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Have there been accidents involving uranium hexafluoride?

There have been several accidents involving uranium hexafluoride in the United States. Summaries of the larger accidents are given in the following paragraphs.

In 1944, a research and development pilot plant for thermal diffusion was temporarily shut down for piping modifications. During reactivation of the plant, a weld ruptured on an 8-ft long cylinder containing gaseous natural UF6 that was being heated by steam. An estimated 400 lb of UF6 was released, which reacted with steam from the process and created HF and uranyl fluoride. This accident resulted in two deaths from HF inhalation and three individuals seriously injured from both HF inhalation and uranium toxicity. The injured individuals eventually recovered, and a follow-up many years later showed no evidence of lasting kidney damage from the uranium exposure.

In 1978 a cylinder containing liquid depleted UF6 was accidentally dropped and ruptured in a storage yard at the Portsmouth Gaseous Diffusion Plant. Cold weather limited the dispersion of the UF6. Cleanup efforts were conducted to collect as much of the released material as possible. No one was injured in this accident. (Note: Storage cylinders contain liquid UF6 only for a few days immediately after filling. Once the cylinder cools the UF6 is a solid and would be released much more slowly if an accident resulted in cylinder rupture).

Another UF6 accident involving a cylinder rupture occurred at a commercial uranium conversion facility (Sequoyah Fuels Corp., Gore OK) in 1986. The accident occurred when an over-loaded shipping cylinder was reheated to remove an excess of UF6. The cylinder ruptured, releasing a dense cloud of UF6 and its reaction products. This accident resulted in the death of one individual from HF inhalation. An additional 31 workers were exposed to the released cloud. Although some of the more highly exposed workers showed evidence of short-term kidney damage (e.g., protein in the urine), none of these workers had lasting kidney toxicity from the uranium exposure.

In addition to these accidents, ten depleted UF6 cylinders containing solid UF6 in storage have been breached over the past 45 years. Most of the breaches were due to corrosion around dents caused by mishandling, with the others due to corrosion around welding defects or from external corrosion alone. Additional information concerning cylinder breaches can be found under the question "What happens if a cylinder of uranium hexafluoride leaks?"

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