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Could a tank or land vehicle be nuclear powered?

  1. Oct 25, 2009 #1
    Submarines are nuclear powered.

    How small of a nuclear-fission powered unit be made and could it be fitted inside a tank or other land vehicles?
     
  2. jcsd
  3. Oct 26, 2009 #2

    QuantumPion

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    Nuclear reactors can be made small and compact. With high-enriched Uranium you can make a reactor the size of a toaster (although its maximum power would be limited due to material constraints). I'm not sure how small steam turbines can be scaled down and still be efficient but I bet a tank-sized one would be possible. I think Ford actually conceptualized some sort of nuclear powered car in the 50's.

    The problem is that shielding does not scale down as well. You still need heavy lead shielding and thick hydrocarbon materials to reflect neutrons. For a tank it might not be out of the question; but a car, in order to protect both the driver and the public, would be far too heavy.
     
  4. Oct 26, 2009 #3
    Does it have to be a steam turbine and, not say, an air turbine? How many miles can you get and would the power output be enough say for reactive electromagnetic armor, electromagnetic gun, and drive train and onboard sensors and computers and electronics?

    I guess the size of the nuclear reactor, along with shielding, would be the size of a M1 Abram's gas turbine engine. Use of electromagnetic armor and gun may reduce weigth of armor and size of projectiles allowing more room and weight for nuclear reactor and shielding.
     
  5. Oct 26, 2009 #4
    It isn't the turbine that is the concern (unless you come up with a BWR-like concept), you would want a PWR to remove heat from the core more quickly with less power needed for the pump. Mileage is a difficult thing to measure without reactor size, fuel enrichment, mass of the transport, among other things. The reactor with shielding would probably be much bigger than an Abram could carry. I'm not completely sure, but I think most of the back half of a nuclear powered submarine is for the plant and turbine.
     
  6. Oct 26, 2009 #5
    If the tank was remote controlled and had no humans on board during military operation (obviously it needs maintance) could the shielding be considerably reduced?
     
  7. Oct 27, 2009 #6
    A tank is something that is going to be shot at, you'll want shielding regardless of whether people are in it or not.
     
  8. Oct 28, 2009 #7
    with enough electrical power can't electromagnetic shielding be used? there's a colloidal solution with magentic-iron particles nanoparticles that cluster around electric fields forming extreme hardness.

    then there's the emp gun
     
  9. Oct 28, 2009 #8

    berkeman

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    You haven't addressed the heat removal aspect that Candyman brought up. What do a submarine and a fixed reactor have that a mobile vehicle doesn't have?
     
  10. Oct 28, 2009 #9
    I'm surprised no one mentioned Pamir. The former Soviet Union built (prototype) mobile reactors on large trucks - they were not self-propelled, but they were on wheels. Of course the conclusions in this thread are entirely correct - the system ran on HEU (45%), was very big (much larger than an ordinary tank), and used small gas turbines rather than steam turbines - with a very exotic working fluid, dinitrogen tetroxide (N2O4) gas.

    http://www.nti.org/e_research/profiles/Belarus/Nuclear/facilities_sosny.html [Broken]
    There's a longer description in a Russian-language news article:

    http://translate.google.com/translate?hl=en&sl=auto&tl=en&u=http://news.tut.by/society/98447.html

    359h9pj.jpg

    It's quite far from being nuclear-propelled, if you consider the specs. The system takes up four large trucks, the reactor one weighing 60 tons - but the electric output is only 630 kW = 845 hp. (Experts - is it cooling that is the limiting factor here?)

    I also found a related paper on the N2O4 Brayton cycle from 1979 - it makes extensive reference to Russian research:

    "Potential performance improvement using a reacting gas (nitrogin tetroxide) as the working fluid in a closed Brayton cycle"

    http://ntrs.nasa.gov/search.jsp?R=7...=false&qs=Ns=ArchiveName%7c0&N=4294946812+295

    ("reacting gas" means it dissociates during the thermodynamic cycle: N2O4 <--> 2 NO2.)

