Argonne National Laboratory Report ANL-6231

9 : : 7 : 7 9 : 5 5 ? 5 9 G -- 8 ; 8 ; = -activity levels of the melt-refining process for EBR-II core fuel was completed. An experiment was also completed on the evolution of fission- product krypton and xenon from an irradiated fuel pim as it was heat to a temperature above the melting point. In tests of alternate materials for use in a meltrefining furnace, a fibrous potassium titanate grain retainer was found to be a very effective heat insulator, but to have less strength than nigid Fibenfrax retainers. The skull remaining in the zirconia crucible after a meltrefining operation must be processed to recover, as partially purified metal, the fissionable material for return to the fuel cycle. Several essentially quantitative reductions of uranium dioxide and skull oxides were achieved in times of less than 8 hr at 800 deg C in dilute magnesium-zinc solutions and in magnesium containing a small percentage (0.5 to 2) of sodium as a wetting agent. Data and equations for solubilities of other elements in liquid cadmium are included. The partition coefficients of a numbsr of representative fissile and fission product elements between the two immiscible liquids, lead and zinc, at about 735 deg C were measured. The free energy of formation of the uraniumthallium intermetallic compound UTl/sub 3/ was measured, using a galvanic cell method. Galvanic cell measurements with the cerium-zinc system at 443 to 742 deg C were also made. The determination of the heat of formation of zirconium tetrafluoride by combustions of zirconium in fluonine was completed. A valus of -372.44 kcal/mole was obtained for the heat of formation of molybdenum hexafluoride. Calorimetric oombustions of boron in fluorine are being continued. Exploratory combustions of magnesium, aluminum, zinc, and cadmium are being carried out. Fuel Cycle Application of Volatility and Fluidization Techniques. Investigation of the stoichiometry of the reaction of plutonium hexafluoride with sulfur tetrafluonide was completed. The investigation of the stoichiometry of the reactions of sulfur tetrailuoride with uranium tnioxide, uranium dioxide, uranyl fluoride, and U/sub 3/O/sub 8/ was also completed. Radiation decomposition of plutoniuna hexafluonide in the presence of uranium hexafluoride at 2.6% per day, was found to be very similar to the value obtained for plutonium hexafluonide alone. In terms of wt.% hydrogen chloride, the solubility of hydrogen chloride in liquid hydrogen fluoride is 0.7 at -38 deg C and 2.4 at -78 deg C. An investigation of the corrosive effsct of hydrogen fluoride-hydrogen chloride gas mixtures on A-nickel has been initiated. Additionai studies of metal fluoninations were concerned with the mechanisms of the nickel-fluonine and nickel-oxygen reactions. Work continued on engineering-scale studies of the Direct Fluorination Process applied to dense uranium dioxide pellet fuel. Decladding runs were made to investigate the effect of close packing of fuel elements on operation of the fluid-bed reactor. Mock-up tests of heat transfer from the surface of fixed packing submenged in a fluid bed were made to determine the effects of bed height and gas velocity. A final dissolution was performed in a series of dissolutions of synthetic fuel assemblies to demonstrate operation of the graphite pilot-plant dissolver. Examination of the walls of the graphite dissolver showed the expected presence of fused salt in the ninddle of the lampblack insulating zone. A fused-salt charge was allowed to freeze in the dissolver to determine the effect that this would have on dissolver components. Extsnsive damage to internal graphite downlines and heaters was found. Reactor Safety. In the continued study of the ignition of uranium it was confirmed that an aggregate or array of pieces ignites at a considerably lower temperature than an individual pices of the same specific area. Continued studies of the effects of halogenated hydroca