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How the energy generated by nuclear fussion is extracted?

  1. Feb 10, 2010 #1
    Anyone knows how? Thanks in advance
    Correction to the question..Not extracted, but "capture"
    I can't think of any word to describe the process.
    Sorry for my poor English speaking skills
  2. jcsd
  3. Feb 10, 2010 #2
    Diverting from the question...
    Here's what i have found.
    The heat generated by the nuclear fusion is being transferred by a water-cooling loop to a heat exchanger to make steam.
    The steam then drives the Turbine to generate electricity.
    From what I understand, the heat is sort of use to heat water and produce steam. From there, the steam is used to drive a turbine to produce electricity.
    Correct me if I'm wrong.

    Adding on, as the heat is being transferred from the Tokamak, to the water, and the water turns to steam. From there steam is moved on to drive the turbine. In this process, the energy is being lost (due to heat loss to surrounding and etc.). The energy generated by the nuclear fusion will not be full utilize. Am I right to say that?
    Last edited: Feb 10, 2010
  4. Feb 10, 2010 #3


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    Are you talking about fusion, or fission? If this is fusion, then I think all of this is hypothetical. I don't think anybody has ever extracted useful energy from a nuclear fusion reactor.

    But in any case, I don't think the aspects of the hypothetical design you're talking about really depend on whether it's fusion or fission. In both cases, a nuclear reaction generates heat, and that heat runs a heat engine. A steam turbine is one possible type of heat engine.

    This is certainly correct. The laws of thermodynamics say that no heat engine can be perfectly efficient. In addition, I believe a lot of the energy from a fusion reactor would come out as gammas, and the gammas won't necessarily be stopped in the working fluid of the heat engine (water,...) The gammas may stop in the walls of the reactor, in the walls of the heat engine's vessel, etc.
  5. Feb 16, 2010 #4
    there are troubles to maintain a stable plasma environment with a desirable economic cost. It is more like you lose more energy in making fusion.
  6. Feb 16, 2010 #5
    There was an interesting article in Eric Drexler's blog:

    http://metamodern.com/2010/01/20/why-fusion-won%E2%80%99t-provide-power/" [Broken]

    The bottom line is that using ITER like approaches to fusion don't lead to anything that is close to cost effective. Fission style power plants are an orders of magnitude cheaper than anything that can be produced by tokamak style power plants. There are also a number of interesting comments on this posting. They discuss other approaches to fusion that would be much cheaper if they work.
    Last edited by a moderator: May 4, 2017
  7. Mar 28, 2010 #6
    The power generation in an ITER type concept is to capture the high energy neutrons (14 MeV) evolved in the fusion process in a lithium breeding blanket. Being neutral the high energy neutrons can readily leave the confined plasma in which the fusion reaction takes place. Depositing 14 MeV neutrons in the lithium is going to mean it needs cooling and this is where the energy can be extracted - basically cooling (boiler?) tubes buried in the blanket pick up heat and convert water into steam and from there onwards it would be pretty much the same as most of the power plants in the world today. Of course bombarding any substance with such high energy neutrons is likely to cause serious issues and its notable that the design of suitable materials is to be carried out in parallel with the design and buildng of ITER. It's no secret that there are some incredibly difficult technical issues to overcome before fusion powered reactors can generate electricity on a commercial scale.
    Last edited: Mar 28, 2010
  8. Apr 26, 2010 #7
    The problem with indirect electrical power production schemes for fusion is, while more gross energy is produced than is consumed, the bands that we presently use are insufficent and the methods we use are inefficient. Heat engines work great when we don't have to put energy into containment as in fission and fossil production. When parasitic loads like containment are as high as they are, in fusion generation, you better be a lot more efficient at capturing energy in all bands than our paultry tech.
  9. Jul 8, 2010 #8
    I was just at a colloquium about ITER. The concept is just as statphys stated. The 'containment' vessel will be surrounded by a lithium breeding blanket where the 14MeV neutrons will deposit their energy. I cannot remember if the lithium itself acts as a coolant (or if water is fed through lines within the lithium blanket) which is then pumped through a heat exchanger/steam generator where the steam plant will be just like a conventional power/nuclear plant. The fusion reactor and associated primary coolant (Lithium) will be contained within the 'reactor containment' structure along with the steam generators. Yes, radiation (neutron/gamma) will deteriorate the structural integrity of the materials as statphys pointed out (called neutron 'embrittlement'), but this is accounted for by the materials chosen at the design stage which is dependent on the expected radiation flux through the material, and they replace these materials when necessary. This generates activated waste (yes, fusion power plants do create waste!), but this waste will decay in a few hundred years instead of 10,000.
    Last edited: Jul 8, 2010
  10. Jul 15, 2010 #9
    One of the most prevalent ideas being circulated is using a liquid salt to capture the energy of the neutron.
  11. Jul 15, 2010 #10
    Everyone is so skeptical of fusion...just because it doesn't work now doesn't mean it won't...we just have to find the right materials. Solar doesn't work on a commercial scale either but everyone loves that...pfff.

    The best fusion tech is the SABR...using an unsustainable fusion source to get rid of transuranic waste...while still producing (net producing) power. Forget Yucca...SABRs and breeders for all.
  12. Jul 15, 2010 #11
    I question whether SABR is really the fusion tech due to the use of a to tokamak; even the biggest supports say that the viability of the tokamak is +50 years.

    As I see it, ICF is the best technology (at least as it stands now); it's only a year or two away...
  13. Jul 15, 2010 #12
    SABR uses a tokamak, but those "viability" timelines are likely for a sustained fusion reaction in a tokamak...I would guess. The technology is already there for SABR.

    ICF? A year or two away? Where?

