[ExI] lockheed's fusion video

spike spike66 at att.net
Wed Oct 22 04:24:56 UTC 2014


 

 

From: extropy-chat [mailto:extropy-chat-bounces at lists.extropy.org] On Behalf Of Adrian Tymes



>>…Imagine you find a way to fuse 3H and a 2H.  Regardless of how you contain that, neutrons fly out.  Magnetic fields cannot contain those, not now, not in the future.  The first solid surface they hit absorbs some of those neutrons.

 

>…You miss my point.  "Go huge" increases the surface area less than the amount of stuff passing through that surface area.  It seems possibly counterproductive…

 

Oh OK.  When you increase the radius of the Tokamak, you decrease the neutron flux by the square of radius.  As I understand it, the neutron flux is inversely proportional to the life of the shield.

 

>…Also, while I know it to be true, I wonder what the main reasons are why magnetic containment can not pull this off.  What are the primary difficulties encountered?

 

Neutral particles are unaffected by either electric fields or magnetic fields.  They can’t be accelerated, steered or anything by any magnetic field.  Charged particles can be, but not neutrinos or neutrons.

 

 

>…That would in theory seem impossible, without mass replacement.  Whatever material it decays into, will then be hit with more neutrons - and more, and more, until it decays into something that can no longer accept neutrons…

 

Well OK, let’s look at it.  Blowing the dust from my old textbooks, which weren’t particularly recent even when I studied them, and unfolding my nucleon chart, I see that stable iron ( nucleon numbers 55,56,57) accepts a neutron or two or three, beta decays to cobalt.  Cobalt accepts a neutron or two, beta decays to nickel.  Accepts neutron or two, beta decays to copper.  Accepts neutrons, decays to zinc.  Zinc to gallium.  Gallium to germanium.  Germanium to arsenic.  Arsenic to bromine, which is a liquid at water-ice temperature, so we needn’t go the next two steps which would take us to krypton, which is a non-reacting noble gas.  At no point in that process do you reach any material which cannot or will not accept a neutron.

 

We could start lower on the periodic chart if we wanted, but we still end up in the same cycle: the element accepts a neutron if the neutron comes in contact with the nucleus (That’s where that neutron capture cross section area number comes from, a description of the probability an atom or ion will capture a passing neutron, regardless of the ionization state of the ion.  Neutrons don’t care how many electrons are whirring about.)  Regardless of where we start on the periodic table, neutrons get absorbed, nucleon number increases, beta decay moves you one position to the right.  Repeat until you hit a noble gas.  Then that atom or ion is gone.


>…Molten lead could in theory handle this - siphon part of it off, separate out the decayed fraction, replace with new led, and inject it in - but you'd need a way of handling the structure.  Perhaps centrifugal pressure could keep the molten lead in a roughly hollow-sphere shape, or at least enough rings that the solid structure containing this molten lead would be minimally exposed.

 

Your notion of some kind of spinning liquid lead chamber is interesting, but I don’t know that it is necessarily any help.  You go from lead to bismuth to polonium to astatine to radon, but either way, as soon as you hit radon, that atom is a fond memory.  Perhaps you could constantly recirculate the liquid neutron-shield, chemically extracting the bismuth and re-injecting the pure lead.


>…Alternately, some design where the shell is made of movable panels (as pictured in the Portal series, especially Portal 2), such that you could move one out of the way once it is saturated or used up but have others behind it so as to not lose sufficient containment.  (Just...whatever you do, and no matter how innocuous a joke it seems, do not name the software in charge of this "GLaDOS".)

 

Ja, something like a kind of onion skin design with sacrificial layers or something.  I need to quit procrastinating, get the numbers, assume away the problem of starting and maintaining a steady stream of 2h / 3H fusion and calculate how much steel we would erode away per unit energy production.  Oy it has been a long time since I did these kinds of calcs. 

 

I still haven’t seen how the Skunk Works’ notion is any improvement over a tokamak. 

 

spike

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