TRANSPORTATION OF ENRICHED REPROCESSED URANIUM

In the last few years the volume of enriched reprocessed Uranium (RepU) transportation increased considerably and became an important issue. While the transport of enriched commercial grade Uranium is standard practice since decades the transport of RepU presents new challenges. Reprocessed Uranium is specified in ASTM C 996 [1]. The limits given there for fission products and actinides are sufficiently low, however the limit specified for 232U of 0.05 µg/gU leads to considerable consequences. The A2?values of 232U and its decay product 228Th are rather small and a concentration of roughly 1 % of the limit specified in ASTM C 996 will exceed the radioactivity allowed in type A packages which are used for the transport of commercial grade Uranium. A possible solution to this problem could be the declaration of RepU as LSA?II and the use of IP?2 packages containing fissile material. However, in some countries it is not allowed to approve IP?2 packages for fissile material. Hence, the consequence is to use a type B(U)F package. A further problem is the decay of the aforementioned 232U. In the decay chain there are nuclides with a high gamma yield at high energies, especially the nuclide 208Tl. The gamma source intensity of fresh RepU increases in one year by a factor of roughly 200, in 2 years by a factor of 350, and in 10 years by a factor of 600! This phenomenon is treated quite differently by different competent authorities. One certificate of package approval contains a rather restrictive limit for 232U which ensures that the limits for the dose rates are kept at all times. Other certificates specify no limit for 232U or restrict the time between reprocessing/ enrichment and transport. In this case, even if the limit given in ASTM C 996 is not exceeded, the dose rates might exceed the limits specified in the Regulations by a factor of up to 3. This paper will illustrate the challenges mentioned and discuss the consequences for transportation of RepU. Key words: reprocessed Uranium, transport of UF6, shielding analysis