Uranium ore is almost entirely U-238, but there is a small fraction of it that is U-235, and radioactive. Some of the mines in northern Saskatchewan have ore so hot that they have to cut it with waste rock for it to be able to go though the mill.
Imagine you are just a dude in a cold place and one day you find a very hot rock. Magic! Is that how the first jacuzzi was invented? Did he just called everyone in the village for a hot bath?
I don't think it's a real weakness, eh? You don't see me moaning and groaning and laying about just because it's nearby. Superman is just acting like a big baby for dramatic effect.
Kryptonite for Kal-El is like radium for John Smith if John Smith was living on an alien planet, the star of which can give him superpowers, unless there's a fragment of radium nearby, draining his powers.
It's quite likely that Superman maintains another identity that would allow him to live something approaching a normal life when he's not performing heroics, and there are quite a few possibilities as to what that identity might be. However, given his vulnerability to Kryptonite, I think we can rule out anyone in a paper-centric profession, such as journalism.