Technical report 6/2015/ENG
EXPERIMENTAL PROGRAMME AT BUKOV UNDERGROUND RESEARCH FACILITY
Authors: Václava Havlová et al.
ÚJV Řež, a.s.
Praha, July 2015
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Authors: Václava Havlová Lenka Rukavičková Lubomír Staš Jaroslav Pacovský Karel Sosna Milan Hokr Miroslav Černík Pavel Špaček Jiří Mikeš Martin Milický Michal Polák
Contents 1 Introduction ...... 11 2 Underground research facility (URF) Bukov ...... 12 3 Concept of the experiment and research proposal...... 14 4 Proposed experimental and research activities in Bukov URF ...... 15 4.1 Detailed geological and hydrogeological characterisation of the underground (URF area and crosscut tunnel area) ...... 15 4.2 Testing of long-term monitoring methods of the processes in the DGR depth ...... 18 4.2.1 Long-term hydrogeological monitoring...... 18 4.2.2 Monitoring of changes in stress state and changes in behavior and character of underground workings over time ...... 19 4.2.3 Monitoring of macro- and micro-seismicity ...... 21 4.2.4 Displacement monitoring on faults ...... 23 4.2.5 Geophysical monitoring with focus on testing the methodologies for rock massif homogeneity verification in the vicinity of mine work ...... 24 4.2.6 Monitoring of microbiological contamination and the gradual colonization of the environment by the microorganisms ...... 28 4.3 Testing of groundwater hydraulic models and radionuclide transport models within DGR fractured rock environment...... 30 4.3.1 Hydrodynamic tests in the boreholes ...... 30 4.3.2 Hydraulic model assessment ...... 32 4.3.3 Programme of migration/tracer tests ...... 34 4.3.4 Determination of groundwater age and origin ...... 42 4.3.5 Transport model testing ...... 43 4.4 Testing of rock mass influence on changes of potential engineering barrier properties ...... 45 4.4.1 Corrosion experiments under anaerobic conditions in granitic host rock ...... 45 4.4.2 The influence of microbes on degradation of engineered barriers and the penetration of microorganisms in bentonite ...... 49 4.4.3 Material interaction experiments (cement, bentonite) ...... 50 4.5 Testing of EDZ and EdZ formation and development in metamorphic rock in DGR depth 53 4.5.1 Different EDZ behaviour due to use of different excavation methods - I...... 53 4.5.2 Different EDZ behaviour due to use of different excavation methods - II...... 54 4.5.3 Different EDZ behaviour due to use of different excavation methods - III...... 56 4.5.4 Influence of internal rock structure and present structural domains on the URF behaviour and stability ...... 57
5 General requirements for ensuring implementation of monitoring, research and experimental work at the Bukov URF ...... 58 6 Conclusions ...... 59 7 References ...... 60
List of figures: Fig. 1 Schematic position of Bukov URF (Dvořáková et al. 2014) ...... 13 Fig. 2 Schematic figure of borehole system for fracture network connectivity study ...... 36 Fig. 3 An example of dipole experiment instrumentation in discrete fracture (NAGRA 2000) ...... 36
Report number: Experimental programme in the Bukov URF SURAO TZ 6/2015/ENG
List of abbreviations: DFN Discrete fracture network DGR Deep geological repository EB Engineering barriers ECPM Equivalent continuous porous medium EdZ Engineering disturbed zone EDZ Excavation damage zone GPR Ground Penetrating Radar GW Groundwater HDT Hydrodynamic Test HG Hydrogeological HLW High level waste NGS Next generation sequencing PCR Polymerase chain reaction P-T Press-temperature QA Quality assurance R&D Research and development REE Rare earth elements SC Supercontainer SNF Spent nuclear fuel SONS State Organisation for Nuclear Safety SRB Sulphate reducing bacteria SÚRAO Radioactive Waste Authority THMC Thermal-hydro-mechanical-chemical URF Underground research facility URL Underground research laboratory UV Ultraviolet light WPT Water pressure test
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Abstract Construction of deep underground facility Bukov enables to perform scientific and experimental activities under conditions close to the condition of the deep geological repository. Until the final site will be selected and a confirmation laboratory will be built within this site, Bukov facility will be used as a test site for evaluation of host rock in the depth that is relevant to the considered depth of deep geological repository. In the presented report a proposal of monitoring, scientific and experimental activities is presented, divided into following topics: 1. Specification of geological and hydrogeological characteristics of URL. The activities will follow up recently launched geological characterization of the site. The outcomes will contain detailed description of lithological variability, structural data and description of ductile, ductile-fragile and particularly fragile structure, which has been intersected by the shaft. Furthermore, they will contain hydrogeological and hydrogeochemical characteristics of saturated fragile structures and underground water in the shaft. 2. Testing of long-term monitoring processes in the repository depth. Within this topic long-term monitoring of processes in the deep underground facility will be studied: • Long-term monitoring of hydrogeology • Monitoring of stress and underground facility changes in time • Monitoring of potential shifts on faults • Geophysical monitoring focused on methods studying the homogeneity of the rock massif • Monitoring of microbial contamination 3. Testing of hydrogeological models and radionuclide models in the fractured repository environment. The focus of this topic is to test transport models using different techniques and experiments in the fractured environment, considering also matrix diffusion Testing will use following activities/techniques: • Hydrodynamic tests in the boreholes • Evaluation using hydraulic model • Migration experiments in boreholes (advection transport, diffusion transport, fracture network connectivity) • Determination of underground water age and origin
4. Testing of host rock environment influence on engineering barrier properties under repository environment. The goal of the methods, mentioned in the report, will be influence of rock massif real conditions on engineering barrier materials (bentonite, cement). Complex experiments will be constructed in order to study several processes in the same time: corrosion, microbial influence, bentonite changes, etc. Following experiments are proposed: • Corrosion experiments
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• Mock-up type experiments • Cement – bentonite experiment
Besides from those experiments, will be studied the microbial influence on the processes in the engineering barrier, evaluating the rate of potential influence on corrosion and material property changes. 5. Testing of formation and development of EDZ an EdZ in metamorphic rocks under repository depth. The goal is to observe EDZ in time so that its development will be observed in relation to the other parameters (massif rheology, changes caused by heat loading, desaturation of the massif, etc.). Within the topic a broad range of techniques and methods was presented, starting with geophysical method towards hydraulic testing or use of geotechnical classification of rock massif.
