Manual of acid in situ leach uranium mining technology

294 Pages·2001·5.05 MB·English

IAEA-TECDOC-1239

Manual of acid in situ
leach uranium mining technology

August 2001
The originating Section of this publication in the IAEA was:
Nuclear Fuel Cycle and Materials Section
International Atomic Energy Agency
Wagramer Strasse 5
P.O. Box 100
A-1400 Vienna, Austria

MANUAL OF ACID IN SITU LEACH URANIUM MINING TECHNOLOGY
IAEA, VIENNA, 2001
IAEA-TECDOC-1239
ISSN 1011–4289
© IAEA, 2001
Printed by the IAEA in Austria
August 2001
FOREWORD
An important part of the IAEA programme for reactor fuels involves eliciting and
circulating information on innovative uranium production technologies. As compared with
conventional mining, in situ leach (ISL) technology is both innovative and relatively young. It
is recognized as having economic and environmental advantages when properly employed by
knowledgeable specialists to extract uranium from suitable sandstone type deposits.

In recent years ISL uranium mining has been producing about 13 to 15 per cent of world
output. Because of its potential for both low cost recovery and having environmental
advantages, the use of the technology will very probably increase. This may occur because
sandstone hosted uranium deposits amenable to ISL recovery are relatively widespread in the
world.

ISL technology recovers uranium using two alternative chemical leaching systems —
acid and alkaline. Acid leach is the more widely employed and has historically produced a
majority of the world’s ISL production. This technology, with its origins in the 1960s, was
developed and employed in the former Soviet Union and the successor states, as well as in
central and eastern Europe. The report describes operational practices developed under the
economic systems, together with the governmental policies and programmes prevailing over
this period. The United States of America is the only other country with an extended history of
ISL uranium production. In the USA, both acid and alkaline leach systems were tested before
alkaline technology was exclusively adopted for environmental reasons. As with all mining
technology, any project must be planned, developed, operated and closed, only when
appropriate consideration is made for environmental impacts.

This report brings together information from several technical disciplines that are an
essential part of ISL technology. They include uranium geology, geohydrology, chemistry, as
well as reservoir engineering and process engineering, It is not intended as a how to do it
manual. However, it does provide insights into many of the considerations related to the
technical feasibility of planning, operating and closing ISL uranium mining projects.

No comprehensive report exits for either acid or alkaline ISL uranium mining.
Furthermore, while there is a significant amount of literature on alkaline leach systems, almost
no English language literature is available for acid technology. Therefore this manual is the
first report published in English providing an extensive description of acid ISL uranium
mining technology. It should also be noted that much of the material may also be of value for
planning or operating alkaline ISL projects.

The IAEA wishes to thank the consultants who took part in the preparation of this report
for their valuable contributions. The IAEA is also grateful to the Member States and
individual organizations for their generous support in providing experts to assist in this work.
In particular it expresses its appreciation to the staff of the All Russian Research Institute of
Chemical Technology for its major contribution. The IAEA officer responsible for this
publication was D.H. Underhill of the Division of Nuclear Fuel Cycle and Waste Technology.
EDITORIAL NOTE
The use of particular designations of countries or territories does not imply any judgement by the
publisher, the IAEA, as to the legal status of such countries or territories, of their authorities and
institutions or of the delimitation of their boundaries.
The mention of names of specific companies or products (whether or not indicated as registered) does
not imply any intention to infringe proprietary rights, nor should it be construed as an endorsement
or recommendation on the part of the IAEA.
CONTENTS
CHAPTER 1. INTRODUCTION AND THEORY OF IN SITU LEACH
(ISL) URANIUM MINING TECHNOLOGY................................................1
1.1. Introduction.......................................................................................................................1
1.2. Geochemical characteristics of ISL sites...........................................................................3
1.3. Reactants — chemistry of leaching...................................................................................5
1.3.1. General information on reactants...........................................................................5
1.3.2. Chemical reactions in sulphuric acid leaching......................................................8
1.3.3. Chemical reactions in alkaline leaching..............................................................10
1.3.4. Criteria for choosing leaching chemistry.............................................................11
1.4. Theoretical background of the uranium ISL process.......................................................12
1.4.1. Principal processes for ISL..................................................................................12
1.4.2. General mechanism of ISL in unconsolidated sedimentary deposits..................13
1.5. Characteristic features of solution flow in ISL................................................................22
1.5.1. Physical properties of solutions affecting migration in the aquifer;
density stratification in the aquifer......................................................................22
1.5.2. Solution flow with pore plugging........................................................................28
1.5.3. Solution flow with gas formation........................................................................42
1.5.4. Dilution of solutions during leaching..................................................................46
1.5.5. Lag of production solutions behind flow.............................................................49
References to Chapter 1............................................................................................................50

