[ExI] Could Thorium solve our energy problem?

samantha sjatkins at mac.com
Fri Jul 9 00:36:53 UTC 2010

John Clark wrote:
> I've been reading about Thorium reactors, in particular Liquid 
> Fluoride Thorium Reactors (LFTR) and I'm very impressed, I don't 
> believe nearly enough is being done in this area. With all respect 
> to Keith Henson I think this is much more likely to provide our energy 
> needs than space based solar. I think this is what fusion wanted to 
> be, certainly it's better than conventional nuclear fission. Consider 
> the advantages:

Thanks for sharing what you found.  This was on my list of things to 
look into in more detail.  If you have some useful links then please 
share them.  

I agree that this is a much more immediate energy solution than space 
based solar, at least SBSP of any design I am familiar with.  The first 
problem with SBSP is the huge mass all the mirrors and collectors 
represent and the high cost of launch.   The second is that you have no 
way to do all the assembly and maintenance required at GEO.  Doing it 
with astronauts is a non-starter.  We would need a lot better space 
robotics than we have.   Of course you could mine near earth asteroids 
first for much of the needed material and volatiles without hauling so 
much mass up the gravity well.  Which we should do anyway including for 
rare earths and precious metals.  But that is a different topic.
> *Thorium is much more common than Uranium, almost twice as common as 
> Tin in fact. And Thorium is easier to extract from its ore than Uranium.
Yes.  I have heard we have 10.000 years at current energy needs of the 
> *A Thorium reactor burns up all the Thorium in it so at current usage 
> that element could supply our energy needs for many thousands, perhaps 
> millions of years; A conventional light water reactor only burns .7% 
> of the Uranium in it.
Not millions but thousands.
> * To burn the remaining 99.3% of Uranium you'd have to use a exotic 
> fast neutron breeder reactor, Thorium reactors use slow neutrons and 
> so are inherently more stable because you have much more time to react 
> if something goes wrong. Also breeders produce massive amounts of 
> Plutonium which is a bad thing if you're worried about people making 
> bombs. Thorium produces an insignificant amount of Plutonium.
> * Thorium does produce Uranium 233 and theoretically you could make a 
> bomb out of that, but it would be contaminated with Uranium 232 which 
> is a powerful gamma ray emitter which would make it suicidal to work 
> with unless extraordinary precautions were taken, and even then the 
> unexploded bomb would be so radioactive it would give away its 
> presents if you tried to hide it, destroy its electronic firing 
> circuits and degrade its chemical explosives. For these reasons even 
> after 65 years nobody has even tried to make bomb out of Uranium 233.
I am so much more concerned with resolving the looming energy crisis 
than with proliferation but nice to know.

> *A Thorium reactor only produces about 1% as much waste as a 
> conventional reactor and the stuff it does make is not as nasty, after 
> about 5 years 87% of it would be safe and the remaining 13% in 300 
> years; a conventional reactor would take 100,000 years. 

> *A Thorium reactor has an inherent safety feature, the fuel is in 
> liquid form (Thorium dissolved in un-corrosive molten Fluoride salts) 
> so if for whatever reason things get too hot the liquid expands and so 
> the fuel gets less dense and the reaction slows down.

> *There is yet another fail safe device. At the bottom of the reactor 
> is something called a "freeze plug", fans blow on it to freeze it 
> solid, if things get too hot the plug melts and the liquid drains out 
> into a holding tank and the reaction stops; also if all electronic 
> controls die due to a loss of electrical power the fans will stop the 
> plug will melt and the reaction will stop.
> *Thorium reactors work at much higher temperatures than conventional 
> reactors so you have better energy efficiency; in fact they are so hot 
> the waste heat could be used to desalinate sea water or generate 
> hydrogen fuel from water.
Interesting.  I was about about to ask what the comparative energy yield 
was and the comparative price per GW.

> * Although the liquid Fluoride salt is very hot it is not under 
> pressure so that makes the plumbing of the thing much easier, and even 
> if you did get a leak it would not be the utter disaster it would be 
> in a conventional reactor; that is also why the containment building 
> in common light water reactors need to be so much larger than the 
> reactor itself. With Thorium nothing is under pressure and there is no 
> danger of a disastrous phase change so the expensive containment 
> building can be made much more compact. 
YAY.  That lowers cost.  

> If you're interested in this technology this might be a good place to 
> start:
> http://blogs.howstuffworks.com/2009/12/01/how-a-liquid-fluoride-thorium-reactor-lftr-works/

Thanks again!

- samantha

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