Joel,
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.
I'm not a nuclear physicist and can't comment on D-D vs D-T
reactions. In natural uranium fuelled, heavy water (CANDU) reactors, D2O is
used as the moderator because of the small neutron capture cross section of
D compared to that of H. Yet, there are enough deuterium targets to produce
lots of tritium by (n, gamma) reactions on deuterium. There are techniques
to strip the tritium out of the heavy water. As for the high energy
neutrons produced in a nuclear reactor, these are, of course, moderated to
thermal energies. They do result in neutron activation of reactor
components but the activity generated in these reactor components is not as
high as that of the fission products in the fuel as it is discharged from
the reactor. Some of the isotopes generated by neutron activation have
relatively short half lives (e.g., Co-60, 5.3 years) but there are some
longe-lived isotopes such as Zr-93 (1.5E6 a). However, Zr is not very
soluble in groundwater, to put it mildly.
Hope this helps.
Chuck Vandergraaf
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