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

Are nuclear batteries possible?

  1. May 4, 2013 #1
    is it possible to make a nuclear "battery" which works off nuclear not electrochemical reactions using berylium/graphite shielding?
     
  2. jcsd
  3. May 4, 2013 #2

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    It is
    Please try to look up those things yourself first. It takes you less time than posting here.
     
  4. May 6, 2013 #3
    i meant fission or something more powerful?
     
  5. May 6, 2013 #4

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    That would be a nuclear reactor. Fission is just one type of nuclear reactions.
     
  6. May 6, 2013 #5
    i know that but what im asking is:theoreticly can you make a nuclear reactor 50cm by 50cm asuming the u-235 was dense enough to reach critical mass?
     
  7. May 7, 2013 #6

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    Without shielding and heat sinks... yes.
     
  8. May 7, 2013 #7

    QuantumPion

    User Avatar
    Science Advisor
    Gold Member

    You can make one even smaller than that. For Pu-239 with a reflector it can be as small as a sphere with radius ~5 cm.
     
  9. May 7, 2013 #8

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    Well, a sphere of plutonium is not a reactor. You need moderation, control mechanisms, cooling cycles, power generation and so on.
     
  10. May 7, 2013 #9
    if it got to 5cm couldnt you just use thermionic methods of power generation instead of steam?
     
  11. May 7, 2013 #10

    QuantumPion

    User Avatar
    Science Advisor
    Gold Member

    Well you don't need a moderator for a reflected plutonium sphere. And it can be designed to be self-regulating. But you're right that it would still need a coolant system, heat exchanger, and thermoelectric converter to actually produce electricity. I imagine the SNAP-10 reactor, at about the size of a microwave oven, is about as small as one could be practically made.
     
  12. May 7, 2013 #11
    assuming break even fusion was achieved how big do you think the smallest fusion reactor could be?
     
  13. May 7, 2013 #12

    QuantumPion

    User Avatar
    Science Advisor
    Gold Member

    Enormous. The ability of a magnetic confinement fusion reactor to produce power is proportional to its volume. ITER will hopefully be the first reactor to achieve better than break-even, I think it has a diameter of something like 20 meters.
     
  14. May 7, 2013 #13
    out of the hypothetical methods of fusion (inertial, z-pinch, laser ect..) what would be the smallest?
     
  15. May 7, 2013 #14

    QuantumPion

    User Avatar
    Science Advisor
    Gold Member

    There are no laser confinement fusion methods close to achieving breakeven, and even if they were they are even more massive machines than the tokamak. There is no compact way to producing fusion power, as all of the various methods require enormous power inputs in either magnetic fields or lasers to produce the conditions required for fusion to occur. These simply cannot me miniaturized.
     
  16. May 7, 2013 #15

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    Well, there is a method to use fusion power within the size of a vehicle. It is a very destructive method, however ;).
     
  17. May 7, 2013 #16
    lol, what is the energy needed to initiate fusion?
     
  18. May 8, 2013 #17

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    In weapons? You need a fission bomb to start fusion, conventional explosives are not powerful enough.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook