It's fine, both of the last two US Rovers are powered off RTGs and several of the deep space probes run off RTGs also. For low Earth orbit and stuff closer to the sun it doesn't make sense but going further out and especially in a place like Mars where solar panels are prone to being covered in dust an RTG power source makes sense.
European Space Agency
The European Space Agency community
Exactly, for its intended use, it's really the best option we have.
Don't worry too much about it: it's not the 80s and we're not the Soviets.
Once it's in orbit it doesn't matter and if there's issues during ascent the source will be hardened to prevent catastrophic release.
Realistically though, just send it up on a falcon 9, the track record on those things is _ astounding_.
Outside an atmosphere like Earth's, everything is already exposed to intense ionizing radiation from the sun/stars. A bit more from an RTG, even a big one, is a drop in the ocean. If we found signs of extraterrestrial life, then we'd want to be extra cautious about not sterilizing by accident, but that's not currently a major concern. And of course, any sort of nuclear rocket propulsion would need to be handed with utmost care, but it's also not a major issue once it's outside the atmosphere.