First I want to say thank you for creating Krastorio 2, I'm really enjoying it!
I usually run around with 2 MK4 shield generators, plus some uranium fuel cells. The shield generators are strong enough that they cancel out the radiation damage from the uranium fuel cells. However, if I pick up half of the fuel cells into my hand, or put half of the fuel cells in my trash slots, I start taking damage. It looks like I'm taking double damage, once for the radioactive item in my inventory, and again for the radioactive item in my hand/trash slots. It is noticeable because the double damage causes my life to drain faster than the 2 MK4 shield generators can keep up with.
Ideally moving items between hand/inventory/trash slots wouldn't change how much radioactive damage is taken.