CONTINUOUS PROCESSES FOR THE DIRECT REDUCTION OF URANIUM HEXAFLUORIDE TO URANIUM TETRAFLUORIDE OF HIGH PURITY AND DENSITY

Technical Report · Fri Oct 31 00:00:00 EST 1958

OSTI ID:4309039

Smiley, S H; Brater, D C

Contrary to the published literature, the single-step reduction of uranium hexafluoride to uranium tetrafluoride with hydrogen was found to be quantitative; ous process, both safe and economical, was developed and adapted for large-scale production use. The uranium tetrafluoride product was of high density and purity. The basoc hydrogen reduction method is actually uncomplicated; uranium hexafluoride and about 100% excess hydrogen both preheated to approximately 500 deg F, are charged into the top of a vertical pipe reactor which is heated to about 1000 deg F, and complete reduction to uranium tetrafluoride is realized almost instantaneously. The uranium tetrafluoride, having a packed density of 220 lb/ft/sup 3/ (3.5 g/cc) and an impurity content of 30 to 50 ppm, is collected in a hopper at the bottom of the pipe. The gaseous products are passed through a metallic filter to remove entrained solids, and pure anhydrous hydrogen fluoride is recovered as a reaction by-product. The only operating difficulty noted is that slow accumultion of fused uranium fluorides. UF/sub 5/, U/sub 2/P/sub 9/, and U/sub 4/F/sub 9/, on the hot reactor walls nece ssitates periodic deslagging of the unit; however, where large quantities of low assay materials are required and relatively large equipment can be used, the loss in operating time is small. The significance of the development of the hydrogen reduction method is best realized by comparing it to existing wet processing schemes. Feasibility studies showed that the latter methods were both economically and operationally unattractive for handing large quantities of uranium hexafluoride. Bulky equipment built to withstand corrosion from aqueous hydrogen fluoride solutions as well as expensive precipitators. filters, dryers, and converters for the required multiplicity of operation. made costs prohibitive. Some modification of the ''hot wall'' method was necessary to process higher assay uranium hexafluoride. Since the equipment must be small to meet criticality dimensional requirments, and opportunities for loss of uranium must be minimized, slagging of the reactor became a serious problem. It was found that the solid deposits could be eliminated entirely if fluorine was added to the uranium hexafluoride stream and the reactor walls were maintained at low temperaure i.e., about 300 deg F. The highly exothermic reaction of the fluroine with hydrogen supplied the energy required to initiate and sustain the reduction, and the major pontion of the reaction appeared to take place in a narrow flame directly below the gas nozzles. The solid product did not stick to the cool ffaotor walls, and a reliable correlation between the uranium tetrafluoride density and the amount of fluorine added was established. A process to reduce uranium hexafluoride with gaseous trichloroethylens was also developed. Complete conversion to uranium tetrafluoride was realized, but under most condition the product was low in density and highly contaminated with the organic by-products; thus,additional treatment was required to make an acceptable material. Pure uranium tetrafluoride could be obtained directly by this method, however, if the stream containing uranium hexafluoride was very dilute. i.e., about 1% uranium hexafluoride in nitrogen Complete reduction of uranium hexafluoride was also possible with liquid trichloroethylene in a spray column, but it was difficult to separate the solid product from the liquid. (auth)

• Research Organization: Oak Ridge Gaseous Diffusion Plant, Tenn.
• NSA Number: NSA-12-014731
• OSTI ID: 4309039
• Report Number(s): A/CONF.15/P/523
• Resource Relation: Other Information: Prepared for the Second U.N. International Conference on the Peaceful Uses of Atomic Energy, 1958. Orig. Receipt Date: 31-DEC-58
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

CHEMISTRY
ADHESION
CHEMICAL REACTIONS
COMBUSTION
CONFIGURATION
CORROSION PROTECTION
CRITICALITY
CYLINDERS
DENSITY
ECONOMICS
EFFICIENCY
ETHYLENE
EVAPORATION
FILTERS
FLUORINE
FUSED SALTS
GASES
HEATING
HIGH TEMPERATURE
HYDROFLUORIC ACID
HYDROGEN
IMPURITIES
LIQUIDS
LOSSES
MAINTENANCE
METALS
NITROGEN
NOZZLES
OPERATION
ORGANIC CHLORINE COMPOUNDS
PREPARATION
PRODUCTION
QUANTITY RATIO
RADIOCHEMISTRY
RECOVERY
REDUCTION
SAFETY
SEPARATION PROCESSES
SOLIDS
SOLUTIONS
SPRAY COLUMN
SURFACES
TEMPERATURE
TRACE AMOUNTS
URANIUM FLUORIDES
URANIUM HEXAFLUORIDE
URANIUM TETRAFLUORIDE
WATER