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 Post subject: Granite EROEI
PostPosted: Apr 04, 2016 9:09 pm 
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So I decided to work out if breeder reactors are actually required for granite crushing to be worthwhile for uranium extraction.

Most estimates indicate that crushing granite into a 50 mesh powder is about 9kWh/t (or was in the 60s)
An estimated 10kWh per ton is required to generate acids, leach the powder and recover the uranium from the leachate.

That means roughly ~20kWh/t of granite processed.
If the granite is ~16ppm for uranium [like typical Cornubian Granite] that gives us 16g/t of uranium using 20kWh/t.
That is roughly 5kWh/g if we assume 25% recovery.


An ESBWR requires 4.2% uranium fuel for 50GWd/t burnup. It will produce roughly 420MWh (electric)/kg of material.
If we take 8kg of NU to make a kilogramme of that fuel then we are obtaining 52.5MWh/kg of NU.
Or 52kWh per gramme of NU.

So only ten percent of the electricity consumed is required for the crushing of the rock, even with a 25% recovery factor.
If we apply more (relatively) cheap SWUs we can shrink the NU requirement to 7kg/kg per fuel and the numbers change to roughly 8% of the energy being required for the mining.

In summary, even without breeders it seems likely that relatively low grade ores like high-heat granites can support a once through LWR cycle.

Which is rather impressive.


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 Post subject: Re: Granite EROEI
PostPosted: Apr 05, 2016 10:03 am 
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I'd still prefer not to have to crush up quite so much granite, at least until we have a reasonable way to reconstitute it.

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 Post subject: Re: Granite EROEI
PostPosted: Apr 05, 2016 12:20 pm 
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Noone would ever dig for sand ever again if we did this, it is true.


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 Post subject: Re: Granite EROEI
PostPosted: Apr 06, 2016 12:23 am 
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E Ireland wrote:
Noone would ever dig for sand ever again if we did this, it is true.
Can you use crushed granite in glass? I suspect it would do very nicely for concrete. But glass?

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 Post subject: Re: Granite EROEI
PostPosted: Apr 06, 2016 10:00 am 
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Good point, however construction sand use in the UK was roughly forty two megatonnes in 2010 - compared to roughly four megatonnes for high Silica sands. At least according to the BGS and their handy mineral planning factsheets that contain all sorts of interesting information about minerals and their use.


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 Post subject: Re: Granite EROEI
PostPosted: Apr 06, 2016 2:59 pm 
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So, one would only have to dig for 1/10th the sand...

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 Post subject: Re: Granite EROEI
PostPosted: Apr 10, 2016 1:27 am 
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If a nuclear age will last for millions of years you will indeed use granite and other very low grade ores.

If you crush the granite you won`t crush it for uranium ore only. Most probably you would crush the granite for another main ore as copper and gain uranium as a welcome by-product.

If you crush the granite you will use a variety of ores and minerals as copper, nickel, molybdenum, rare earth, gold, thorium from the granite. This might change your equation.

Best regards

Holger


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 Post subject: Re: Granite EROEI
PostPosted: Jan 24, 2017 12:46 pm 
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Location: idaho falls
E Ireland wrote:
So I decided to work out if breeder reactors are actually required for granite crushing to be worthwhile for uranium extraction.

Most estimates indicate that crushing granite into a 50 mesh powder is about 9kWh/t (or was in the 60s)
An estimated 10kWh per ton is required to generate acids, leach the powder and recover the uranium from the leachate.

That means roughly ~20kWh/t of granite processed.
If the granite is ~16ppm for uranium [like typical Cornubian Granite] that gives us 16g/t of uranium using 20kWh/t.
That is roughly 5kWh/g if we assume 25% recovery.


An ESBWR requires 4.2% uranium fuel for 50GWd/t burnup. It will produce roughly 420MWh (electric)/kg of material.
If we take 8kg of NU to make a kilogramme of that fuel then we are obtaining 52.5MWh/kg of NU.
Or 52kWh per gramme of NU.

So only ten percent of the electricity consumed is required for the crushing of the rock, even with a 25% recovery factor.
If we apply more (relatively) cheap SWUs we can shrink the NU requirement to 7kg/kg per fuel and the numbers change to roughly 8% of the energy being required for the mining.

In summary, even without breeders it seems likely that relatively low grade ores like high-heat granites can support a once through LWR cycle.

Which is rather impressive.


Neat analysis!

Where did you get your numbers? (grinding energy/t, concentration of U in the granite, etc.)

Is there a reference that gives an estimate of how big (tonnes or cubic meters) that pluton is? Others like it?

Thanks.

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 Post subject: Re: Granite EROEI
PostPosted: Jan 24, 2017 3:53 pm 
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darryl siemer wrote:

Neat analysis!

Where did you get your numbers? (grinding energy/t, concentration of U in the granite, etc.)


I dug them out of various reports i found at the time, the grinding energy one in particular was difficult to find.
I will try and dig them out and get back to you.
Uranium content varies wildly from 8-20+ppm.
Although with a CANDU-SEU cycle you can make these energy figures look wasteful of uranium so it almost doesn't matter.
darryl siemer wrote:
Is there a reference that gives an estimate of how big (tonnes or cubic meters) that pluton is? Others like it?

The Cornubian Granite batholith (contains multiple plutons) has been estimated at a volume of approximately 68,000 cubic kilometres. But most of that is under the Celtic Sea as it stretches a 100km beyond the Scilly Isles, half way to the edge of the continental shelf.
Even 1% of the reserve would run to 13.6 million tonnes of uranium in place.


