Uranium hexafluoride (UF6) is synonymous with the nuclear industry as the basis for both the gaseous diffusion and gas centrifuge enrichment processes. The U.S. Department of Energy currently maintains approximately 57,000 cylinders containing a total of almost 700,000 metric tons of depleted UF6. Of special concern is the reaction of UF6 with water due to the corrosion caused by the hydrogen fluoride (HF) produced, which can significantly degrade the tanks commonly used for storage. Additionally, UF6 is highly toxic, and the thermochemistry of its hydrolysis is important to the environmental pathways of any accidentally released UF6.

This presentation will summarize results of a search for transitions states of the direct UF6-water gas-phase hydrolysis reaction using Density Functional Theory and small-core, relativistic pseudopotentials. No symmetric transition state leading to the direct formation of uranium oxide tetrafluoride, UOF4, was found, indicating that the gas-phase hydrolysis includes more steps than commonly mentioned mechanisms. One asymmetric transition state was found, and this appears to be the first published transition state for the important gas-phase reaction of UF6 with water.