Gas pressure build-up in radioactive waste disposal repositories

Directorate-General For Research And Innovation European Commission

Description

Hydraulic and mechanical effects
Nuclear energy and safety

Informations

• Publié par: DIRECTORATE-GENERAL-FOR-RESEARCH-AND-INNOVATION-EUROPEAN-COMMISSION
• Nombre de lectures: 9
• Langue: English
• Poids de l'ouvrage: 9 Mo

Extrait

ISSN 1018-5593
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European Commission
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Gas pressure build­up in
radioactive waste disposal repositories:
hydraulic and mechanical effects
Report
EUR 16753 EN European Commission
nuclear science
and technology
Gas pressure build-up in
radioactive waste disposal repositories:
hydraulic and mechanical effects
T. Manai
Geostock
7, rue E. et A. Peugeot
F-92563 Rueil-Malmaison
Contract No FI2W/CT91/0093
Final report
Work carried out under a cost-sharing contract with the European
Atomic Energy Community in the framework of its fourth R&D programme
'Management and storage of radioactive waste' (1990-94)
Part A, Task 4: 'Disposal ofe waste'
Directorate-General
Science, Research and Development
1996 EUR 16753 EN Published by the
EUROPEAN COMMISSION
Directorate-General XII
Science, Research and Development
B-1049 Brussels
LEGAL NOTICE
Neither the European Commission 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, 1996
ISBN 92-827-5920-2
© ECSC-EC-EAEC, Brussels · Luxembourg, 1996
Printed in Luxembourg ABSTRACT
Several origins of gas generation were identified (in the literature) from a deep underground
radioactive waste disposal.
The integrity and the safety of the underground disposal can be disturbed by the gas
pressure build-up inducing a crack propagation and an important modification in the water
flow behaviour.
The objective of this project is to study the impact of gas generation and gas migration in
term of hydraulic effects and mechanical effects.
In order to predict the mechanical behaviour of the host rock when gas pressure builds-up,
a new bifurcation theory has been developed and implemented in a software. This model
has the ability to detect crack initiation and follow crack propagation.
The prediction of this model has been confirmed by experimental data.
The hydraulic impact of gas migration has been studied by simulating twelve scenarios of
gas migration including two types of repository, three host rock types and two types of gas
generation flow rates.
The simulation shows that the gas will reach the aquifer and the time scale of such
migration to the biosphere depends on the host rock characteristics which play a major role
in the gas migration. The safety assessment of the radioactive waste disposal is a trade-off
between lowering flow velocities and better confining gas in cavity.
This report gives an overview of the results of modelling hydraulic effects and mechanical
effects and experimental results.
Ill CONTENTS
ABSTRACT IH
CHAPTER - INTRODUCTION 1
CHAPTERI - FUNDAMENTALS 5
11.1. CAPILLARY PRESSURE AND RELATIVE PERMEABILITY 8
11.2. FLOW EQUATION 9
11.3. SOLUBILITY OF THE GAS PHASE IN THE LIQUID PHASE 10
11.4. DIFFUSION 1
CHAPTER HI - LABORATORY EXPERIMENTAL RESULTS1
111.1. EXPERIMENTAL METHODOLOGY AND PROCEDURE3
111.2. DISCUSSION OF RESULTS4
111.3. PROPOSED GAS MIGRATION MODELLING 17
CHAPTER IV - MECHANICAL MODELIZATION USING NEW BIFURCATION THEORY 2
IV.1. INTRODUCTION 29
IV.2. ANISOTROPIC DAMAGE MODEL 31
IV.2.1. Preliminaries - Damage variable
IV.2.2. Strain energy function and D-generated residual effects 32
IV.2.3. Elastic-damage response and damage growth3
IV.2.4. Modelling options - Comments on evaluation of material parameters5
IV.3. TANGENT STIFFNESS TENSOR AND 3-D LOCALIZATION DETECTOR7
IV.3.1. Tangent stiffness - Localization problem
IV.3.2. Computational procedure for localization detection8
IV.4. FAILURE INCIPIENCE THROUGH STRAIN AND DAMAGE LOCALIZATION 40
IV.4.1. Results for axisymmetric proportional strain paths and conventional "triaxial" loading 4
IV.4.2. Effects of anisotropy: off-axes straining and structural analysis 4
IV.5. CONCLUSION 42
CHAPTER V - GAS PROPAGATION RISK 53
V.1. INTRODUCTION5
V.2. PRESENTATION OF CASE STUDIES6
V.2.1. Case study definition
V.2.2. Repository and domain descriptions
V.2.2.1. First type of repository
V.2.2.2. Second type ofy
V.2.3. Rock petrophysical properties9
V.2.3.1. Data's origin
V.2.3.2. First rock sample (#2)
V.2.3.3. Second rock sample (#3) 60
V.2.3.4. Third rock sample (#6)
V.2.4. Backfill material properties
V.2.5. Fluid properties
V.2.6. Sources of gas -1
V.2.7. Two-phase flow simulations
V.2.7.1 Presentation of the flow simulator
V.2.7.2. Boundary conditions2
V.2.7.3. Initial conditions
V V.3. SIMULATION RESULTS FOR THE FIRST TYPE OF REPOSITORY 63
V.3.1. Which simulation results ? 6
V.3.2. First gas rate scenario
V.3.2.1. First rock sample (#2)
V.3.2.2. Second rock sample (#3)4
V.3.2.3. Third rock sample (#6)
V.3.3. Second gas rate scenario
V.3.3.1. First rock sample (#2)
V.3.3.2. Second rock sample (#3)5
V.3.3.3. Third rock sample (#6)
V.4. SIMULATION RESULTS FOR THE SECOND TYPE OF REPOSITORY 66
V.4.1. Which simulation results ? 6
V.4.2. First gas rate scenario
V.4.2.1. First rock sample (#2)
V.4.2.2. Second rock sample (#3)7
V.4.2.3. Third rock sample (#6)
V.4.3. Second gas rate scenario8
V.4.3.1. First rock sample (#2)
V.4.3.2. Second rock sample (#3)
V.4.3.3. Third rock sample (#6)
V.5. ANALYSIS OF SIMULATION RESULTS9
CHAPTER VI - CONCLUSIONS 71
AKNOWLEDGEMENTS5
REFERENCES7
ANNEXES 8
A. Two-phase water-gas rock relative permeability and capillary tables 83
B. Fluid PVT tables "
C. Gas saturation maps for the first type of repository 89
D. Pressure graphs for the first type ofy 9
E. Gas saturation maps forthe second type of repository 103
F.e graphs for the second type ofy 13
VI CHAPTER I
INTRODUCTION