It's very easy mix in radioactive materials with conventional explosives to make a dirty bomb... provided you have access to radioactive materials. You put nuclear reactors in cargo ships, anyone that can board and commandeer a cargo ship now has access to radioactive materials and therefore the capability building a dirty bomb.

There’s an R^2 drop off as you travel away from the sun. Sure if you're going to Saturn, solar isn't going to work well. We already use nuclear batteries for those missions, but it's some butt clenching with that because if the rocket goes boom instead of getting to space (which happens sometimes) it would spread some radioactive material around.

But it's going to be a long time before we're building space stations beyond Mars (it'll be a long time before we go beyond the Moon the way things are going) so it's going to be solar power for most space things other than the odd probe we send to the outer planets.