Large UF6 Cylinder Cleaning and Maintenance

Worldwide, commercial quantities of UF6 are stored and shipped in special steel cylinders of primarily 30 inch and 48 inch diameter. In order to maintain the integrity credentials required for continued use as a transportation container, each of these cylinders must be washed and recertified every five years. A small residue of UF6, called a “heel” is first washed from the cylinder then a series of physical tests designed to demonstrate the integrity of the cylinder is performed. Successful completion of the physical testing “re-certifies” the cylinder for five additional years of service. The washing and re-certification tasks are usually performed as an ancillary effort at uranium UF6 fabricators, enrichment plants or conversion plants. Often the process is looked upon as a necessary nuisance by those performing the work. DAHER-TLI, however, is currently developing what is believed to be the first of its kind stand-alone cylinder washing and recertification facility. At first it will process only 48 series cylinders containing less than 1% 235U UF6. The process is unique in that extra steps are taken to remove internal scale from the inner cylinder walls. A newly developed three-step uranium recovery process for the wash solutions produced during the cylinder washing is also featured. A high-purity uranium by-product results from this work. Recertification of each cylinder follows the washing and uranium recovery. Options to dispose of retired cylinders are mentioned.