Selection of the activities will become as a base for R&D programme at URL Bukov. The basic presumption for implementation of mentioned activities are: • Development of supporting on-ground centre • Development of supporting technical and scientific team in-situ • Development of high quality contractors • Ensure DIAMO smooth and pro-active support • Ensuring of shaft working system • Ensuring that the experiments will not influence each other • Supporting laboratory research and modelling programme
Keywords Underground research facility, Bukov, deep geological repository, R&D programme
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Abstrakt
Otevření podzemního výzkumného pracoviště (PVP) v podzemním díle Bukov umožní provádět výzkumné a experimentální práce v podmínkách, které se blíží podmínkám HÚ. Bude sloužit jako testovací lokalita pro hodnocení chování hornin kandidátních lokalit v hloubce odpovídající předpokládané hloubce hlubinného úložiště do doby, než bude vybrána finální lokalita a vybudována konfirmační podzemní laboratoř v této lokalitě. V této zprávě je předložen návrh monitorovacích, výzkumných a experimentálních prací, rozdělených na tyto oblasti: 1. Upřesnění geologické a hydrogeologické charakteristiky podzemního díla (prostory podzemní laboratoře a přístupového překopu). Tyto práce plynule naváží na geologickou charakteristiku lokality prováděnou v rámci aktuálně probíhajícího ZL. Výstupy budou zahrnovat podrobný popis litologické variability, strukturních dat a popis duktilních, křehce-duktilních a zejména křehkých struktur zastižených podzemním dílem. Dále budou obsahovat hydrogeologickou a hydrochemickou charakteristiku zvodněných křehkých struktur a podzemních vod přítomných v podzemním díle. 2. Testování metod dlouhodobého monitoringu procesů probíhajících v hloubce úložiště. V této oblasti bude výzkum zaměřen na dlouhodobý monitoring procesů v podzemní laboratoři. Půjde zejména o: • Dlouhodobý monitoring hydrogeologických poměrů • Monitoring změn napětí a změn chování a charakteru podzemního díla v čase • Monitoring makro- a mikro-seismicity • Monitoring případných posunů na vrtech • Geofyzikální monitoring se zaměřením na testování metodik na ověření homogenity horninového masivu • Monitoring mikrobiologické kontaminace a postupného osidlování prostředí mikroorganismy 3. Testování modelů proudění podzemní vody a transportu radionuklidů v puklinovém prostředí hlubinného úložiště. Cílem těchto prací je pomocí různých technik a přístupů testovat modely transportu prvků v puklinovém prostředí se zohledněním možné difúze do horninové matrice. Testování bude využívat • Hydrodynamické testy na zlomech • Hodnocení pomocí hydraulického modelu • Migračních experimentů s více vrty (advektivní transport) a jedním vrtem (difúze do matrice, konektivita puklinové sítě) • Určení stáří a původu podzemních vod • Různých transportních modelů pro posouzení jejich použitelnosti a k vyhodnocení samotných experimentů
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4. Testování vlivu horninového prostředí v hloubce úložiště na změny vlastností uvažovaných inženýrských bariér. Cílem těchto prací bude sledování vlivu reálných podmínek horninového masivu, jež přibližné odpovídají podmínkám HÚ, na materiály inženýrských bariér. Provedeny budou zejména komplexní experimenty, které umožní sledování několika jevů najednou (koroze materiálů úložného obalového souboru – změny bentonitu v reálných podmínkách – vliv mikrobiální činnosti). Půjde o experimenty: - Zaměřené na korozi (korozní sondy) - Experiment typu Mock-Up - Interakční experiment cement - bentonit Kromě těchto experimentů bude sledován vliv mikrobiálních kolonií na vlastnosti bentonitu a cementu a na míru koroze materiálů ukládacího obalového souboru v podmínkách in-situ. 5. Testování vzniku a vývoje EDZ a EdZ v metamorfovaných horninách v hloubce úložiště. Cílem je sledování vzniku EDZ v čase tak, aby byl podchycen její další vývoj ve vztahu k různým parametrům (reologie masivu, změny způsobené teplotním zatížením, odvodnění masivu atd. V této oblasti byla představena nejširší škála prací, od geofyzikálních metod po hydraulické testování či umístění tenzometrických svorníků až po využití geotechnické klasifikace horninového masivu. Výběr z těchto prací poslouží jako základ pro návrh experimentálního programu PVP Bukov. Základním předpokladem pro implementaci těchto aktivit je: ● Vybudování podpůrného povrchového pracoviště ● Vybudování podpůrného místního odborného týmu na PVP Bukov ● Vytvoření erudovaného týmu dodavatelů pro zvolené práce ● Zajištění fungujícího systému práce v důlním díle ● Zajištění neovlivnění jednotlivých experimentů ● Aktivní součinnost podniku DIAMO ● Podpůrný laboratorní program a program modelování (zmíněno mnohokrát výše) ● QA systém
Klíčová slova Podzemní výzkumné pracoviště, Bukov, hlubinné úložiště, experimentální program
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1 Introduction
The report was prepared in the frame of the SURAO project "Scientific support of deep geological repository safety assessment", being a part of spent nuclear fuel (SNF) and high level waste (HLW) deep geological repository (DGR) development programme. The goal of the project is to gain selected data, models, arguments and other information, needed for evaluation of potential sites, concerning long-term safety. In July 2014 the contract, concerning providing scientific support for safety assessment, was signed with UJV Řež, a.s. and its subcontractors (Czech geological survey, Czech technical university, Technical university in Liberec, Institute of Geonics Czech academy of Science, Arcadis, CZ, a.s. , Progeo, s.r.o., Chemcomex Prague a.s. and Research Centre Řež) on the basis of the public tender. The support is provided in the following areas:
i. spent nuclear fuel and other high level waste form behaviour under deep geological repository conditions, ii. spent nuclear fuel and high level waste material container behaviour under deep geological repository conditions, iii. behaviour of buffer, backfill and other construction materials under deep geological repository conditions, iv. construction of disposal holes and its influence on surrounding rock properties v. rock massif behaviour vi. radionuclide transport from deep geological repository vii. other site characteristics, potentially influencing DGR safety
The goal of the report is to prepare a conceptual proposal of the experimental programme that could enable 1. testing of long term monitoring of processes, taking place in the DGR depth 2. testing of radionuclide transport model in DGR fractured environment 3. testing of rock mass environment influence on considered engineering barriers and their properties 4. EDZ and EdZ formation and development in metamorphic rocks in DGR depth 5. specification of geological specification of the underground research facility
Such knowledge should 1. contribute to understanding of processes, taking part in the DGR depth and enable to simplify in this way Safety Case preparation, necessary for DGR site selection 2. enable testing methods that could be applied after site selection for gathering knowledge, data and arguments that will be used for DGR safety evaluation and demonstration in the selected site.
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2 Underground research facility (URF) Bukov
Underground research facility Bukov, located in the depth of 600 m under surface (further URF) will be used as a testing facility for evaluation of rock behaviour in the depth, corresponding to the expected DGR depth until the final site is selected and until the confirmation underground repository is built under appropriate DGR conditions. In 2013 Radioactive waste repository authority (SURAO) through its contractor DIAMO, s. p. (GEAM branch) launched a project of underground research facility Bukov (Bukov URF). Its main goal is characterisation of Czech Massif crystalline rock in the depth of 500 - 900 m under the surface to be used within DGR sitting research in Czech Republic. A site close to the Bukov shaft (B1, Bukov village, Žďár nad Sázavou district; Vysočina county) was selected. The site is located in the south part of Rožná uranium mine. URF Bukov is situated 300 m from Bukov mining pit on the 12th floor, approx. 520 m under the surface. Concerning geology, Bukov URF is situated in Strážek part of Moldanubia, mainly consisted of migmatised paragneisses, migmatites, orthorules and granulites, with rich layers of amphibolites, marbles and quartz. Undisturbed rock at the site is evaluated as impermeable. Values of hydraulic conductivity vary between 5.10-10 m/s and 1.10-12 m/s. The rate of crystalline rock permeability, beyond the weathering zone, is dependent mainly on the number and opening of both fractures and dislocations. Both structures in the area have namely NW direction. Ondřík et al. (2010) presented that the most permeable are the transverse and diagonal dislocations. On the other hand indicative dislocations are almost impermeable for water flow due to the secondary phylosilicate infill.
