Energy From Thorium Discussion Forum

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PostPosted: May 03, 2011 2:54 pm 
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dezakin wrote:
Ludicrous speed, go. The question being asked by original poster is isomorphic to 'Hey guys, where can I get weapons grade material to run an unshielded reactor without containment at my house ? By the way, does anyone know the best way to get the timing right on a spherically symmetrical implosion device?'

While think the antiproliferation argument is a bunch of nonsense for powers that allready can build their own weapons, I have a sneaking suspicion that laws preventing people from making atomic weapons in their basement might not be a terrible idea.


unshielded? god no.
i mean, the U232 decay products are kind of gamma-happy, but that could be pretty well mitigated by the hastelloy as well as the concrete containment going over the entire thing (and i'll probably just build the thing underground anyway)

also, is u233 really weapon's grade? i wouldn't want to be near any weapon which used it as a core, because again, the gamma from those U232s can actually mess up your electronics, and possibly even set the entire thing off on its own! YIKES!

no thank you


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PostPosted: May 03, 2011 2:56 pm 
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Forge wrote:
I thought about this for a little bit today. General reading here and elsewhere indicated that generally, higher purity, higher density, higher temperature are all associated with smaller size.

No point trying for breeding. No point trying for near criticality.

Anyway, I'm still learning about this stuff and someone mentioned MIT courses online. So went over and had a squiz through, and saw some stuff on plasma physics. Ah, fusion. But.. why limit plasma work to fusion? Can a fission device work as a plasma circuit?

Turns out some people are looking into this sort of thing as a space power source.

But.. getting back to a micro device, why not a small plasma circuit (is there such a thing?) circulating thorium? Add a neutron beam (is there such a thing at small scale?) and a MHD generator.. power?

So. 200g of material, circulating in a plasma circuit, with power developed and modulated by the intensity of a co-linear neutron beam.

Looked up thorium and plasma and found vague references to a thorium plasma battery, but no real info.

Anyway, a random, uninformed idea to throw into this discussion.


that's a pretty bonkers idea
I LIKE IT!

however i'd have no clue how to build something like that. but then again, something like THAT could skip all the headaches of fluorine corrosion, and magnetic containment could keep a good chunk of the plasma from obliterating the walls.


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PostPosted: May 03, 2011 5:29 pm 
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JAK wrote:
also, is u233 really weapon's grade? i wouldn't want to be near any weapon which used it as a core, because again, the gamma from those U232s can actually mess up your electronics, and possibly even set the entire thing off on its own! YIKES!no thank you

Sure, U233 has neutronic properties similar to Pu239. While gammas make it a particularly unattractive weapon for nation states, some suicidal lunatic who made it in his basement could plausibly make a reasonably destructive device. Really, the smaller the reactor, the more it has in common with weapons design.

Seriously, you'll have far better luck scaling up the reactor to at least the megawatt range and operating as a local power distributor. If you absolutely must have a super low power output design, you'll be better off trying to get a dry storage cask for spent fuel on your lawn and hook it up as a heat pump for several decades of free heat. Good luck with the paperwork on that, but its far more likely than getting approval for something that uses highly enriched fuel in your basement.


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PostPosted: May 03, 2011 6:14 pm 
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Here's what you want:

http://media.cns-snc.ca/uploads/branch_data/branches/quebec/slowpoke/Slowpoke_reactor_photos.jpg

.....a nice little ~10kW SLOWPOKE reactor -- the core of which is seen being assembled at left.


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PostPosted: May 03, 2011 6:44 pm 
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jaro wrote:
Here's what you want:

http://media.cns-snc.ca/uploads/branch_data/branches/quebec/slowpoke/Slowpoke_reactor_photos.jpg

.....a nice little ~10kW SLOWPOKE reactor -- the core of which is seen being assembled at left.


but that's not a LFTR.


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PostPosted: May 03, 2011 9:40 pm 
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All nuclear reactors are just short of critical. When a neutron hits a fissile nucleus it can promptly decay or it can take many minutes to decay. Reactor are critical when including the slow decay but not critical by the prompt decay alone. This means we have a time scale of minutes on which to control the reactor and damp it when it gets too hot. If the reactor were not critical we would have to rely on spontaneous decay which are so few per second that we would get only a few watts not gigawatts.


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PostPosted: May 03, 2011 11:46 pm 
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Um, wow.


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PostPosted: May 04, 2011 2:01 am 
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edpell wrote:
All nuclear reactors are just short of critical. When a neutron hits a fissile nucleus it can promptly decay or it can take many minutes to decay. Reactor are critical when including the slow decay but not critical by the prompt decay alone. This means we have a time scale of minutes on which to control the reactor and damp it when it gets too hot. If the reactor were not critical we would have to rely on spontaneous decay which are so few per second that we would get only a few watts not gigawatts.


err...ok
as for heat; again, molten salt fuels means it can change density slightly with heat, and self-limits


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PostPosted: May 06, 2011 2:07 pm 
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anyone know of some pertinent equations i can use to figure out which reactor core design i should be looking at? pretty much all of them would need reflectors or moderators, since the core can't be that big (i won't have much fuel + it doesn't need to produce much power)
there's the cylindrical "pinch" design, the sphere, the vat, ect.

my objectives would be moderately low cost, simplicity (simplest possible fuel cycle), and very high safety. What i don't really care about is power output (since even a small reaction will probably be enough to drive a 25kw turbine. i'll probably use steam instead of helium anyway, whichever would be safer and simpler and cheaper.

are there some calculations i can run, given graphite volume, fuel percentage, size of reactor vessel, ect?


