Characterization of clay (bentonite)/ crushed granite mixtures to build barriers against the migration of radionuclides

European Commission Directorate-General For The Information Society And Media Directorate-General For Research And Innovation

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Diffusion studies and physical propertiesTask 3 Characterization of radioactive waste forms: A series of final reports (1985-89) No 35
Nuclear energy and safety

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• Publié par: EUROPEAN-COMMISSION-DIRECTORATE-GENERAL-FOR-THE-INFORMATION-SOCIETY-AND-MEDIA-DI
• Nombre de lectures: 12
• Langue: English
• Poids de l'ouvrage: 3 Mo

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ISSN 1018-5593
Commission of the European Communities
Characterization of clay (bentonite)/crushed granite
mixtures to build barriers against the migration of
radionuclides: diffusion studies and physical properties
Task 3 - Characterization of radioactive waste forms
A series of final reports (1985-89)
No 35
Report
EUR 13666 EN Commission of the European Communities
- ' ■.•■•••. ■' -i ¡y
t í ,
Characterization of clay (bentonite)/crushed granite
mixtures to build barriers against the migration of
radionuclides: diffusion studies and physical properties
Task 3 ­ Characterization of radioactive waste forms
A series of final reports (1985­89)
No 35
E. Mingarro, P. Rivas, L P. del Villar, B. de la Cruz,
P. Gómez, A. Hernández, M. J. Turrero, M. V. Villar,
R. Campos, J. Cozar
Ciemat
Avenida Complutense 22
E-28040 Madrid
Contract No FI1W/0191-E (\T)
Final report
This report was prepared for the European Atomic Energy Community's
cost-sharing research programme on radioactive waste management and disposal (Task 3 - Section 3)
Directorate-General
Science, Research and Development
.1
CUR'; P E.tnw 1. PARI
EUR 13666 EN 1991 N.C. Published by the
COMMISSION OF THE EUROPEAN COMMUNITIES
Directorate-General
Telecommunications, Information Industries and Innovation
L-2920 Luxembourg
LEGAL NOTICE
Neither the Commission of the European Communities nor any person
acting on behalf of the Commission is responsible for the use which might
be made of the following information
Cataloguing data can be found at the end of this publication
Luxembourg: Office for Official Publications of the European Communities, 1991
ISBN 92-826-3066-8 Catalogue number: CD-NA-13666-EN-C
© ECSC-EEC-EAEC, Brussels • Luxembourg, 1991
Printed in Luxembourg Abstract
In Spain it is being considered the possibility of making a storage of radioactive
waste in granitic rocks, using Spanish clays as backfill and sealing materials. The study
and selection of these materials is the objective of the project, done with financial
communitary support under contract CEC No FI1W-0191-E (TT).
With the aim of minimizing the chemical-mineralogical disequilibrium between the
granitic rock and the artificial barrier, it has been studied the possibility of using molten
granite as an additive and illite as clayish material, instead of the normal use of smectite
(montmorillonite).
The studies have been done with thirty commercial Spanish clays and two kinds
of granites and have been orientated to the selection of materials and the optimization
of the mixtures clay-granite, chemical characterization, mechanics and physics of the
mixtures and compacted blocks, determination of their behaviour in the gradient fields
of temperature, pressure and chemical potentials and to the determination of the
migration parameters. INDEX OF CONTENTS:
Page
1
INTRODUCTION
1.- CHARACTERIZATION AND SELECTION OF MATERIALS °
1.1.- ANALYZED MATERIALS 3
1.2.- PRESELECTION OF THE CLAYEY AND GRANITIC MATERIALS 3
1.2.1.- MINERALOGICAL CHARACTERIZATION OF THE CLAYEY
AND GRANITIC MATERIALS
1.2.2.- PHYSICO-MECHANICALN OF THE
CLAYEY MATERIALS 5
1.2.3.- PHYSICO-CHEMICAL CHARACTERIZATION OF THE CLAYEY
MATERIALS 8
1.3.- SELECTION OF TWO TYPES OF CLAY AND ONE GRANITE 9
2.- CHARACTERIZATION OF THE COMPACTED BLOCKS AND