Bukov URF groundwater geochemistry is namely of Ca–HCO3 type, showing mostly low mineralisation type (up to 0.3 g/l).
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Fig. 1 Schematic position of Bukov URF (Dvořáková et al. 2014)
URF technical layout was designed in consistency with State Organisation for Nuclear Safety (SONS) requirements, concerning demands of any future research activities, namely on smooth blasting altogether with Excavation Damage Zone (EDZ) minimalisation. Underground facility consists of 300 m long crosscut tunnel, being mined from B1 2 shaft in the 9, 2 m2 profile. Presented figure (see Fig. 1) is one of the proposed possibilities and its final design is nowadays under development. In the URF area drilling and laboratory chambers are located in regular manner. Rock bolts will be used to provide support for the underground sections supplemented with yieldable TH arches in areas exhibiting more complicated geological conditions (Dvořáková et al. 2014).
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3 Concept of the experiment and research proposal
The basic approach towards the project gaining the project goal is identification of potential experimental and technical activities. Experiment proposals were discussed across the research team extended for additional research and scientific institutions. The experience from previous research, experimental and exploration activities were exploited altogether with modelling and data interpretation. Those were gained within international scientific projects - e.g., space configuration, influence on the surrounding environment, different feature dominance etc. The main approach toward determination of potential research activities consist of a) Selection of main experiments that exhibit some of the following features: a. Those that are large and occupy significant area of URF b. Those that need special location c. Those that influence surrounding rock environment (due to increase temperature, changes in the hydraulic or rock stress field) b) Identification of characterisation, evaluation or testing activities that precede the experiments or follow them up c) Identification of activities that characterise defined properties of URF rock environment d) Determination of long-term monitoring potential
The mentioned steps led to defining the following activity areas 1) Specification of URF geological and hydrogeological characteristics (URF area and crosscut tunnel area) 2) Testing of long term monitoring of processes that could take place in the DGR depth 3) Testing of water flow models and radionuclide transport models in the DGR fractured environment 4) Testing of rock environment on the EB material properties under DGR conditions 5) Testing of EDZ and EdZ formation and evolution in metamorphic rocks under DGR depth In the following chapters monitoring, research and experimental activities are focused on fulfilling the project goals. The presentation of each activity is laid in the questionnaire format in order to keep the same format and description for all of them. The experiments are formulated in close connection with modelling program, including both predictive and post- mortem modelling. Many activities are often interconnected. Such connections are marked within the text. However, the most problematic for clear work description were Testing of long term monitoring, namely of geophysics, together with Testing of EDZ and EdZ formation and evolution were the procedures and methodologies are close to each other. Moreover, choice and use of those methods are rather broad. The exact choice will be possible only after at least general description of the URF geological environment.
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4 Proposed experimental and research activities in Bukov URF
4.1 Detailed geological and hydrogeological characterisation of the underground (URF area and crosscut tunnel area)
Goal of the experiment: The work will be continuation of the site geological characterization, carried out in the frame of the current project „Comprehensive characterization of the Bukov URF“. Outputs will include a detailed description of lithological variability, structural data and description of ductile, brittle-ductile and mainly brittle structures encountered by the underground work, including update of a 3D structural-geological model created within the above mentioned ongoing project. Furthermore, it will include hydrogeological and hydrochemical characteristics of water-bearing brittle structures and of groundwater present in the underground. Conceptual proposal: Geological mapping, mineralogical, petrological, petrophysical and geochronological characterization of the rock environment, altogether with documentation of groundwater influxes and study of groundwater composition will be involved within this task. These works will be followed by the update of the Bukov URF 3D structural-geological model. Technical solution: The work will be realized across the entire underground facility, including the access tunnel. Drilling work will not be required (except of approximately 20 cm long boreholes for determination of the petrophysical characteristics). However, it will be necessary to ensure free access to the tunnel walls in order to perform geological measurements and sampling of water and rocks from the walls. This research will be realized mainly by non-invasive surface measurement and sampling, with the exception of small rocks sampling of dm3 volume. That is presumed not to be in conflict with other research experiments. Based on the use of existing geological data and the application of analytical methods from the fields of structural geology, petrology, mineralogy, geochronology and petrophysics, a detailed and comprehensive characterization of the geological environment will be conducted. Resulting data will be also used for updating the site 3D structural-geological model. The result will be a conceptual model of the geological environment development in Bukov URF with many implications for later experiments. The model will characterize significant stages of the local geological environment development from Variscian to the present time. Based on the methods of anisotropy of magnetic susceptibility (AMS), optical microscopy and microstructural analysis (e.g., using electron back-scattered diffraction – EBSD) basic parameters of the identified deformation fabrics will be characterized and quantified. These data will allow a comprehensive assessment of the rock environment anisotropy. Based on the optical microscopy and microanalysis, the rock-forming minerals, their relationships, mineral chemical composition and their potential variability will be analysed. Defined PT paths, related to major lithology estimates, and PT condition estimate, related to
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the formation of selected types of metamorphic fabrics, will be defined using thermodynamic modelling, microscopy and microanalysis of mineral parageneses Furthermore, based on geochemical data sets (silicate analyses, analyses of REE and trace elements) chemical composition of major lithologies, in close relation to their petrographic composition and structure, will be assessed Significant attention will be paid to the chemical composition and distribution of alterations and secondary minerals in the rocks (e.g., chlorite, actinolite, clay minerals). On the basis of these data it will be possible to assess the rock chemical and physical properties such as the resistance to GW alterations or mineral distribution in the rock. The later significantly affects anisotropy of the rock environment. Mineral infill and alterations in the vicinity of major tectonic zones will also be analyzed. Mineralogical and geochemical research of fissure and vein mineralization will be also conducted, including mineral identification, determination of the succession of minerals, determination of PT conditions of their formation, determination of composition and sources of fluids. The main methods of this research will include, except above mentioned methods electron microscopy, X-ray diffraction analysis, cathodoluminiscence, fluid inclusion analysis, analysis of stable C and O isotopes in carbonates. Petrophysical analysis of rocks will focus on the following parameters: • Magnetic susceptibility (k) • Laboratory Gamma Spectrometry – contents of U, eU (Ra), eTh and K • Density parameters – bulk density (Do), mineralogical density (Dm) and porosity (Por) • The electrical resistivity characteristics (R) • In selected cases micro seismic properties (anisotropy of p-waves) All the above mentioned petrophysical methods will be conducted predominantly as non- destructive; if possible on a single piece of oriented drill core with given diameter and length. Each of major lithologies will be characterized by a minimum of five samples to obtain a representative data set. Hydrogeological research in the underground research facility will include documentation of all groundwater inflows to the tunnel and to nearby parts of the Rožná mine. Documentation will be performed after completing the excavation, after adaptation of galleries for the individual experiments and during drilling of research boreholes. Documentation will include a description of water-bearing brittle structures, measurement of inflow recharge, physical and chemical characteristics of groundwater (water temperature, pH, Eh, dissolved oxygen content and specific electrical conductivity) and water sampling for chemical analyses. Content of major cautions and anions, selected trace elements and GW radioactivity will be determined in each water sample. Age and origin of groundwater will be also studied in selected sites (see Section 4.3.4 "Determination of the age and origin of Bukov URF groundwater "). Selected inflows will be equipped with drainage troughs and sheets that will allow the discharge measurement. Measurement will be, according to the accessibility of inflows, made repeatedly. Significant inflows will then be included in the monitoring network (see Section 4.3.1 "Long-term hydrogeological monitoring”). The hydrogeological data will be used to characterize the regime and the properties of the groundwater in the area of the planned underground research facility Bukov and in its vicinity. This would include the identification of significant conductive structures, pro-links
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between HG results and structural geology and time evolution evaluation of the groundwater chemical composition and inflow discharge values. Special requirements • 230V / 400V power supply • gallery lighting, electricity switchboard • assistance of mine staff during the installation of the HG part of instrumentation • oriented drill cores for petrophysical analyses Experiment duration As necessary according to technical works etc., the minimum is three years Further potential use of the experiment All other experiments in URL Bukov will use results of the descriptive characteristics of geological and hydrogeological parameters as the input data for evaluation of different experiments and process numerical simulations tested in the URF.
