49 CFR 173.421
Excepted packages for limited quantities of Class 7 (radioactive) materials.
(a) A Class 7 (radioactive) material whose activity per package does not exceed the limits specified in § 173.425 and its packaging are excepted from the specification packaging, marking, labeling and, if not a hazardous substance or hazardous waste, the shipping paper and certification requirements of this subchapter and requirements of this subpart if:
(1) Each package meets the general design requirements of § 173.410;
(2) The radiation level at any point on the external surface of the package does not exceed 0.005 mSv/hour (0.5 mrem/ hour);
(3) The nonfixed (removable) radioactive surface contamination on the external surface of the package does not exceed the limits specified in § 173.443(a);
(4) The outside of the inner packaging or, if there is no inner packaging, the outside of the packaging itself bears the marking “Radioactive”;
(5) Except as provided in § 173.426, the package does not contain more than 15 grams of uranium-235; and
(6) The material is otherwise prepared for shipment as specified in accordance with § 173.422.
(b) A limited quantity of Class 7 (radioactive) material that is a hazardous substance or a hazardous waste, is not subject to the provisions in § 172.203(d) or § 172.204(c)(4) of this subchapter.