Glow discharge and atmospheric pressure plasma processes have been studied in applications for decontamination of plutonium (Pu) and uranium (U) contaminated objects. In these processes, U or Pu contamination on objects such as gloveboxes are converted to a volatile metal hexafluoride which can be pumped away leaving the object free of contaminants. It appears feasible to apply this technology to recovering spent fuel without the large waste by-products of present wet chemistry processes. The plasma etch rates are rapid in bulk but are eventually quenched in the decontamination process as non-volatile chemical products build up on or near the contaminated surface. A pulsed plasma system has been proposed that reduces or eliminates the quenching action while continually exposing new bulk U material in the spent fuel. There are several advantages of plasma reprocessing over existing aqueous acid- or flame-based methods: 1) plasma is a dry process in which no liquid wastes are generated, 2) plasma is a fast process in which reactive species produced in the plasma increase reaction rates significantly over chemical processes, 3) plasma is a low temperature process whereby the electron temperature is high but the ion temperature is low thereby eliminating serious material issues observed in flame-based techniques while preserving the high electron energies needed to break chemical bonds, 4) the plasma method does not rely on stoichiometric mixtures of U and the reactive ion since the acceleration energy in the plasma sheath can easily break chemical bonds, and 5) plasma is a safe and reliable process because toxic chemicals in wet chemistry (e.g., F_2) can be replaced with nontoxic and relatively inexpensive CF_4 or NF_3 source gases. The application of a plasma process to recycling spent fuel would significantly reduce the amount of waste generated while reducing the cost of reprocessing.
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