Energy From Thorium Discussion Forum

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 Post subject: Nuclear sustainability
PostPosted: Dec 04, 2010 8:30 pm 
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In case anyone's interested. My thoughts concerning the world's U and Th reserves. Feel free to critique.

http://channellingthestrongforce.blogsp ... nable.html


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PostPosted: Dec 05, 2010 11:52 am 
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Some points on ocean U extraction. The often suggested bottleneck (even by Mackay) is the circulation speed of ocean water, which is more than 1000 years. There is however a complication. Dissolved ocean U is in chemical equilibrium with rock and sediment in contact with ocean water. In other words, ocean floors, continental shelfs etc. These all contain far high concentrations of U. If U is extracted from seawater, there will be leeching in from the rock and sediment towards the ocean water. The speed at which the equilibrium reconsititutes itself is thus the primary bottleneck. Given the high surface area in contact with ocean water, the reconstitution is likey much faster than 1000 years, even under very rapid U extraction. If the reconstitution turns out to be 100 years then Mackay's estimate is about 10x too low. Seawater U is more sustainable than even the big resource figures makes us imagine.


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PostPosted: Dec 05, 2010 5:27 pm 
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This also suggests that gathering the nodules on the bottom of the ocean may be a much more concentrated source than the water itself.


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PostPosted: Dec 06, 2010 4:07 am 
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Lars wrote:
This also suggests that gathering the nodules on the bottom of the ocean may be a much more concentrated source than the water itself.


Clever observation! The interesting issue is that those nodules are usually quite deep, whereas mining the water can be done on the surface and where it is convenient such as near a harbor in warm water or near a nuclear powerplant once through cooling outlet. So how does this play out financially – higher ore concentration of the precipitates versus easier extraction locations for the water mining?


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PostPosted: Dec 06, 2010 6:31 am 
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I rather suspect we'll be using breeders of one sort or another before widespread oceanic U extraction comes into vogue.


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PostPosted: Dec 06, 2010 6:43 am 
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Fast breeders or thorium breeders will sustain nuclear energy for centuries. As far as oceans are concerned, energy from currents may be a better idea.


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PostPosted: Dec 08, 2010 4:37 am 
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Cyril R wrote:
Clever observation! The interesting issue is that those nodules are usually quite deep, whereas mining the water can be done on the surface and where it is convenient such as near a harbor in warm water or near a nuclear powerplant once through cooling outlet. So how does this play out financially – higher ore concentration of the precipitates versus easier extraction locations for the water mining?


Hmmm. How does the cooling water flow rate compare to the rate at which you'd need to extract uranium?

Uranium in seawater is 3.3 parts per billion. If your 1 GW(e) plant dumps 1.5 GW(th) to seawater with a 5 C temperature rise, then it must dump that heat into 71 metric tons of seawater per second. That water is carrying 0.23 grams/second of Uranium, or 7400 kg/year.

Okay, so it's not going to work for a modern PWR, but if you can catch half that uranium, and if you can fission a quarter of what you catch, you can make a seawater cooled reactor that never needs refuelling.

Kinda neat that this eliminates depending on ocean currents to pump seawater through huge mats hanging out there for every barnacle in sight to live on. Presumably whatever anti-fouling measures are taken on the cooling water will work for the uranium absorption system too.


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PostPosted: Dec 08, 2010 8:49 am 
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True, U-Pu breeders can sustain themselves completely on the uranium in their own cooling water. Its one of those ‘gee whiz’ things that’s actually true and a type of good PR tidbit that we’d want to be using more often.

(sales speech)We are currently involved in developing a new type of anti biofouling for once through cooling and recirc cooling systems. Normally pulse chlorination is the preferred method, but our new process lets the condenser temp increase for a short time period up to 20 K a couple of times per day. This higher temp detaches macro organisms and kills micro organisms. It works as well as chlorination without the chemical worries and the first measurements show fewer macro organism kills (it scares most of them away rather than killing them all). It should work well with an absorbent U recovery operation, with no chlorine to mess up your polymers. (/sales speech).


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