The definition of "nacelle", as provided by Locutus of Bored
indicates the secondary hull is
a nacelle in and of itself because
that is where the "engine" (warp core) is located.
So life support could be, as I would expect, somewhere, probably deep and center of the secondary hull. Perhaps behind a fire wall between engineering and the aft shuttle bay. (just guessing, of course)
All that said, anyway it's spun, '"behind" the aft nacelle' is still pretty silly sounding.