Energy From Thorium Discussion Forum

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PostPosted: Mar 03, 2010 10:50 pm 
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Axil wrote:
Not quite yet.

Reference:

http://pintassilgo2.ipen.br/biblioteca/2006/11539.pdf

When Uranium mining ends, there is always Phosphate. Phosphate waste contains decent concentrations of 230Th in equilibrium (1508 +- 57 Bq /kg ), and there is endless tons of phosphate waste accumulated around the world with more tons produced daily in perpetuity.

That same reference shows the activity level of 232Th to be about 1/3 that of 230Th.
Th230 half-life is 7.5e4
Th232 half-life is 1.4e10
So the ratio of Th230 to Th232 is 3*7.5e4 / 1.4e10 or 16 ppm.
If we use this as the source for our Th232 we pick up 16ppm U232 (48ppm in a truly thermal reactor).
My guess is that the story will be the same regardless of the source of the thorium unless you are going to start isotropic enrichment of the thorium.


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PostPosted: Mar 04, 2010 12:53 am 
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Lars wrote:
Axil wrote:
Not quite yet.

Reference:

http://pintassilgo2.ipen.br/biblioteca/2006/11539.pdf

When Uranium mining ends, there is always Phosphate. Phosphate waste contains decent concentrations of 230Th in equilibrium (1508 +- 57 Bq /kg ), and there is endless tons of phosphate waste accumulated around the world with more tons produced daily in perpetuity.

That same reference shows the activity level of 232Th to be about 1/3 that of 230Th.
Th230 half-life is 7.5e4
Th232 half-life is 1.4e10
So the ratio of Th230 to Th232 is 3*7.5e4 / 1.4e10 or 16 ppm.
If we use this as the source for our Th232 we pick up 16ppm U232 (48ppm in a truly thermal reactor).
My guess is that the story will be the same regardless of the source of the thorium unless you are going to start isotropic enrichment of the thorium.



I dispute your figure of Th230 assay concentration and your general line of thinking on this issue. Th230 is greatly enriched in uranium tailings. Since Th-230 occurs in equilibrium with U-238, it is valid to assume that there exists 1.5 megatons of Th230 in uranium mine tailings since there is 1.5 megatons or more of depleted U238 in world wide storage.

It is also reasonable to assume that this untouched toxic plague can be turned into a valuable resource by the Lftr.

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PostPosted: Mar 04, 2010 2:06 am 
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Axil wrote:
I dispute your figure of Th230 assay concentration and your general line of thinking on this issue. Th230 is greatly enriched in uranium tailings. Since Th-230 occurs in equilibrium with U-238, it is valid to assume that there exists 1.5 megatons of Th230 in uranium mine tailings since there is 1.5 megatons or more of depleted U238 in world wide storage.

It is also reasonable to assume that this untouched toxic plague can be turned into a valuable resource by the Lftr.


The calculations were not for uranium tailing but rather phosphate. The ratios were based on the decay information in the paper. Just what is it that you are disputing?

Second, just because Th230 and u238 are in equilibrium is no reason to presume that there is an equal quantity of Th230 and u238. Based on the half-lives of 7.54e4 and 4.47e9 we would expect the ratio of Th230 to U238 to be 1.68e-5 or 17ppm. So we could estimate the quantity of Th230 in the tailings from 1.5e9kg U as 25,000kg Th230. A key question though is how much Th232 is also present. Assuming the total Th concentration in the tailings is less than 700ppm(of the U) then this could be a viable source - for a while. Roughly enough for 1000 GWe-years of LFTRs if you extract it all. I don't happen to know the total GWe-years we have so far in LWRs but it is a lot more than 1000 - so you'd end up continuing the uranium mines to extract the 230Th and throwing away the uranium.


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PostPosted: Mar 06, 2010 1:40 pm 
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Agree !


Upon more refection you have a point. There is a lot of waste piles out there that have a concentration of 17 ppm; uranium and phosphate mining tailing together with coal ash piles; gigatons of wastes.

It may not be cost effective to dig through all of it for just a measly 17 ppm of Th230. It would make the world a cleaner place and mitigate the sins of the past … and the present but cleaning up after such sins cost lots of money.

It may be cheaper to go with a purpose built ultra fast spectrum reactor; say a fusion/fission hybrid. This reactor would irradiate th232 in the fusion neutron spectrum. By using the CANDU lattice concept with a sodium moderator and the stopping distance between blanket tubes optimized to take advantage of the 11.610 MeV threshold Th232(n, 3n)Th230 reaction, a great deal of Th230 can be manufactured. It is a short step from Th230 to U232.

For those who aspire to the “pure” thorium fuel cycle, having and abundant source of cheap U232 to provide a denaturant for u233 is important. Without a goodly supply of U232 available, the pure cycle may not be able to meet high and possibly unreasonable assay levels imposed by fearful regulators harried and pressured by the anti-nuke politicos. It looks like the supply of U232 could be a possible bottleneck in the rapid ramp up of the pure cycle so thought and ideas to mitigate this bottleneck will be valuable.

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