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Development of the Process for the Recovery and Conversion of 233UF6 Chemisorbed in NaF Traps from the Molten Salt Reactor Remediation Project

Guillermo D. Del Cul, Alan S. Icenhour, Darrell W. Simmons

Nuclear Technology

Volume 136 / Number 1 / October 2001 / Pages 89-98


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The Molten Salt Reactor Experiment (MSRE) site at Oak Ridge National Laboratory is being cleaned up and remediated. The removal of ~37 kg of fissile 233U is the main activity. Of that inventory, ~23 kg has already been removed as UF6 from the piping system and chemisorbed in 25 NaF traps. This material is in temporary storage while it awaits conversion to a stable oxide. The planned recovery of ~11 kg of uranium from the fuel salt will generate another 15 to 19 NaF traps. The remaining 2 to 3 kg of uranium are present in activated charcoal beds, which are also scheduled to be removed from the reactor site. Since all of these materials (NaF traps and the uranium-laden charcoal) are not suitable for long-term storage, they will be converted to a uranium oxide (U3O8), which is suitable for long-term storage.

The conversion of the MSRE material into an oxide presents unique problems, such as criticality concerns, a large radiation field caused by the daughters of 232U (an impurity isotope in the 233U), and the possible spread of the high-radiation field from the release of 220Rn gas. To overcome these problems, a novel process was conceived and developed. This process was specially tailored for providing remote operations inside a hot cell while maintaining full containment at all times to avoid the spread of contamination. This process satisfies criticality concerns, maximizes the recovery of uranium, minimizes any radiation exposure to operators, and keeps waste disposal to a minimum.

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