Yes you are totally overestimating the risks of that.
Yes it would be risky to take the lens through airport security. The X-ray machine could malfunction and fry your balls. Or the guy inspecting your bag could drop your lens. He may also say "I dont give a shit that you can ask (require) us to hand inspect your film, I'm gonna X-ray it" and fog your film.
Yes, I have no idea if the FD 55F1.2 is radioactive, but I SERIOUSLY doubt it. This lens was made LONG after non-radioactive glass and clear-non-glass-solids (plastics and synthetic minerals) were developed.