49 CFR § 173.416 - Authorized Type B packages.
Each of the following packages is authorized for shipment of quantities exceeding A1 or A2, as appropriate:
(a) Any Type B(U) or Type B(M) packaging that meets the applicable requirements of 10 CFR part 71 and that has been approved by the U.S. Nuclear Regulatory Commission may be shipped pursuant to § 173.471.
(b) Any Type B(U) or B(M) packaging that meets the applicable requirements in “IAEA Regulations for the Safe Transport of Radioactive Material, SSR-6” (IBR, see § 171.7 of this subchapter) and for which the foreign Competent Authority Certificate has been revalidated by DOT pursuant to § 173.473. These packagings are authorized only for export and import shipments.
(c) A package approved by the U.S. Nuclear Regulatory Commission under a special package authorization granted in accordance with 10 CFR 71.41(d) provided it is offered only for domestic transportation in accordance with the requirements in § 173.471(b) and (c).