Energy From Thorium Discussion Forum

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PostPosted: Jul 16, 2013 9:34 pm 
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For use in rhetorical arguments, I was wondering if someone could point me towards something that definitively shows the costs and problems if any with "mining" granite for the thorium and uranium content.

Wikipedia tells me that granite contains about 10 to 20 ppm uranium, and a certain kind of granite, called "Conway granite", contains about 56 ppm EDIT: thorium.

Furthermore,
http://www.world-nuclear.org/info/Nucle ... hosphates/
that tells me that it was economical apparently to obtain uranium from phosphate rock, and the US obtained about 20% of its uranium from phosphate rock in the 1990s. It says that phosphate rock contains about 70 to 200 ppm uranium.

Are these numbers accurate and indicative of the general constitution of these rocks? Is it also true that most of the (continental) crust of this planet is made up of granite?

It's my understanding that we could mine granite for the thorium and uranium content, and the phosphate rock thing helps bolster the case to me, but I would prefer some more expert opinions and citations that it can be done.

Finally, to paraphrase Alvin Weinberg, we literally could "mine" just granite, the most common constituent of the accessible surface of this planet, to "burn" in nuclear reactors at prices within the same ballpark at today's prices because the ore itself constitutes only a small price of the end electricity, right? I want to use this in rhetorical arguments saying that we will never run out, and we have to sooner worry about the sun going red giant than we do about running out of granite.


Last edited by Joshua Maurice on Jul 18, 2013 5:51 am, edited 1 time in total.

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PostPosted: Jul 17, 2013 12:01 am 
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Slightly off topic but if were talking about fuel sustainability we've never really attempted to tap thorium reserves in any meaningful way, so there is some uncertainty there, but for any near term utilisation of Th we have more than we know what to do with. Beyond that if we develop systems that can burn a reasonable portion of the U238 present in natural U we have more than enough U to power the planet for a very very long time, there should be no need to mine granite. Using U and Th together seems to work pretty well most of the time.

See the following discussion of how U from seawater can keep the planet ticking over for a very very long time if we ever have trouble accessing Th at an acceptable price.

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PostPosted: Jul 17, 2013 12:37 pm 
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GraniteUandTh.pdf [623.85 KiB]
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A bit dated but ORNL did a study on pulling Th and U out of granite to give themselves an idea of the ultimate unlimited resource. Depending on the granite, they were estimating 25 to 89$ a pound for Th+U (80% or more Th) back in 1963.

David L.


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PostPosted: Jul 17, 2013 3:33 pm 
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Thank you very much good sir.


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PostPosted: Jul 18, 2013 5:42 am 
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Also check the energy return on energy invested, for the mining. The EROEI has to be much larger than 1 for an energy source to be practical and affordable.

http://nuclearinfo.net/Nuclearpower/Ura ... stribution

10 to 20 ppm ore means a mining EROEI of 16 to 32 with today's LWRs. So it's pretty good already even with relatively wasteful LWRs, using only 1/200th the theoretical energy in the total fuel (fissile plus fertile). Even the least resource efficient MSR, a small converter with uranium only, would do maybe 2x better than the LWRs, so you're up to 32-64 EROEI already with this granite. Full fledged thorium reactors would do orders of magnitude better still, but it's mostly academic at that point.


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