Sorry, I had a brainfart there. You're completely right.

The tube itself emits xrays, but soft xrays have a very high chance of being absorbed by Carbon, Nitrogen and Oxygen. And since that's mostly what makes up a human, that's kinda bad.

Also he's digging up diamonds, which is in rocks full of radioactive materials. Diamond mine tailings are famously radioactive (and interesting) due all the thorium and radium in them.