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 Post subject: Re: Granite EROEI
PostPosted: Jan 24, 2017 5:33 pm 
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E Ireland wrote:
darryl siemer wrote:

Neat analysis!

Where did you get your numbers? (grinding energy/t, concentration of U in the granite, etc.)


I dug them out of various reports i found at the time, the grinding energy one in particular was difficult to find.
I will try and dig them out and get back to you.
Uranium content varies wildly from 8-20+ppm.
Although with a CANDU-SEU cycle you can make these energy figures look wasteful of uranium so it almost doesn't matter.
darryl siemer wrote:
Is there a reference that gives an estimate of how big (tonnes or cubic meters) that pluton is? Others like it?

The Cornubian Granite batholith (contains multiple plutons) has been estimated at a volume of approximately 68,000 cubic kilometres. But most of that is under the Celtic Sea as it stretches a 100km beyond the Scilly Isles, half way to the edge of the continental shelf.
Even 1% of the reserve would run to 13.6 million tonnes of uranium in place.


One problem with any sort of non breeder reactor implemented "nuclear renaissance" is that trying to run the future with them would make too big of a mess.

If I've done my math right, providing 30,000 GWe-year's worth of juice with reactors generating 52.5 MWr/kg of NU that's from 14 ppm U, 2.75 g/cc granite, would require the excavating/processing of about 500 "Berkeley Pits" (Butte MT's 1780 ft deep, 675 acre abandoned copper mine - one of the EPA's biggest superfund projects) worth of rock/per year. Kinda scary.

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 Post subject: Re: Granite EROEI
PostPosted: Jan 24, 2017 6:22 pm 
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darryl siemer wrote:
If I've done my math right, providing 30,000 GWe-year's worth of juice with reactors generating 52.5 MWr/kg of NU that's from 14 ppm U, 2.75 g/cc granite, would require the excavating/processing of about 500 "Berkeley Pits" (Butte MT's 1780 ft deep, 675 acre abandoned copper mine - one of the EPA's biggest superfund projects) worth of rock/per year. Kinda scary.


SEU CANDU can probably make something approaching ~91MWhr/kg with 0.1% tails fraction (utilising modern enrichment techniques).
If we invest in enriched zirconium-90 in the calandria and pressure tubes of the reactors we can get ~15% more burnup from the fuel, taking us to something like ~104-105MWh/kg.
Which cuts the number of pits required in half.


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 Post subject: Re: Granite EROEI
PostPosted: Jan 25, 2017 1:56 am 
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Darryl, how does that compare with the amount of basalt you'd have to grind up for your CO2 reduction plan, assuming you wanted to drop the atmospheric concentration from 400 to 300 ppm ? I know Schuiling claimed his olivine proposal would need to chew up a volume of rock equivalent to Kauai.
http://i2.cdn.cnn.com/cnnnext/dam/asset ... er-169.jpg
Basalt I think you said would need about double the volume as olivine for equivalent carbon dioxide fixation, and so I suppose twice as much energy for grinding it, assuming similar rock hardness.
Are there any ultramafic ores with good grades of uranium, or thorium ?
Edit - 'Granite is heat resistant, wear resistant whereas Basalt is heat resistant, pressure resistant, wear resistant.' Granite hardness 6 - 7, basalt 6.


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 Post subject: Re: Granite EROEI
PostPosted: Jan 25, 2017 3:24 am 
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Uranium consumption and price are going down of late. All that stone breaking and crushing may not find any takers.
The good news for nuclear energy is IMSR and Russian fast breeders.
Rich uranium ores are found in Canada. Thorium is available as by-product of rare earth mining.
So, just provide thorium blankets in IMSR and fast reactors (even LWR and PHWRs) and you have fissile to burn all of easily available quantities of uranium and thorium for your energy requirements for millania.


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 Post subject: Re: Granite EROEI
PostPosted: Jan 25, 2017 1:39 pm 
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jon wrote:
Darryl, how does that compare with the amount of basalt you'd have to grind up for your CO2 reduction plan, assuming you wanted to drop .....


It depends upon which basalt we use. If we choose the "dunite" assumed for the ATTACHMENT's "all in CDR scenario" dropping the atmosphere's CO2 conc. from 400 to 300 ppm (v/v) would require about 250 km3 of rock - about the same amount of granite that would have to mined to power one 30000 GWe year's worth of LWR power (the paper explains where "30000" comes from). If "average Idaho basalt" is used (probably a superior soil amendment), it'd take about three times that much.


Attachments:
Soil chem RAL's change accepted 2.docx [743.06 KiB]
Downloaded 65 times

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 Post subject: Re: Granite EROEI
PostPosted: Jan 25, 2017 2:00 pm 
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jagdish wrote:
Uranium consumption and price are going down of late. All that stone breaking and crushing may not find any takers.
The good news for nuclear energy is IMSR and Russian fast breeders.
Rich uranium ores are found in Canada. Thorium is available as by-product of rare earth mining.
So, just provide thorium blankets in IMSR and fast reactors (even LWR and PHWRs) and you have fissile to burn all of easily available quantities of uranium and thorium for your energy requirements for millania.


U prices will immediately spike if the world really does decide to implement a nuclear renaissance - esp with anything other than full-blown breeders (GOOGLE "uranium cartel"). As currently envisioned, IMSRs & THORCONs aren't all that much more "sustainable" than are today's LWRs. In principle, Russia's (or GE-Hitachii's S Prism) LMFBRs could do the job if (& only if) accompanied by as yet-unproven, practical/affordable, fuel reprocessing systems.

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