The problem with breeder reactors isn't, and never has been, an engineering one. It's a relatively simple process, so far as nuclear physics is concerned. The problem is that the anti-nuclear cowards don't want to make plutonium easily available. Nevermind the fact that we already have one of the largest nuclear arsenals (maybe the biggest, given Russia's gross mismanagement as of late), and pose no real proliferation risk, since we already have all the plutonium our hearts desire.