Breeder First. Its designed to enrich 4 cells at a time , 8 total per uranium cell (just shy of 8, 90%ish charged on 2nd round) its considered "Perfect" once you have water flow correct and the breeding is going will not gain or lose any heat.
Best part is if you forget about it or miss the swap time for new cells or new uranium it wont go critical it will just start cooling down slowly (thx to the HD it has to take its time) So to heat it back up or the first time you go to heat it up.
Now for help with this i expect mixed answers .. well i guess i do lol. i Am currently saving to build this legit, i did the design on creative when i was testing Ic2 out. The issue i am having is that its 9 Reactors linked together and no i dont mean 9 single 6chamber Reactors with wiring connecting them. I mean every single one shares chambers if you remove one you remove a chamber for another Reactor. In this design you have 9 reactors 8 of which are 6Chamber(#1-4,6-9) the middle Reactor (#5) has only 4chambers i could not get the last 2 on with out breaking the other 8, or spreading them all out by one which has them connected but ruins the whole thing IMO. In my setup they are all connected Via Red Stone to turn off and on at the same time, all of the run times are the same (except #5 see below) if one goes critical they all will lol. So for all intensive purposes its 1 reactor.
If i remember correctly its 1700ish ticks before they go critical. I would only run for 1000ish before turning them off, either way 1 min timer with all 9 on with current setup is about 1.6mil EU.
Considering some changes to #5 to bring it more in line with run time / 9 uranium cells. Along lines of