I seem to be immune to radiation (from one source of uranium) when wearing power armor MK2 with a regular shield generator (MK1; the green one), but not with any of the other higher tiered shield generators.

I took a look at the code: 7.25 base damage plus 8% of the max shield (8% of 200) = 23.25 damage which gets lowered by 4 and reduced by 45% by the armor (= 10.5875 damage), which is lower than the shield recharge rate of 12/s of the shield generator.

Higher tiered shield generators have higher max shield (150; 200; 300), so the damage is higher (19.25; 23.25; 31.25), but their recharge rate isn't increased as much (12; 13.5; 16.2).

Is this intended? It doesn't seem very logical that the better your shields are, the more damage you take... And it will kill you faster after the shields run out?

TL;DR:
Power armor MK2 + Shield MK1 + Uranium = no damage
Power armor MK2 + Shield MK2 + Uranium = damage?
Power armor MK2 + Shield MK3 + Uranium = more damage??
Power armor MK2 + Shield MK4 + Uranium = lots of damage???

Thanks for the report, I will fix it in the next version.
Pratically the damage to the shield are done in percentage, but in the case of the shield mk1, the ratio for recharing rate is more than the damages received.