Characterization of Depleted Uranium Hexafluoride Cylinders for Packaging and Transport in the Future

It is well known that the International Atomic Energy Agency (IAEA) has amended its safety series with a new name and included new thermal protection requirements for international shipment of non-fissile and fissile-exempt packages of uranium hexafluoride (UF6). Currently, only fissile packages of UF6 require this thermal protection. There will be a significant economic impact on the domestic UF6 industry should the Department of Transportation (DOT) adopt verbatim IAEA requirements for domestic shipments. As it is anticipated that these more conservative requirements and question their technical basis. The applicable standards currently referenced by TITe 49 of the code of Federal Regulations (49 CFR) [1] include the American National Standards Institute (ANSI) N14.1 (1990, 1987, 1982, 1971) Packaging of Uranium Hexafluoride for Transport [2], American Society of Mechanical Engineers (ASME) Section VII Code for Unfired Pressure Vessels [3], and Department of Energy (DOE) Report ORO-651, (latest revisions have been changed to USEC-651) Uranium Hexafluoride, A Manual of Good Handling Practices [4], a non-regulatory document. These documents are quite extensive covering all areas of UF6 management as well as overlap in several areas creating an inconsistency in standards. Much of this inconsistency is a result of non-uniform conservatism already built into multiple standards applicable to the safe management of UF6 and the blanket application of rigorous conservatism to all phases of UF6 management. This paper will address the apparent inconsistencies between two specific transportation and use requirements: fill limit and wall thickness. At this time, the subject documents do not distinguish any differences in requirements for handling, transporting or storing UF6 cylinders. The paper will also summarize recent investigations regarding the ASME Code calculations for specifications of UF6 cylinders under various conditions of handling which will provide evidence on the extent and degree of conservatism.