Regarding the part of Joel W. Cannon's post where he wrote:
> ...
> I left because I found physics more interesting.
Ah, a person after my own heart.
>First, fusion reactors (as opposed to reactions) do produce
>significant radioactive contamination through activation. The very
>high energy neutrons (14 Mev) present a challenge to the person trying
>to convert the energy of a neutral particle into electricity, and to
>find shielding that will stop the neutrons and not fall apart.
Joel, maybe you can help me out here. Even though my field is physics,
(statistical mechanics) I'm much the layman regarding the intricacies of
controlled thermonuclear reactions. But I was sort of under the
impression that the neutron flux came from the use of tritium in the
fuel. (The reactants had more neutrons than protons, and the products,
primarily He-4, had mostly equal numbers of both.) I assume that the
reason for using tritium-enriched fuel is because such fuel would either
achieve ignition under less extreme conditions or be less subject to
some of the various instabilities the habitually plague tokamak plasmas
than a reaction powered by a pure deuterium fuel would have to deal with.
It seems that the neutron activation problem could be eliminated or
greatly reduced by use of a pure deuterium fuel. But then maybe the
engineering problems related to instabilities, quenching and the like
might never be able to be overcome? If the use of tritium-enriched
fuel proves to be absolutely necessary for the feasible harnessing of
thermonuclear fusion, then we would seem to have a *further* radioactive
waste problem than that of neutron activation of the shielding,
containment vessel, and other parts of the reactor. Since tritium is a
man-made element which is manufactured in *fission reactors* we would
also have to deal with the waste produced by them as the tritium fuel is
manufactured. Admittedly a pure deuterium fuel would not have such a
problem since it could be separated from ordinary water by relatively
benign isotopic separation techniques.
David Bowman
David_Bowman@georgetowncollege.edu
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