Is it theoretically possible to add fuel cells at an optimal rate in nuclear reactors in a 3x3 formation (with one in the middle) or does the heat not transfer without a heat cable specifically tied to that reactor, but reactors that it's adjacent to?

I also heard that it's technically optimal to put fuel cells in a spaced out manner, and i think setting up a mechanism to insert fuel cells on a timer would be very cool to learn as well, but i'm not sure how i'd handle that, either. so far i have a 2x2 reactor square but id like to switch to nuclear entirely at some point