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Rutherford Reactor?

Posted by: Psiberzerker - Thu Jan 12, 2012 12:05 am
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Rutherford Reactor? 
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Post Rutherford Reactor?   Posted on: Thu Jan 12, 2012 12:05 am
I'm not sure if it's the proper term, but I refer to the Rutherford reaction as Alpha bombardment of Nitrogen 14 to produce a Proton decay to Oxygen 17. Now, Nitrogen 14 is common as 70-80% of the air we breathe, so all you'd need is an Alpha source, like a Helion gun, or radioisotope, and liquid nitrogen tank to produce Oxygen, and Protons (Hydrogen nuclei) to react for energy.

Correct me if I'm wrong, but I was thinking that orbital gas miners could use this as fuel generation for LEO stations to power mass launches to orbit. Any forseeable problems with this?

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Post Re: Rutherford Reactor?   Posted on: Wed Jan 18, 2012 7:41 am
The main problem that I can see is that you'd need an incredible amount of radioactivity to create an appreciable amount of fuel in a reasonable time. I haven't done the math though.

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Post Re: Rutherford Reactor?   Posted on: Wed Jan 18, 2012 5:37 pm
Of all the charged particle reactions, D+T (deuterium + tritium)is the easiest to promote and requires the lowest collision energy of all known reactions. It has not been accomplished yet (except explosively), and when it is accomplished, that will be the basis for fusion power for some time, as the next easiest, D+D is much more difficult.

The reactions like B+H Li+H F+H N+He etc are very much more difficult--higher required collision energy and lower cross section (essentially probability of reacting from a collision).

There are many textbooks on nuclear reactions and I suggest reading a few.


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Post Re: Rutherford Reactor?   Posted on: Wed Jan 18, 2012 7:29 pm
DT has been accomplished, you can do it on your desk. The problem remains extracting energy from energetic neutrons.


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Post Re: Rutherford Reactor?   Posted on: Wed Jan 18, 2012 8:42 pm
Ben may be referring to the plasma discharge neutron generators, used in well logging and other applications calling for short pulses of neutrons. They work by accelerating a mix of D, T ions and hitting a carbon, titanium, or other hydride target. The voltage used for DT ones are about 50 KV and produce some millions of neutrons/discharge, The DD ones require about 150 KV and produce fewer neutrons.

The DD ones produce about 2.5 Mev, and DT about 14 Mev, and the neurtons carry off most of the energy (80% for DT). In a reactor, that energy is to be converted to heat in a lithium breeder blanket to make more T to be fed into the reactor.

The plasma tubes do not come anywhere near power out being as great as the power to run them. Confined plasma hot fusion may eventually be achieved. Most physics people think so.

"Cold Fusion"-- never. That was a fantasy driven hysteria.


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Post Re: Rutherford Reactor?   Posted on: Thu Jan 19, 2012 12:01 am
There's that, and also inertial electrostatic confinement which is much more elegant. It is confined hot plasma DT fusion. It does not break even.

Capturing neutron energy isn't as solved as you suggest, and there are enough unknowns that a cold process may be possible just as a hot process may never break even.


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Post Re: Rutherford Reactor?   Posted on: Thu Jan 19, 2012 12:46 am
quoting from Ben:

"...and also inertial electrostatic confinement which is much more elegant. It is confined hot plasma DT fusion..."
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Electrostatic will probably not work, as that requires charged plasma, and electrostatic repulsion is so strong density of any such plasma will be way too low. Also it will be impossible to avoid short circuit of the high voltage gradients involved.
=================

"Capturing neutron energy isn't as solved as you suggest..."
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Capturing neutrons is easy. Every fission reactor does that and the engineering is well understood. Main difference between fission/fusion is that a high percentage of the total energy is from the neutrons. Probably just engineering issues, not a problem.
=====================

"...and there are enough unknowns that a cold process may be possible..."
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The famous Pons/Fleishman "process" was widsh driven hysteria. That never happened and cannot. Those who believe in it are using testimonials as arguments, not properly done, repeatable demonstrations. It has the hallmarks of religion.
=================

"...just as a hot process may never break even."
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Hot confined plasma has not yet, but efforts are getting closer. Preponderance of opinion is that it can be done.

The ITER may do it. Then, from how that behaves, some improvement may lead to a practical reactor.