CHAPTER 2. GEOLOGIC AND HYDROGEOLOGIC CONDITIONS FOR
IN SITU LEACH (ISL) MINING.................................................................51
2.1. Classification of deposits amenable to ISL mining.........................................................51
2.2. Hydrogeological conditions for ISL................................................................................56
2.3. Influence of composition of ores and rocks on the ISL process......................................59
2.3.1. General.................................................................................................................59
2.3.2. Influence of mineral composition of ores on the ISL process.............................60
2.3.3. Effect of host rock composition on the ISL process............................................60
2.4. Uranium ores and ore-forming minerals..........................................................................63
2.5. Minerals formed during ISL and their influence on the process.....................................65
References to Chapter 2............................................................................................................67

CHAPTER 3. GEOLOGY OF SANDSTONE TYPE URANIUM DEPOSITS..................69
3.1. Lithology and facies of deposits. Classification by lithology and
permeability of ore and host rocks...................................................................................69
3.2. Investigation of geochemical features of deposits and epigenetic alteration...................72
3.3. Study of the morphology of ore bodies and parameters of uranium mineralization.......73
3.3.1. Orebody morphology...........................................................................................73
3.3.2. Mapping uranium mineralization........................................................................76
3.4. Study of the composition of ores and host rocks.............................................................80
3.5. Exploration for uranium deposits for ISL........................................................................86
3.5.1. Exploring and delineating uranium deposits for ISL extraction..........................86
3.5.2. Parameters for resource evaluation for ISL extraction........................................88
3.6. Geophysical studies used in uranium ISL........................................................................91
3.6.1. General.................................................................................................................91
3.6.2. Investigations of ore and host rocks using logging methods...............................94
3.6.3. Surveying drift, drill hole diameter and geothermal
characteristics of measurements..........................................................................94
References to Chapter 3............................................................................................................95
Bibliography to Chapter 3.........................................................................................................95

CHAPTER 4. HYDROGEOLOGICAL EVALUATION OF
URANIUM DEPOSITS................................................................................97
4.1. General.............................................................................................................................97
4.2. Hydrological studies at various stages of the evaluation.................................................97
4.2.1. Preliminary evaluation.........................................................................................97
4.2.2. Further investigation............................................................................................98
4.2.3. Detailed exploration.............................................................................................99
4.3. Pump tests........................................................................................................................99
4.4. Static monitor wells.......................................................................................................100
4.5. Geophysical methods of assessing flow properties..........................................................101
4.6. Hydrogeological zoning of ISL deposits..........................................................................103
References to Chapter 4..........................................................................................................104

CHAPTER 5. MODELLING AND LABORATORY INVESTIGATION.......................105
5.1. Modelling the ISL process.............................................................................................105
5.1.1. General concepts................................................................................................105
5.1.2. Ore sampling......................................................................................................108
5.1.3. Preparation for column leaching........................................................................109
5.1.4. Column leaching................................................................................................111
5.1.5. Leach modeling in ground trays.........................................................................113
5.1.6. Modeling leaching from clayey ores..................................................................116
5.2. Determining permeability properties of unconsolidated rock and ores.........................118
5.2.1. General...............................................................................................................118
5.2.2. Determination of initial hydraulic conductivities for rock and ores..................119
5.2.3. Variations of hydraulic conductivity of rock and ore during leaching..............120
References to Chapter 5..........................................................................................................122
Bibliography to Chapter 5.......................................................................................................122

CHAPTER 6. WELLFIELD LEACH TESTS AT ISL DEPOSITS..................................123
6.1. General concepts and the sequence of leach tests.........................................................123
6.2. Well patterns at ISL test sites........................................................................................124
6.3. Information requirements for leach test sites.................................................................134
6.4. Calculation of leaching characteristics and evaluating their reliability.........................138
References to Chapter 6..........................................................................................................146

CHAPTER 7. WELLFIELD SYSTEMS FOR ISL MINING OF
SANDSTONE DEPOSITS.........................................................................147
7.1. ISL wellfield systems.....................................................................................................147
7.2. Flow networks for major wellfield pattern systems......................................................149
7.3. Selection of the optimal design ISL well patterns.........................................................152
7.4. Classification and description of ISL operating systems in sandstone deposits............154
7.4.1. Linear well patterns...........................................................................................155
7.4.2. Vertically staged systems...................................................................................158
7.4.3. Rectangular systems..........................................................................................159
7.4.4. Cell pattern systems...........................................................................................160
7.4.5. Barrier systems..................................................................................................160
7.4.6. Combined systems.............................................................................................162
7.5. Stages of designing ISL.................................................................................................162
References to Chapter 7..........................................................................................................163

CHAPTER 8. PROCESSING OF SOLUTIONS...............................................................165
8.1. Composition of production solutions............................................................................165
8.2. Filtering production solutions........................................................................................166
8.3. Ionic form of uranium in leaching solutions..................................................................166
8.4. Adsorption of uranium..................................................................................................168
8.5. Dynamics in treatment of solution by using ion exchange............................................173
8.6. Uranium desorption from anionic resin.........................................................................175
8.7. Methods of separating uranium from eluates................................................................176
8.8. Transportation of uranium products..............................................................................176
8.9. Process schemes for treatment of recovery solution......................................................178
8.10. Adsorption/desorption equipment for processing recovery solutions...........................180
8.11. Complex processing of leaching solutions in the future................................................184
Bibliography to Chapter 8.......................................................................................................185

