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The short answer is that realistic fusion plants would have few advantages over uranium fission plants that exist today. Long answer: Fuel: Both are likely to

by bcoates 14y ago

The short answer is that realistic fusion plants would have few advantages over uranium fission plants that exist today. Long answer: Fuel: Both are likely to use expensive but not scarce fuels but produce so much output from it that it doesn't matter. Cost: Almost entirely in the plant infrastructure for both. Fusion is likely to be at a permanent disadvantage here, as both coal and fission plants are simple compared to hypothetical fusion plants. Waste: Likely small advantage to fusion, as it probably won't produce proliferation-sensitive waste just a bunch of irradiated eqiupment and buildings that are easier to deal with. Safety: It'll probably be more dangerous to work at a fusion plant than a fission one by orders of magnitude, but the negligible danger to people outside the plant will be lower. A Fukushima/Chernobyl situation at a fusion plant would be bad but less bad. NIMBY: Equal for both, the scariness of an energy generating technology is inversely proportional to its practicality. Did you know that Einstein predicted that a fusion containment loss would cause the atmosphere to light on fire in a runaway reaction that kills all life on earth except for oil company executives and people who work in the advertising industry? Do we really want to take that risk with our children?

eliben 14y ago
Genuinely curious - aren't fusion plants both safer and use cheaper-to-get and more-abundant materials?
- ISL 14y ago
  See other posts referencing D-T and other fuel cycles. The D is deuterium and the T is tritium. Hydrogen-Hydrogen fusion is more challenging than more exotic types. D-T is, in a sense, the easiest, but both ingredients have non-trivial costs. http://en.wikipedia.org/wiki/Fusion_power#Fuel_cycle http://en.wikipedia.org/wiki/Fusion_power#Fuel_cycle The GP post is erudite on activation. Fusion creates a lot of neutrons, which will render the reactor assembly itself radioactive, especially on short timescales. The waste problem is smaller, especially when compared to non-reprocessed fission waste, but not zero. An upside to fusion is the lack of usable bomb material in the waste stream. So, safer, yes, but not completely safe.
  - DennisP 14y ago
    Deuterium is pretty cheap. It's 1/2500 of the hydrogen in seawater and easy to separate. Tritium is bred from lithium, which isn't rare either. The main problem here is that tritium breeding limits the rate at which you can build new reactors. So tritium is going to stay pretty valuable for a while but that price will go down as we build more reactors breeding it. Neutrons are definitely a problem, and that's one advantage of General Fusion's design, which has lots of lead and lithium to capture the neutrons. Of course the whole problem goes away if one of the boron fusion projects works out.
    - ISL 14y ago
      Looks like deuterium is ~$3000/kg, as heavy water is ~$600/kg [1]. Less expensive than I thought, but still far more expensive than hydrogen at <$0.01/kg when purchased from my local public utility. It's unfair to compare with hydrogen though - this study [2] suggests that fusion and wind power are roughly comparable in cost. [1] http://reactorscanada.com/2008/05/21/is-there-enough-heavy-water-for-more-candu-reactors/ http://reactorscanada.com/2008/05/21/is-there-enough-heavy-w... [2] http://www.energyresearch.nl/energieopties/kernfusie/achtergrond/economie/ http://www.energyresearch.nl/energieopties/kernfusie/achterg...
      - DennisP 14y ago
        The best comparison is really to the 12 million kilograms of coal that generates the same amount of energy: http://www.euronuclear.org/info/encyclopedia/f/fusion.htm http://www.euronuclear.org/info/encyclopedia/f/fusion.htm I'm guessing your second link is based on tokamaks, which are generally considered likely to be far more expensive than some of the lesser-known designs. If they project tokamaks to be competitive with wind then I'm pretty encouraged.
- bcoates 14y ago
  It depends on what kind, as there aren't any viable fusion designs yet. If they involve gigantic magnets or largish amounts of material at surface-of-the-sun temperatures or incredible amounts of neutron flux, costs are going to be high and safety is going to be a problem even compared to fission. If they can miniaturize it like the Lockheed guy in the OP wants then not so much but nobody really knows if that's possible.
InclinedPlane 14y ago
You don't know what you're talking about. A "fukishima/chernobyl" situation at a fusion plant simply cannot happen. Period. First off, containment is trivial because a shut-down fusion plant generates zero heat and pressure. Zero. Which means that even in a worst case scenario you can just press the big red button and walk away, then come back perhaps years later for any on-site mitigation work. Compare this to a fission reactor where the fission products will continue to generate enough heat to cause a lot of mischief if you don't apply active cooling continuously for decades. Also, whereas in a fission reactor the byproducts tend to include huge quantities of the worst sorts of hazardous radionuclides such as Sr-90, I-131, and Cs-137 (which are picked up by the human metabolism and then happily radiate your vital organs from within until you die) in contrast a fusion reactor's load of hazardous isotopes is almost trivial. There's a small amount of "activated" isotopes formed by the neutron flux transmuting the structure of the reactor, but this is easily mitigated by picking low activation materials for construction and also by the fact that the materials will tend to be kept in place. The other major risk is Tritium release, but Tritium is not terribly dangerous (it doesn't bioaccumulate, it dilutes rapidly, and it does not stay in the human body long) and the amount that could be released is likely to be small. Saying that a possible accident at a fusion plant would be "bad but less bad" than Chernobyl is like saying that a paper cut would be "bad but less bad" than a guillotine. They are simply not comparable.

