[ RadSafe ] Diffusion, Uranium and all that

Dan McCarn hotgreenchile at gmail.com
Mon Dec 28 14:14:56 CST 2015

Hi Guys:

A little mining geology as it impacts isotopic distribution of produced
yellowcake uranium:

Most of the uranium being produced in Central Asia (Kazakhstan) is mined
using acid ins situ leach (ISL) methods from regional redox-controlled
roll-fronts in sandstone. The amount of acid ISL mined product has
increased significantly over the years. One issue that has arisen is that
there is preferential recovery of U-234 causing issues after enrichment.
U-238 decays with a ~5 MeV alpha given the nucleus a ~30 KeV kinetic
rebound. This forces the then Th-234 out of the crystal lattice (uraninite)
often into connate water around the uraninite. The Th-234 decays to Pa-234
and then U-234 by beta decay. When mined, the U-234 is preferentially
swept-up by the ISL solutions causing the resulting product to be out of
secular equilibrium with U-238. The reason for this is probably because
calcite is present along the apex of the deposit which reacts with the
H2SO4 to form CaSO4-2H2O (Gypsum) which has 2.4 times the molar volume of
calcite, reducing the formation transmissivity, reducing solution flow
through the ore, and total recovery of the deposit. George Capus (AREVA)
wrote a paper about this a number of years ago in an IAEA Technical meeting.

When enriched, the U-234 separates with the U-235 giving the enriched
product more activity then would be if the source material was in secular

Just a heads-up, since the enriched product gives higher radiation
exposures to nuclear workers manufacturing the fuel assemblies.

Dan ii

Dan W McCarn, Geologist
108 Sherwood Blvd
Los Alamos, NM 87544-3425
+1-505-672-2014 (Home – New Mexico)
+1-505-670-8123 (Mobile - New Mexico)
HotGreenChile at gmail.com (Private email) HotGreenChile at gmail dot com

On Mon, Dec 28, 2015 at 12:50 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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