Doesn't Thorium 232 need plutonium to initiate a fertile reaction into a 
fissile one. That is converting Th232 into U233?  I have read of Rubbia's 
proposal for subcritical reactions driven by a proton or laser beam. I have 
zero idea if it is workable. The abundance of thorium is unassailable when 
compared to u235. I am at the point to think if the human species has time 
enough, and we may not ( I view nuclear war as far more likely then AGW), the 
we should pursue all kinds of dark horses to see if they will pay off?


-----Original Message-----
From: John Clark <johnkcl...@gmail.com>
To: everything-list <everything-list@googlegroups.com>
Sent: Sat, Nov 16, 2013 1:44 pm
Subject: Re: Nuclear power


On Fri, Nov 15, 2013 at 4:19 PM, Russell Standish <li...@hpcoders.com.au> wrote:



> For all the arguments pro and con nuclear fission, including an
impassioned speech by a 16 year old last night to a UN Youth Voice
competition, what never seems to be discussed is the elephant in the
room of how much uranium resources we have.IIUC, if all fossil fuel

power plants were replaced by conventional fission reactors, we'd burn
through our uranium supplies in about 50 years flat. 


I don't know where you got that figure, I suspect that long ago in a galaxy far 
far away some tree hugger pulled it out of his ass and then repeated it so 
often on the internet that people started treating it as fact. At any rate if 
we're running out it's hard to figure out why today Uranium prices are the 
lowest they've been in 8 years. 


> So fission reactors do not solve the problem. Of course there is fast breeder 
> technology, but everbody is so shit scared about all the plutonium that would 
> then appear on the market, making it incredibly easy for rogue states to 
> construct nuclear weapons


Uranium fast breeder scare the shit out of me too and for the same reason, I 
don't like Plutonium. But I do like Thorium reactors, in particular  Liquid 
Fluoride Thorium Reactors (LFTR) . I think LFTR's are  what fusion wanted to be 
but never achieved, despite tens of billions of dollars poured into it a fusion 
reactor has never produced one watt more power than was put into it. Certainly 
LFTR's are better than conventional nuclear fission. Consider the advantages:

*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.

*A Thorium reactor burns up all the Thorium in it, 100%,  so at current usage 
that element could supply our energy needs for many billions of years; A 
conventional light water reactor only burns .7% of the Uranium in it. We'll run 
out of Thorium in the Earth's crust about the same time that the sun will run 
out of Hydrogen.

* 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 70 years no nation has a Uranium 233 bomb in its 
weapons inventory.

*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.

* 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. 

 John K Clark  


   





 





 
 that I don't see that happening
any time soon either.

Cheers


--

----------------------------------------------------------------------------
Prof Russell Standish                  Phone 0425 253119 (mobile)
Principal, High Performance Coders
Visiting Professor of Mathematics      hpco...@hpcoders.com.au
University of New South Wales          http://www.hpcoders.com.au
----------------------------------------------------------------------------

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