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View Diary: The Race for Fusion (75 comments)

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  •  Can you list these practical difficulties please? (0+ / 0-)

    I think I know what they are, but unless you're well versed in the field I doubt that you do.

    •  I had friends working at Rochester's (2+ / 0-)
      Recommended by:
      wilderness voice, BusyinCA

      ...Laboratory for Laser Energetics, which explored using 'inertial containment' in the form of concentric laser beams to trigger fusion in Deuterium pellets. The project collapsed after burning though many millions of dollars amid allegations of impropriety in its finances, and the director committed suicide. Bizarre but true. Research on this method is now centered at Lawrence Livermore.

      I don't claim to be especially well versed in the field, but from what I do understand, the difficulties are extremely daunting. It's damn near impossible to keep plasma contained well enough using magnetic fields to maintain the kind of temperature and density necessary to sustain fusion in the 'standard' designs descended from the Tokamak model. The instant the plasma stream touches the physical containment shell, it cools drastically and fusion halts. Assuming you are able to somehow stably maintain the temperature/density level required to achieve fusion, you have to feed in a steady supply of Deuterium without permitting this much colder 'fuel' to cool the plasma below the critical point. You also have to remove the accumulating Tritium somehow before it poisons the fusion reaction. Oh, and massive neutron flux poses enormous problems in the area of materials making up the 'core' of the fusion reactor, even if you don't have to deal with all the ugly stuff a fission reactor generates. And 'harvesting' the resultant heat energy without halting the reaction by cooling the plasma too far is nowhere near being solved as I understand it.

      The alternative approach exploring lasers and inertial containment has its own problems, including the near-impossibility of maintaining perfect alignment of massively powerful laser beams aimed by scores of delicate precision mirrors by necessity exposed to the fusion core...

      •  Intertial fusion (0+ / 0-)

        is entirely different from magnetic fusion when it comes to the challenges for economical power.

        And I don't know what you're talking about, because the Omega program at Rochester is still going strong:

        The NIF program at Livermore is, of course, much bigger but much of their research is focused on nuclear bomb physics, using laser fusion to get around START treaties regarding testing.

        None of the problems you list are the primary problems facing magnetic confinement fusion. Tritium is not the byproduct, it is the fuel (D-T fusion is the easiest). Alpha particles, i.e. Helium ash is what needs to be flushed out, but not before their energy is used to maintain the plasma temperature. Harvesting the energy is also not the problem, it involves capturing the released neutrons in surrounding blankets, heating them up, and turning water to steam.

        The challenges for inertial fusion are not even close to what you state. They have to do with non-symmetrical instabilities in the expanding shock front. Alignment of the laser beams is trivially easy, the optics are far away, and everything close to the fusion reaction is destroyed and needs to be replaced after every shot.

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