Radioactive
A radioactive weapon contains unstable radioactive components. When the wielder rolls a natural 1 on an attack roll, she is exposed to dangerous radiation and must succeed at a Fortitude save or be inflicted with radiation sickness. (For radioactive blast weapons, the user must attempt a Fortitude save if any of the attacks are a natural 1). This is considered a low level of radiation. The DCs for this save and the disease are each equal to the weapon’s critical hit DC.
Source
Armory pg. 30
