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Nuclear Waste + the Sun

  1. Jan 13, 2012 #1
    okay so I don't want this to be an argument on whether dumping nuclear waste into the sun is feasible or practical or not, as I'm pretty sure it's not

    rather I'd like to ask a question that my mom asked me once when I was trying to argue the idea to her. She asked me: "well if you dumped so much radioactive material into the sun, how do you know what will happen if you do that? What if something terrible happens that we could not have predicted?"

    My opinion was that the sun is a giant furnace and is already emitting radiation in all sorts of forms and adding a relatively tiny amount of heavy elements to it is not going to have a profound effect on the sun's behavior. She was not convinced, basing her opinion on the fact that I really had no idea what I was talking about, and I really don't.

    So, would anything bad happened if we dumped all of our radioactive waste material into the sun? http://ca.answers.yahoo.com/question/index?qid=20100205151923AAzOMTF this guy gives an estimate around the middle of his post that there's 60,000 tons of radioactive waste in the world.

    if the sun is about 2x10^30 kg, and 60,000 tons is 54.4x10^6 kg, will dumping 2.72e-23% of the sun's mass of radioactive material do anything? What if we had a hell of a lot more nuclear waste, let's say 60 trillion tons, over the course of many years and a big increase in nuclear power plant production, would that much do anything?

    What if we dump it all in at once? Will that be different from dumping over a relatively long period of time?

    I guess the basic question here is: what happens to nuclear waste if you vaporize it? And then also would it come spraying out of the sun back at us?

    EDIT: maybe this should have gone in the nuclear part of the forums, but I was particularly interested in the sun part of the question
     
    Last edited: Jan 13, 2012
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  3. Jan 13, 2012 #2

    Drakkith

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    Dumping nuclear waste of any REALISTIC amount into the Sun would have absolutely no noticeable effect. The Sun could swallow something the size and mass of our Moon and it would have a negligible effect on the overall workings of the Sun.

    Throwing waste into the Sun would turn the material into a plasma, meaning that the atoms that make it up would be partially or completely ionized. They would still be radioactive, and would decay as normal, but given the amount compared to the size of the Sun it would do almost nothing.

    As for your Mom, you can tell her that we DO know what would happen. We know exactly what would happen because we can study the Sun, perform experiments here on Earth at the same temperatures, and plenty of other reasons.
     
  4. Jan 13, 2012 #3

    mathman

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    I haven't done any quantitative analysis, but I suspect if the entire earth was dumped into the sun nit much would happen.
     
  5. Jan 13, 2012 #4
    so it wouldn't shoot out any nasty radiation because of the vaporization of the radioactive material?
     
  6. Jan 13, 2012 #5

    D H

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    I can't let this part go unchallenged.

    Dumping nuclear waste is silly, and not because of the supposed problems with regard to what that dumping would do to the Sun. It's silly because it would be much, much cheaper to send the waste out of the solar system than to dump it into the Sun.

    That we don't have the ability to put 60,000 tons of payload into space, period, is a different question.
     
  7. Jan 13, 2012 #6

    Drakkith

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    Why is it cheaper to send out of the Solar System instead of into the Sun DH?
     
  8. Jan 13, 2012 #7

    DaveC426913

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    Hm. At first I agreed with D_H but I'm missing something.

    To drop it into the sun, you'd need to slow it by the Earth's speed of revolution about the sun - 67,000mph or 18 miles per second.

    But escape velocity from the sun at Earth distance is actually 26 miles per second.

    So according to my calcs, it requires less delta v to drop it in than boost it out.

    D_H?
     
  9. Jan 13, 2012 #8

    Drakkith

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    Is there not a way to use the planets to slow it down further and use less energy? (Edit, of course, this wouldn't be reliable since the planets move, so I guess it doesn't matter) Also, what is the escape velocity of the Solar System from Earth's distance?
    And yes, it does make alot more sense now. If we don't slow it down enough it simply goes into an elliptical orbit of the Sun correct?
     
  10. Jan 13, 2012 #9
    whoah, why? Why not just, well, point it at the sun after it achieves Earth's escape velocity?

    I'm betting it has something to do with conservation of kinetic and gravitational potential energy, right?
     
  11. Jan 13, 2012 #10

    D H

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    Escape velocity is √2 times circular orbital velocity. We're already going at circular orbit velocity, so the required Δv is (√2-1)*orbital velocity. In other words about 41.4% of orbital velocity. To send something plunging into the Sun entails canceling almost all of that orbital velocity. 41.4% is a whole lot less than 100%, particularly given the exponential nastiness of the ideal rocket equation.
     
  12. Jan 13, 2012 #11

    DaveC426913

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    Yes. It's moving in an orbit at 67,000mph, just like Earth is. You've got to cancel that.
     
  13. Jan 13, 2012 #12

    D H

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    Nope. It's all about the required delta V, how much one needs to change the velocity.


    By the way, this is the reason mankind has sent so few space vehicles to Mercury compared to the outer planets. Sending a vehicle to Mercury is expensive.
     
  14. Jan 13, 2012 #13
    okay, so I can understand that in order to get into orbit around Mercury, you need to change the orbital velocity (relative to the sun) of the rocket to the orbital velocity of Mercury, but...

    oh I just answered my own question. To get it to "orbit," and by orbit I mean crash into, the Sun, its orbital velocity would have to be 0, therefore... yeah

    thanks, makes sense now!
     
  15. Jan 13, 2012 #14

    DaveC426913

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    Right. Of course.

    To escape the SS, we've already got 18mi/s from Earth's orbit. Only 6mi/s more and we're outta there.

    Whereas hitting the sun requires cancelling the full 18mi/s.
     
  16. Jan 13, 2012 #15
    Why not slow it just enough to place it in a decaying orbit around the sun? You don't have to send it plunging directly in.
     
  17. Jan 13, 2012 #16

    Vanadium 50

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    Where does this "decaying orbit" come from? What is the force causing it to decay?
     
  18. Jan 13, 2012 #17

    russ_watters

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    Sci fi movies...
     
  19. Jan 13, 2012 #18

    Bobbywhy

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    I am concerned about the initial phase of this proposal: the launch phase. What would be the risk to us and our environment if the launch vehicle exploded? Seems to me it would be a huge risk of radiation contamination; so great that I would not agree with the idea at all.
     
  20. Jan 13, 2012 #19
    Conversely if we had the technology to put 60,000 tons of highly radioactive waste into space with zero probability of failure, then I'm pretty sure we could think of something easier mechanism to deal with this. For example, if we had that level of space technology, we could probably build solar power microwave satellites so that we wouldn't have to worry about nuclear waste at all.

    One thing that I wonder about is that I'm wondering if the environment impact of all of those rockets would be worse than than the impact of the radioactive waste.
     
  21. Jan 14, 2012 #20
    Sorry, I'm not familiar with orbits. I assumed that under a certain critical velocity an object would just continue spiraling inwards, but I suppose the orbit would just get more eccentric?
     
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