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Thread: Fusion and Quantum computing

  1. #1
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    Fusion and Quantum computing

    Just how much will nuclear fusion and quantum computing change the world? I've heard them hyped as game changers that will shake the world up. Just how will they really change the world? No hype, what will their impact really be?

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    I think that nuclear fusion would change the world a lot. Quantum computing, not so much.

    If we make viable nuclear fusion, then electricity will potentially become cheaper and we will not have to rely on fossil fuels as much, which would have major ramifications both for our economy and for geopolitics. Quantum computing is just something that will make certain types of problems much easier to solve.
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    With fusion, currently it looks like reactors would be very large and expensive to build, and if they fuse the most likely fuels, will have their own issues with radioactive waste and radiation. Radioactive waste and radiation can be handled, but then the same is true with conventional nuclear (fission) technology. It isn’t clear to me that fusion would have an economic or practical advantage over conventional nuclear, at least, not how it looks now (there’s no way to know what new technologies might be available a hundred years from now, but I’m thinking about the most promising technology now, something that might lead to a commercial reactor in 60 years).

    I think a better case could be made for conventional nuclear reactors making a big difference. Sometimes I’ve thought about an alternate history where the U.S. did something like France, and had about 70% (vs. the current 19%) of electricity supplied by nuclear at this point, with hydro, wind and solar supplying most of the rest. Then at this point, we would be in a much better place on the energy and CO2 production front, expanding all non-fossil energy production, including advanced conventional nuclear reactors to allow the phase out of all fossil fuel use.

    Of course, that didn’t happen, and with the current political/social climate isn’t likely to in the US at least, but who knows? China seems to be pushing ahead with conventional nuclear development and research. One possibility would be relatively small and inexpensive modular reactors that could be built fairly quickly, and if attitudes change in Western counties, they could be a big factor in the coming decades.

    As for quantum computing, it would definitely make a big difference in cryptography. Yes, they would be able to do some other things that are impractical now, but I don’t know enough to say if there are other areas that would likely make a big difference.
    Last edited by Van Rijn; 2020-Jul-13 at 02:50 AM.

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    Quote Originally Posted by Van Rijn View Post
    With fusion, currently it looks like reactors would be very large and expensive to build, and if they fuse the most likely fuels, will have their own issues with radioactive waste and radiation.
    I could be wrong, but I was under the impression that with the deuterium-tritium reaction that is currently being planned for ITER, you have one stable and one unstable (tritium) input, and that the output is helium-4, so stable. There are the neutrons, of course, but they decay so you don't really get waste, right?
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    Quote Originally Posted by Jens View Post
    I could be wrong, but I was under the impression that with the deuterium-tritium reaction that is currently being planned for ITER, you have one stable and one unstable (tritium) input, and that the output is helium-4, so stable. There are the neutrons, of course, but they decay so you don't really get waste, right?
    The devil is in the detail. Most of the energy produced in a D-T reaction is in the form of high energy neutrons. These will either interact with a lithium blanket to produce tritium (necessary to fuel the reactor since there is little natural tritium - in fact, tritium budget is a big design issue) or reactor structure. Tritium has a short half life (about 12 years) but any isotope of hydrogen is something of an escape artist - it is very tricky keeping it from escaping into the environment. And, of course, it is chemically the same as hydrogen, so will be incorporated into biologically important compounds.

    The neutrons that interact with the structure will cause damage over time and transmute some of it into radioactive isotopes. Some of the inner reactor wall will be eroded (mostly by plasma escaping the magnetic field in a Tokomak) and some parts of the structure will likely require replacement over the lifetime of the reactor due to neutron caused damage and embrittlement. Some of that material would need to disposed of as (likely low-level) nuclear waste. Further, when the reactor is decommissioned, much of the reactor would be disposed of in at least a low level nuclear waste facility.

    I donít see it as anything that couldnít be handled in a reasonable fashion, but anti-nuclear activists rarely base their opposition on careful technical arguments, and Iíve already seen various anti-nukes dismiss D-T fusion technology along with conventional fission because they both produce radiation and radioactive waste.

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    This is pretty technical but I found it interesting. It gets into some of the issues I was discussing in far more detail:

    Fusion Neutrons: Tritium Breeding and Impact on Wall Materials and Components of Diagnostic Systems

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    Quote Originally Posted by Van Rijn View Post
    This is pretty technical but I found it interesting. It gets into some of the issues I was discussing in far more detail:

    Fusion Neutrons: Tritium Breeding and Impact on Wall Materials and Components of Diagnostic Systems
    Thanks for that. The problems with high energy Neutrons was the reason a plan to use diesel explosions to promote fusion in tiny droplets of heavy water inside diesel oil droplets, was dropped.
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    Quote Originally Posted by profloater View Post
    Thanks for that. The problems with high energy Neutrons was the reason a plan to use diesel explosions to promote fusion in tiny droplets of heavy water inside diesel oil droplets, was dropped.
    ...I'm pretty sure that wasn't the reason.

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    Quote Originally Posted by profloater View Post
    Thanks for that. The problems with high energy Neutrons was the reason a plan to use diesel explosions to promote fusion in tiny droplets of heavy water inside diesel oil droplets, was dropped.
    You’re welcome. Do you have a reference to the diesel/fusion concept? I’m not familiar with it, and the concentrated energy requirements to initiate nuclear fusion is generally understood to be beyond chemical reactions so I’m not sure how that would work.

    Could this be related to sonofusion experiments perhaps? If so, that wasn’t replicable by other researchers.

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    Quote Originally Posted by Van Rijn View Post
    Youíre welcome. Do you have a reference to the diesel/fusion concept? Iím not familiar with it, and the concentrated energy requirements to initiate nuclear fusion is generally understood to be beyond chemical reactions so Iím not sure how that would work.

    Could this be related to sonofusion experiments perhaps? If so, that wasnít replicable by other researchers.
    Not just the energy requirements, the temperature and pressure conditions needed for fusion are pretty much incompatible with chemistry. You're way past breaking CO2 and H2O into monatomic carbon, hydrogen, and oxygen and well into stripping all their electrons off before you start even the easiest fusion reactions. A burning droplet of diesel oil isn't going to produce any neutrons.

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