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Gem*star (ads)

  1. Apr 5, 2010 #1
    So the latest thing I've seen being talked about is GEM*STAR (Green Energy Multiplier*Subcritical Technology for Alternative Reactors)


    They claim they are leveraging the ever improving efficiencies in producing neutrons, which will result in the viable application of accelerator-driven spallation for sub-critical reactors.

    Are accelerator-driven reactors in our near future, and could they even be used for propulsion? Or will the 180 meters of LINAC remain unshrinkable?
  2. jcsd
  3. Apr 7, 2010 #2
    We have been discussing something similar in the previous forum thread... see https://www.physicsforums.com/showthread.php?t=390161 (hybrid fusion fission reactor prospects)

    The accelerator driven systems have also been considered in Europe, but using a cyclotron rather than a linac - needs less space! But research in the field has cooled down. It seems to be too expensive. In addition, nuclear waste transmutation could be done in fast critical reactors - without an accelerator!

    In the previous forum thread, laser driven systems have been considered. The basic idea is that rather than the external neutrons being produced by (proton) spallation, they are produced by laser dirven fusion of D-T.
  4. Apr 7, 2010 #3


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    Not really. There's http://myrrha.sckcen.be/" [Broken]for instance, but also at SINQ if I remember well.
    Last edited by a moderator: May 4, 2017
  5. Apr 7, 2010 #4
    But what's the most energy-efficient way to produce the supplementary neutrons? Laser-fusion or proton spallation? It's not clear to me which is the most energy efficient way, but it seems that energy efficiency should dictate the choice.

    Is it possible to use electrons for spallation to generate the neutrons? I was just musing whether it might be useful to use some kind of nanotube cathode for extra precision and energy efficiency in producing the electron beam. I'm also thinking that an electron accelerator could be much more compact than a conventional linac or even a cyclotron.

    A more compact accelerator could then allow for a more compact nuclear power generation system, which could perhaps then be used for space propulsion. I'm wondering if an accelerator-driven system could be combined with a particle-bed reactor design to produce high power output on demand, without danger of runaway reaction. The higher burnup fraction of particle-bed combined with the ability of ADS to burn up fission products might make for mutually beneficially complementarity.

    Last edited: Apr 7, 2010
  6. Apr 7, 2010 #5


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    I'm not sure from where the electron beam idea originates, but an electron beam of energy similar to that of a proton beam is not going to drive a nuclear reaction.
  7. Apr 8, 2010 #6
    Electron spallation will not work. Even with high energy protons it is a problem to produce enough neutrons. 1 GeV protons for example will produce only around 30 neutrons per proton in a heavy spallation target. This is why the laser fusion approach for neutron production is interesting. The number of neutrons produced depends on the gain of the system. In principle very high gains can be obtained.
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