USEC PERFORMS SUCCESSFUL ANALYTICAL TESTING OF PADUCAH TIGER OVERPACK

ODUCTION/BACKGROUND USEC performed several finite element analyses (FEAs) of the Paducah Tiger Overpack—the protective overpack used to ship ten-ton, ANSI N14.1 type 48X cylinders containing enriched uranium hexafluoride (UF6)—to supplement the original test data for a renewal application for the package’s certificate. The FEA also was used as a basis to increase the authorized UF6 capacity. During the process, USEC determined that the package would be enhanced by the addition of an aluminum stiffening plate placed inside the overpack in front of the cylinder valve. By adding the plate for extra valve protection, USEC successfully updated a nearly 30-year-old package design. This plate also promoted even distribution of heat across the cylinder head during the 800° C thermal event in spite of the heavy damage within this localized area experienced in the drop test. The Paducah Tiger overpack has been used for nearly 30 years to ship ten-ton UF6 cylinders from the Paducah Gaseous Diffusion Plant to the Portsmouth Gaseous Diffusion Plant. During this time, the Paducah plant operated as the front end of the uranium enrichment process, enriching uranium from the natural assay of 0.711 weight % 235U to approximately 2 weight % 235U, then sending it to Portsmouth to be further enriched to customer specifications. As USEC ceased enrichment operations at the Portsmouth plant in June of 2001, the Paducah Tiger is now used to ship UF6 enriched to 4.5 weight % 235U to the Portsmouth plant for purification and laboratory analysis before the material is delivered to the customer. The Paducah Tiger is certified under the Nuclear Regulatory Commission (NRC) regulation, 10 CFR 71, as a Type A-Fissile package. USEC’s Paducah Tiger overpacks can be shipped by both rail and truck.