Diffusion in crushed rock and in bentonite clay

Dissertation

Markus Olin

Research output: Thesis › Dissertation › Monograph

Abstract

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.
Original languageEnglish
QualificationDoctor Degree
Awarding Institution
  • University of Helsinki
Award date21 May 1994
Place of PublicationEspoo
Publisher
Print ISBNs951-38-4413-7
Publication statusPublished - 1994
MoE publication typeG4 Doctoral dissertation (monograph)

Fingerprint

bentonite
clay
rock
ion exchange
sorption
cation
Laplace transform
experiment
Green function
montmorillonite
repository
numerical method
porous medium
anion
hydraulic conductivity
magnesium
porewater
potassium
calcium
sodium

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

Olin, M. (1994). Diffusion in crushed rock and in bentonite clay: Dissertation. Espoo: VTT Technical Research Centre of Finland.
Olin, Markus. / Diffusion in crushed rock and in bentonite clay : Dissertation. Espoo : VTT Technical Research Centre of Finland, 1994. 102 p.
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abstract = "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.",
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",
author = "Markus Olin",
note = "Project code: KET4351",
year = "1994",
language = "English",
isbn = "951-38-4413-7",
series = "VTT Publications",
publisher = "VTT Technical Research Centre of Finland",
number = "175",
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Olin, M 1994, 'Diffusion in crushed rock and in bentonite clay: Dissertation', Doctor Degree, University of Helsinki, Espoo.

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 -

Olin M. Diffusion in crushed rock and in bentonite clay: Dissertation. Espoo: VTT Technical Research Centre of Finland, 1994. 102 p.