I wonder what the trade is like between acres of cooling vanes vs. acres of solar panels. I guess it would depend on the efficiency of both.
In space, in a vacuum, studies apparently have shown that solar wins for the inner solar system. (And that's solar panels winning just compared to the reactor mass. Adding the radiator issue makes them win further out.)
On Mars, solar probably wins in terms of pure power/mass ratio, but solar requires storage for night power (so nearly double the panel area, plus the mass of the battery system) and extra power for heating (which the reactor gives you for free.) And in winter, the numbers get worse.
Same for the moon, except near the poles. With 24hr (or close to it) sunlight, solar wins. Anywhere else, nukes rule.
Mars's atmosphere is thin, but the temperature is very cold... seems like there ought to be a way to take advantage of that.
I was being dismissive: in reality a small reactor suitable for a base wouldn't need much cooling on Mars; after all, we're not talking gigawatt scale plants. So a small set of radiators — sticking up vertically, angled perpendicular to the path of the summer sun — would be plenty. But even that may nor be necessary, you'd use the waste heat for heating the base itself, then the lower grade heat for a greenhouse. At that point, the surface area is probably great enough for the atmosphere to carry the heat away without any special radiators.
[That atmosphere on Mars is annoying. It's too thin to be useful, but thick enough to get in the way. So it can carry enough heat away to make solar heating barely enough to keep greenhouses warm during the day, and at night (and in winter) you'd need loads of extra heating. Mars makes it hard to put up a freakin' greenhouse. And people want to live there.]