one of which is needed to keep the chain reaction going. You could look this up.

So this would provide 200 MeV from fission and 3.3 MeV from fusion, for a whopping 1.7% gain.

At most.
 
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  • #10
All neutrons in a fission reactor are captured by something. The most desirable outcome is another uranium nucleus, releasing 200 MeV: On average you need one fission reaction to trigger one more fission reaction. Capture by hydrogen is one of the ways fission reactors lose neutrons, and the loss is so significant that reactors need to work with enriched uranium (most reactors), with water where most hydrogen is deuterium (e.g. CANDU) or they have to avoid water (e.g. gas-cooled reactors or molten salt reactors). Yes, capturing a neutron with a proton releases 2 MeV, but that's a minor effect compared to the impact on the neutron balance.
 
  • #11
Thanks!
 
  • #12
Vanadium 50 said:
Honestly, I don't think you have thought this through. And you should have, it would let you post a better question.

pn fusion produces 2.2 MeV per fusion. You could look this up.
A typical uranium fission releases 200 MeV per fission. You could look this up.
A typical uranium fission releases 2.5 neutrons, one of which is needed to keep the chain reaction going. You could look this up.

So this would provide 200 MeV from fission and 3.3 MeV from fusion, for a whopping 1.7% gain.

At most.
Thanks!
 

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