Imports of enriched uranium and plutonium require a specific import license from the Nuclear Regulatory Commission (NRC) under 10 CFR Part 110. DOE authorization may also be required depending on the material and end use. IAEA safeguards documentation and export authorization from the country of origin are additional prerequisites for fissile materials.

Actinium-225, actinium-227, californium-253, and several other medically significant isotopes are specifically enumerated under subheading 284442. Other radioactive isotopes and their compounds not elsewhere specified fall under 284443. The specific isotope identity, confirmed by the supplier's certificate of analysis and shipping manifest, determines the correct line.