[extropy-chat] Nuke 'em

Jeff Davis jrd1415 at yahoo.com
Thu Oct 27 05:03:05 UTC 2005


Let me add to Roberts remarks below, that the
situation with reactor fuel has become quite more
complex.  Setting aside the whole next generation
reactor design question -- pebble bed reactors and
other innovations -- there is something called MOX. (I
just discovered it while trying to find out the
composition of "spent" reactor fuel.)

Mixed Oxide Fuel (MOX)

Here are the bullet points

1) MOX is a means to "burn" the plutonium remaining in
spent reactor fuel to provide energy and make

2) MOX provides about 2% of the new fuel used today,
but this proportion is increasing. 

3)MOX also provides a means of burning weapons-grade
plutonium (from military sources) to produce
electricity, though using thorium-plutonium fuel is
another possible means of achieving this. 

I also discovered:
CANDU(Canada Deuterium Uranium) FUEL CYCLES 

(Which I take to suggest a continuous recycling of
used nuke fuel until the energy is largely consumed
and the waste is not amenable to the extraction of
weapons-grade material.)

>From the abstract:
The CANDU® reactor is the most versatile commercial
power reactor in the world. It has the potential to
extend resource utilization significantly, to allow
countries with developing industrial infrastructures
access to clean and abundant energy, and to destroy
long-lived nuclear waste or surplus weapons plutonium.
These benefits are available by choosing from an array
of possible fuel cycles. 

And from the Introduction:

There are currently 23 CANDU reactors in operation and
six under construction around the world, for a global
market share of 6%.
(So it's not just vaporware.)

Best, Jeff Davis

   "Everything's hard till you know how to do it."
                           Ray Charles

--- "Robert J. Bradbury" <bradbury at aeiveos.com> wrote:

> On Sun, 23 Oct 2005, Samantha Atkins wrote:
> > I don't see how that is true in any meaningful way
> after reading
> > this.  Please show me how a pebble bed reactor
> always makes plutonium
> > or is even well suited for such use.
> Samantha, Pu production is a natural consequence of
> the basic fission reaction.
> Reactor grade fuel is a mixture of U-235 + U-238. 
> (Uranium is more than 99% U-238,
> reactor grade fuel is somewhat enriched with U-235,
> weapons grade is highly
> enriched with U-235.  This is why the current debate
> over what Iran is doing
> is problematic.  If you can make reactor grade, all
> one has to do is run
> the centrifuges somewhat longer to get weapons
> grade.)
> The basic fission reaction in any nuclear reactor
> produces neutrons (this
> is what makes the whole thing "go").  Neutrons that
> are captured U-238
> which is present producing Np-239 which then decays
> into Pu-239.  If Pu-239
> captures another neutron it produces Pu-240.  [See
> 1,2].  Argonne & the EPA
> have good pages about various Uranium & Plutonium
> isotopes and half-lives [3,4].
> The basic "nuclear" fission reaction is:
>   U-235 + 1n --> Xe-134 + Sr-100 + 2n
> Presumably the initial neutron is from either cosmic
> rays or the decay
> of other naturally occuring radioactive elements. 
> Using 1 neutron and
> getting 2 neutrons is what starts the chain
> reaction.  If any of those
> neutrons are absorbed by any U-238 you end up with
> plutonium.  You can
> structure the reactors to increase or decrease the
> production of Pu
> by controlling the speed of the neutrons but I
> strongly doubt you
> can eliminate Pu production entirely unless you
> completely replaced
> the U-238 with some other isotope (presumably one
> that comfortably
> absorbs neutrons without becoming radioactive). 
> That would probably
> be an extremely expensive process due to the fact
> that natural uranium
> is mostly U-238.  (You can't use pure U-235 as I'm
> fairly sure that
> either gets very hot and melts or explodes.)
> Robert
> 1.
> http://nuclearweaponarchive.org/Library/Plutonium/
> 2.
> 3. http://www.ead.anl.gov/pub/doc/uranium.pdf
> 4. http://www.ead.anl.gov/pub/doc/plutonium.pdf
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