There are more than one subjects in the Growtopia Wiki using this name.
Radioactive Bits are consumables added as part of the Gone Fishin'! update that are obtainable from fishing with any bait (excluding the Uranium Glowing Lure) in a nuclear-detonated Uranium Block with a Water on it.
|Tiny Radioactive Bit||50|
|Small Radioactive Bit||25|
|Large Radioactive Bit||10|