The water would be inputted, and taken out at a hotter temperature -

I don't know how this would work with cooling as they are multiple buildings - I also remember vaguely that water can be used as a moderator correct? so maybe that would open up complexity or adaptability ?

I think maybe an external building, like the reactor interface, like a cooling interface building, could do that .. I don't know.

You're supposed to use the cooling towers to do this, although i suppose i could make another building which consumes heat and outputs hot water

cooling rods does sound like a good idea, actually. I think I'll implement this for 0.2.7

i think you are referring to RBMK 1000 reactors that used to cooldown the reactor by using water flow that turned into steam and powered turbines which is actually a great way to build a reactor if you make mechanism that will control it as too much water will make it stop and not enough water would make it explode so input of water with flow control would be a great idea