Is storage of uranium hexafluoride safe?
The advanced age of some of the steel cylinders in which the depleted UF6 is contained, and the way in which the cylinders were stored (sometimes too close together to permit inspection, and sometimes in direct contact with the ground, due to settlement of cylinders, leading to enhanced cylinder corrosion) have created a potential environmental and safety hazard. While depleted UF6 does not present as significant a radiological hazard as other radioactive materials, it is a potential chemical hazard if not properly managed.
In October 1992, the Ohio Environmental Protection Agency (OEPA) issued a Resource Conservation and Recovery Act (RCRA) Notice of Violation to the Portsmouth Gaseous Diffusion Plant. The Notice of Violation stated that the OEPA had determined depleted UF6 to be a solid waste, and that the Department had violated Ohio laws and regulations by not evaluating whether such waste was hazardous. The Department differed with this assessment, and in February 1998, reached an agreement with OEPA, which defers RCRA characterization of depleted UF6 stored at the Portsmouth Plant until 2008, as long as the Department complies with a Depleted UF6 Management Plan as agreed to by OEPA and makes good faith efforts to evaluate potential use or reuse of the depleted UF6.
The State of Tennessee raised nearly identical RCRA issues in 1997 regarding depleted UF6 stored at the East Tennessee Technology Park (ETTP) near Oak Ridge. A negotiated settlement resulted in a consent order issued by the Tennessee Department of Environment and Conservation on February 8, 1999. Among other things, the order requires conversion of all depleted UF6 stored at the ETTP, or removal of the storage cylinders from the State by December 31, 2009.
Following the OEPA Notice of Violation in 1992, the Department took the initiative to reevaluate its long-term strategy for managing the DUF6 inventory. In 1994, work began on the Programmatic Environmental Impact Statement for Alternative Strategies for the Long-Term Management and Use of Depleted Uranium Hexafluoride (DOE/EIS-0269, April 1999). In 1995, the Department also began an aggressive program to better manage the aging depleted UF6 cylinders. In part, this program responded to the Defense Nuclear Facilities Safety Board (DNFSB) Recommendation 95-1, Safety of Cylinders Containing Depleted Uranium, which DOE fully accepted. Included were more rigorous and frequent inspections, painting and refurbishing of cylinders, and construction of concrete-pad cylinder yards. The results of the analysis in the PEIS indicated that continued cylinder storage is safe if the current surveillance and maintenance activities are continued. The Cylinder Management program's implementation has been successful, and as a result, on December 16, 1999, the DNFSB closed out Recommendation 95-1.
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