> From: David_Bowman@georgetowncollege.edu
>
> 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
>
I am pretty fuzzy here. I worked with fission reactors and I spend
more time on statistical physics than on nuclear engineering. Its my
recollection that 1) the cross sections for D-D reactions (deuterium,
deuterium) make a D-D reaction much less feasible than a D-T reactor;
and that 2) Tritium will be produced in a D-D reactor so you can not
escape the high energy neutrons. I don't recall the reactions.
Tritium would definitely be a problem. I don't recall the amount of
tritium compared to current light water reactors (or Canadian heavy
water reactors) so I can't put it in context. Chuck may have better
information.
------------------------------------------------------------------------------
Joel W. Cannon | (724)223-6146
Physics Department |
Washington and Jefferson College |
Washington, PA 15301 |
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