These ships can be found guarding Sapiens stations. They have a radioactive weapon, and radiation-immune armor.
These ships aren't particularly strong, except for their radioactive weapon. You can only be irradiated if you have armor that isn't radiation-immune, and your armor gets hit by the weapon (i.e. shield is down or no shield and you get hit).
Note: These ships leave radioactive wrecks. Don't dock with them unless you have radiation-immune armor, or your ship will be irradiated, regardless of whether your shields are up or not.