Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Endothermic nuclear fusion reactions

  1. Mar 26, 2005 #1
    Could anyone give me a few examples of endothermic fusion reactions between elements solid at room temperature?
  2. jcsd
  3. Mar 27, 2005 #2


    User Avatar

    Staff: Mentor

    There is no fusion (nuclear I presume) reaction at room temperature. One of the reactants must have sufficient kinetic energy to cause fusion with the other.
  4. Mar 27, 2005 #3
    Looks like I misworded my question.

    I meant an endothermic nuclear reaction between two elements which exist in solid state at room temperature. I am not concerned with the temperature at which they react, only they should exist as solids at room temperature.
  5. Mar 27, 2005 #4


    User Avatar

    Staff: Mentor

    If both materials are solid, then there will be no nuclear reaction between the elements.

    Solid state precludes most chemical reactions, except perhaps atomic diffusion, i.e. diffusion of the atoms of one element among the atoms of the other.

    Neutrons can certainly diffuse at room temperature and be absorbed in a nuclear reaction, but I don't think that's what you mean.
  6. Mar 27, 2005 #5
    I don't mean this. I don't care about the state, temperature or any other variables of the elements during and before the nuclear reaction. The only thing I am concerned about is that the elements before the reaction if cooled down to room temperature should become solids.

    Boy, I really need to work on my communication skills.
  7. Mar 27, 2005 #6
    They are not at room temperature and they are not solid. They share the property of being solid at room temperature.
  8. Mar 27, 2005 #7


    User Avatar

    Staff: Mentor

    Sid, sorry about that. Your communication skills are fine. I misunderstood.

    Well excluding the elements H, He, N, O, the halides F, Cl and Br, noble gases, and Hg, all others are solid at room temperature.

    One could conceivably use any nucleus of an element, which solid at room temperature, and fuse it with another element solid at RT. This is the approach to transmutation and production of heavy elements, e.g. from http://www.webelements.com/

    244Pu + 48Ca -> 288Uuq + 4n

    208Pb + 58Fe -> 265Hs + 1n

    208Pb + 62Ni -> 269Ds + 1n

    208Pb + 64Ni -> 271Ds + 1n

    208Pb + 70Zn -> 277Uub + 1n

    248Cm + 48Ca -> 292Uuh + 4 n

    The reactants are solid at room temperature. I have not determined if these reactions are indeed endothermic.

    See - http://everything2.com/?node_id=1051761

    Most likely the reactions using Ca are exothermic, but the ones using Fe, Ni and Zn are probably endothermic, based on the binding energy per nucleon.

    See also - Fusion of 6,7Li with lead and bismuth isotopes

    You also might find this interesting - Heavy-Ion Fusion-Evaporation Reactions


  9. Mar 27, 2005 #8
    Thanks a lot. :)
  10. Mar 27, 2005 #9


    User Avatar

    Staff: Mentor

    Interesting question you asked. It prompted me to look at some of the research going on.

    For example - http://cyclotron.tamu.edu/heavy_ion_reactions.htm

    Unfortunately, not a lot of details are provided, and the good stuff is buried in costly scientific journals. However, some articles may be available through a university library.

    Apparently, there is research being done on heavy element fusion related to supernovas.

    I vaguely remember someone looking at Be+Be fusion, S+S fusion, and on up to Fe+Fe fusion, but I don't remember where. On the other hand, this all relates to stars, which are certainly not at room temperature (298K). :wink:
  11. Mar 28, 2005 #10


    User Avatar
    Gold Member

    A fusion reaction is exothermic (i.e. gives off net energy) between elements with atomic numbers less than iron. Elements with more protons than iron are exothermic in fission reactions, and endothermic (i.e. require an infusion of energy to happen) in fusion reactions. Elements with fewer protons than iron are exothermic in fusion reactions, and endothermic in fission reactions.

    Typically, fusion reactions involving atoms heavier heavier than iron (and hence, usually endothermic) involve shooting one kind of atom in a particle accellerator at a target made of the element. This is how many of the artificially created elements at the end of the periodic table are made.

    Moreover, generally speaking, the farther you get from iron, the more energy intensive a nuclear reaction will be. Thus, uranium, the highest atomic number naturally occurring element, is the element of choice for fission reactions (or even better, non-naturally occurring plutonium). Likewise, hydrogen, being as far as possible from iron in the other direction, is the element of choice for fusion reactions. The table on this page: http://library.thinkquest.org/3471/nuclear_models_body.html shows nuclear binding energies v. atomic number. A formula for calculating binding energy can be found here: http://library.thinkquest.org/17940/texts/binding_energy/binding_energy.html

    The additional constraint is that a useful fusion reaction has to fuse atoms that have a plausible and stable endpoint in a single collision. This is why, for example, you don't want to use the simplest isotype of hydrogen, for example, which has only a single proton and no neutrons. You need four of them to get helium, and that can't happen in a single reaction.

    Thus far, the general conclusion has been that the inconvenience of dealing with a fuel like hydrogen, is outweighed by the benefits of getting the maximum bang for your buck in a fusion reaction.
    Last edited: Mar 28, 2005
  12. Mar 28, 2005 #11


    User Avatar

    Staff: Mentor

    See also Nuclear Binding Energy at hyperphysics

    Also binding energy released in a reaction is given by

    BE = mreactantsc2-mproductsc2, > 0 exothermic (excess energy), < 0 endothermic.

    if m is in amu then use 1 amu = 931.478 MeV.


    207.976652071 amu, http://wwwndc.tokai.jaeri.go.jp/cgi-bin/nuclinfo2004?82,208
    57.933275558 amu, http://wwwndc.tokai.jaeri.go.jp/cgi-bin/nuclinfo2004?26,58

    265.130085 amu, http://wwwndc.tokai.jaeri.go.jp/cgi-bin/nuclinfo2004?108,265
    1.00866491574 amu, http://wwwndc.tokai.jaeri.go.jp/cgi-bin/nuclinfo2004?0,1

    -0.228822287 amu
    -213.142926 MeV, very endothermic.

    D+T however

    2.014101778 amu
    3.016049278 amu

    4.002603254 amu
    1.008664916 amu

    0.018882886 amu
    17.59 MeV, exothermic

    Actually, p can be fused with B11 - 1H1+5B11 -> 3 2He4, but this is a difficult reaction requiring very high temperatures and consequently significant energy losses due to recombination and excitation of the B ions.
    Last edited: Mar 28, 2005
  13. Mar 28, 2005 #12
    Thanks again. I really appreciate your help.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Endothermic nuclear fusion reactions
  1. Nuclear reactions (Replies: 2)

  2. Nuclear fusion (Replies: 5)