[extropy-chat] Energy & Global Warming [was: Partisans and EP]

[Eugen Leitl]

On Sun, Feb 11, 2007 at 12:19:29PM -0500, Keith Henson wrote:

> There is an unrecognized problem with nuclear power.  I believe all of you 
> are aware of the North Korean fizzle.  The reason for the fizzle is they 
> almost certainly used reactor grade Pu, which has a high percentage of Pu 

It's trivial to use briefly irradiated rods before you Purex the plutonium
out of it (it's easier to work with, too, since the activity is lower), so 
I don't think they're that incompetent.

> 240.  Pu 240 has a high rate of spontaneous fission which causes the bomb 
> to go off in a low grade mode before it is completely assembled.  Weapons 
> grade Pu is 90% or better Pu 239.  It is made by pushing slugs of U though 
> a reactor fast enough that little of the Pu formed picks up a second 
> neutron.  The slugs are then chemically separated to recover the Pu.  It's 
> a trade off between grade and production rate.

Even with reactor-grade Pu you should be getting a bit more than a dirty
fizzle. Pressurizing the weapon pit with a few g of tritium shortly
before assembly isn't rocket science. 
 
> Some years ago it occurred to me that exceptionally high grade Pu 239 could 
> be made by briefly exposing U 238 in solution to neutrons, sorting the Pu 

Light water, or heavy water solution? 

> with ion exchange and pumping the solution back though the reactor to 
> convert more U 238 to Pu 239.  This should generate low cost Pu 239 upwards 
> of 99%.  Considering that over a fuel consumption cycle a power reactor 
> generates a number of kg of neutrons, tapping a few percent in this loop 
> would produce a considerable amount of super weapons grade Pu.

Sounds elegant. Also, rather straightforward: 
	http://www.springerlink.com/content/3026827616472750/
 
> The other point of a space elevator is that much access to space (thousands 
> of tons a day) you could put sunshades in the sun/earth L1 location and 
> directly control climate.

You don't need a space elevator. Linear motors (maglev mass drivers) can
easily launch Moon-side fabricated material into Earth orbit (perhaps
with aerobraking). If your LEO parasols double as PV arrays tracking
Earth-side rectenna arrays by realtime beamforming via phased array
the energy problem disappears into thin air. 

At 1.3 kW/m^2 24/7/365 outside the atmosphere (and still some kW/m^2
at noon) energy is not a problem, PV technology is.
 
> Incidentally, I agree that in spite of all the problems, vast number of 
> nuclear reactors are the only other large enough non carbon approach.

I disagree
http://home.austarnet.com.au/davekimble/peakuranium.htm
Switching to thorium is a solution in search of a problem:
we have methane, coal, biomass, photovoltaics, wind, hydro,
geothermal and tidal sources.

About 0.6% of Germany's surface (comparison: 12% of it is sealed,
about half that actually covered with structures) converted to PV
is enough to cover the energy needs (I forgot whether I included
industry, I probably did). And that's Germany, where "cities are
just a few kilotons apart".

The issue is bringing costs down for a better ROI. The crossover
solar/fossil is not very far before us, given current trends.

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