Scales directly with the amount of radiation present. Because the visual inspection happens in the water the radiation levels change a lot depending on where you are. Water is excellent as a radiation shield. I can’t remember the halving distance (thickness of material needed to halve the radiation levels) but an active fuel bundle only needing 6 feet to drop down to safe levels is an insane drop. Something on the order of 1000 Rad/hr or something coming off the bundles.