People saying that bananas are slightly radioactive was never about highlighting that bananas are particularly radioactive, it's just a coomon example to show that everything is radioactive.

You probably recieve more radiation by being outside for 1 minute than standing next to a million bananas for a month.

Not that it even matters, most of the radiation will be stopped by the air before ever reaching you, and then most of the minute amount that reached you will be stopped by your skin.

Unless you're literally standing next to the demon core, you basically have nothing to worry about.