On Titan, all you need is a naked pile in a gore-tex sleeve with a wind turbine at the top, catching convection. Or maybe plunge it into a methane sea and drive a wind turbine from the boil-off. No need for cooling.
On orbit or on an airless body, a naked pile at the end of a long boom can be allowed to heat to a fierce glow. Photovoltaics ranged around it, at a distance, produce power directly. Again, no need for cooling.
BTW, there is a recently release grand-strategy game called Terra Invicta that gets it right - the same solar panel module that gives you 40 power units in LEO (or 260 at Mercury!) will produce just 3 power units at Ceres. So its all fission, followed by various fusion designs for any stations further from the sun than Earth/Luna & for basically all ships.
BTW, as for launching reactors into space - I think that at least the fuel elements will have to be launched for quite a while, the industrial base required for nuclear fuel refining and fuel assembly fabrication is just too massive for early deployment space-side. Lot of other stuff - dirt for shielding, coolant, possibly even some primitive radiators - could likely be made in space relatively quickly.
Still, nuclear fuel that has not yet been through a reactor is just a bunch of toxic heavy metal - not ideal if it burns s up, but possibly quite a bit better than plutonium from an RTG. Also being dense and quite small in volume, it could very well be shipped in a big ball of ablative shielding, just in case.
Thankfully reactors in space have a lot of benefits compared to terrestrial use - ships and space stations can use the so called shadow-shield to protect the ship/station in its shadow and just let the radiation go into the void of space in all other direction. Makes docking a bit tricky as well as running multiple reactors (you need to take neutron cross-propagation into account), but should be still doable.
For surface or asteroid stations - there shouldby plenty of mass for any shielding and no biosphere to contaminate or possibly not even any hydrosphere or atmosphere to spread radioactive particles - on the other hand, this also makes cooling harder.