Energy From Thorium Discussion Forum

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PostPosted: Dec 15, 2008 9:25 am 
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Alex P wrote:
Of course it is a very interesting and useful application, but I guess that one of the goal at least in the long term should be to harvest the enormous quantity of uranium 238 stored everywhere both as depleted uranium in the uranium enrichment tails (about 0,2%) and in low enriched uranium in LWR or CANDU spent fuel (about 1% or 0,2%, respectively). Only a fast breeder operating in the uranium-plutonium cycle can do that and as far as I understand the molten salts fast version is - at least - the most proliferative resistant

It is rightly the main reason for nuclear 'Haves' to go for fast breeders including molten chlorides salt reactors. By not claiming more and more uranium they shall be rendering a service to the rest, besides consuming up the spent once through fuel stocks. They could move to thorium as an extension and for lower cost if so proved. The uranium poor should also move to fast breeders and then to thorium. 500 ppm ores being dug up means digging up 2000 times the ore greatly spoiling land for other uses. There is strong resistance to uranium mining everywhere not only from environmentalists but also local residents.


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PostPosted: Dec 15, 2008 12:12 pm 
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It is not a goal to use up 238U or 232Th. They are both so very abundant that the idea of using them up is hopeless. It would be nice to use 238U instead of 232Th simply because there would be no need to mine it. We have heaps and heaps of the stuff already and wonder what to do with it. BUT, the mining required for either one is trivially small. If everything else were equal I would choose 238U to reduce the mining but this is WAY down the tradeoff list and everything else is very unlikely to be equal.

Likely cost (specifically for the on-site processing) will be the biggest reason to choose between no fertile in the fuel, 238U in the fuel, or 232Th in the fuel. Waste and proliferation worries (whether real or merely political) will also influence this choice.


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PostPosted: Dec 21, 2008 4:57 am 
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The only problem with 238U-239Pu cycle is that fast spectrum is required to obtain break even conversion for a long fuel life and high burn up. There is compensation in the form of high energy intensity, less corrosive chloride salts if you go to a chloride MSR. Separation of 37Cl shall be required but it is not radioactive and is less corrosive. Being a quarter of all chlorine, cost of separation shall be less than that of 235U or deuterium. Sodium coolant in a fast reactor shall have to be avoided, replacing it either by a salt solvent/coolant in an MSR or by a gas.


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PostPosted: Dec 21, 2008 10:07 am 
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jagdish wrote:
There is compensation in the form of less corrosive chloride salts


Neither fluoride nor chloride ions are corrosive to metals, what's actually corrosive in a molten salt is the metal ions, chiefly the U(IV). But in a molten chloride reactor, you will get some sulfur from (n,alpha) reactions, mostly in Cl-35, and that is actually corrosive.


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