Coating of crystalline nuclear waste forms to improve inertness
Microspheres of a crystalline waste form prepared by sol-gel processing were successfully coated with layers of pyrolytic carbon and silicon carbide to isolate the radioactive wastes from the biosphere. A separate process for cesium immobilization was developed which loads 5 wt% Cs onto zeolite particles for subsequent coating. Pyrolytic carbon-coated particles showed leach rates approx. =2 to 4 orders of magnitude less than the candidate reference borosilicate glass waste form. Aqueous leach-test results of coated waste forms were below detection limits of such sensitive analytical techniques as atomic absorption and inductively coupled plasma atomic emission. Significant progress was made in applying sol-gel and fluidized bed coating technology to the solidification of high-level nuclear wastes. The authors successfully prepared microspheres containing simulated wastes of Synroc-B, Synroc-D, a modified Synroc-D where alumina was previously removed from the waste, and a very high waste-loading composition containing 90% waste and 10% ZrO/sub 2/. Each of these compositions was sintered at 1000/sup 0/C and coated with pyrocarbon at temperatures as low as 1000/sup 0/C. Silicon carbide can be applied to these pyrocarbon-coated particles at temperatures as low as 900/sup 0/C for additional inertness or for oxidation resistance. Cesium was isolated by pyrocarbon-coating cesium-loaded zeolite. Pyrocarbon and SiC coatings successfully reduced the leach rates to below detection limits.
- Research Organization:
- Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830
- DOE Contract Number:
- W-7405-ENG-26
- OSTI ID:
- 5993833
- Journal Information:
- Am. Ceram. Soc. Bull.; (United States), Vol. 65:8
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
HIGH-LEVEL RADIOACTIVE WASTES
LEACHING
SURFACE COATING
RADIOACTIVE WASTE PROCESSING
SOLIDIFICATION
CESIUM
CRYSTALS
MEASURING METHODS
MICROSPHERES
PYROLYTIC CARBON
SILICON CARBIDES
SOL-GEL PROCESS
SYNROC PROCESS
SYNTHETIC ROCKS
ZEOLITES
ZIRCONIUM OXIDES
ALKALI METALS
CARBIDES
CARBON
CARBON COMPOUNDS
CHALCOGENIDES
DEPOSITION
DISSOLUTION
ELEMENTS
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MANAGEMENT
MATERIALS
METALS
MINERALS
NONMETALS
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
PROCESSING
RADIOACTIVE MATERIALS
RADIOACTIVE WASTES
ROCKS
SEPARATION PROCESSES
SILICON COMPOUNDS
SYNTHETIC MATERIALS
TRANSITION ELEMENT COMPOUNDS
WASTE MANAGEMENT
WASTE PROCESSING
WASTES
ZIRCONIUM COMPOUNDS
052001* - Nuclear Fuels- Waste Processing
360201 - Ceramics
Cermets
& Refractories- Preparation & Fabrication