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Oscillating Isotope?

  1. Apr 18, 2015 #1
    Are there any semi-stable or stable isotopes that can be made to oscillate between their self and their decay products?

    Specifically some kind of fission/fusion reaction where the decay is easily reversed with something like pressure (assuming the reversal is quick enough that the majority of the energy required/released by the reaction doesn't have time to get far away from the particle?)
     
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  3. Apr 18, 2015 #2

    vanhees71

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  4. Apr 18, 2015 #3

    mfb

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    Not in the controlled way you are probably looking for. All those processes release a lot of energy in one direction, and give two or more reaction products. The reverse direction would need those reaction products shooting together at the right energy.
    Those processes are also way too fast - of the order of 10-20 seconds. Pressure does not influence individual reactions at all. It can just increase the probability that things come close (like for fusion).

    Stars during helium burning have a process that gets reversed frequently - two helium nuclei merge to beryllium which quickly decays to two helium nuclei again. Only in very rare cases the beryllium absorbs another helium to become stable carbon.
     
  5. Apr 18, 2015 #4
    What would happen if you could encase beryllium in a shell of a magnetostrictive alloy - when it decayed would the helium escape or would it be able to be squeezed back together?
     
  6. Apr 18, 2015 #5

    mfb

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    There is no realistic way to force two specific helium nuclei to come together. They are just too small.
     
  7. Apr 18, 2015 #6
    But would they escape? If you had just split a beryllium atom inside a shell of magnetostrictive material (the force of the material squeezing down may be negligible compared to the force required to put the helium back together) the same energy levels that the beryllium had would be there if the helium couldn't escape so wouldn't it be conceivable to balance the reaction on that specific energy between decay and fusion and use the force of the shell to push it back together or pull it apart?

    To put this another way, it wouldn't be an attempt to extract energy or store energy, but to have a material you could trigger into changing mass.
     
  8. Apr 18, 2015 #7

    mfb

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    Escape from what?
    You get two helium nuclei moving through space. What is supposed to keep them where? You can keep them in your container with a size of a few millimeters with strong magnetic fields. That is as "constrained" as two humans constrained to be somewhere in the inner solar system (12 orders of magnitude in size scale). If you don't have a good vacuum, the nuclei quickly lose their energy.
     
  9. Apr 19, 2015 #8
    I was thinking of "constrained" as a shell of some metal around them ("around" meaning the single beryllium isotope would be encased in a metal lattice and be driven into an unstable state to create the two hellium isotopes).
     
  10. Apr 19, 2015 #9

    mfb

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    The beryllium isotope is an unstable state - it decays within a femtosecond. Then you have two helium nuclei and you are done.
    I still don't understand what is supposed to be constrained to what and why.
     
  11. Apr 19, 2015 #10
    Beryllium and helium were just an example set from what you said to try to relate the idea (they'd probably make a pretty bad pair in the context of the question since they are both very low mass density on the scale of the overall compound required and the fact you would have to subtract a neutron to get the unstable isotope of beryllium after initially building the compound material of beryllium surrounded by a shell [to say nothing of being such a small atom it would likely escape the containment of the shell of metal around it]).

    The objective would be a material that can change inertial mass by exploiting the change in mass between isotopes.
     
  12. Apr 19, 2015 #11

    mfb

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    They are the best thing I could find that has some sort of nuclear process that gets reversed somewhere in nature.

    Light isotopes are better then, as they have a larger relative mass difference. But even then the differences will be very small.

    Controlling nuclear reactions is problematic, especially for radioactive decays.
    7Be is an interesting case. It can only decay via electron capture with a half-life of 53 days. If you fully ionize it, it is stable as there is no electron it could capture.
     
  13. Apr 19, 2015 #12
  14. Apr 20, 2015 #13
    It seems if you were trying to construct a metamaterial (kind of a bastardization there - since it seems it would be somewhere between a bunch of nanoparticles and a metamaterial) to have variable inertial mass exploiting the differences in different isotopes the bulk of the mass of the material would likely be in the support structure (the shell holding the whole reaction together) - so the mass density differences of the reactive isotopes seem to weigh in more than the mass differences of the reaction itself and you'd still need something large enough to be contained (I'm guessing the distance between atoms in a Terfenol-D [the highest magnetostrictive alloy] for instance are going to be far enough apart to let something as small as helium slip through [especially when the helium is imparted with a high kinetic energy]). The best option might actually end up being something like Terfenol-D with the terbium replaced by an unstable isotope of holmium since both would be contained within the material and the lower-energy terbium state of the cycle would add excess forces to force it back into holmium - but I'm just guessing here.
     
  15. Apr 20, 2015 #14

    mfb

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    I don't get the point of the magnetostrictive material. Everything solid will stop helium nuclei within a millimeter or less, the type of material does not matter.
    No.

    You seem to have some misconceptions about radioactivity. It has no similarity to chemical reactions, where things like the molecule or crystal structure would be relevant.
     
  16. Apr 20, 2015 #15
    The goal would be a bunch of individual reactionary isotopes with shells (1-atom or 1-molecule thick all around - nowhere near 1mm all around) that can contain the reaction.

    At some point the forces exerted by the surrounding material has to play into it - even if it is a very very finite amount if you are keeping a two-way reaction balanced at the point between the two cycles of the reaction you'd only need a nudge.
     
  17. Apr 20, 2015 #16

    mfb

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    That does not exist.
    No. Influences from other atoms are completely irrelevant for radioactive decays (something like 15 orders of magnitude too weak to be relevant). They just determine the position of the atoms.
     
  18. Apr 20, 2015 #17
    You can actually build structures like that by combining two different materials in the form of plasma and carefully controlling the ratio of the two along with the exposure time.

    Right. But if you can trigger decay and fusion so logically you can combine those two controls into a single package and you would need to contain them - whether that is with ionization or externally generated magnetic fields, RF or the pressure induced from surrounding matter are the details I'm looking for with this question. Specifically: are there two isotopes that are relatively easy to get to fuse or decay into eachother?
     
  19. Apr 20, 2015 #18

    mfb

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    Containing products of nuclear decays? Do you have a reference for that?

    No. We can induce fission or radioactive decays via neutrons for some nuclei, and we can do fusion with other nuclei. Those are not reverse processes.

    You can use particle accelerators to smash all sorts of different nuclei together, but then you get a huge mess of many different nuclei as result.
    Nothing like this would help at all.
    No.
     
  20. Apr 20, 2015 #19
    Even if were possible to get a reversable nuclear reaction, what would be the use of it?
    The total mass - energy involved is unchanged by the time you have converted A to B then back to A again.
    You will have acheived exactly nothing.
     
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