operational nuclear reactors have already flown. A flying test bed Convair B36 bomber contained radiation shielding and an operational reactor...they did not power the aircraft but were flying around to see if it could be done.
if you see an image of a B36 bomber with a giant radiation symbol painted on the vertical fin, than that is the one!
also, ideas for nuclear powered train locomotives have been around for along time...also turbine trains.
I even once witnessed a turbine powered auto at a fair back in '64 I think. not a jet pushing the thing like on the salt flats, but hooked up to a transmission like a large lincoln or cadillac.
jon
bring back NERVA