by bcoates 14y ago

eliben 14y ago

Genuinely curious - aren't fusion plants both safer and use cheaper-to-get and more-abundant materials?

ISL 14y ago
See other posts referencing D-T and other fuel cycles. The D is deuterium and the T is tritium. Hydrogen-Hydrogen fusion is more challenging than more exotic types. D-T is, in a sense, the easiest, but both ingredients have non-trivial costs. http://en.wikipedia.org/wiki/Fusion_power#Fuel_cycle http://en.wikipedia.org/wiki/Fusion_power#Fuel_cycle The GP post is erudite on activation. Fusion creates a lot of neutrons, which will render the reactor assembly itself radioactive, especially on short timescales. The waste problem is smaller, especially when compared to non-reprocessed fission waste, but not zero. An upside to fusion is the lack of usable bomb material in the waste stream. So, safer, yes, but not completely safe.
- DennisP 14y ago
  Deuterium is pretty cheap. It's 1/2500 of the hydrogen in seawater and easy to separate. Tritium is bred from lithium, which isn't rare either. The main problem here is that tritium breeding limits the rate at which you can build new reactors. So tritium is going to stay pretty valuable for a while but that price will go down as we build more reactors breeding it. Neutrons are definitely a problem, and that's one advantage of General Fusion's design, which has lots of lead and lithium to capture the neutrons. Of course the whole problem goes away if one of the boron fusion projects works out.
  - ISL 14y ago
    Looks like deuterium is ~$3000/kg, as heavy water is ~$600/kg [1]. Less expensive than I thought, but still far more expensive than hydrogen at <$0.01/kg when purchased from my local public utility. It's unfair to compare with hydrogen though - this study [2] suggests that fusion and wind power are roughly comparable in cost. [1] http://reactorscanada.com/2008/05/21/is-there-enough-heavy-water-for-more-candu-reactors/ http://reactorscanada.com/2008/05/21/is-there-enough-heavy-w... [2] http://www.energyresearch.nl/energieopties/kernfusie/achtergrond/economie/ http://www.energyresearch.nl/energieopties/kernfusie/achterg...
    - DennisP 14y ago
      The best comparison is really to the 12 million kilograms of coal that generates the same amount of energy: http://www.euronuclear.org/info/encyclopedia/f/fusion.htm http://www.euronuclear.org/info/encyclopedia/f/fusion.htm I'm guessing your second link is based on tokamaks, which are generally considered likely to be far more expensive than some of the lesser-known designs. If they project tokamaks to be competitive with wind then I'm pretty encouraged.
bcoates 14y ago
It depends on what kind, as there aren't any viable fusion designs yet. If they involve gigantic magnets or largish amounts of material at surface-of-the-sun temperatures or incredible amounts of neutron flux, costs are going to be high and safety is going to be a problem even compared to fission. If they can miniaturize it like the Lockheed guy in the OP wants then not so much but nobody really knows if that's possible.

InclinedPlane 14y ago

You don't know what you're talking about. A "fukishima/chernobyl" situation at a fusion plant simply cannot happen. Period. First off, containment is trivial because a shut-down fusion plant generates zero heat and pressure. Zero. Which means that even in a worst case scenario you can just press the big red button and walk away, then come back perhaps years later for any on-site mitigation work. Compare this to a fission reactor where the fission products will continue to generate enough heat to cause a lot of mischief if you don't apply active cooling continuously for decades. Also, whereas in a fission reactor the byproducts tend to include huge quantities of the worst sorts of hazardous radionuclides such as Sr-90, I-131, and Cs-137 (which are picked up by the human metabolism and then happily radiate your vital organs from within until you die) in contrast a fusion reactor's load of hazardous isotopes is almost trivial. There's a small amount of "activated" isotopes formed by the neutron flux transmuting the structure of the reactor, but this is easily mitigated by picking low activation materials for construction and also by the fact that the materials will tend to be kept in place. The other major risk is Tritium release, but Tritium is not terribly dangerous (it doesn't bioaccumulate, it dilutes rapidly, and it does not stay in the human body long) and the amount that could be released is likely to be small. Saying that a possible accident at a fusion plant would be "bad but less bad" than Chernobyl is like saying that a paper cut would be "bad but less bad" than a guillotine. They are simply not comparable.