Sorption of Cationic Radionuclides on Chlorite and Sericite formed by the Hydrothermal Alteration - 18180
- Dept. of Quantum Science and Energy Engineering, Graduate School of Engineering, Tohoku University, 6-6-01-2, Aramaki, Aza-Aoba, Aoba-ku, Sendai 980-8579 (Japan)
Chlorite and sericite formed by the hydrothermal alteration of granite distribute predominantly around the geological repository in deep underground. These minerals often cover the surface of a solid phase and fill the fracture of granite considered as the natural barrier to the migration of radionuclides leaching from radioactive waste. Therefore, to assess the practical performance of the natural barrier, it is necessary to clarify the interaction between radionuclides and these minerals. This study examined the sorption of cationic radionuclides by chlorite and sericite through batch experiments, whereby Cs{sup +}, Sr{sup 2+}, and Eu{sup 3+} were used as tracer ions. In these experiments, powder-form chlorite or sericite was mixed with the solutions of the tracer ions to a liquid/solid ratio of 10 ml/g, and the resulting mixture was allowed to incubate for 2-7 days. The concentration of tracer ions was set to 1 mM and that of NaCl to a specific value in the 0-0.6 M range. The solution pH was 3, 5, or 8. As a result, tracer ions were significantly adsorbed by chlorite and sericite, regardless of pH or NaCl concentration, except when NaCl concentration reached the high value of 0.6 M. The distribution coefficient for europium ions at pH 5 was estimated to be 2-7 mL/g in chlorite and 10{sup 3}-10{sup 4} mL/g in sericite. These values significantly exceeded that measured for feldspar (2-4 mL/g), the predominant component of granite before it undergoes any hydrothermal alteration. These results suggest that cationic radionuclides will be immobilized through sorption in chlorite and sericite filling granite fractures, even if these thermal-fluid-formed minerals cover the surface of granite. (authors)
- Research Organization:
- WM Symposia, Inc., PO Box 27646, 85285-7646 Tempe, AZ (United States)
- OSTI ID:
- 22975359
- Report Number(s):
- INIS-US--20-WM-18180
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
CESIUM IONS
CONCENTRATION RATIO
EUROPIUM IONS
FELDSPARS
GEOLOGIC DEPOSITS
GRANITES
HYDROTHERMAL ALTERATION
LEACHING
OXYGEN COMPOUNDS
PERFORMANCE
PH VALUE
RADIOACTIVE WASTE DISPOSAL
RADIOACTIVE WASTE STORAGE
RADIOACTIVE WASTES
RADIOISOTOPES
SODIUM CHLORIDES
SORPTION
STRONTIUM IONS
TRACER TECHNIQUES
UNDERGROUND DISPOSAL