Chemical exchange reactions for the separation of the principal uranium isotopes have been investigated for systems consisting of uranium hexafluoride and nitrogen oxide-derived complexes of uranium hexafluoride.nThese exchange reactions were found to be impractically slow, but when they were catalyzed by HF, equilibrium time was reduced from about 100 hours to less than 2 hours. This led to an approach based on contacting two-phase immiscible solvent systems. The most promising system consisted of NOUF6 dissolved in HF, a polar ionizing solvent that catalyzes the exchange, and UF6 dissolved in Freon-114 (C2F4C12). This system yielded a 235U/238U single stage separation factor of 1.0016 at 25°C after one hour of contact time. 235U enrichment was always observed in the heavier (Freon-114) UF6-containing phase. The system was investigated further in a column-type operation to determine how well it might operate in a large scale operation. This work was discontinued when difficulties were encountered in adapting the system to multi-stage operation or cascading. No efficient economic means could be found for interconverting NOUF6 and UF6 in their respective solvents and the work was discontinued.
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