49 CFR 173.457
Transportation of fissile material, controlled shipments—specific requirements.
Shipments of fissile material packages that have been assigned a transport index of greater than 10 for criticality control purposes in accordance with 10 CFR 71.59 must meet the requirements of this section and § 173.441(a) or (b).
(a) For fissile material, controlled shipments, the offeror or carrier, as appropriate, must incorporate transportation controls which:
(1) Provide nuclear criticality safety;
(2) Protect against loading, storing, or transporting that shipment with any other fissile material; and
(3) Include in the shipping papers the description required by § 172.203(d) of this subchapter.
(b) Fissile material, controlled shipments must be transported:
(1) In an exclusive use conveyance;
(2) Except for shipments by aircraft, in a conveyance with an escort having the capability, equipment, authority, and instructions to provide administrative controls necessary to assure compliance with this section;
(3) In a conveyance containing no other packages of any Class 7 (radioactive) material required to bear one of the labels prescribed in § 172.403 of this subchapter. Specific arrangements must be made between the offeror and the carrier, with instructions to that effect issued with the shipping papers; or
(4) Under any other procedure approved by the Associate Administrator for Hazardous Materials Safety in accordance with part 107 of this subchapter.