fusion terminology

by Khashishi
Tags: fusion, terminology
Khashishi is offline
May7-13, 10:46 PM
P: 833
Ok, I am a fusion physicist, but I still don't know what the strict criterion is for calling a nuclear reaction a fusion reaction. Yes, it's a collision between two nuclei that results in a bigger nucleus. But, then [itex]^{11}B + ^{1}H \rightarrow 3 \alpha[/itex] is usually called a fusion reaction. Isn't it more like fission?

Is it called fusion because most of the energy released comes from the low binding energy of hydrogen-1?
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HallsofIvy is online now
May8-13, 07:27 AM
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[itex]^{11}B+ ^1H\rightarrow 3\alpha[/itex] starts with two particles (on the left) and ends with one particle (on the right). Isn't that what "fusion" means?
Bandersnatch is offline
May8-13, 07:30 AM
P: 563
Quote Quote by HallsofIvy View Post
[itex]^{11}B+ ^1H\rightarrow 3\alpha[/itex] starts with two particles (on the left) and ends with one particle (on the right). Isn't that what "fusion" means?
[itex]^{11}B+ ^1H\rightarrow \alpha + \alpha + \alpha[/itex]

How about now?

mfb is offline
May8-13, 09:59 AM
P: 10,840

fusion terminology

@Bandersnatch: :D

That reaction could be both, fusion and fission.
I think (something with protons)+(something with protons) -> (something) is fusion. It might be followed by a fission reaction.
the_wolfman is offline
May8-13, 01:35 PM
P: 135
I agree that the p+B reaction doesn't fit into the typical cookie cutter text book definition of "fusion." But IMO its the best label.

Its helpful to at the binding energies per amu

H-1 is 0. MeV/amu
He-4 is 7.07 MeV/amu
B-11 is 6.93 MeV/amu

Notice that B-11 and He-4 have roughly the same binding energy per amu. This means that most of the energy (7.1 out of 8.7 Mev) released is coming from the conversion of hydrogen to helium. Thus from an energetic standpoint I argue that this is a fusion reaction.

Also the technology required to extract power from this reaction is similar to other fusion reactors but very different from a typical fission reactor. Thus I also argue that from a practical standpoint it useful to categorize p+B with other fusion reactions.

Note that p+B is not unique. If you look up the CNO cycle you'll see that there are several intermediate fusion reactions that involve H reacting with an medium sized nucleus resulting in helium and a smaller product nucleus. Example (H+N-15 = He-4 + C-12).
physwizard is offline
May8-13, 02:25 PM
P: 153
Quote Quote by Bandersnatch View Post
[itex]^{11}B+ ^1H\rightarrow \alpha + \alpha + \alpha[/itex]

How about now?
good one!

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