The entire heat source, the active part of the core, very easily fits in a small room (at a mean power density somewhere around 100 MW/m^3 for water-cooled reactors).
I'm talking about the difficultly of heat removal, not trying to minimize size or complexity or anything.
Sure, but you gotta consider the entire system, so adding the heat pumping system actually may decrease the overall power generated per unit of volume; at least, certainly increase cost and decrease reliability. I wonder if thousands of SMRs spread over an area wouldn't actually generate more power per acre.
I'm talking about the difficultly of heat removal, not trying to minimize size or complexity or anything.