Roasting and dissolution studies on nonirradiated thorium dioxide/uranium dioxide pellets

Technical Report · Thu Dec 31 23:00:00 EST 1981

DOI:https://doi.org/10.2172/5296379· OSTI ID:5296379

Pickett, J B; Fowler, J R; Mosley, Jr, W C

Bench scale roasting and dissolution of ThO/sub 2/ and ThO/sub 2//UO/sub 2/ ractor-grade ceramic pellets were studied at the Savannah River Laboratory to define the key parameters affecting dissolution. Pellet breakup, and subsequent dissolution rates, were determined for ThO/sub 2/ and ThO/sub 2//UO/sub 2/ pellets roasted in air or in oxygen. Roasting ThO/sub 2//UO/sub 2/ pellets in air at temperatures from 400 to 900/sup 0/C caused the pellets to crack but not fragment. Roasting whole pellets or fine powdered materials decreased the rate of dissolution in a nitric acid solution containing a fluoride catalyst. Roasting 100% ThO/sub 2/ pellets did not cause cracking or affect the subsequent dissolution rate. Mixed ThO/sub 2//UO/sub 2/ ceramic pellets dissolved at a faster rate than the 100% ThO/sub 2/ pellets. The effect of MgO and CaO on dissolution rate was determined. MgO (approx. 1.0 wt %) increased the dissolution rate of ThO/sub 2/ pellets, an effect which was similar to that obtained by the addition of 20% UO/sub 2/ to the ThO/sub 2/ pellets. The combination of 1% MgO and 20% UO/sub 2/ did not result in an additional increase in dissolution rate. However, the addition of 0.25 to 0.50 wt % CaO did increase the dissolution rate of 80% ThO/sub 2//UO/sub 2/ ceramic pellets. High temperatures (and pressure) were ineffective in dissolving thoria-based fuels in HNO/sub 3/ in the absence of a fluoride catalyst. A process flowsheet outlining the required head end steps for the reprocessing of thoria-based fuels was developed.

• Research Organization: Du Pont de Nemours (E.I.) and Co., Aiken, SC (USA). Savannah River Lab.
• DOE Contract Number: AC09-76SR00001
• OSTI ID: 5296379
• Report Number(s): DP-1590; ON: DE82008956
• Country of Publication: United States
• Language: English

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ACTINIDE COMPOUNDS
AIR
ALKALINE EARTH METAL COMPOUNDS
CALCIUM COMPOUNDS
CALCIUM OXIDES
CATALYSTS
CERAMICS
CHALCOGENIDES
CHEMICAL REACTIONS
COHERENT SCATTERING
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DIAGRAMS
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FLOWSHEETS
FLUIDS
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INORGANIC ACIDS
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
MICROSCOPY
MIXTURES
NATIONAL ORGANIZATIONS
NITRIC ACID
NONMETALS
NUMERICAL DATA
OXIDATION
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PELLETS
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URANIUM COMPOUNDS
URANIUM DIOXIDE
URANIUM OXIDES
US AEC
US DOE
US ERDA
US ORGANIZATIONS
VERY HIGH TEMPERATURE
X-RAY DIFFRACTION