X-Message-Number: 20225
Date: Mon, 30 Sep 2002 13:23:42 -0700
From: <>
Subject: Re: CryoNet #20208 (Nukes)

> Message #20208
> Date: Sun, 29 Sep 2002 09:30:43 -0400
> From: Thomas Donaldson 
> Subject: CryoNet #20197 - #20206
> 
> There seems to be a unified view that the
> pollution of nuclear
> power will stay with us for a long time. That
> is, thousands of
> years. At least 2 ways to deal with that
> problem in far less
> than 1000 years can be suggested:
> 
> 1. Throw the waste into the Sun.
>     Yes, we'll have to store it for a while
> until our space
>    technology advances far enough that we can
> do this safely,
>     but that's likely to be far less than 1000
> years.


COMMENT:
I think it will always be cheaper to bury it in continental subduction zones
than shoot it into the sun (which itself is a last resort for space since it
costs roughly twice the total delta-V as shooting it into Jupiter or
intersteller space).


> 
> 2. Process it into useful elements
>    The problem that many get hung up on here is
> that such 
>      processing can also produce material
> useful for weapons.
>    However anything useful for weapons can also
> be used for
>      quite peaceful applications. Moreover any
> country able to
>    make its own fuel for nuclear reactors
> ALREADY has the 
>    ability to make nuclear weapons.


COMMENT:
Not necessarily.  Canada runs power reactors on natural uranium and heavy
water (easier to make than U-235 enriching). For that matter, the US made the
Nagasaki bomb from Pu from Hanford reactors fueled with nothing but natural U
and very pure graphite-- no fuel enrichment was needed, but of course fuel
reprocessing after the fact, was. Hanford weapons reactors were scaled up and
water-cooled versions of the Fermi pile, which also did not use enriched fuel.

Moreover, there are a lot of countries that buy enriched fuel made somewhere
else, which are watched over in various ways so that they don't use their
power reactors to make bombs.  One way is to make sure they themselves don't
reprocess.

If countries do reprocess, it helps if they are monitored to make sure they're
only reprocessing completely spent fuel rods, so they don't get weapons grade
Pu (which is relatively pure Pu-239 with not a lot of Pu-240). The Pu from
fully cooked rods makes poor bombs fully cooked fuel rod Pu is so thermally
hot from Pu-240 decay that it causes thermal problems in normal bomb designs,
and would have to be extensively reworked into actively cooled weapons that
were assembled just before use. That would be problematic for terrorists who
don't want something literally too hot to handle or smuggle.
However, it can be done with difficulty (bombs made from reprocessed reactor
Pu are possible-- we tried it to see), which is why the US doesn't like other
countries to do fuel reprocessing at all. The other problem is that if a
country reprocesses, it's always easier for it to smuggle through some
undercooked fuel to make a batch of weapons grade Pu.

> So how
> could that processing
>    really make a serious difference. 


See above.



>    Not only could processing give us some
> fissionable elements,
>      but even radioactive elements which decay
> fast enough can
>      provide useful energy. Think of Strontium
> 90, which has
>    already been used in probes of the outer
> Solar System, where
>    Solar power ceases to be practical at all.


The Pioneer, Voyager, Galileo and Cassini missions have all used Pu-244, but
you may be right that Sr-90 has been used somewhere. Still, the same argument
applies. Such isotopses are only useful in very limited applications-- they'll
never be a source of major power because without purification isotopes they
just don't provide enough heat to be worth the tremendous sheilding you need
to handle them. And purification to get out the alpha emitters is very
expensive.


> And if those 
>    elements decay slowly, then that decay
> produces correspondingly
>      less damage. And it is the slowly decaying
> elements which
>    take the longest to decay: like 10,000 years
> or more.

The last sentence here gets the Yogi Bera award. Thanks for sharing that,
Thomas.

Steve Harris

Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=20225