[ RadSafe ] Diffusion, Uranium and all that

Joseph Preisig jrpnj01 at gmail.com
Mon Dec 28 14:18:12 CST 2015


     A good MS level accelerator/nuclear/particle physicist knows how to do
the things you list.  An engineer might not.

     Ion sources are used to make ions for acceleration.  Yes, there might
be a few accelerators, calutrons for each step of enrichment.  The
accelerator beam, upon magnetic focusing/bending, keeps the Uranium from
plating out on the side walls of the accelerator beamlines.  The
acceleration process does not have to be high energy, but must have enough
energy to accelerate the beam somewhat.  The calutron beam energy is
probably adequate.  The electric, or magnetic fields, used to separate U235
from U238 are quite controllable and adjustable, these days.  Beam currents
can be controlled from the accelerator control panel, or perhaps measured
using a Faraday cup or whatever.  Don't know much about how the separated
U235 or U238 is collected eventually.  They did this in the Calutron
somehow.  Maybe it is a deep, dark Calutron secret???  One could probably
direct each separated beam along a beamline until it is collected somehow.
In the Migma target chamber, there was a device called Charlie's Elbow
(Charlie Powell) which measured beam currents and was rotatable through
some (position) angles (adjustable).

     Yes, accelerators and beamlines need good vacuum.  This is quite
do-able.  Beamlines and accelerators reach low vacuum via a mechanical
vacuum (one or more) and then diffusion pumps are turned on to provide
higher vacuum.

     You probably don't need a Van de Graaff accelerator to do this Uranium
separation --- a smaller one will do.  Back when Fusion Energy Corporation
was in business, there were all kinds of PhD's, engineers,
undergrad/graduate students around who could do this stuff.  Nowadays, just
go to a University with a Van de Graaf accelerator around, and ask to speak
to the local scientific staff, professors or grad students.  Don't know if
diffusion separation is more economical than accelerator separation.  Back
in the Calutron days at Oak Ridge, cost wasn't much of an issue.  It was
more important to build a Uranium or Plutonium weapon quickly.

     Joe Preisig

On Mon, Dec 28, 2015 at 2:50 PM, Brennan, Mike (DOH) <
Mike.Brennan at doh.wa.gov> wrote:

> Separating the different flavors of U is easy, in the abstract.  The
> actual engineering is rather more involved.
> The various electro-magnetic separation schemes involve vaporizing the
> uranium compound, ionizing it, then using the fact that heavier ions don't
> corner as well as lighter ions to separate the U-235 from the U-238.  This
> would be easier if there were a greater mass difference, or if the elements
> the U is compounded with didn't have isotopes with almost as great a mass
> difference.  Or if you didn't need to keep a vacuum in your machine, to
> keep the air from scattering your ion beam.  Or if the ions didn't want to
> plate out on the walls of your machine at the first opportunity.  Or if you
> had anything but the most indirect ways of telling what was going on inside
> your machine.  I figure that anybody who decides this is the path they are
> going to follow to enrich uranium should be offered technical hints, at
> least half of which should be good.
> -----Original Message-----
> From: radsafe-bounces at health.phys.iit.edu [mailto:
> radsafe-bounces at health.phys.iit.edu] On Behalf Of Joseph Preisig
> Sent: Friday, December 25, 2015 7:52 PM
> To: radsafe
> Subject: [ RadSafe ] Diffusion, Uranium and all that
> Dear Radsafe,
>      There are a few ways to separate U235 from U238.  Diffusion, laser
> separation, use of Accelerators/calutrons etc.  See the internet for
> diffusion and laser separation.
>       Start with Uranium ore.  Chemically or otherwise, separate the
> Uranium from other rock, dirt, impurities.  What you have is Uranium Oxide,
> U3O8, or whatever.  For gaseous diffusion, convert the Uranium to UF6 or
> whatever.
>       For accelerator/calutron separation, refer to the book by Livingston
> and Blewett, the internet, or other books.  If one ends up with a bunch of
> U235 and a bunch of U238, think about putting the U238 into a reactor and
> making Plutonium.  This process is described in Nuclear Physics books by
> Kaplan, Segre and so on.  Many nuclear/particle physics grad students
> become competent in these accelerator concepts in grad school.  Sometimes,
> Grad students from China/Taiwan have copies of fundamental physics graduate
> level texts (Goldstein, JD Jackson, Arfken, Matthews and Walker, Schiff,
> etc.) that are in paperback form and were printed in China/Taiwan.
>     At ORNL during WW2, some accelerators were used to obtain U235.  These
> were called Calutrons, and from recent movies I have seen on TV, there were
> many Calutrons at ORNL.  Quite an effort.  These calutrons had rather large
> beam pipes, perhaps somewhat like heating ducts in your family home.  There
> were magnets external to the ducts, some for bending the alleged beam and
> some for rather crudely keeping the beam in the beam pipes.  Similar
> accelerators to the Calutron might be the Cosmotron at Brookhaven Lab, and
> the Zero Gradient Synchrotron at Argonne Lab (USA).  One of  the external
> magnets for the Cosmotron used to be outside of the Alternating Gradient
> Synchrotron building (BNL).
>      Later on, particle accelerators started to have smaller beampipes and
> started to use the concept of Alternating Gradients (magnets focused beam
> in the horizontal and/or vertical directions as the beam went forward).
> The magnets were electromagnets, and not so much Permanent Magnets.  See
> Livingston and Blewett about all this, (and weak focusing and strong
> focusing).  The Alternating Gradient stuff was developed at Brookhaven Lab,
> and possibly also suggested independently by Christofilos.  Alternating
> Gradient magnets are used in many serious particle accelerators in many
> different countries.  This technology was invented quite a while ago now,
> and is in the public domain.
>      So, all I will say now is that one could build a modern accelerator
> using Alternating Gradients, modern magnets etc. to separate U235 from
> 238.  It is all quite do-able and there is nothing secret about it.  Such
> an accelerator would work better than a Calutron.  Clearly, one is using
> the charge to mass ratio to separate U235 from U238.  One can use electric
> fields, magnetic fields and/or both to do the separation.  See E and M
> books by Lorrain and Corson, Reitz and Milford, Kip etc.  Heck a kid in the
> Trenton, NJ area won the Trenton Science Fair by building a mass
> spectrometer in the 1970's.  Nothing new here, but it is interesting and
> fun.
>      Joe Preisig
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