Spherical tokamak as model for next steps in fusion energy

Discussion in 'General Science & Technology' started by Plazma Inferno!, Aug 25, 2016.

  1. Plazma Inferno! Ding Ding Ding Ding Administrator

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    Among the top puzzles in the development of fusion energy is the best shape for the magnetic facility—or "bottle"—that will provide the next steps in the development of fusion reactors. Leading candidates include spherical tokamaks, compact machines that are shaped like cored apples, compared with the doughnut-like shape of conventional tokamaks. The spherical design produces high-pressure plasmas—essential ingredients for fusion reactions—with relatively low and cost-effective magnetic fields.
    A possible next step is a device called a Fusion Nuclear Science Facility (FNSF) that could develop the materials and components for a fusion reactor. Such a device could precede a pilot plant that would demonstrate the ability to produce net energy.
    Spherical tokamaks could be excellent models for an FNSF, according to a paper published online in the journal Nuclear Fusion on August 16. The two most advanced spherical tokamaks in the world today are the recently completed National Spherical Torus Experiment-Upgrade (NSTX-U) at the U.S. Department of Energy's Princeton Plasma Physics Laboratory (PPPL), and the Mega Ampere Spherical Tokamak (MAST), which is being upgraded at the Culham Centre for Fusion Energy in the United Kingdom.

    http://phys.org/news/2016-08-spherical-tokamak-fusion-energy.html

    Paper: http://iopscience.iop.org/article/1...AFE52ED590B68DFDF84.c1.iopscience.cld.iop.org
     
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  3. Dinosaur Rational Skeptic Valued Senior Member

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    This is a technology that has been pursued for many decades.

    It seems unattainable due to the fierce repulsive forces between protons.

    Note that electromagnetic forces are circa 10E37 times gravitational forces.

    A half ounce magnetic will cause a steel pin to leap circa an inch from the surface of the earth.
    The repulsive forces are counteracted by gravity & the high speed of particles in the core of stars. Note that temperature is a measure of particle speed.
     
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  5. Seattle Valued Senior Member

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    It's not unattainable as it's already been done long ago. Yes, fusion is helped along in the stars by magnitudes of gravity that we don't have here on Earth but that has been offset by magnetic fields in the tokamak.

    We need to get to temperatures in the 150 million C range (as I recall). No materials can contain plasma at those temperature so it is contained by a very strong magnetic field. It's already being done.

    The issues are scale, cost, the learning curve and going from producing power to actually transferring it to the power grid and to do so at a comparable cost with existing technology.

    The main practical issue is that we spend so much on large multi-year/decade projects like ITER when it would be better to build smaller units where there can be more trial and error just like any other new technology.
     
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  7. sculptor Valued Senior Member

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    I was beginning to think that the tokamak was a failed design concept.
    It seems that building them bigger and more expensive has led nowhere.
    Accurate?
     
  8. Seattle Valued Senior Member

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    It is taking so long to build ITER that new technology has come along that won't even be in ITER and it costs so much no one can afford to keep building them. The Tokamak design in general is still viable I think. MIT and Princeton (I think) have smaller reactors with greater magnetic fields and those designs should have the same power as an ITER design at half the size and cost.

    There was a reason to build ITER bigger. It was a matter of scale. What doesn't produce more power than it consumes on a smaller scale can produce more than it consumed on a larger scale.

    The big issue is just that you need to be more active and build smaller units and quickly learn what works and what doesn't work, make improvements and then build an improved version. You can't do this if what you are building costs billions of dollars and takes decades to build.

    With more funding of the smaller products I think we would have competitive fusion power generation fairly quickly.
     
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  9. paddoboy Valued Senior Member

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    Yes, certainly, but just because something is proving to be difficult to achieve, is no reason to give up. [if that is what you are suggesting]
     
  10. timojin Valued Senior Member

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    Does Australia or New Zealand provides any money ?
     
  11. paddoboy Valued Senior Member

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    I don't know, but does it make any difference. Or are you just plain ignorant of the advantages that are at our feet if this could be commercially viably achieved.
    The waste for example from such technology is a very small fraction of what nuclear fission reactors produce.
    Hope that helps.
     
  12. timojin Valued Senior Member

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    over 30 years paying tax on a death horse I am not in favor I am slowly installing on my house solar panels looking forward to be independent of nuclear energy suppliers
     
  13. Seattle Valued Senior Member

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    Timjin, that's great. Good for you. It's good to look to clearer sources of energy and those that are renewable. It's not sunny everywhere and not all the time and it's not efficient for all of our energy needs.

    Unlike current nuclear energy plants, which use fission and produce "dirty" byproducts and have the potential for meltdown and an uncontrolled reaction, fusion has virtually none of that. If the plant has a problem, the fusion just stops, there is no possibility of meltdown and there are no long-term dirty byproducts and very limited short-term products (mainly from radioactive parts that have to be replaced from time to time).

    The hydrogen used as fuel is more or less unlimited as well.
     
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  14. paddoboy Valued Senior Member

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    I have had solar panels installed for 5 years now.
     
  15. Dinosaur Rational Skeptic Valued Senior Member

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    From Seattle Post #39
    Might you have a link?

    As far as I know, no fusion experiment has produced more output than input energy.

    BTW: I think the magnetic fields in various attempt at fusion energy are used to hold target particles in a small volume so they can be zapped by lasers. The magnetic fields do not apply the immense gravitational pressure at the core of a star.
     
  16. Seattle Valued Senior Member

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    http://www.bbc.com/news/science-environment-24429621

    The magnetic fields don't do the same thing that gravity does. They are another way of approaching fusion since we can't do it the same way that is done in the Sun.
     
  17. Dinosaur Rational Skeptic Valued Senior Member

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    If you read the entire article, net energy out is still less than net energy in.

    Even when net energy out is greater than net energy in, the technology might not be commercially worthwhile.

    There will still be the problem of making the net excess usable in a commercial context. The high temperatures involved might preclude commericial use.
     
  18. Seattle Valued Senior Member

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    I agree it's not all a done deal. That's why I think they need to build more and smaller units so that there is some trial and error. ITER takes too long to build and is too expensive and not much will be learned from it.

    The guy who runs the unit at MIT thinks that current technology will result in more output than input and that getting that output to a commercial grid can be done. Currently it will still be at a cost that is greater than the alternative but still in the ballpark so if more units were actually being built the learning curve should allow for it to be commercially viable.

    There is no way to know this for sure until it's done however. My point was just that this isn't pie in the sky stuff anymore it seems.
     

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