Not significant. iirc, NASA's nuclear batteries are designed to survive re-entry and the resulting collision, meaning you aren't going to have to deal with vap

Not significant. iirc, NASA's nuclear batteries are designed to survive re-entry and the resulting collision, meaning you aren't going to have to deal with vaporized plutonium in the air, and cleanup in the event of an accident wouldn't be too bad. We are not talking about nuclear reactors here. Only basic nuclear decay. No criticality. The key thing is the packaging, to make sure you aren't contaminating an area when something goes wrong.