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PostPosted: May 06, 2011 5:23 pm 
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JAK wrote:
are there some calculations i can run, given graphite volume, fuel percentage, size of reactor vessel, ect?

The basic calculation is the "four factor formula" :

Image

Just plug in some numbers (for additional info see Basic Nucl. Eng. textbook by Foster & Wright) :

Image


For heterogeneous lattice arrangements you may want to try the two-group neutron diffusion calcs....

http://dl.dropbox.com/u/11686324/Pseudocode_for_Fortran_program_Hetero_6-XI-07.doc
http://dl.dropbox.com/u/11686324/missing_data_for_Hetero_15-I-08.doc


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PostPosted: May 06, 2011 8:58 pm 
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oh boy, that looks like fun
off to some reading i suppose.

of course this step is critical before design can even begin, i'd love to shoot for a moderately low temperature (300-500C) design, so i can just use stainless steel to save cash. again, i really DO NOT need it to be that hot.


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PostPosted: May 07, 2011 5:25 am 
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well using a simple 30% efficiency (which is easily reachable, this is a modest estimate), the reactor would need to produce 90 Kw of thermal power to convert into roughly 25 Kw electrical

the question then becomes what volume of salt at what flow rate and what temperature = 90 Kw thermal, and from THERE i can transition into how to design the core.


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PostPosted: May 08, 2011 12:15 am 
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JAK I like your DIY, mad-scientist approach. That's not to say that it's legal or practical.

I didn't know that about the U-233, I assumed it was illegal in any quantity (like many drugs). Thorium is legal to possess, in any quantity, as far as I know (check with your lawyers, etc). The problem would be getting this U-233.

In theory, perhaps, maybe, you do what I had proposed, in my thought-experiment, of taking some more naturally occurring neutron source (or an alpha source and transform it with beryllium) and use a neutron lens, to bombard a very small amount of thorium to create your own U-233 for use in your thorium reactor. I don't know what you're planning on doing, perhaps a foot-warmer sized device. But you still have to worry about the salt chemistry and those salts are pretty damned nasty, not to mention expensive. Hastelloy-N, from what I recall, is only the best thing with have, not really adequate over a long time.

I am a DIY type of guy, sort of a mad-scientists, but in the end I really think that LFTR and other nuclear power devices are best left to the fully-funded professionals. It's frustrating, I know. I had all sorts of interesting designs of wind turbines better than what's on the market, and then I discovered LFTR and...the wind was taken out of my sails...LFTR is the answer for the vast populace...but for DIY people perhaps it is better to muck about with wind turbines and hope that our professionals can get the LFTR done.

In the end, the ability of a society to create and support the advanced science, technology, and operations infrastructure needed for advanced nuclear power is what will determine the long-term viability of that society. Cheap, reliable, safe power is what makes the economic world go around.


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PostPosted: May 08, 2011 3:28 pm 
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well the more i look into the research notes of other LFTRites, it seems that there are much cheaper and possibly better alternatives to the expensive stuff used at ORNL

there are a couple alternatives to hastelloy-N for the reactor and piping walls which aren't QUITE as expensive and possibly easier to form (ceramics like silicon carbide). not to mention FLiBe isn't the only potential carrier salt, it's kind of expensive since you need lithium-7 specifically. There are a couple sodium-based carrier salts which could do a similar job at lower temperatures (which would be good for my design)

as for the U233, the MSRE only used about .16% of the stuff inside the carrier salt. At my 200 gram limit, i could make about 120kg of fuel/carrier salt mixture and still be completely legal (that's like 260 pounds!).

of course the devil is in the details here, as i still don't know how hot the fuel salt needs to be to achieve 90kw thermal, and thus what kind of core size i'll need or how much moderator is required.

As from the beginning, my real concern is that damn fluorine. but i have some ideas for that, like putting any fluoride gas operation within a tightly sealed plastic housing with a few fluoride detectors that will shut down the reactor if they detect any above the allowed limits. Speaking of which, i could probably make an entire safety system from an Arudrino chip array and code it all in C, with lots of parity bit checks to sniff out possible errors caused by gamma or neutron emissions.

I really think this could work, it's more an issue of cleverly working around the current roadblocks, rather than plowing through them with cash.

I'm going to try to make a model of this thing in the popular game Minecraft and upload a youtube video, it'll be fun :D


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PostPosted: May 09, 2011 11:51 pm 
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JAK, you sound a lot like David Hahn... have you read about him? See how his career has gone?
http://en.wikipedia.org/wiki/David_Hahn

I think he would have done better to attend U of T & get credentials and a job as a nuke. Less work, better pay, less rads, more respectable, etc. Warmer climate.

Failing that, there's always solar heat, which fortunately is not illegal. This guy, Don Stephens, claims to have a way to make it work in any temperate climate, including freezing fogs.

http://www.greenershelter.org/


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