The Kilopower reactor presents far lower radiological risks than RTGs in the event of complete disassembly within Earth's environment.
Pu-238 has a specific activity of 634 billion Bq/g, nearly 8 million times that of the Kilopower reactor's U-235 fuel (80 thousand Bq/g). Once the reactor attains criticality, it produces fission products that have even higher specific activity than Pu-238. But the reactor can remain safely inactive until the risky launch phase is over. There is no way to inactivate the decay of Pu-238 for the launch phase.
The risks of RTG launch are handled by using designs with high mechanical/thermal robustness to encapsulate the plutonium ceramic. I think that they were already safe enough. But the Kilopower reactor is inherently low-radiotoxicity before criticality, which makes it safer yet during the launch phase.
To simplify the other more detailed response, It's just Uranium at that point. Even highly enriched Uranium isn't that radioactive by itself, it's once you start operating the reactor that it starts generating highly radioactive waste.
The new fuel rods going into it are totally safe from a radioactivity perspective. Here's a picture of a man holding a fuel rod bundle with nothing more than gloves on. http://nuclearstreet.com/images/img/dw037.jpg
One can't help but notice from his shirt and his hair that the picture was taken in the 1970s. Lots of awful practices still existed then; who's to say this isn't a picture of that?
At all stages the material can be handled with no more protection than gloves. It is roughly as dangerous as handling lead fishing weights until the fuel actually attains criticality.
I don't know why people downvoted this, it's entirely correct. Although I guess the larger concern than the radiation would be the heavy metal poisoning but in any case it's still fine, just treat it like you would any other heavy metal.
The Soviets launched over 30 satellites with nuclear reactors in the past. The US also launched one. Most of them are still in orbit and I only know of one that scattered nuclear waste all over Canada.
Edit: it looks like there was one launch failure that ended in the reactor dropping into the ocean, and one end-of-life failure that also resulted in the reactor dropping into the ocean. However, normal procedure was to decommission them by boosting into a higher orbit, which means debris and radiation from them has been an ongoing problem for other satellites - i.e. radioactive droplets of sodium coolant.