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4.2 Testing of long-term monitoring methods of the processes in the DGR depth
4.2.1 Long-term hydrogeological monitoring
Goal of the experiment: The aim of hydrogeological monitoring is the evaluation of variability the development of GW flow and chemical composition in the broader vicinity area of URF. Data, gained from the other mine part outside the facility area will be used as background ones during evaluation of the experiment impact on the hydrogeological conditions in their close vicinity Conceptual proposal: Long-term groundwater regime and GW chemical composition will be monitored in the URF and in the adjacent parts of the mine. Monitoring will include discharge measurement of the outflows from the fault zones and from the research boreholes, complemented with the observation of pressure conditions, determination of major ions contents, trace elements, radioactivity and finally with GW chemical and physical properties from separate outflows. Technical solution: The measurements will be a direct continuation of recent monitoring programme launched during 2015 as a part of the sub-project "Comprehensive characterization of the Bukov URF" and will based on the research described in Section 4.1. Significant inflows (leakage) of groundwater to the underground facility and BZ-XIIJ into the crosscut tunnel will be equipped with drainage troughs and sheets that will allow the measurement of discharge. The discharge of selected inflows will be measured continuously using flow metres, tipping buckets, graduated cylinders with spouts (Danaids) or graduated cylinders with self-emptying. The choice of measurement method will depend on the discharge value, the position (height above the gallery floor) and the technical possibilities of installation. The inflow temperature will be measured at the same time. The monitored network will comprise also selected inflows in adjacent parts of the mine. Research boreholes with groundwater outflow will be equipped with packers and with an assembly including pressure and temperature sensors, flow metres with data loggers, pressure gauges and drain taps. This assembly provides g continuous monitoring of temperature, pressure values and values of borehole yield. Groundwater samples will be collected from the monitored inflows. The content of major ions, trace elements, radioactivity, and GW physical and chemical characteristics will be set for each sample. Measurement of water temperature, pH, Eh, dissolved oxygen content and specific electrical conductivity will be a part of each sample collection. Expected sampling intervals in the first years of URF operation would be once per month with subsequent prolongation to the interval once per quarter of the year. The total outflow from the gallery will also be continuously measured. Due to the low hydraulic gradient and high runoff discharge the ultrasonic Doppler flow meter would be most probably the most appropriate method of measuring. The hydrogeological data resulting from long-term monitoring (and also resulting from all tests and experiments), will be compiled into the annual assessment of the hydrogeological
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regime in the URF Bukov area. Evaluation will include updating of the entire area hydraulic model, being affected by the experiments implemented in the Bukov URF. Specific requirements: • 230V / 400V power supply • gallery lighting, electricity switchboard • assistance of mine staff during the installation of the HG part of instrumentation • protection of equipment against damage.
Duration of the experiment: Throughout the entire operation in the underground facility. Further potential use of the experiment: The result of monitoring will be the time series of GW physical and chemical parameters in the URF and its vicinity. These data are a necessary basis for further experiments which will prove transport or reactive properties of groundwater and rock environment. The data set will be used for mathematical modelling in the gradually updated hydraulic model of the Bukov URF and for local hydraulic and transport models of the individual tests and experiments (Section 4.3.2 and 4.3.5).
4.2.2 Monitoring of changes in stress state and changes in behavior and character of underground workings over time
Goal of the experiment: In the underground faciliy, or more precisely in its surroundings, the stress state of the rock mass will be monitored based on measurements made in this area before the construction of the laboratory. Objective of the stress state monitoring is to describe and evaluate the current stress state of the location in relation to the assumptions based on the geological history. Simultaneously, the reaction, namely the speed of reaction of the rock mass, on the construction of an underground facility will be monitored in relation to the long-term stability of the construction. At the same time, changes should be determined and the intensity of effects on a stress field should be studied realizing some experiments (e.g. 4.3.1, 4.3.3, 4.4.1, etc.) Conceptual proposal: The method of hydraulic fracturing (hydrofracturing, HF) will be used for the overall evaluation of stress effects. The overcoring methods will be applied for determination of values of stress fields in selected locations. Changes in stress fields will be monitored using the tensiometric CCBM measurements of deformation and string stressmeters placed in boreholes. In this case, measurements after the construction of the facility, particularly in the vicinity of structures separating the blocks, will be supplemented. HF has already determined a high massif fracturing in the studied location. According to the HF methodology, it is necessary to create one separated fracture in the tested section of the borehole. CCBO is an one spot measurement. Therefore, application of CCBO in more locations is very useful in terms of determining the shape of the stress field. CCBO can be realized in any dry borehole of 76 mm designated for other experiments.
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Effective interpretation of measured data depends on the mathematical model of the stress state of the location. It is expected that the measured data will be verified by means of mathematical modelling: • describe the original state of stress in the studied location and its development in the vicinity of the underground facility • monitor changes in stress field caused by the construction of the facility over time • monitor changes in stress field caused by realization of experiment Experiment realization: It is planned to build monitoring stations at the end, in the middle and at the beginning of the facility tunnel or, alternatively, in the access crosscut. Geotechnical differences of blocks should be taken into consideration. All stations will include: For hydrofracturing: vertical down hole of about 50m, supplement vertical upper hole of about 30m. For overcoring: 2-3 upper holes drilled in right, left side of the mining work and, if appropriate, in the ceiling. Alternatively, the orientation of foliation can be taken into consideration in relation to the orientation of boreholes. The length of holes is up to 25m. Overcoring should be done at least in three distances (e.g. in 5, 10 and 20-25m). For monitoring of changes in a stress field: CCBM probes can be installed at the bottom of the boreholes used for overcoring or, if possible, other monitoring equipment can be placed in the resting part of the borehole (for example, stressmeters). For monitoring of stress field changes induced by realization of other experiments (e.g. 4.3.1., 4.3.3, 4.4.1): place additional boreholes in the vicinity of the source of stress activity in geometry with regard to subsequently elaborate an appropriate mathematical model describing the condition. During the construction of the experiments, where materials of experiments (concrete, bentonite, etc.) get in contact with rock formations, it will be appropriate to provide continuous measurement of stress changes by means of hydraulic pressure cells (always with temperature monitoring). In the vicinity of measuring sensors, all monitoring boreholes should be equipped with thermometers and hygrometers. Monitoring and recording of measured data will be continuously controlled by the monitoring system with remote access via the Internet. Prior to instrumentation, all structural elements passing through the borehole and their orientation should be documented (e.g. using ultrasonic or optical cameras enabling oriented image recording of the borehole wall (ABI, OBI, HiRAT, OPTV)). It is required to test mechanical properties of the borehole related to the determination of the stress state, including the anisotropy of properties. The laboratory determined values (mainly deformation properties) should be compared with the measurements in situ, e.g. by the method "GOODMAN JACK".