    I don't know too much about ICF, my plasma prof (Stacey) pretty much shuns it and teaches tokamaks mostly. I doubt tokamak research would continue as such if ICF were so close...my guess is that it isn't that close.
  14. Jul 15, 2010 #13


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    That's a little disengenuous. Fusion doesn't work at all, (meaning there has never been a sustained, positive energy output reaction created by humans), whereas solar works great - it's just expensive.

    The reason I'm skeptical of fusion is how long it is taking. When the process of fission was discovered it took the rediculously short period of about 15 years for it to be implimented for power generation. We've known about fusion for more than half a century and have actively been pursuing harnessing it for many decades with seemingly little progress toward and no timeframe for success.
  15. Jul 15, 2010 #14


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    I think the NIF is supposed to be operational this year (not sure if it's still on schedule), but who knows how well it will go.


    I've also never understood how you get net energy out of ICF -- does anybody know how the NIF plans to get energy out?
    Last edited by a moderator: Apr 25, 2017
  16. Jul 15, 2010 #15


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    Oh, the same old way. Rats.

    https://lasers.llnl.gov/programs/ife/ [Broken]

    Last edited by a moderator: May 4, 2017
  17. Jul 16, 2010 #16
    Any new science is a huge learning process. It's not a question of IF we can harness fusion energy, it's a question of how long it will take use to get to that level of technology.
  18. Jul 16, 2010 #17
    All 192 beams are currently online, and experiments are bean done to see how the targets and beam delivery effect the implosion. They are also slowing increasing the energy in each shot (up to the limit of 1.8MJ). All current data shows that the required conditions will either be met or exceeded when a full power shot is done.
    Last edited by a moderator: Apr 25, 2017
  19. Jul 16, 2010 #18
    My point was that neither solar or fusion work on the scale necessary. Fusion, correctly, doesn't work at all, though it is a materials/technology issue holding it back. Solar is taxing both in terms of finances and resources. Additionally, the technology issue holding solar back is storage capabilities. I mean, the solar plane was cool and all, but solar also cannot be implemented wide-scale yet.

    Sure, maybe solar tech will be more viable that fusion, in which case we won't need fusion. Solar is likely the end all of power techs (unless the sun goes out).

    And yeah, fission technology was captured very quickly but that doesn't mean we will never get fusion. Getting fusion is like holding the sun (of course it will take longer than fission, much longer).

    BTW, nice astro-bling, Russ.
  20. Jul 16, 2010 #19


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    Thats still factually wrong and rediculously misleading. Solar works just fine: there are both private and commercial solar plants hooked up to the electrical grid right now generating power. If we chose to do it, we could replace a substantial portion of our electric power generation with solar.

    Even if you could spin that in a way that wasn't still factually wrong, it would still be like me claiming both Chase Utley and I are injured right now, which is keeping us out of the starting lineup of the Phillies. It's rediculously misleading.
    Is that it? Just materials and technology issues? That's also all that's holding me back from finishing my starship!
    Sure. So is the coal power industry. That's so bland of a statement as to be meaningless.
    No, it isn't. Solar power is too small of a fraction of the grid for storage to be necessary. It can simply be plugged directly into the grid and give power when it can and not when it can't - just like wind.

    What's holding solar power back from being the ultimate solution for our electic power needs is cost. Now cost can be a technological issue too, but solar plants still function and do a good job for what they do.
    The solar plane has nothing to do with solar power in our electrical grid. Solar power is being implimented on an industrial scale, right now.
    That's a meaningless sentence: since fusion is currently non-functional, there is no question of viability for it. Solar has limited viability, but limited viability will always be greater than nothing.
    I never said we wouldn't, but these misleading statements you are giving can't be allowed to go without correction.
  21. Jul 16, 2010 #20
    Well, that's what happens when people (me) ramble about things they don't know. Good to learn some things...and at least only half of what I say is "meaningless" or "misleading." I'll take the hint (or rather large indication, case), and I do appreciate the corrections. It's always good to point out the BS...even it is mine.

    Good stuff. Haha.
  22. Jul 18, 2010 #21
    This is what ITER is designed to achieve; break-even. If they can achieve this and/or surpass it, then commercial fusion 'will be' viable in the not too distant future. ITER groundbreaking has just started, and the plant is not expected to go online until sometime in 2016. I'm still a little sckeptical as to how 'economical' fusion power will be given that it will have a much higher initial capital cost to build, even more so than fission power plants.

    I think that they are finally at a point where sustainable fusion is attainable is promising given that they've been working on it for over half a century. I think you will be hard pressed to say that fusion power is 50 years off after ITER starts running tests, but I've always been an optimist. They could run into snags, but with the HUGE budget involved, I'm pretty certain that whatever they need, they'll get pretty quick; they really are getting close. I'm looking forward to what the news will read in 2016...
  23. Jul 19, 2010 #22


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    To me 'viable' 'commercial fusion' is synonymous with economic fusion. So 'break-even' fusion may indeed happen with ITER in the near future, but with all the other problems I doubt ITER will show commercial viability.
  24. Jul 20, 2010 #23
    You're glossing over some major problems though. IF solar replaced a substantial portion of your power generation, then we would need to have it in a place where whether conditions are extremely stable; we can't have a substantial portion of our power generation not work when the whether doesn't permit it. As such, you now run into the issue of transmission lines to bring the solar generated power from where it is collected, to where it is needed; this is no small task.

    Renewable should be part of the temporary solution to our energy needs, but if you look at the expected increase in the demands for energy over the next 50 years, solar, wind, hydro, etc are not going to cut it collectively. We need a new core method of energy generation and fusion is the answer. Renewables are a bridge to fusion.

    Do vastly complicated technically challenges exist in getting fusion commercially viable? Absolutely. Does that mean we can't do it? What do you think scientists and engineers would have said was possible 50 years ago and what is possible now?
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