From: dietz@cs.rochester.edu (Paul Dietz)
Subject: Re: Justification for the Space Program
Organization: University of Rochester
Distribution: usa, world
Date: Fri, 25 Dec 1992 13:03:15 GMT

In article <Bzt8Dw.Fzs@mentor.cc.purdue.edu> blumb@sage.cc.purdue.edu (Bill Blum) writes:

>>By most objective measures, the world is getting better.  The world
>>has never been, on average, wealthier, healthier, better fed, or
>>better educated than it is today.  These are *facts*.  You can look up
>>the numbers.  These trends have been going on for decades, in spite of
>>the continuous (and continuously wrong) doomsaying.

> Gee, Mr. Dietz.  Go to Somalia.  Talk with the people.  They would strongly
> disagree with you about being better off.

What a load of crap.  Of course there are people who are in bad
situations.  But these extreme points prove nothing, except that the
world is not completely perfect.  As I said, ON AVERAGE, the world is
getting better.  Fewer people (in absolute numbers, not just as a
fraction of the world's population) are living in countries that
experience famines that did a generation ago.  On average, people are
getting more nutrition, and living longer.


>It is a FACT that the future is uncertain.              
>(_Introduction to Nuclear Engineering_, 2nd Edition, John Lamarsh)
>-begin quote-
>
>	Whether sufficient uranium will be available to fuel expanding
> world nuclear capacity is an issue of continuing controversy even among
> experts.  Uranium itself is not an especially rare element.  It is present
> in the earth's crust at a concentration by weight of about four parts per
> million, which makes uranium more abundant than such common substances as
> silver, mercury, and iodine.  There are an estimated 10^14 tons of uranium
> located at a depth of less than 12 or 13 miles, but most of this is at such
> low concentrations it WILL PROBABLY NEVER BE RECOVERED, (boldface added by
> me) 


I cannot imagine what you are trying to prove by this quote.  Let's
consider a world with 10,000 1 GWe reactors.  It will consume
somewhere less than 20,000 tons of uranium per year.  Those 10^14 tons
would last 5 billion years at that rate.

So, indeed, much of that uranium never gets recovered -- because it
decays, or the sun burns out, before we need it!  Note that being at a
depth of 12 or 13 miles doesn't really matter, because we would use it
so slowly that erosion (and isostatic uplift) would move it to the
surface sufficiently quickly.

I understand that if you pulverize granite and wash with acid, about
1/3 of the uranium and thorium can be easily mobilized (the rest could
be recovered by more vigorous treatment).  This fraction eluted from a
ton of granite is equivalent to about 15 tons of coal, if used in some
sort of breeder.  However, no doubt richer deposits will be attacked
first (for example, organic-rich shales; the Chattanooga Shale, for
example, is estimated to contain 5 million tons of uranium at about 60
ppm).

I know of no nuclear experts who think there is not sufficient
recoverable uranium to run a breeder-based economy for far longer than
is reasonable to plan for.  There is some controversy on how long
burner reactors can be fueled without breeding, especially if the
number of such reactors grows.  Fortunately, accelerator breeders
can be used to make fuel for burner reactors, with a doubling time
of about 3 years, so if fuel ever did become unexpectedly short
we could adapt quickly.

	Paul F. Dietz
	dietz@cs.rochester.edu


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