Thorium oxide powder properties which are important to ThO/sub 2/ and ThO/sub 2/--UO/sub 2/ fuel pellet fabrication (LWBR development program)

Technical Report · Thu Jan 01 04:00:00 EST 1976

OSTI ID:7257833

Clayton, J C

Some key thoria property characteristics as well as critical processing conditions both subsequent and prior to ThO/sub 2/ powder preparation were evaluated with respect to the fabrication of thoria pellets. The monocrystalline thorium oxalate precipitates retained their external plate shape on conversion to polycrystalline ThO/sub 2/ particles by calcining, with porosity located at the boundaries of the microcrystalline ThO/sub 2/ grains. This internal porosity rendered the oxide friable and readily comminuted by micronizing. Upon calcining at higher temperatures or for longer times, the internal porosity gradually sintered out as the ThO/sub 2/ grains grew within each particle decreasing the powder surface area and increasing the particle strength, thus resulting in ThO/sub 2/ powder less tractable to comminution. An equation is given that relates the thoria powder specific surface to the calcination conditions. Because of the high adsorptive capacity of ThO/sub 2/ powders for CO/sub 2/, the surfaces of the particles and their internal pores become coated with almost a complete monolayer of CO/sub 2/ upon exposure to air at room temperature. Other impurities, termed intrinsic, are incorporated within the particle during thorium oxalate precipitation; examples are sulfur which can survive sintering temperatures in hydrogen and an unidentified impurity which is volatile at temperatures slightly higher than the normal calcining temperatures (approximately 1000/sup 0/C) and which is highly effective in reducing thoria grain growth upon sintering. Still other impurities, termed extrinsic, are introduced during calcining and thoria powder comminution.

• Research Organization: Bettis Atomic Power Lab., West Mifflin, PA (USA)
• DOE Contract Number: EY-76-C-11-0014
• OSTI ID: 7257833
• Report Number(s): WAPD-TM-1230
• Country of Publication: United States
• Language: English

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ACTINIDE COMPOUNDS
CALCINATION
CHALCOGENIDES
CHEMICAL REACTIONS
DECOMPOSITION
FABRICATION
FUEL PELLETS
GRAIN GROWTH
OXIDES
OXYGEN COMPOUNDS
PELLETS
POROSITY
POWDERS
PYROLYSIS
SINTERING
THERMOCHEMICAL PROCESSES
THORIUM COMPOUNDS
THORIUM OXIDES
URANIUM COMPOUNDS
URANIUM DIOXIDE
URANIUM OXIDES