Criticality safety review of 21/2-, 10-, and 14-ton UF6 cylinders

The U.S. regulations governing the packaging and transportation of UF6 cylinders are contained in the publication 10CFR71. Under the current 10CFR71 regulations, packages are classified according to Fissile Class I, II, or III and a corresponding transport index (TI). UF6 cylinders designed to contain 2 1/2-tons of UF6 are classified as Fissile Class II packages, with a TI of 5 for the purpose of transportation. The 10-ton UF6 cylinders are classified as Fissile Class I with no TI assigned for transportation. The 14-ton cylinders are not certified for transport with enrichments greater than 1 wt % because they have no approved overpack. This work reviews the suitability of 2 1/2-ton UF6 packages for reclassification as Fissile Class I with a maximum 235U enrichment of 5 wt %. Additionally, the 10- and 14-ton cylinders are reviewed to address a change in maximum 235U enrichment from 4.5 to 5 wt %. Based on this evaluation, the 2 1/2-ton UF6 cylinders meet the 10CFR71 criteria for Fissile Class I packages, and no TI is needed for criticality safety purposes. Similarly, the 10- and 14-ton UF6 packages appear suitable for a maximum enrichment rating change to 5 wt % 235U. (Author)