Chemical Processing Technology Quarterly Progress Report, April-June 1962

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 determination of dissolution rates over a wide range of conditions. The addition of oxidants to 4.8M hydrofluoric acid used for the continuous dissolution of 3% uranium-Zircaloy- 2 fuel decreased the amount of uranium-containing residue in the dissolver at the expense of a decreased dissolution rate. Oxidized fuel was dissolved in 4.8M hydrofluoric acid by use of heat to initiate the reaction: the oxide film remained behind as a dissolver residue. Uranium in the dissolver product was oxidized to the extractable form by one minute treatment at 92 deg C with aluminum nitrate complexer solution: only 59% was extractable after 24-hour treatment at room temperature. Several hundred hours operation of a continuous bench scale unit indicated that uranium buildup should not be a problem in the dissolver since an apparent equilibrium was soon established. After 650 hours of operation, a Monel dissolver showed some signs of localized corrosion but exhibited generally good resistance. Preliminary results in a study of aluminum alloy dissolution rates, initiated because of unusually slow dissolution of certain aluminum-based fuel elements, showed that nickel and copper ions in solution significantly retarded the dissolution rate while iron had an accelerating effect. Examination of specimens from the permanent ICPP raffinate storage tanks for aluminum process wastes indicated negligibie corrosion to date. Electrolytic dissolution studies progressed to a bench scale basket-type dissolver operating at currents up to 500 amperes with Nichrome fuel. Sudden current failures were essentially eliminated by use of platinum liners and a canted dissolver basket, but sustained operation was not attained because of a gradual decline in current as dissolution caused recession of the contact points on the dissolving rods. An in-line solution analyzer for nitric acid and Nichrome salt concentrations in the dissolver effluent operated satisfactorily. Additional supporting studies include measurement of certain dissoiver solution physical properties, comparison of cathode potential measurements with laboratory data on corrosion rates, determination of polarization resistance of platinum in nitric acid, and continued investigation of the effect of irradiation on electrolytic dissolver insulator components. Operation of the Demonstrational Waste Calcining Facility for 1050 hours during this period, under three different experimental conditions, demonstrated that the facility can be continuously operated in a routine manner and that the solids loading in the cyclone and scrubbing sections can be reduced to, and controlled at, satisfactory levels. Preparations are being made for a run with a sodium-24 spike to the feed to evaluate the final off-gas decontamination equipment prior to operation with high- level wastes. Supplemental pilot plant and laboratory studies include use of sand to control bed particle size, investigation of the role of boric acid and phosphoric acid in control of alumina crystal form, and exploratory studies on the nature of the products of calcination of stainless steel and Nichrome nitrates. Additional studies on an experimental air pulser showed good agreement between experimental data, analog simulation, and an approximate linear solution which can be studied by hand calculation methods. Further studies on the removal of tributyl phosphate and its decomposition products from dilute aqueous streams indicate that phosphorus species from plant solutions may be absorbed by, and eluted from, hydrous zirconium oxide. (auth