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Description: Aqueous zirconium fuel processing studies, directed at adapting the hydrofluoric acid process to continuous dissolution-complexing in order to increase the capacity of the ICPP process, resulted in two successful approaches to the complexing-feed adjustment step. Continuous in-line adjustment (conversion of uranium(IV) to uranium(VI) necessary for extraction) was accomplished in one minute or less at approximately 90 deg C; surges of dissolver product from the operating dissolver up to 1.9 times the flow sheet rate did not inhibit the oxidation of the uranium at this temperature. Batchwise mixing in air of dissolver product solution with complexer solution oxidized the uranium within two minutes at 23 deg C or higher. Further studies of continuous zirconium dissolution indicated that precipitation of uranium at the acid inlet can be a problem, probably because of local concentration gradients of free HF, which result in conditions of low uranium solubility. Control of dissolver acid composition by electrical conductance measurement appeared possible due to the linear relationship of conductance with acid concentration. Aluminum alloy dissolution rates in nitric acid were found to vary significantly, depending on the type and amount of alloying agent. Silicon, nickel, and copper in the alloy significantly decreased the dissolution rate. Batch dissolution times for standard test coupons ranged from 14 minutes for a high purity aluminum to 1400 minutes for an alloy containing 2.9 percent silicon. In the electrolytic dissolution of Nichrome in a bench-scale basket dissolver, the substitution of titanium for niobium as the anode basket material significantly reduced the contact resistance. Current interruption due to contact failure was essentially eliminated, and contact resistance on the titanium was sufficiently low that increasing solution resistance due to acid depletion became a major contributor to current decline as dissolution progressed. The indirect solution-contact electrolytic dissolution principle was further studied, producing data on electrode ...
Date: December 28, 1962
Creator: Bower, J.R. ed.
Partner: UNT Libraries Government Documents Department