CHAPTER 9. WELLFIELD DEVELOPMENT FOR ISL OPERATIONS......................187
9.1. General...........................................................................................................................187
9.2. Construction and operation of injection and recovery wells.........................................189
9.3. ISL well design..............................................................................................................190
9.3.1. Design of recovery wells...................................................................................192
9.3.2. Injection well design..........................................................................................196
9.3.3. Design of observation wells...............................................................................197
9.3.4. Exploration and control boreholes.....................................................................199
9.3.5. Design of anchor borehole.................................................................................199
9.3.6. Design of wells for controlling lateral excursions of leaching solutions...........199
Bibliography to Chapter 9.......................................................................................................201

CHAPTER 10. ISL WELL OPERATIONS.........................................................................203
10.1. Methods for pumping ISL production solutions to the surface.....................................203
10.2. Leach-field well performance........................................................................................206
10.3. Causes of reduced injection well efficiency..................................................................208
10.4. Factors reducing the recovery wells productivity..........................................................212
10.5. Causes of leach-field well failure..................................................................................213
10.6. Well work-over..............................................................................................................215
10.7. Control of leaching-field parameters in ISL process.....................................................218
Bibliography to Chapter 10.....................................................................................................219
CHAPTER 11. INVESTIGATION AND ACTIONS FOR
ENVIRONMENTAL PROTECTION........................................................221
11.1. General (concept)..........................................................................................................221
11.2. Contamination of surface and recultivation of land......................................................221
11.3. General information on contamination of underground water in ISL...........................223
11.4. Evaluation of groundwater contamination....................................................................228
11.4.1. General (conception).......................................................................................228
11.4.2. Calculation of contaminated groundwater halo after ISL termination............230
11.4.3. Likelihood of water supply contamination......................................................231
11.5. Research on groundwater environmental protection.....................................................234
11.5.1. General............................................................................................................234
11.5.2. Methodology for evaluating interacting parameters in field conditions..........235
11.6. Processes for groundwater restoration...........................................................................236
11.6.1. Cleaning by precipitation with reagents..........................................................238
11.6.2. Cleaning via electrical adsorption technology.................................................238
11.6.3. Cleaning solutions by compressed air.............................................................238
11.6.4. Washing with formation water........................................................................239
11.6.5. Method of natural attenuation.........................................................................239
11.6.6. Method for accelerating groundwater natural attenuation...............................240
References to Chapter 11........................................................................................................241
Bibliography to Chapter 11.....................................................................................................242

CHAPTER 12. DESIGNING IN SITU LEACHING FACILITIES.....................................243
12.1. Summary feasibility report............................................................................................243
12.2. Major technological decisions.......................................................................................244
12.2.1. Geotechnology of mining................................................................................244
12.3. Processing of solutions..................................................................................................247
12.4. Wells and pumping equipment......................................................................................248
12.5. Transportation of injection and recovery solutions.......................................................249
12.6. General purpose services, power supply, operational organization...............................256
12.6.1. Central research laboratory..............................................................................256
12.6.2. Maintenance, garage and storage services.......................................................257
12.6.3. Industrial engineering and management..........................................................258
12.7. General construction decisions, construction engineering............................................259
12.7.1. General construction decisions........................................................................259
12.7.2. Construction engineering................................................................................259
12.8. Protection of the environment.......................................................................................259
12.8.1. Protection of the atmosphere...........................................................................259
12.8.2. Protection and utilization of water resources..................................................259
12.8.3. Protection and utilization of land....................................................................260
12.9. General layout and transport..........................................................................................260
12.9.1. General layout.................................................................................................260
12.9.2. Transportation.................................................................................................260
12.10. Calculated cost of construction...................................................................................260

CHAPTER 13. BY-PRODUCT RECOVERY FROM IN SITU LEACHING OF
SANDSTONE URANIUM DEPOSITS IN UZBEKISTAN......................261
13.1. Identifying by-product components.............................................................................262
13.2. Valuing of each product; present and future demand..................................................263
13.3. Investigating the analysis of distribution, concentration of
rare elements in ores and enclosing rock.....................................................................263
13.4. Development of economic by-product recovery.........................................................266
Bibliography to Chapter 13.....................................................................................................266

ANNEX I. GLOSSARY....................................................................................................267

ANNEX II. THE IMPORTANCE OF ENVIRONMENTAL
IMPACT ASSESSMENT FOR PLANNING
ISL URANIUM MINING PROJECTS...........................................................275

ANNEX III. BIBLIOGRAPHY...........................................................................................280

ANNEX IV. UNITS OF HYDRAULIC CONDUCTIVITY,
TRANSMISSIVITY, RECHARGE AND FLOW RATES.............................281

CONTRIBUTORS TO DRAFTING AND REVIEW............................................................283
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