Abstract
Original language | English |
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Qualification | Doctor Degree |
Awarding Institution |
|
Award date | 21 May 1994 |
Place of Publication | Espoo |
Publisher | |
Print ISBNs | 951-38-4413-7 |
Publication status | Published - 1994 |
MoE publication type | G4 Doctoral dissertation (monograph) |
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Keywords
- radioactive wastes
- low-level radioactive wastes
- intermediate-level radioactive wastes
- diffusion
- porous materials
- rocks
- bedrock
- waste-rock interactions
- radionuclide migration
- ion exchange
- modelling
- clays
- bentonite
- montmorillonite
Cite this
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Diffusion in crushed rock and in bentonite clay : Dissertation. / Olin, Markus.
Espoo : VTT Technical Research Centre of Finland, 1994. 102 p.Research output: Thesis › Dissertation › Monograph
TY - THES
T1 - Diffusion in crushed rock and in bentonite clay
T2 - Dissertation
AU - Olin, Markus
N1 - Project code: KET4351
PY - 1994
Y1 - 1994
N2 - Diffusion theories for porous media with sorption are reviewed to serve as a basis for considering diffusion in simple systems like sand or crushed rock. A Fickian diffusion and linear sorption model is solved both by analytical Laplace transform and Green's function methods and by numerical methods, and then applied to small-scale experiments for Finnish low- and medium-level operating waste repositories. The main properties of bentonite are reviewed. The hydraulic conductivity of compacted bentonite is so low that the major transport mechanism is diffusion. A Fickian diffusion and linear sorption model is applied to bentonite. The main component of bentonite, montmorillonite, has a high ion-exchange capacity and thus, transport in bentonite consists of interactive chemical and diffusion phenomena. A chemical equilibrium model, CHEQ, is developed for ion-exchange reactions in bentonite water systems. CHEQ is applied to some bentonite experiments with success, especially for monovalent ions. The fitted log-binding constants for sodium exchange with potassium, magnesium, and calcium were 0.27, 1.50, and 2.10, respectively. A coupled chemical and diffusion model, CHEQDIFF, is developed to take account of diffusion in pore water, surface diffusion and ion-exchange reactions. The model is applied to the same experiments as CHEQ, and validation is partly successful. In the diffusion case, the above-mentioned values for binding constants are used. The apparent diffusion (both for anions and cations) and surface diffusion (only for cations) constants used are 3.0.10-11 m2/s and 6.0.10-12 m2/s, respectively, but these values are questionable, as experimental results good enough for fitting are not available.
AB - Diffusion theories for porous media with sorption are reviewed to serve as a basis for considering diffusion in simple systems like sand or crushed rock. A Fickian diffusion and linear sorption model is solved both by analytical Laplace transform and Green's function methods and by numerical methods, and then applied to small-scale experiments for Finnish low- and medium-level operating waste repositories. The main properties of bentonite are reviewed. The hydraulic conductivity of compacted bentonite is so low that the major transport mechanism is diffusion. A Fickian diffusion and linear sorption model is applied to bentonite. The main component of bentonite, montmorillonite, has a high ion-exchange capacity and thus, transport in bentonite consists of interactive chemical and diffusion phenomena. A chemical equilibrium model, CHEQ, is developed for ion-exchange reactions in bentonite water systems. CHEQ is applied to some bentonite experiments with success, especially for monovalent ions. The fitted log-binding constants for sodium exchange with potassium, magnesium, and calcium were 0.27, 1.50, and 2.10, respectively. A coupled chemical and diffusion model, CHEQDIFF, is developed to take account of diffusion in pore water, surface diffusion and ion-exchange reactions. The model is applied to the same experiments as CHEQ, and validation is partly successful. In the diffusion case, the above-mentioned values for binding constants are used. The apparent diffusion (both for anions and cations) and surface diffusion (only for cations) constants used are 3.0.10-11 m2/s and 6.0.10-12 m2/s, respectively, but these values are questionable, as experimental results good enough for fitting are not available.
KW - radioactive wastes
KW - low-level radioactive wastes
KW - intermediate-level radioactive wastes
KW - diffusion
KW - porous materials
KW - rocks
KW - bedrock
KW - waste-rock interactions
KW - radionuclide migration
KW - ion exchange
KW - modelling
KW - clays
KW - bentonite
KW - montmorillonite
M3 - Dissertation
SN - 951-38-4413-7
T3 - VTT Publications
PB - VTT Technical Research Centre of Finland
CY - Espoo
ER -