CHEMICAL PROCESSING TECHNOLOGY QUARTERLY PROGRESS REPORT, APRIL-JUNE 1961

Abstract

The Idaho Chemical Processing Plant did not operate on fuel recovery during this period, due to extensive renovation and modiflcation of facilities. Potasslum fluoride was found to be an undesirable additive to the barium precipitating agent used in formation of barium fluozirconate, because of precipitation and loss of uranium, although essentially complete precipitation of zirconium was achieved. Addition of hydrofluoric acid with barium precipitant, to achieve a fluoride/zirconium mole ratio of 5.5, was found to give a total zirconium recovery of 05%, including approximately 10% recovered after concentration of the supernate from the original precipitation. Removal of 97% of the zirconium and fluoride from zirconium -uranium dissolver solutions was achieved by precipitation with two moles of sodium formate per mole of zirconium. Uranium was readily recovered from the concentrated filtrate and wash solution by TBP extraction. The preparation and characterization of zirconium nitrate dibutylphosphate are described, and the solubility in Amsco was found to be similar to that of the uranlum dibutylphosphate complex (2 to 4 x 10/sup -5/ M). Stability studies indicated very little, if any, oxidation of ferrous to ferric iron ln a normal raffinate environment, and ferrous iron has a very low molar extinction coefficsent (0.8) compared with that of uranium (15) in the spectral region near 415 m mu . Pilot plant studies of the fluidized-bed calcination process for reduction of radioactive liquld wastes to the more-easily-stored solid form was continued in the two-foot-square calciner with production, for the first time over a prolonged period of continuous operation, of alpha alumina-free product from a feed contalning substantial sodium. Intra-particle porosities ranging from 0.04 to 0.60 were obtained. Differences in alpha-forming tendency of amorphous aluminas with varied calcination histories were demonstrated but attempts at correlation with known variables in fluid bed calciner operation were not successful. Rapid (< 5 minutes) precipitation of zirconium, fluoride, and aluminum was achieved by addition of calcium oxide (CaO/F ratio = 1.5) as a slurry at 60 deg C. The second and third runs in the Demonstrational Waste Calcining Facility were conducted. Addltional studies on removal of long-lived radioisotopes from waste solutions indicated that strontium can be removed from relatively acidic solutions (up to lM) by absorption on Amberlite 200 cation exchange resin. A study of the anodic potential-current density relationships during the eIectrolytic dlssolutlon of type 304 stainless steel, undertaken to deflne optimum operating conditions, revealed that at a temperature of 60 deg C or higher, anode operation was practical over a wide range of solution compositions (1 to 10M acid) and high current densities (up to 2 amp/cm/sup 2/), since passivation, limiting current density, and gas evolution were avoided. A new technique in electrolytic dissolution was demonstrated. The metal to be dissolved is placed in a tubular dissolver through which an acid dissolving solution is passed; electrodes, not in direct contact with the metal but immersed in the electrolyte, are located at the ends of the dissolver. A series of electrolytic cells is formed within the dissolver. Dissolution rates of 2.5 mg/cm/sup 2//min at current efflciencies of 1000% were demonstrated for stainless steel. Titanium and niobium test coupons were resistant to corroslon in locations in an operating electrolytic dissolver where stainless-steel specimens were rapldly destroyed. Plastic specimens, which had prevlously been shown to be reslstant to the chemlcal envlronment in an electrolytic dissoIver, were exposed to gamma irradiation (up to 10/sup 9/ R) while exposed to the dissolver solution; only polyethylene, in this group, adequately reslsted the comblned radiation and chemical conditions to warrant further testing as a possible insulating and supporting material for dlssolver construction.