Recommendations for on-line reading about breeder reactors?

Eugen Leitl eugen at leitl.org
Tue Oct 21 01:58:35 PDT 2003


On Tue, Oct 21, 2003 at 05:13:41AM +0000, Michael Shields wrote:

> > 20 ppm U/Th in granite is not really what I'd call ore (pitchblende ~4%
> > uranium).
> 
> Who said anything about granite?

Because that's the largest potential source.

	http://www.worldwideminerals.com/WWS/InvRel.nsf/Public/Uranium

"The concentration of uranium needed to form an economic mineral deposit
varies widely depending on its geological setting and physical location.
Average ore grades at operating uranium mines range form 0.03% U to as high
as 12+% U but are most frequently less than 0.15%. (These figures do not
apply to by-products operations)."

So basically everything below 0.03% is not worth mining, using current
technology. Processing low-grade ore requires increasingly larger amounts of
energy, and produces more waste and barren landscapes. Sure, you can use
biological leeching and enrichment, and enrich from sea water, and stuff.
But what for? You can use the energy used for that directly. Makes much
better ROI, and no weapon fissibles nor radioisotopes in the ecosystem. 
 
> As with oil and other resources, "conventional sources" means reserves
> that are known and could be feasibly and economically mined today.
> This will likely increase over time.  For example, as copper demand

Most of the current oil comes from known fields. We're extracting
considerably larger fractions today. You will not find any major high-grade
uranium ore fields. Modern means of prospection have screened large areas.
What is left is larger and larger deposits of lower and lower grade ore.

> has increased sharply in the last few decades, so have our estimates
> of available copper in the earth's crust:
> http://mmsd1.mms.nrcan.gc.ca/icsg/focus/copper_world/sd.htm

Nuke is irrelevant for terrestrial energy production. The reason we don't go
photovoltaics is simply because we're too low tech. We're appallingly stupid.
 
> > The solar constant is about 1380 W/m^2. Who's crazy enough to go nuclear,
> > unless you're in deep space?
> 
> Do we have enough silicon to produce photovoltaic cells to power

No one in his sane mind would suggest using silicon PV. Even thin-film
silicon cells. The technology closest to break-even is thin-film organic and
polymer, later polymer/quantum dot. We're talking about rolls of cheap
sturdy polymer film you can buy at WalMart and lie on the ground, weighing
them down with rocks. Less flimsy variations on the same scheme you can cover
facades and roofs with. Then you can go artificial tree route, but you'd do
better by populating LEO with PV arrays made from lunar material, and just
leave rectenna arrays on the ground (stations track them with phased-array
beam synthesis during flyby).

> significant portions of the world?  Estimates of reserves are "not
> available" according to the US Geological Survey.
> http://minerals.usgs.gov/minerals/pubs/commodity/silicon/760303.pdf


Dude, silicon is not a mineral. It's the
second most abundant element in the Earth's crust, making up 25.7% of it
by weight. Typically, you use pure quartz sand (because iron chlorides are
hard to get rid of in current SiCL4 based process), but you can make silicon 
from about anything. It's extensively used in steel production. The expensive
stuff is pure monocrystalline Si, which is why you don't want to use that
for photovoltaics. 
 
> What is the cost of building factories to produce all those PV cells?

You can use self-replicating factories, which are autopoietic. But, polymer 
cells are dirt cheap in principle. It's just a different polymer, and you
have to seal the sandwich well (quantum dots are much more resistant to photo
and oxy degradation).

> Here is a study saying that over the life of a cell, including
> manufacturing and disposal, it will contribute more to global warming
> than fission.
> http://fti.neep.wisc.edu/FTI/pdf/fdm1185.pdf

I can make it sound even worse if I use lightweight GaAs cells. Duh.
 
> It's not clear-cut.

It is, if you use high-school knowledge of physics and not braindead
premises.

-- Eugen* Leitl <a href="http://leitl.org">leitl</a>
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