DETERMINATION OF THE MIXTURES CLAY/GRANITE 13
2.1.- FREE SWELLING AND SWELLING PRESSURE
2.2.- HYDRAULIC CONDUCTIVITY 15
2.3.- THERMALY7
2.4.- SHEAR PROPERTIES9
2.4.1.- SIMPLE COMPRESSION TEST 20
2.4.2.- TRIAXIAL TESTS1
2.5.- DETERMINATION OF THE MIXTURES2
3.- ANALYSIS OF THE MODIFICATION OF THE CLAYS PROPERTIES
AS A FUNCTION OF THE TREATMENT TEMPERATURE 24
3.1.- TEXTURAL AND MICROSTRUCTURAL MODIFICATIONS
3.1.1.- MINERALOGICAL TRANSFORMATIONS 25
3.1.2.- DEHYDRATION OF THE TWO TYPES OF CLAYEY MATERIAL 26
3.1.3.- PROPERTIES MODIFICATIONS: SPECIFIC WEIGHT,
SURFACE AREA AND POROSITY OF THE CLAYEY
MATERIALS SUBJECTED TO THERMIC TREATMENT 28
-V 3.1.4.- PLASTICITY PARAMETERS OF THE CLAYEY MATERIALS
SUBJECTED TO THERMIC TREATMENT 31
3.1.5.- SWELLING PARAMETERS OF THE CLAYEY MATERIALS
SUBJECTED TO THERMIC TREATMENT2
3.1.6.- HYDRAULIC CONDUCTIVITY OF THE CLAYEY MATERIALS
SUBJECTED TO THERMIC TREATMENT3
3.1.7.- STRENGHT TO COMPRESSION OF THE THERMICALLY
TREATED CLAYS 3
3.1.8.- LIMITING TEMPERATURE4
4.- ANALYSIS OF THE DEFORMATION AND HYDRAULIC CONDUCTIVITY
OF THE COMPACTED BLOCKS AS A FUNCTION OF THE
HYDROSTATIC PRESSURE AND TEMPERATURE 36
4.1.- HYDRAULIC CONDUCTIVITY OF THE CLAY AS A FUNCTION
OF THE TEMPERATURE
4.2.- CLAYS CONSOLIDATION 37
4.3.- SHEAR PROPERTIES 41
4.3.1.- TRIAXIAL DRAINED TEST 43
4.3.2.-L UNDRAINED TEST, WITH MEASUREMENT OF
THE INTERSTITIAL PRESSURES4
5.- ANALYSIS OF THE SOLUTION DIFFUSSIVITY IN THE
COMPACTED BLOCKS6
5.1.- DISTIBUTION COEFFICIENTS OF 137Cs AND 60Co 4
5.2.- DIFFUSSION ESSAYS 48
6.- MINERALOGICAL STABILITY OF MONTMORILLONITE AS A
FUNCTION OF TEMPERATURE; REACTION TIME AND PRESENCE
OF IONS K+ _ 52
7.- CONCLUSIONS 56
Tables9
Figures 95
Micrographs 12
REFERENCES 133
VI -INTRODUCTION
To guarantee the protection of the biosphere is the
ultimate aim of the concept of radioactive waste storege in
geologically stable formations, in which should be integrated
the properties of the different barriers considered: geologic
barrier, artificial barrier and kinds of agglomerating agents
used in the waste.
In Spain it is being considered the possibility of making
an storage in granitic rocks, using Spanish clays as backfill
and sealing materials. The study and selection of these
materials is the objective of the proyect, done with financial
communitary support under contract CEC n« FI-1W-0191-E (TT).
With the aim of minimizing the chemical-mineralogical
disequilibrium between the granitic rock and the artificial
barrier, it has been studied the possibility of using molten
granite as an additive and illite as clayish material, instead
of the normal use of smectite (montmorillonite).
The studies have been done with thirty commercial Spanish
clays and two kinds of granites and heve been orientated to the
selection of materials and the optimization of the mixtures
clay-granite, chemical characterization, mechanics and physics
of the mixtures and compacted blocks, determination of their
behaviour in the gradient fields of temperature, pressure and
chemical potentials and to the determination of the migration
parameters.
The development of the activities have been done in
accordance with the following working program:
-1 -1. Characterization and selection of materials.
2. Determination of the mixtures and characterization of
the compacted blocks.
3. Analysis of the properties variations as a function of
the temperature.
4. Analysis of the deformation and the hydraulic
conductivity in the compacted blocks as a function of
the confining pressure and temperature.
5. Analysis of the solution diffusivity in the compacted
blocks.
6. Mineralogical stability of the smectite as a function
of temperature and reaction time.
This inform it has been structurated following the working
program and it is a resume of the information obtained in the
two years of work and that is contained in the Annual Progress
Reports of 1988 and 1989, and it develops more extensively the
information obtained in the last six months of extension of the
contract.
2-