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B Centrifuging Nuclear Waste

  1. Feb 13, 2019 at 6:28 PM #1
    My first question on this forum, and I'm diving in head first. While working on a project that has very little to do with physics, I stumbled upon a list of products that result from a Uranium-235 fission reaction. To my surprise, there is a lot of good stuff in that nuclear waste. Specifically, I am interested in rhodium.

    Considering that we have stockpiles of nuclear waste that are decades old, is there some reason that no one is centrifuging to recover rare earth elements? I fully understand that the waste is still radioactive, but the stuff I want is safer than tap water after 50 years of half-lives. Am I missing something here?
     
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  3. Feb 13, 2019 at 8:34 PM #2

    Drakkith

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    An offhand guess would be that there's simply not that much of it, and the fact that it's in a highly radioactive environment makes it economically prohibitive to recover.
     
  4. Feb 13, 2019 at 9:42 PM #3

    Vanadium 50

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    They do extract valuable materials from nuclear waste - usually radioisotopes like Ru-106. They are much (~100x) more valuable than, e.g. Rhodium, which is ~$20/g.
     
  5. Feb 13, 2019 at 10:39 PM #4

    mfb

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    In the rare cases where there is no long-living isotope of an element (as in Rhodium) it is possible, but chemical separation methods are much easier than centrifugation. You have to get a very pure sample, otherwise it is too radioactive for most applications. There has been some work to extract rhodium, but making it commercially interesting is difficult. Wikipedia has a description.
     
  6. Feb 14, 2019 at 12:05 PM #5
    Thanks for the responses everyone. I just looked at the price of Rhodium as a commodity, and it is somewhere around $2,750 per ounce ($97/g). Maybe not as valuable as Ru-106, but still prohibitively expensive for a lot of applications. My latest project (only in the planning stages) requires enough rhodium that the automotive industry would never adopt it. They won't even use all-metal catalytic converters despite their gains in efficiency and longevity. If manufacturers ever did apply my idea, the value of Rh would skyrocket due to lack of supply. According to Wikipedia, Rh accounts for about 3.6% of U-235 fission products, which sounds like a lot to me. However, the article does not specify how much is Rh-103 and how much is Rh-105.

    That Wikipedia page is exactly what got me started down this rabbit hole. I was thinking of centrifuging because Rh for automotive use would not need to be very pure. Some contamination with Ru-102 and Ru-104 would not be a problem since ruthenium has similar properties. Ru-103 is the only radio isotope you would need to worry about, and it decays into the the desired product. Maybe chemical extraction is easier. I haven't looked into it that far.
     
  7. Feb 14, 2019 at 8:43 PM #6

    mfb

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    You'll have to calculate a bit to get fission yield numbers from it, but the study cited there quotes >400 g/ton for rhodium, and as far as I understand they exclude Rh-105 as they look at long-living products only. Reference 1 might have better numbers.
     
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