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Physics/paramagnetic fissile product separation


QUESTION: Hi Dr Nelson,

I recently read a paper on separating uranium nano particles from waste water by exploiting the paramagnetic properties of uranium. This was achieved by concentrating a solenoid field on small piece of steel wool with the waste water flowing through it. the steel wool created pockets of larger flux intensity where the uranium particles agglomerated.

I am wondering if this principal (paramagnetic separation) could be applied to LFTR uranium/protactinium scrubbing in substitution of the proposed hexaflouride gas pryoprocessing?

kind regards,
nicholas smith

ANSWER: The chemical environments are quite different.  In general, separating something as heavy as uranium  from something as light as water via magnetic mechanisms should be quite a bit more efficient than separation from something similar like a heavy metal, whereas chemical separation will be far more effective.  The only way to be sure would be to try, and that would be one expensive experiment.  If procactinium is paramegnetic at all, of which I have no idea and I doubt anyone does due to its radioactive nature, then it would probably fail.

---------- FOLLOW-UP ----------

QUESTION: You are such a pessimist.

the paper that I read involved parametric capture within turbulent flow regime in a horizontal axis assembly. This means that no gravitational separation was involved and thus relative density was not involved. Well it was, but turbulent viscous shear effect would be a far more influential force.

Protactinium's mass magnetic susceptibility is about half that of Uranium. and lighter lanthanides have many orders of magnitude lower magnetic susceptibility.

I know that the experiment would be way too expensive to propose without some concrete theoretical evidence. And I know that ANSYS Fluent, the gold standard in CFD, could not even attempt such a complex system without some serious replacement coding.

I guess a constituent question that could be answerable is, what happens when you hit an ionic fluid with a super magnet?

Kind regards,
Nicholas Smith

Actually, I'm generally an optimist when it comes to inventions and interesting techniques.  Actually, protactinium appears to have a higher mass magnetic susceptibility than you might want to check your source ( is usually good).  That might be useful for any scrubbing process.  What happens with an ionic fluid when you "hit it" with a high magnetic field depends greatly on its velocity.  In general, you'll create currents and inhibit flow, which could make the entire flow process quite complex.  If you're determined to get that deep in the weeds then we're going beyond the scope of this forum, but I can recommend the book Hydrodynamic and Hydromagnetic Stability by Chandrasekhar as a reference.  Admittedly, it's a painfully detailed reference and I wouldn't wish that level of math on anyone but a good theorist, but if you're determined to figure this problem out then you might want to start there.


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Dr. Stephen O. Nelson


I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.


I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.

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