    Perhaps you may be interested in nuclear propelled airplanes? The US designed such a system, and found it viable.

    http://www.ornl.gov/info/ornlreview/rev25-34/net425.html [Broken]

    There are photos of the test engines on wikipedia (they are located at Idaho National Lab):

    800px-Aircraft_reactor_experiments_2001.jpg

    http://en.wikipedia.org/wiki/Aircraft_Reactor_Experiment
     
    Last edited by a moderator: May 4, 2017
  11. Oct 28, 2009 #10
    How much heat does a toaster sized fission box need to have removed?
     
  12. Oct 29, 2009 #11

    QuantumPion

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    According to wiki, an M1 Abrams tank's engine is 1500 HP. So at 30% thermodynamic efficiency, ~3700 kW. That's quite a bit of heat flux for a toaster! :)
     
  13. Oct 29, 2009 #12
    good point
     
  14. Oct 29, 2009 #13

    mheslep

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    It might a bit more efficient than that, the Abrams uses a turbine engine - at least when running at full power it should exceed 30% efficiency.
     
    Last edited: Oct 29, 2009
  15. Oct 29, 2009 #14

    mheslep

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    While miniature nuclear reactors are interesting, miniaturization is not the main problem to my mind. The question is how does one make the reactor safe in the case of a catastrophic accident (or attack for a military vehicle) AND relatively useless from a weapons proliferation stand point.


    I don't know how to answer these two questions. What type of reactor would be most benign if the vehicle carrying it hit an IED or was hit by a train at a crossing? CANDU? Anyone?
     
  16. Oct 29, 2009 #15

    QuantumPion

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    If you don't want the enemy to be able to steal your reactor and make it into a weapon, you can use reactor-grade plutonium (pu+239 + pu-240).

    As for making a reactor sturdy enough to survive conditions related to warfare, I'd imagine some sort of self-contained metal cooled reactor would be best. But no matter what the design is, even if heavily shielded and protected, a direct hit from a big bomb or armor penetrating shell or what have you will ruin your day. :p
     
  17. Oct 29, 2009 #16

    mheslep

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    Alright, if we somehow lose reactor grade plutonium (> 19% Pu-240) that's been in an operational reactor, what's the difficulty in separating out the Pu-239 to weapons grade Pu? We want that to be at least hugely difficult if not impossible. Would it require a separation process on a grand scale requiring the resources of a nation state?

    Well some of these small reactors (http://www.world-nuclear.org/info/inf33.html" [Broken]) are designed so that the fission reaction stops by default if the reactor gas/liquid metal flow stops for any reason, so that should eliminate the run away case. Then we're left with the escape to the atmosphere of what products? What dosage is possible?
     
    Last edited by a moderator: May 4, 2017
  18. Oct 30, 2009 #17

    QuantumPion

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    Separating Pu-240 from Pu-239 is much much harder than separating U-235 from natural uranium. If you had the technology to do isotopic separation to begin with you wouldn't bother trying to separate highly radioactive reactor fuel when you can dig uranium out of the ground.

    Depends on many factors, such as the fuel composition, burnup, and how it is dispersed. I wouldn't want to be anywhere nearby though. :p
     
    Last edited by a moderator: May 4, 2017
  19. Oct 30, 2009 #18
    What about if they boost the efficiency of a beta-voltaic type battery, or nuclear thermal battery. You might eventually reach a power density where it could propel a car or something, without having to worry about a full reactor that can runaway. Just crazy drivers and accident lawsuits.


    If my deadly nuclear tank gets hit on enemy territorry, dosage from leaking fuel elements is their problem. (evil laugh).
     
  20. Oct 30, 2009 #19

    mheslep

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    This seems to suggest that reactor grade Pu presents no proliferation risk. Yet Pu output from commercial nuclear operations is cited as a proliferation risk, by e.g. the MIT Nuclear report.

    Well I wouldn't want to be anywhere near a 500,000 gal fuel depot that was attacked, but we consider that an acceptable risk - a baseline if you will. I'm curious in weighing the risk against such a baseline for smallish reactors.
     
  21. Oct 31, 2009 #20
    There's still a large amount of Pu-239 in reactor grade fuel, more than 50% if I remember right. It would be very difficult and require a lot of energy, but it could be separated out. Also, Pu-240 is fertile, so if it could potentially be used as well.
     
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