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Danger and risks of fusion power

  1. Aug 7, 2017 #1
    As someone who has had an interest in the potential outcome of various scientific en-devours, I have weighed potential outcomes of things that interest people to be good to potential outcomes they may not have yet seen as being bad. I wonder if anyone has asked the questions about how our potential future source of clean energy that may turn out to be bad? First I Would say i have read some peer reviewed papers about potential negative effects and will reference them bellow, but I point out they are based on current concepts of the solution. The concern I have with fusion power is that if a way of making it reasonably energy dense and efficient for both DT and DD fusion there is no excluding the possibility that the technology can be used to make fissile material.

    I have approached this question as a simple thought experiment, if there is a fusion device/reactor that can contain DT/DD fusion as a dense sphere of plasma, a way may be found to place fertile material around the region of plasma where fusion occurs. It could be placed in diluted form, mixed with another metal or as a fluoride salt for example and cycled through, to remove irradiated material that has been transmuted. The present status quo is that fertile material is difficult to make or obtain, and this prevents proliferation, but if fusion power can provide a rich source of neutrons, the greatest obstacles to proliferation could be removed. Based on simple calculation I find that a 1GW source of DD fusion(optimally) would be able to irradiate enough U-238 to make 7-8kg of Pu-239 in about a day, at between 50% efficiency. On more realistic calculations, it’s about a month, since fission waste would cause problems, and provide too much energy feedback.

    I wonder what other would have to say to my conclusion?

    Not that sovereign states do or don't or won’t attempt clandestine fissile material production anyway, what about private clandestine fissile material production. There are some natural road blocks, obtaining fertile material is not very easy, once you start irradiating the material, 20%.> may undergo fission from high energy neutrons. But otherwise, at 8kg a month at the low end isn't good., ! What do you guys think, both as people and as scientist about how institutions would react to this?

    http://web.mit.edu/fusion-fission/HybridsPubli/Fusion_Proliferation_Risks.pdf
     
    Last edited by a moderator: Aug 16, 2017 at 12:11 PM
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  3. Aug 7, 2017 #2

    phinds

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    I think from the time that the first hominoid picked up a stick and hit another one with it, technology has been observed to have potential negative consequences. Should we just stop trying to evolve technology?
     
  4. Aug 7, 2017 #3

    etudiant

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    I think that when an impoverished small polity such as North Korea builds nuclear weapons and delivery vehicles for them, the hopes of halting 'nuclear proliferation' are overtaken by reality.
    The best hope for avoiding a nuclear war is no longer to halt nuclear spread, but rather to make sure all have enough skin in the game that they will not be inclined to blow it up. On that basis, I think cheap power from fusion would be hugely desirable.
     
  5. Aug 8, 2017 #4
    This subject was treated (among other topics) in a recent article in the Bulletin of Atomic Scientists— http://thebulletin.org/fusion-reactors-not-what-they’re-cracked-up-to-be
    ----------------------

    As for “fertile material,” It may not be difficult to get lots of depleted uranium (DU) There are numerous industrial uses, and you can legally buy DU if you have a federal license. There is a thread somewhere in this forum about DU.
    ----------------------------

    With the right configuration, you don’t have to worry too much about fission reactions in your plutonium generator because the cross section for Pu production in U-238 increases as the neutron energy drops. That is, you want low-energy down-scattered neutrons, which cannot fission U-238 (fission threshold at least 1.5 MeV). So put the uranium where it cannot be struck directly by fusion neutrons. Use depleted uranium, to minimize fissioning of U-235 with slow neutrons. Remove the Pu-239 before it builds up and becomes a significant neutron target.
     
  6. Aug 8, 2017 #5
    There will never be “cheap power from fusion.”—it would be the most expensive energy source of any type. It’s far more likely that fusion neutrons would be used to produce valuable isotopes (including u-no-what) rather than pressed into the task of boiling water.
     
  7. Aug 8, 2017 #6

    etudiant

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    I hope that you are mistaken, but agree that the current ITER program, a desultory effort by a motley group of researchers working against an indefinite schedule, is very likely to make your forecast a reality.
    Presumably there are more economical options that can be discovered if there is a coherent effort to do so, but imho that does not exist at present. The US contribution to ITER was the high voltage power components. Rather than source these in the US, as might have been expected for an important new technology initiative, it was decided that they could be more cheaply procured from South Korea. The were duly delivered and are now quietly corroding sitting unconnected outside at the ITER site, pending the eventual completion of the plant sometime well after 2020. Meanwhile, the meter keeps running, so the costs increase steadily, supporting your stance.
     
  8. Aug 15, 2017 at 11:50 PM #7
    To my understanding, in order to complete the fuel cycle, the reactor needs to breed tritium. This is why current designs typically call for a Li-6 capture layer. This has the added benefit of having a large cross section.

    I'm not saying it's impossible to leech off of the neutron flux, just that every tritium not produced by the reactor is a tritium that has to be produced some other way (typically fission reactors or accelerators). And the other ways can be breed plutonium sources as well. So it's really just shuffling around where the neutrons come from, a fusion reactor doesn't really add capacity, and because it requires tritium because losses are inevitable, you could argue that it's a constant drain on capacity.
     
  9. Aug 16, 2017 at 10:37 AM #8
    Your statements apply to reactors fueled by deuterium-tritium. But reactors fueled only by deuterium are feasible in principle. And ALL the neutrons from the D-D reactions are available for producing isotopes, Pu-239 or otherwise. The fusion component of the first hydrogen bomb (“Mike”) was fueled solely by liquid deuterium.

    As for DT-fueled reactors, it’s certainly true as you say that every neutron is needed to produce tritium. The problem is that neutrons are back-scattered all over creation, and not all of them enter the lithium-containing blankets. Plenty of down-scattered neutrons will find their way into pumping ducts, heating and fueling ducts, and diagnostic ports. These slower neutrons are prime candidates to be soaked up by U-238 placed in these ducts and ports.

    If just 1% of the neutron production in a reactor producing 2,500 to 3,000 MW fusion (1,000 MWe) is captured in U-238, the Pu-239 production will exceed 50 kg per year.
     
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