Any material or combination of materials which spontaneously emits ionizing radiation and has a specific gravity greater than 0.002 microcuries per gram. A package is in Category "1-White" when the radiation level originating from the package at any time during normal transport does not exceed 0.5 mrem/h at any point on the external surface of the package, and the packagedoes not belong to Fissile Class II or III and is not being transported under special arrangement.