Tim Wescott wrote:



Any peaceable nuclear reactor needs U-235 to fire the reaction -- it's
just that the common type (non-breeder) doesn't need much.

I'm not so sure about the absolutely needing a breeder reactor -- AFAIK,
you get Pu from ordinary reactors, just in small quantities. In fact,
(again, AFAIK), part of the reprocessing of nuclear fuel is getting the
Pu out.
Yes, that's the deal, typical power and research reactors produce
239 Pu SLOWLY, and if you leave the fuel in too long, you get too
much 240 Pu, which is undesirable. Of course, if you have decades
of reactor operation to harvest, instead of the Manhattan project
kind of insane timeline, then it is less of a problem.

The Manhattan project was truly amazing, they built something that
was only a theoretical possibility in just a couple years,
in the MIDDLE of a huge war!

Jon