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Post Re: Rutherford Reactor?   Posted on: Thu Jan 19, 2012 3:30 am
What about using a pair of particle accelerators and have the two streams collide? Stream D and stream T? I am not sure about this but I think temp.is harder to hold then momentum? You dont spend any energy on confinement.

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Post Re: Rutherford Reactor?   Posted on: Thu Jan 19, 2012 4:07 am
IEC works, and has been demonstrated for decades.


Last edited by Ben on Fri Apr 20, 2012 1:53 am, edited 1 time in total.



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Post Re: Rutherford Reactor?   Posted on: Thu Jan 19, 2012 1:35 pm
To anyone interested, for more on IED, see Polywell and Farnsworth-Hirsch Fusor on Wikipedia.

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Post Re: Rutherford Reactor?   Posted on: Thu Jan 19, 2012 4:56 pm
Sigma's idea:
What about using a pair of particle accelerators and have the two streams collide? Stream D and stream T? I am not sure about this but I think temp.is harder to hold then momentum? You dont spend any energy on confinement.
----------------

Problem with that is that only a small fraction of collisions result in reaction. Most just scatter an collisions between charged particles.

The total energy to make enough collisions per reacting one is greater than the output.

In a thermal confined plasma system the ions make many collisions before one reacts. The main energy loss here is "bremstrahlung" radiation--soft X rays from the high speed collisions of electrons with each other and ions. This energy comes out whether there are reactions or not.

So, a running thermal reactor will emit from the reacting volume X rays and neutrons of 2.5 and 14 Mev from DD and DT reactions respectively, and that will be absorbed in a blanket and converted to heat.

The blanket will have to be lithium, to use the neutrons to replace the tritium.

An additional problem is the need to minimise leakage of plasma from the confinement and evaporate wall material which would contaminate the plasma.

As the bremstrahlung effect is proportional to atomic number squared, 1% carbon in the plasma will increase X rays 36% ofer that from pure hydrogen.

10% helium in the plasma will increase that by 40% over that for pure hydrogen.

A likely wall material may be graphite, because, when hot the crystal structure tends to heal. Graphite fission reactors are periodically run to high temp to anneal and release the "Wigner energy", the energy stored up in the form of displaced atoms.


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Post Re: Rutherford Reactor?   Posted on: Sun Jan 22, 2012 3:10 am
so far, only fission reaction been realized well enough. to power rockets with compact nuclear reactors would be nice, but safety issues have kept these conceptions away from practice :(

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Post Re: Rutherford Reactor?   Posted on: Sun Jan 22, 2012 3:17 pm
Previous fission reactor comment: If you don't mean high acceleration off the ground nuclear, a space based low acceleration system would be fairly easy, except for licensing, certification issues.

A 100 KW to 1 MW system could be taken to orbit with a "clean" core, not run yet so no initial fission products, and a core of less than weapon grade U235 concentration.

For unmanned probes, the reactor might just have shielding between the core and electronics. Could be plasma thruster like Vasimir.

For manned, a rotating tether system with the reactor rotating around the crew cabin, with propellant, supplies between. The reactor could be several 100 meters distant.

Once in orbit, acceleration needs only to be 1/1000 g or so.


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Post Re: Rutherford Reactor?   Posted on: Sun Jan 22, 2012 6:59 pm
ckpooley, i meant "off the ground" case, about low acceleration -- Yep: there looks far better. as far as i know, Rosatom did step in to R&D compact reactor 4 low acceleration, SAFE-400 would be useful too. 4 propulsion, either VASIMIR or SPT-290.


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Post Re: Rutherford Reactor?   Posted on: Sun Jan 22, 2012 7:22 pm
SarKOY: Off the ground means high acceleration hydrogen fueled thetmal system
that was researched years ago, given up.

It required gigawatt levels and high risk of leaking fission producta at low altitudes. Nowadays, probably impossible politically.

Am low acceleration starting at LEO may be possible, but there would have to be assurances it could get up to at least higher orbit if it fails to escape.

This would involve a smaller reactor, maybe 10-100 KW for unmanned probe and 1 MW for manned.

Politics and difficulty certifying it will probably prevent it.

Someday if a light enough fusion process can be devised it may be easier. But first a fusion process that sits on the ground must come first, and that is likely to be too heavy to fly anywhere.


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