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Specific requirements: ● Prior to determining the location of the monitoring stations, respectively of individual testing boreholes, the planned geophysical methods (see 4.2.5) should be applied. It could significantly help to select places in the massif which will be particularly appropriate for the monitoring of stress changes. ● Annual comparison campaign of geophysical measurements describing the entire geolaboratory is recommended. ● At the end of an experiment, additional overcoring using the installed CCBM probes should be performed in order to calibrate stress measurements. ● Testing boreholes could form a drainage path during hydraulic experiments. ● Hydrofracturing: during measurements, an artificial kerf in length of some decimeters is formed. It influences the surrounding environment. Especially, it affects the hydraulic conductivity. Damages in the borehole wall can be also caused by the application of the “GOODMAN JACK” method. ● Stress experiments are negatively influenced by experiments which result in formation of uneven thermal and stress fields. ● Supply of water and compressed air for hydrofracturing. ● 230V/24V power supply for monitoring equipment ● Technical support by DIAMO during installations ● Internet connection ● Protection of equipment from damage Experiment duration: ● In order to determine the original state of stress, this experiment should be realized prior to other loading experiments. ● The monitoring part of experiments has to be started before realizing other experiments. It has to continue over the entire time of the underground facility operation. Further potential use of the experiment: ● Knowledge of the shape of the stress field can be further used for the interpretation of hydrogeology in the massif. ● Monitoring changes in the stress state can facilitate the interpretation of realized experiments, particularly the permeability (see 4.2.1., 4.3.1, 4.3.3, 4.3.5).
4.2.3 Monitoring of macro- and micro-seismicity
Goal of the experiment: The aim of the seismological monitoring is to document and to evaluate the site in terms of its response to the dynamic phenomena in the massif. These phenomena can be caused either by local construction intervention into the rock massif and/or can originate from the distant URF surrounding. The use of acoustic emission monitoring enables to document inelastic or brittle deformational processes in the close vicinity to the sensors. Such processes can be caused e.g., by installation of the experiments causing additional loading stress to local parts in the rock massif.
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Conceptual proposal: Assessment of vibration effects induced by various sources from URF surrounding will be based on the seismological monitoring. According to the results of previous observations, mostly technical seismicity will be recorded, e.g., vibrations caused by operations in the surrounding mine workings and surrounding quarries (especially blasting), very intensive vibrations caused by mining rock bursts (in the area of Lubin and Upper Silesian Basin), and natural seismicity (particularly earthquakes from the Alps). The aim of this monitoring is also to detect potential occurrence of mining induced seismic events in the surroundings of the facility. These vibrations apparently will not evoke damage to the underground facility but they can cause resonant vibrations of some elements. Irradiated energy in the form of acoustic emission is the initial demonstration of the rock massif breach. Observing such an effect will enable to identify the weakened/influenced areas in the rock massif as a consequence of realized experiments. Technical solution Seismic pillar for the sensors anchoring for seismological monitoring needs to be constructed in the underground facility or in its vicinity. Data (triggered regime) will be transferred and interpreted in a batch mode. Previous experience shows that a sufficient range of seismic channel is 2 Hz - 200 Hz. Interpretation of the data will be performed in both time and frequency domains to sufficiently evaluate induced vibrations in the underground facility. Acoustic emission monitoring will be carried out according to the progress of the experiments, during which it is possible to expect formation of weakened zones. Acoustic sensors are placed in short small-diameter boreholes. The number of sensors is dependent on the range of the expected weak zones. Depending on the situation estimation, either the origin of acoustic events or their localization will be monitored. Specific requirements: • Seismology o a seismic pillar with 230V/50Hz power supply o telephone / internet network • Acoustics: o a short small diameter boreholes o 230V/50Hz power supply and telephone / internet network o cable connections from the sensors to the registration apparatus
Duration of the experiment • Seismology: during the operation time of the underground facility • Acoustics: during the experiment time, with well-estimated time overlap
Further potential use of the experiment • Seismology: evaluation of seismic load of the underground facility • Acoustics: determination of rock massif disturbance during the individual experiments
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4.2.4 Displacement monitoring on faults
Goal of the experiment: Similar to the section 4.2.2, the main goal of the measurement will be the rock massif stability evaluation. The data will contribute as a further indicator of the stress and its changes during excavation and experiment installation. The data would become one of the information sources, concerning the rock stability. Furthermore, the data about fault displacement will complement the point stress measurements (in boreholes). All together they can contribute comprehensively to the information about the rock stress and deformation, both caused by natural processes, by excavations or by the experiments, launched in the underground facility. The understanding of relations between the displacements and other monitored data will help to the future prediction of the displacements in the repository site, or directly in the disposal boreholes. Conceptual proposal: Dilatometers, recording the relative displacement between two points on the opposite sides of the rock discontinuity, will be placed into the selected intersecting discontinuity parts within the excavated tunnel walls. The monitoring should start early during the excavations to see its effect on the deformations. However this will be hardly possible. The displacements will be observed in all 3 axes, with emphasis on maximal accuracy. In parallel, several methods for micro-deformations of contact and dilation cracks in the disposal borehole lining will be used. Technical solution: The distribution of sensors should cover various orientations of discontinuity planes, various scales (according to an expected range of the discontinuity), various distances from the expected influencing point (typically rock heating experiments, borehole pressure tests, additional excavations). Also it would be convenient to place the measurement on some of the fractures with flow rate observation, within the hydraulic and the transport experiments. There are more possible solutions – sets of uniaxial dilatometers (vibration wire principle or induction – LVDT) coupled to three directions or devices based on optical interference in two planes, detecting both the triaxial displacement and the rotations. The former types allow direct electronic processing of a numerical value in the output signal, while the latter require a more complicated processing by the image analysis in an industrial PC onsite. The required measurement resolution and accuracy should be in micrometres (or the first units of micrometres). It is necessary to perform also complementary temperature measurements, in order to distinguish the displacements from the local rock thermal expansion and from the “external” processes. We do not expect special needs for rock preparation; the devices will be typically placed on the vertical tunnel walls by the standard anchoring methods. The dimensions must be appropriate to the particular fault/discontinuity dimensions (anchoring in a sufficient distance into the “intact” rock that can differ from centimetres to tens of centimetres). The orientation of the individual devices will be regarding to an efficient evaluation – along the discontinuity or along axes of the global coordinate system. Specific requirements: ● 230V power supply for unattended data record) ● Ethernet for online transmission
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● In case of optical measurement, larger space by the wall for equipment placement (cameras, PC) ● Protection against mechanical damage
Duration of the experiment Throughout the entire operation time of the underground facility. Further potential use of the experiment Stress monitoring, seismic monitoring, geophysics, influence of geotechnical and hydraulic experiments
4.2.5 Geophysical monitoring with focus on testing the methodologies for rock massif homogeneity verification in the vicinity of mine work
The objective is to describe the state of the rock mass and its changes with time in a representative volume of the rock mass around a construction. This area is very closely interconnected with the areas, presented in the Chapters 4.5.1 and 4.5.2. Conceptual proposal Complex geophysical measurements executed at Bukov shaft, Rožná I mine, at crosscut gallery BZ-XIIJ and its surroundings have shown that geophysical methods can provide valuable information about geological structure, characteristics, and behaviour of the rock massif including the EDZ zone. We therefore consider necessary to continue with application of proven geophysical methods in further surveying and research works and to continue with identifying additional indirect surveying methods that could be used to study the rock massif under the ground. Usage of geophysical methods for underground works in the current state of knowledge can be divided into two basic groups: fully tested methods (group A) and methods requiring testing before their implementation, including development of necessary metres, development of processing and interpretation software, and further development of metering methodologies (group B). Group A – the methods already tested 1. Small-scale methods (magnetic susceptibility, dose rate, temperature); Small-scale methods (magnetic susceptibility, absorbed dose rate, temperature) are just complementary methods. This type of measurements does not pose any financial or instrumentation related demands. Capability of these methods to point out anomalies in Bukov rock massif has been proven during experimental measurements carried out within the framework of GEOSTAB project. Thermal field anomalies were particularly interesting (relationship with the underground water regime?). Their inclusion into the group of geophysical methods describing the rock massif is based on recently approved certified method “Geophysical methods for rock massif documentation”. Definite benefits have been demonstrated by the electrical resistivity tomography and seismic tomography methods. 2. Electrical resistivity tomography; 3. Seismic refraction using hammer blows;
