I want to build a breeder... how do i get the depleted fuel rods working now?
Uranium breeding was taken out. In its place you now have a 100% chance to get a depleted fuel rod, which you run through a thermal centrifuge to get 4 U238 per fuel rod, as well as 1 small plutonium per fuel rod. You can use 3 large piles of plutonium and 6 U238 for MOX fuel rods, which have half the life time of Uranium rods, but produce more energy (and not more heat) the hotter the reactor is, up to 5x at 100% heat. When you thermal centrifuge the depleted MOX you will get 3 plutonium per rod, and 1 small pile of plutonium per rod. Since you get 3 plutonium back MOX does not actually use any plutonium while running, instead it is more of a catalyst to cause the U238 to react. The plutonium that you get from centrifuging the MOX can be used for more MOX, or used in an RTG for small amounts of energy continuously, forever.
Edit: Partially ninja'd by Omicron.