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...Lesson for Nasa! US Airmail and Aviation



 
 
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  #81  
Old May 20th 06, 04:12 AM posted to sci.space.policy,sci.space.history,sci.space.station
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Default ...Lesson for Nasa! US Airmail and Aviation

In article .com,
Hyper wrote:
...and the limits imposed on fission by uranium supply.


Isn't the problem of supply obviated by using breeder reactors?


If you build the breeder reactors, and the corresponding reprocessing
plants; there are non-trivial political obstacles to doing so, not to
mention some remaining technical issues with existing breeder designs.

And what about the kilotons of U238 in storage?


What about them? U-238 isn't a reactor fuel, not without breeding.

Likely recoverable reserves of U-235 (not counting seawater and granite,
both of which are very difficult to mine economically) correspond to about
300 TW-yr of energy. Unfortunately, world power demand is going to grow
by tens of TW in the next half-century, so that just isn't enough to base
a long-term energy infrastructure on. Breeding -- preferably U-233 from
thorium rather than Pu-239 from U-238 -- would fix that, but it means
restarting breeder-reactor technology work quickly, and then building a
lot of breeder reactors and reprocessing plants in a hurry.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |
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  #82  
Old May 20th 06, 07:36 AM posted to sci.space.policy,sci.space.history,sci.space.station
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Default ...Lesson for Nasa! US Airmail and Aviation

Still, it's not an engineering / resource limitation, rather a
political one. That was actually my point.

  #83  
Old May 20th 06, 12:29 PM posted to sci.space.policy,sci.space.history,sci.space.station
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Default ...Lesson for Nasa! US Airmail and Aviation

Henry Spencer wrote:

Likely recoverable reserves of U-235 (not counting seawater and granite,
both of which are very difficult to mine economically) correspond to about
300 TW-yr of energy.


I don't understand why you say this about seawater uranium. Estimates
for the cost of extraction using the Japanese amidoxime technology
are as low as 10,000 yen/pound (with some development):

http://npc.sarov.ru/english/digest/1...appendix8.html

(a web page containing a copy of the results of a Japanese
study.)

IMO, the advances needed to reach this performance level for
this technology are much less than those needed to bring SPS
to maturity. At $100/lb -- less than a factor of three above
the last spot market price of U I saw -- the uranium should
be affordable in a once-through cycle. Reprocessing doesn't
make economic sense (from avoided uranium costs) until natural
uranium reaches around $700/lb, IIRC.

Paul
  #85  
Old May 22nd 06, 04:27 AM posted to sci.space.policy,sci.space.history,sci.space.station
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Default ...Lesson for Nasa! US Airmail and Aviation

In article ,
Paul F. Dietz wrote:
Likely recoverable reserves of U-235 (not counting seawater and granite,
both of which are very difficult to mine economically) ...


I don't understand why you say this about seawater uranium. Estimates
for the cost of extraction using the Japanese amidoxime technology
are as low as 10,000 yen/pound (with some development)...


"With some development." I say this because I'm deeply skeptical about
some of those development steps, especially the ones that don't appear in
the oversimplified treatments. "Reality is, there are a lot more boxes in
the diagram, all of which cost money." (Jordin Kare, talking about
something else entirely, but it fits here too.)

For example, I see no mention of the problem of keeping the collection
system free of barnacles and other sea life, a problem that's never been
fully solved even for ships.

Bear in mind that we're talking about doing chemical processing on an
enormous scale. To get 30 TW-yr worth of U-235 per year, assuming
complete recovery of U-235 from natural uranium, would require complete
extraction of the uranium content of about a cubic kilometer of seawater
per *minute*. I'm not aware of any chemical process -- not even
purification of drinking water -- which has ever been done on anything
like that scale.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |
  #86  
Old May 22nd 06, 02:36 PM posted to sci.space.policy,sci.space.history,sci.space.station
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Default ...Lesson for Nasa! US Airmail and Aviation

Henry Spencer wrote:

For example, I see no mention of the problem of keeping the collection
system free of barnacles and other sea life, a problem that's never been
fully solved even for ships.

Bear in mind that we're talking about doing chemical processing on an
enormous scale. To get 30 TW-yr worth of U-235 per year, assuming
complete recovery of U-235 from natural uranium, would require complete
extraction of the uranium content of about a cubic kilometer of seawater
per *minute*. I'm not aware of any chemical process -- not even
purification of drinking water -- which has ever been done on anything
like that scale.


Henry,

The chemical processing proper is done on the saturated adsorber. This
has already been tested, in the ocean, and fouling was not a problem.
Understand that this chemical processing is only a small part of the cost of
the extraction, since the adsorber is something like 1% uranium when
it's pulled out for processing. It would be nice to reuse the adsorber
several times, but you don't need to reuse it hundreds of times in
order for the economics to work out.

Yes, lots of water would need to be processed. To fuel a single large
nuclear reactor, with absorbers in a 2 m/s ocean curremt, you'd need
to absorb the uranium in an area ~700 m^2 perpendicular to the current.
That's not excessive (although it would be spread out, and adsorption
wouldn't be 100%). Of course 30 TW requires a much larger
system, but then ANY energy system capable of supplying that much
energy will be extremely large and extremely expensive. The global
economy is really big, and it will be able to (and have to!) spend
many trillions of dollars on energy over the coming century.

If you want to be concerned about fouling, worry about growth
of organisms on the support structure, not the adsorber itself
or its cages (if this was what you *were* worrying about, then
I agree it would need to be addressed.)

Paul
  #90  
Old May 23rd 06, 12:57 AM posted to sci.space.policy,sci.space.history,sci.space.station
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Default ...Lesson for Nasa! US Airmail and Aviation

In article ,
Derek Lyons wrote:
For example, I see no mention of the problem of keeping the collection
system free of barnacles and other sea life, a problem that's never been
fully solved even for ships.


Send a diver or ROV out and wipe the thing down now and again -
problem solved long ago.


Not for things that have surface areas of hundreds or thousands of square
kilometers, it hasn't been. A collector system that can sweep cubic
kilometers of seawater per minute won't be small.

And barnacles in particular don't just "wipe" off most kinds of surface;
if I recall correctly, they can even anchor themselves fairly solidly to
Teflon, which is quite a trick. Maybe if you wipe often enough to clear
the larvae off before they can anchor...

Oh, something workable can probably be developed. But I'm not convinced
it's a trivial issue, not for something on this scale -- it could easily
be a major source of difficulty and expense -- and it's an example of the
sort of practical problem which needs to be considered and apparently
hasn't been, yet.

This is promising work, yes, but it's way too early to call it an assured
source of TW-yr/yr quantities of uranium.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |
 




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