Hydrothermal reactions of shales and clay minerals with cesium phases representative of spent reactor fuel
The immobilization of cesium extracted from spent fuel (SF) by ion exchange and direct chemical reaction with clay minerals and shales was investigated under hydrothermal, closed-system conditions. The exact cesium phases in SF are not known with certainty, but Cs/sub 2/MoO/sub 4/, Cs/sub 2/U/sub 2/O/sub 7/, CsI, and possibley Cs/sub 2/O have been cited as possibilities. Various clay minerals and shales are mixed with these cesium sources along with 50 percent by weight of water, sealed in gold ampules and treated at 30 MPa pressure and 100, 200, and 300 C for 4 months, 2 months and 1 month respectively. Pollucite, (Cs, Na)AlSi/sub 2/O/sub 6/, was the principal interaction product, but CsAlSiO/sub 4/, was also observed along with unreacted or hydrothermally altered aluminosilicates. The cesium concentrations of the product solutions were measured to determine the partitioning of cesium between the liquid and solids. Results varied substantially, depending on the particular cesium and clay or shale phases, the temperature, and the duration of the run. Fixation of up to 97 percent of the cesium was observed in some solids. In addition to formation of Cs-aluminosilicates, cesium was fixed on cation exchange sites by interlayer collapse in montmorillonite. The interactions of Cs/sub 2/MoO/sub 4/ with clays or shales also resulted in the formation of powellite (CaMoO/sub 4/) because calcium was available in the reaction mixture. The U/sup 6 +/ from ..beta..-Cs/sub 2/U/sub 2/O/sub 7/ was reduced to form uraninite by sulfide and/or organic rich shales. An interaction product of ..beta..-Cs/sub 2/U/sub 2/O/sub 7/ with clays and shales is (Cs,Na)/sub 2/(UO/sub 2/)/sub 2/(Si/sub 2/O/sub 5/)/sub 3/.4H/sub 2/O, an analog of weeksite. The reaction products pollucite, CsAlSiO/sub 4/, and uraninite from SF-rock interactions serve to immobilize cesium and uranium because cesium in the Cs-Al-silicates is extremely difficult to exchange and uranium in uraninite has very low solubility.
- Research Organization:
- Battelle Memorial Inst., Columbus, OH (USA). Office of Nuclear Waste Isolation; Pennsylvania State Univ., University Park (USA)
- DOE Contract Number:
- AC06-76RL01830
- OSTI ID:
- 5554879
- Report Number(s):
- ONWI-262; ON: DE82007864; TRN: 82-010644
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
CESIUM
CHEMICAL REACTIONS
ION EXCHANGE
SOLVENT EXTRACTION
CESIUM COMPOUNDS
CESIUM URANATES
CHLORITE MINERALS
ILLITE
KAOLINITE
MICA
MOLYBDATES
MONTMORILLONITE
SHALES
EXPERIMENTAL DATA
HIGH PRESSURE
HIGH TEMPERATURE
MEDIUM TEMPERATURE
RADIOACTIVE WASTE DISPOSAL
SPENT FUELS
WASTE-ROCK INTERACTIONS
WATER
X-RAY DIFFRACTION
ACTINIDE COMPOUNDS
ALKALI METAL COMPOUNDS
ALKALI METALS
ALUMINIUM COMPOUNDS
ALUMINIUM SILICATES
CLAYS
COHERENT SCATTERING
DATA
DIFFRACTION
ELEMENTS
ENERGY SOURCES
EXTRACTION
FUELS
HYDROGEN COMPOUNDS
INFORMATION
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MANAGEMENT
MATERIALS
METALS
MINERALS
MOLYBDENUM COMPOUNDS
NUCLEAR FUELS
NUMERICAL DATA
OXYGEN COMPOUNDS
REACTOR MATERIALS
ROCKS
SCATTERING
SEDIMENTARY ROCKS
SEPARATION PROCESSES
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
URANATES
URANIUM COMPOUNDS
WASTE DISPOSAL
WASTE MANAGEMENT
400702* - Radiochemistry & Nuclear Chemistry- Properties of Radioactive Materials
400105 - Separation Procedures
052002 - Nuclear Fuels- Waste Disposal & Storage