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4. Seismic well logging; and 5. Seismic tomography. All of the above-mentioned methods provide important information about geologic structure in the vicinity of direct exploratory works and/or between them. Group B – the methods under development Continuing research of geophysical methods implementation for rock massif monitoring should focus on two main areas: 1. Study of the EDZ (see also 4.5) Previous geophysical works indicated that certain knowledge about the EDZ zone can be obtained with seismic refraction method where impacts are applied on the walls of mine work and from electric resistivity tomography measured also on the side of cross gallery or gallery. It would be useful to develop and test new measurement methods or methodologies in the future. Main methods that could be used comprise: • seismic radiography with rays parallel with the gallery wall (modification of the “cross hole” method); • usage of ground penetrating radar (GPR) with high frequency aerials; and • microVES utilization. Technical solution: Location of geophysical measurements depends on the layout of individual direct surveying works. No additional exploratory works need to be excavated for geophysical works with the exception of “parallel seismic surveying”. Instrumentation required for the geophysical measurements will always be installed before measurement and removed after its completion. Each phase of geophysical works is to be terminated after completion of all field geophysical measurements. Should any non-geophysical activities in straight exploratory galleries cause their blocking or other damage, the geophysical works will be limited to the scope possible with regard to the work damage Parallel seismic radiography The application of this method requires drilling of three lines of boreholes (fans), located three to ten metres apart. The boreholes of the first fan are used to generate a seismic signal. Further two fans are used to measure the time of arrival of the seismic signal. Using this differential measurement, the uncertainty of precise detection of the origin of a seismic disturbance is excluded. The number of boreholes in the fan is governed by the requirement for the precision to identify the shape of the EDZ. It appears to use four to six boreholes in one fan as the most suitable method. Boreholes 10 to 20 metres long can be drilled coreless and their minimum diameter should be at least 50 mm. The boreholes in the measuring fans can also be used for other measurements, but only for the ones that will not require a permanent installation of measuring systems in boreholes. Using repeated measurement it is possible to detect the time development of the EDZ. These measurements do not affect the rock mass in their surroundings. Use of land-based radar (GPR) for the EDZ To identify the state of the EDZ, it is appropriate to test the possibilities of land-based radar. For measurement it will be necessary to use an antenna with a higher frequency, probably
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500 MHz It would also be suitable to test antennas with a higher and a lower frequency. All antennas should be shielded. The radar record should show the thickness of the loosened rock mass, and, if possible, also the top of the concentrated stress zone. Groundwater could have an adverse effect in the rock mass. However, it is likely that the first EDZ on the sides and roof of a crosscut will be groundwater free. If groundwater occurs in the next zone, then it is likely that the boundary between the first zone and the second zone will become a better reflective surface for electromagnetic radiation. A very clear negative effect can be expected from any metal objects. This method could be applied only where no solid metal lining occurs in the mine working. However, it can be assumed that if a timber support is behind props, then GPR can be used. This method of measurement will not require any mining preparatory works. All areas where there is no “conflict” with other measurements can be used for measurement, i.e. that there is no threat of damage to other installed gauges. The only condition is that no other activity would take place over the duration of geophysical measurements at the site.
2. Investigation of the rock mass geological structure The following methods are useful for rock massif studying: • usage of ground penetrating radar (GPR) with low frequency aerials; • newly developed possibility of “electrical borehole measurements”; and • reflection seismology application.
Specific requirements: Location of geophysical measurements depends on the layout of individual direct surveying works. Special boreholes will be drilled for the parallel seismic surveying, geoelectric methods, and/or other selected methods. Geophysical measurements in these boreholes will be carried out in different geometric arrangement combinations (borehole, borehole – borehole, borehole - gallery (inset) wall). Changes of physical - mechanical characteristics of the rock massif will be monitored in time, in various directions with regard to possible anisotropy, layering, fissure systems, etc. Each phase of geophysical works is to be terminated after completion of all field geophysical measurements. Should any non-geophysical activities in straight exploratory galleries cause their blocking or other damage, the geophysical works will be limited to the scope possible with regard to the work damage. Geophysical methods, which can be used, comprise: Use of land-based radar (GPR) for identifying the geological structure GPR is a method particularly detecting in the rock mass the boundary between rocks with different electrical properties. Therefore, it can be assumed that, in addition to geoelectrically differing lithological boundaries, it can also yield information about the tectonics that could represent a “mirror” for electromagnetic beams. Low frequency aerials will have to be used for this purpose. The lower the frequency of the aerial, the greater will be the depth reach of the method. It would be more advantageous to
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use shielded aerials for these measurements, too. These should prevent reflection of electromagnetic radiation from the opposite wall of the gallery. As the shielded aerials are commonly available only for the frequencies of 100 MHz and higher, it is not possible to expect any significant depth reach. The estimated reach would be up to 10 metres. The reach will be greatly influenced by the underground water and its mineralization. It would be optimal to include also the lower frequency aerials (without shielding) in order to find out whether or not the multiple reflections from the working walls influence the useful signal. Similarly, it is necessary to test the possibilities of “borehole” radar in various applications: single borehole, borehole – borehole, and - if possible - also in borehole – gallery application. These measurement methods will not require any preparatory works performed using mining methods. Measurement can be performed at all places where there will be no “conflict” with other measurements, i.e., when there will be no risk of damage to other installed metres. These metres will be installed only for the duration of geophysical measurements. The only prerequisite is that no other activities will be performed at the site for the duration of geophysical measurements. Electrical radiography The question of water transport through fissures of various origins and various orientations represents one of the fundamental questions in hydrogeological assessment of the rock massif. “Electrical borehole measurements” appear to be a feasible tool for obtaining this information. In well logging methods, this principle is called the “electric well logging”. A suitably chosen electrode layout system together with special apparatus should suggest which fissures “communicate” and which, on the contrary, are “isolated”. This method could be applied in available boreholes and/or in boreholes that will be made accessible for the period of the geophysical measurement. Perforated plastic casing pipes do not have a negative impact on the measurement. After the geoelectric measurements are completed, the boreholes can be used for other purposes. Practically no geophysical measurements can provide results that could be designated as “certainty”. We always have to realize the fact that we work with indirect methods and that the results are obtained with given probability. It is even difficult to express such probability with some specific figures. When determining the probability of fissure systems interconnection, it is possible to assume that such probability will be relatively high. Seismic reflection Should the geophysical methods be required to provide information about geological structure in greater distances from gallery walls, the reflective seismology could give certain hope in this respect. Normal methodology used in surface surveys would, however, have to be modified and also the metering equipment would have to be adapted. It would be advantageous to use higher frequency sensors and/or sensing systems with reduced reception angle. This method should provide answers regarding geological boundaries within higher dozens of metres from the gallery walls and - in case of more powerful seismic signal source - even in the first hundreds of metres. This measurement could be relatively easily applied in the invert and walls of mine galleries. Measurement in the gallery ceiling would be considerably more difficult as the rock massif on the gallery ceiling is rarely accessible. When more powerful seismic sources are to be used, it may be necessary to drill very short holes (up to one meter) for seismic sources installation. Mine galleries will be free for other use after reflective seismology measurements completion.
