I have a Physics question for which I could not find the answer on the Internet, so I would like to see if y'all know the answer to it.

I have found that heavy water will have a different boiling point compared to light water, and this trend is present between various isotopes of an element. Based on this research, I have hypothesized that Uranium can be enriched using the procedure below.

  1. Make UF6 (s)

  2. Sublime it in a glass tube

  3. Lower temperature with such precision, that one isotope of Uranium still remains in the gaseous form while another isotope has turned back into a solid.

  4. Separate the gas and solid without disrupting the fragile temperature balance.

Although this link is for Germanium isotopes, it states that there is a 0.15 Celcius change of melting points between isotopes. https://www.sciencedirect.com/science/article/abs/pii/S0921452618300863

So, here are my questions.

Would this apply similarly to Uranium, and how would the use of UF6 affect this boiling point difference?

How exactly does the boiling/melting point change between differing isotopes? And is there a particular formula for finding the melting point for a particular isotope? (I assume it would take in the number of neutrons and some other info)

In addition, is it possible to adjust the temperature of the entire system with decimal grade precision?

Furthermore, would the above setup work at all?

Also, if UF6 is too sensitive, would melting Uranium metal in a kiln with decimal precision temperature adjustability work?

Finally, is there a good, reliable source for melting point differences between isotopes?

I would like to first say that this is all purely theoretical and that I will take no action upon the information obtained; it is all merely a thought experiment to enhance my understanding of Chemistry and Physics. I mean, it's not like I'm gonna make a nuclear bomb; I'm just a normal HS student in the US. If you still think that this information might be dangerous out here, please PM me so we might work something out, like meeting via Zoom/Skype/Phone or something; I am very flexible about that.

I hope y'all have a great day.

  • $\begingroup$ Note that there is a separation method that uses an IR laser to do the separation, but obviously, the details are classified. $\endgroup$
    – David White
    Apr 4, 2021 at 0:44
  • 1
    $\begingroup$ Since your question is basically about distillation, you might get more practical advice from Chemistry rather than here at Physics. We can migrate the question for you if you'd prefer to have it only in one place. If you end up posting your question on both sites, it's polite to link each post to its partner and to explain why you might hope for different advice from the different audiences. $\endgroup$
    – rob
    Apr 4, 2021 at 1:39
  • $\begingroup$ @rob Yes, that would be wonderful, thank you very much! $\endgroup$
    – Young Jun Lee
    Apr 4, 2021 at 5:16
  • $\begingroup$ @DavidWhite While that is true, enrichment via lasers(AVLIS, or SILEX for uranium) requires extreme precision. That is why I was seeking an alternative method, and it seemed like boiling/melting point differences seemed slightly more manageable than the 0.01nm difference between the excitement energy differences between U-235 and U-238. Thank you for your contribution, and I hope you have a nice day! I think you will also find this link entertaining. $\endgroup$
    – Young Jun Lee
    Apr 4, 2021 at 5:20
  • $\begingroup$ @DavidWhite en.wikipedia.org/wiki/Atomic_vapor_laser_isotope_separation $\endgroup$
    – Young Jun Lee
    Apr 4, 2021 at 5:20

1 Answer 1


Of course isotopes may be separated by distillation, but it's useful, AFAIR, only for hydrogen isotopes. For uranium, gas centrifuge is proven much cheaper, to some orders of magnitude: https://ru.wikipedia.org/wiki/Газовая_центрифуга (translate this page, it contains more information than English Wikipedia article).

The essence of this technology is known for decades, and included in basic chemistry textbooks. Only engineering/technological know-hows are sort of classified. But in the politics, mass media, and perhaps on stackexchange, the whole topic is still considered taboo and is surrounded by fear.

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – andselisk
    Apr 5, 2021 at 21:46

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