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Author Topic: Is Boron power "Fission" or "Fusion"?  (Read 1048 times)

Offline evan_au

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Is Boron power "Fission" or "Fusion"?
« on: 07/02/2016 09:46:29 »
Some people are promoting nuclear power using the reaction:
H1 + B11 → C12 → 3He4 +8.6MeV

Would you call this "fission" or "fusion"?

See, for example: http://www.ialtenergy.com/lawrenceville-plasma-physics.html


 

Offline alancalverd

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Re: Is Boron power "Fission" or "Fusion"?
« Reply #1 on: 07/02/2016 10:13:18 »
Since the nuclide products are heavier than the inputs, it must be fusion.
 

Offline chiralSPO

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Re: Is Boron power "Fission" or "Fusion"?
« Reply #2 on: 07/02/2016 14:04:21 »
This equation doesn't sit right with me. Why would 12C decompose into 3 4He? 12C is very stable, and stars release energy when fusing 4He together to form 12C.

Without looking up the numbers, it would appear then that the fusion of 1H and 11B would have to be the exothermic step, and the fission of 12C would be endothermic. Would it not make more sense to find a way to stop the second step from happening so that more energy can be harvested? If the second step were exothermic, wouldn't we already have developed 12C fission reactors?

EDIT: I suppose that the 12C formed could be in a very excited state that would facilitate decay...
« Last Edit: 07/02/2016 14:28:12 by chiralSPO »
 

Offline alancalverd

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Re: Is Boron power "Fission" or "Fusion"?
« Reply #3 on: 07/02/2016 16:18:06 »
Some confusion here. Promising reactions are, apparently,

Proton–boron fusion    1p + 11B    →    34He    + 8.7 MeV
Proton–nitrogen fusion    1p + 15N    →     12C + 4He    + 5.0 MeV[2]

so it is possble that there is an intermediate metastable 12C in the first reaction.
 

Offline chiralSPO

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Re: Is Boron power "Fission" or "Fusion"?
« Reply #4 on: 07/02/2016 22:54:39 »
As far as the question of fission of fusion goes, I think it would be most accurate to call it a nuclear reaction that is neither (or both). I don't know if there are agreed upon technical terms for other types of reactions, but I would imagine there are.

By analogy to chemical reaction classifications, fusion ≈ synthesis, fission ≈ decomposition, and the reaction discussed here seems more akin to substitution (really like an addition-fragmentation, which is not very common)
 

Offline evan_au

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Re: Is Boron power "Fission" or "Fusion"?
« Reply #5 on: 08/02/2016 09:27:46 »
Quote from: chiralSPO
the fusion of 1H and 11B would have to be the exothermic step
This reaction has a phenomenally high activation energy, requiring energies around 300keV (temperatures well over a billion degrees absolute), an order of magnitude more than some Hydrogen fusion options.

Temperature is a property of an ensemble of particles, so you can't really measure the temperature of a single C12 particle, even one that is mashed together out of two incoming energetic particles.

But three He4 nuclei emerging at high velocity from the reaction is a clear way to deliver thermal energy released by the reaction.

It is the need for at least two reaction products that causes the problems with most candidates for nuclear fusion, because one of these products is often a high-energy neutron that is difficult to shield, and makes the surrounding structures radioactive.
 

Offline alancalverd

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Re: Is Boron power "Fission" or "Fusion"?
« Reply #6 on: 08/02/2016 22:47:48 »
Generating 300 keV protons is a doddle - you can do it with an off-the-shelf power supply.
 

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Re: Is Boron power "Fission" or "Fusion"?
« Reply #6 on: 08/02/2016 22:47:48 »

 

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