And 2 new designs which can work together to make a 706.75 eu/t effective combination of 1 breeder-hybrid and 2 power reactors. It needs 5.859 uranium per cycle (50,000 seconds) and produces 708 million EU from which 1.25 million EU is used to power industrial centrifuges (also copper and tin for the cells + 100 coaldust for the near-depleted uranium cells to depleted-isotope cells). It also takes 1/4th of a industrial centrifuge's time (it runs 25% of the time). Not taking into account the tin, copper and 100 coaldust needed (but I did take into account the EU's needed for the centrifuge) the efficiency will be 120.6. (Sorry in advance if any mistakes got into this post. It's pretty late here and I should be sleeping.)
I'm not much for optimizing MK I reactors, but your power reactors can be improved greatly. This, for example, is strictly better. In terms of efficiency, I found maximizing EU/t per heat generated is very important. This boils down to Quad thorium, and single plutonium together. Another Quad thorium cell gets you up to 420 EU/t as well. Just reiterating, I have no clue how to do heat fan layouts, and someone could probably do those way more effectively.
Join the dark side of Mark V's sometime.