RADIANT-HEAT SPRAY-CALCINATION PROCESS FOR THE SOLID FIXATION OF RADIOACTIVE WASTE. PART I. NONRADIOACTIVE PILOT UNIT

Technical Report · Wed Feb 01 04:00:00 EST 1961

OSTI ID:4838291

Allemann, R T; Johnson, Jr, B M

The spray calcination of simulated wastes was studied in a relatively small scale reactor 8 in. in diameter and 10 ft tall. A wide variety of compositions were handled without difficulty, including wastes generated by TBP- 25, Darex, and Zirflex processes as well as many possible compositions of acidic and neutralized, high-level Purex wastes. The product characteristics, such as particle size and density, varied somewhat with the feed composition. The powder, made up of flakes of exploded droplets, was generaily rather fine, and as much as 95% could pass through 325-mesh screen. Density of the powder ranged from 0.12 g/cc for aluminum nitrate-type waste to 1.2 g/cc for Purex waste adjusted in composition by the addition of sugar and phosphoric acid. Considerable attention has been given to the use of additives to increase the bulk density of the powder product, to form a powder which subsequently can be melted into a consolidated solid for final storage, and to promote more complete calcination of the powder during its short residence time in the reactor. When phosphoric acid was added to simulated Purex acidic waste, the resultant product melted at 800 to 900 deg C. The properties of calcined powder also were altered; bulk density was increased roughly from 0.5 to 0.85 g/cc; and the surface area average particle size was more than doubled. The addition of other anions, such as sulfate and borate, was studied. Boric acid or sodium tetraborate may be added to wastes containing considerable aluminum to produce true glass matrices on calcination and fusion. The bulk density of calcined powder from an aluminum nitrate-type waste was increased from 0.12 to 0.7 g/cc by the addition of sodium tetraborate. Sugar is a useful additive for a number of reasons. First used to promote melting of particles of phosphnte-treated feed during their residence in the reactor, it was also used to decompose sodium nitrate and unstable ferric and aluminum sulfates, and to neutralize excess sodium hydroxide in more feed compositions. Thermal conductivity of the powder product was low, ranging from 0.05 to 0.135 Btu/ (hr)(ft/sup 2/)( deg F/ft) over temperatures of 100 to 400 deg F, and was primarily dependent on density rather than composition. Melting and consolidating the product greatly increased the conductivity, to the vicinity of 0.6 Btu/(hr)(ft/sup 2/)( deg F/ft) for borate-type glasses, for example. The extent of calcination was not greatly affected by the feed rate up to 4 gph. It generally decreased slightly except with feeds adjusted by the addition of sugar. Calcination increased at higher feed rates. Short-duration corrosion tests of the spray calciner with typical Purex calcination conditions indicated good resistance for two possible construction materials---Inconel and AISI 446 SS. Porous metal filters were used most successfully for separation of the powder and gas, but corrosion may limit their applicability and necessitate the use of ceramic elements. Cyclones were not very successful in the small unit but may be applicable on a larger scale. With porous metal filters, de-entrainment factors of 10/sup 4/ and 10/sup 8/ from the feed to the condensate and the off-gases, respectively, were measured. Ruthenium and cesium volatilization was less than 2% with both acidic and basic feed liquors, as measured by including in the feed augmented quantities of inactive isotopes of each element. The temperature profile of a radial cross section of the reactor (below a 2-ft nozzle zone) was absolutely flat within limits of measurement. This fact, and measurements of the degree of turbulence within the reactor, indicated that scaleup of the unit to a 2 1/2-ft-diameter unit, for example, probably is feasible without a marked decrease in volumetric capacity. (auth)

• Research Organization: General Electric Co. Hanford Atomic Products Operation, Richland, Wash.
• DOE Contract Number: AT(45-1)-1350
• NSA Number: NSA-15-030303
• OSTI ID: 4838291
• Report Number(s): HW-65806(Pt.I)
• Country of Publication: United States
• Language: English

Related Subjects

ALUMINUM NITRATES
ALUMINUM SULFATES
BORATES
CALCINATION
CERAMICS
CESIUM
CORROSION
CYCLONE SEPARATORS
DECOMPOSITION
DENSITY
FILTERS
GLASS
IRON SULFATES
MELTING
NICKEL ALLOYS
PHOSPHORIC ACID
POROSITY
POWDERS
PUREX PROCESS
RUTHENIUM
SODIUM NITRATES
SUGARS
SULFATES
SURFACES
TEMPERATURE
THERMAL CONDUCTIVITY
TURBULENCE
VOLATILITY
WASTE DISPOSAL AND PROCESSING
WASTE PROCESSING