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Specific requirements ● A possibility of material and equipment transport to the underground ● A power supply of 230V close to a near the inset ● Boreholes with stable walls without large cavities and falling rock fragments
Duration of the experiment Over the entire time of the underground facility operation. Further potential use of the experiment Stress monitoring, seismic monitoring, effects of geotechnical, hydraulic, and thermal experiments
4.2.6 Monitoring of microbiological contamination and the gradual colonization of the environment by the microorganisms
Goal of the experiment: The research will focus on the monitoring of bacterial colonization in different parts of the Bukov URF as well as on description the conditions and the impact of this colonization (humidity, time of the opening, temperature, oxygen concentration, and water composition of the satiating area). This colonization will be compared to the indigenous microflora in the granitic groundwater. The aim will be to obtain data on the occurring microbial communities and to evaluate the real risks of bacterial corrosion on the integrity and durability of the waste package and bentonite barriers. A comprehensive description of the colonization of a specific geological environment is a prerequisite for a complete assessment of the set of environmental effects on the underground repository in the long time periods. The focus on a functional analysis of the metabolic capabilities of the individual microbial groups is in such a case more essential than the taxonomic description of the colonization. This will significantly help to assess the possible negative impact on the DGR. The risk will be evaluated; finally the uncertainties will be determined. Conceptual proposal: Granitic groundwater and skims from the surface of the mine tunnels will be sampled during the project. In addition to monitoring of the most frequently occurring strains using advanced sequencing methods the individual strains directly responsible for bacterial corrosion using real-time PCR will be also monitored. The most common producers of bacterial corrosion represent sulphur-reducing bacteria (SRB) as an anaerobic bacteria and iron and manganese oxidizing bacteria. The procedure will allow detecting the most frequently occurring strains and the bacteria specific strains responsible for the corrosion. Technical solution: The following overview of procedures operates with the samples taken from the different parts of the URF. Those will be coordinated with other activities in the URF. The collected samples will be transported to the laboratory where will be analyzed. The laboratory analyzes will consist of: ● Isolation of DNA ● Real-Time PCR directed to individual selected biological markers
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● NGS analysis of microbial colonization ● Evaluation of data collected by the monitoring ● Selection of biological markers ● Report elaboration Specific requirements: ● The need for aseptic conditions during the sampling ● The need for training the personnel ● The time-sequence of the individual sampling ● Adequate transport to the laboratory Duration of the experiment: Throughout the entire operation of the URF. It is necessary to coordinate the sampling and the tests with other partners. Further potential use of the experiment: A comprehensive description of the geological environment of the immediate vicinity of the planned repository, implementation of methodologies for routine evaluation of conditions with the possibility to transfer to any other site and the addition of abiotic characteristics in the framework of specific investigation work
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4.3 Testing of groundwater hydraulic models and radionuclide transport models within DGR fractured rock environment
The basic premise for such activities is the following sequence of the tasks • detailed geological and hydrogeological description of the experiment site following the general geological and hydrogeological description of the all mine • comprehensive system of boreholes for experimental activities • complex geophysical measurements in selected boreholes (except video inspection, acoustic-oriented cameras ABI (Hirata), optical camera-based OBI (OPTV), density logging and acoustic P and S waves measurement along the borehole comes into consideration. Some geoelectric geophysical measurements even seem to be suitable for such a purpose) • Selected suitable and thoroughly tested borehole instrumentation • Selected tracers for testing of the experimental system (non-active) • Selected radiotracers (if they are selected to be used) • Thoroughly selected methods for tracer detection, both active and non-active • Complementary laboratory program Modelling programme should implement at least part of the following activities • hydraulic and transport model development and testing on the basis of structural and geological models • regularly updated hydraulic model of the of the experiment/URF vicinity, potentially being influenced by the experiment progress • upscaling for effective development of hydraulic field model in the large scale • use of discreet fracture network concept on the basis of geological characterization of brittle structures • models of individual hydrodynamic test • models of individual experiments itself • testing of different concepts in transport modelling (DFN vers. ECPM etc.) for selected experiments • predictive and post-mortem modelling are both inevitable parts of any experiment programme in large scale
4.3.1 Hydrodynamic tests in the boreholes
Goal of the experiment: The aim of hydrodynamic tests is determination of rock hydraulic properties and their variability in the URF area. The permeability of fracture networks in the micro (rock matrix) and macro (massif) scale will be studied simultaneously.
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. Conceptual proposal: Hydrodynamic tests (water pressure tests and/or pumping tests and pulse tests) will be carried out in the selected research boreholes and in the boreholes designed for various types of the experiments. Evaluation of tests will be based on mathematical modelling. Permeability of rock matrix will be studied on drill core samples in the laboratory. Testing will take place in the regular, consecutive intervals in the entire borehole profile and partly in detail at the selected positions, determined for the subsequent experiments. The latter could be for example a characterization of conductive fracture for migration experiments or on the contrary determination of a suitable interval of undisturbed rock matrix. Technical solution: All available and technically suitable boreholes in the URF and in its surroundings will be used for the study of the rock hydraulic properties. In the absence of suitable boreholes in the area outside the experiment, new boreholes should be drilled. Water pressure tests (WPTs) will be the basic type of the tests. During WPTs water is pumped under constant test pressure into the borehole section, separated by the packers. The amount of water, being pumped in is measured simultaneously. Supplementary type of tests would be the pumping tests and the pulse tests. Supplementary tests will be used namely for result comparability and can be also used by mathematical models for evaluation and/or verification. The only requirement toward tested boreholes is stable walls. Furthermore, testing will be carried out according to the requirements of a particular experiment. The tests will take place at three levels: Tests in the research boreholes beyond the experimental area will be used to determine the hydraulic properties of the encountered rocks and fracture systems in deep level of underground facility. Tests in the boreholes, designated for experiments, will verify the hydraulic properties of the fracture network and the rock matrix in the immediate vicinity of the experiment. Tests will allow the processing of detailed site model for transport experiments and evaluation of the experiment influence to the hydraulic properties of rocks. Tests in wells near the thermal experiments will verify the extent of fracture permeability changes due to temperature variations and related changes in the rock mass stress. Influence of the orientation of the individual tested fractures / faults on the change of permeability will be observed. Two to three vertical or inclined downhill boreholes will be drilled for these tests. Tests in boreholes will be performed – before the start of the experiment, during the experiment and after its termination. Extended monitoring focused on the effect the flow regime will be a part of all hydrodynamic tests. Changes of hydrostatic pressure and recharge values will be observed on available adjacent monitoring points in the URF Bukov. The test progress will be simulated using mathematical hydrogeological models. The mathematical model will be calibrated to measured data and will provide more precise image of rock environment geometry and will determine hydraulic parameters. The evaluation method will depend on the test specific configuration (type of the test, test instrumentation,
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test method for monitoring etc.) and by the knowledge degree of the geological and tectonic structure of URF specific parts (geometric model). Hydraulic resistance will be determined as the hydraulic conductivity coefficient for the tested borehole sections and the lithological types. Furthermore, hydraulic parameters of fracture networks (effective network connectivity, effective fracture opening) will also be determined. Hydraulic conductivity of the rock matrix will be determined on drill core samples as well as the hydrodynamic tests in boreholes. Sample selection will include all rock types encountered. Specific requirements: • 230V / 400V power supply; • transport of material and equipment underground; • supply of water; • boreholes with stable walls without extensive caverns and falling debris of rocks; • logging of boreholes in advance before starting the tests – especially acoustic TV, calliper, resistivity; • vertical or inclined downhill boreholes. Duration of the experiment: Simple or repeated measurements would last few days or few weeks in a single borehole. Hydrodynamic tests will be carried out depending on technical availability of boreholes. The radius of impact will depend on the geological environment, which will be tested. For tests in the rock matrix, the maximal radius is in first tens of centimetres, for the tests on significantly conductive structure, the maximal radius is in tens to hundreds of metres (along the structure). In disturbed rock environment (inexpressive and closed fractures) and short-term testing period the test radius will reach a maximum in metres. Further potential use of the experiment: The results of hydrodynamic tests would the basis for transport experiments and mathematical models. .
4.3.2 Hydraulic model assessment
Goal of the experiment: The aim of hydraulic modelling assessment will be testing of the models, using real data acquired at similar depth to the planned DGR depth. Input options, potential of credible simulation and prediction of the specific task results (hydrodynamic tests - HDT, impact of the experiments on the natural conditions, etc.) in the fractured rock environment will be tested in the context of the system description, continuously being obtained by geological survey and hydrogeological monitoring.
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Conceptual proposal: Geological description and hydrogeological test (suitable form of HDT) for each geotechnical object (borehole) provide data for potential model simulations: for geometric model realization and for mathematical simulation of hydraulic processes during the test. Data from subsurface geological survey, regular hydrogeological monitoring and ongoing tests/ experiments will enable to compile and to continuously update hydraulic (hydrogeological) model of the flow regime around the facility. The result provided by the model will be the analysis of the influence of individual experiments on natural hydrogeological regime. 3D structural model and hydraulic model are the bases for any solute transport model. Technical solution Each drilled borehole in the URF will be described in detail in terms of the geological and tectonic rock characterization. These data will be processed accordingly into the form of 3D structural model of the borehole vicinity. 3D structural model (processed geological data) will be used for the hydrogeological model domain geometry generation or it will complement existing domain. The domain geometry has to be prepared in suitable form for hydraulic calculation (primarily calculation of hydraulic head) in certain hydrogeological computing code. 3D structural model will be extended to the flow model. The credible input, generalization and upscaling of the available data from the resistive and capacitive parameter tests will be tested. Derivation of such parameters should be done through the calibration of stationary and transient models, simulating the progress and results of HDTs. Suitable HDTs will be simulated in a predictive form. Calculated and measured data will be compared afterward to evaluate the efficiency of modelling process. Furthermore, model simulations of individual hydrogeological tests and effects of experiments will be used for continual supplement and update of the hydraulic model. This will be part of a regular annual hydrogeological evaluation of the groundwater flow regime in the area of Bukov laboratory. Modelling allows uniform evaluation of spontaneous leakage and pressure test results. In both cases the flow of water is considered, but at different scales and different directions and configurations. The aim of the modelling will be to describe the hydraulic parameters of the environment in the way they are in consistency with both types of measurement. That means to validate the entire process of evaluation. Implementation of hydraulic models in the URF environment would allow: ● to specify and test suitable methods of hydraulic modelling, ● to determine the level of uncertainty in the use of mathematical models, ● to perform a sensitivity analysis of the influence of each input parameter on the results of the solution, ● to systematically and synthetically processed data from geotechnical, geological and hydrogeological works performed in the PVP Bukov, ● to provide a hydrogeological analysis for the hydrogeological evaluation of all experiments performed in Bukov facility,
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● to provide the necessary basis for transport models. Specific requirements ● software for hydraulic modelling based on the concept of discrete fracture/fracture networks; ● coordinated information shared with geology, hydrogeology and engineering procedures in the implementation and monitoring of the HDT. Duration of the experiment Throughout the entire time of the underground facility operation. Further potential use of the experiment Hydraulic modelling provides data for hydrogeological evaluation of the flow regime in specific parts of Bukov URF and will form the basis for subsequent experiments to solve the transport or reactive properties of groundwater and rock environment as a geological barrier. Model data will be used for detailed planning and evaluation of the various tests and experiments. Hydraulic gradient distribution and locations of permeable zones will enable to predict the direction and velocity of tracers’ movements. According to these results the suitable locations of boreholes and their permeable sections for tracer injection can be designed as well as the levels of pressure during their injection.
4.3.3 Programme of migration/tracer tests
The main goal of the proposed activities will be testing and verification of radionuclide transport codes and models under real conditions of crystalline host rock. The conditions would be verified on the bases of real experimental activities. Basically, the first step comprises the exact definition of the planned tracer test, i.e. if the main goal of the tracer test should be • host rock environment characterization (e.g., fracture network characterization) • transport processes of relevant tracer in fractured host rock environment and/or undisturbed rock matrix. Following potential focus of the tracer tests could be expected - Transport processes understanding: o migration tracer test in the system of several boreholes, o diffusion experiment in the undisturbed rock massif, - Fracture network connectivity description: o Tracer tests on the specified fracture network, using specific dyes.
A unique possibility to use radioactive tracer for migration experiments seems to be evident, considering the existence of the controlled zone for activities with ionizing sources in Rožná mine.
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Migration tracer tests in the system of several boreholes Goal of the experiment: The goal of the experiment is to understand to transport and retention processes of selected tracers in Bukov URF fractured environment. Moreover, models and codes for their description will be tested within proposed experiments. Conceptual experiment proposal: Basically, the most important premise for tracer tests in this case is drilling of suitable borehole system within selected fracture network; Such a fracture network should enable tracer tests with different types of tracers. It is expected that the main focus of the tests should be transport processes (advection, diffusion). However, modification of borehole system with a suitable instrumentation could be also used for complicated tests as for example fracture network connectivity tests, determination of fracture wetted surface etc. Controlled zone in the Rožná mine enables to use radiotracers for experimental activities, namely due to possibility to approach the real DGR system conditions, altogether with low detection limits. The experiments will provide data for activities in the chapter 4.3.5. Transport model testing. Predictive and post-mortem modelling on the other hand will contribute to prediction of experiment procedure and result evaluation. Technical solution: The suitable rock block has to be found within Bukov URF, assuring following assumptions: ● conclusively identified fracture(s) that would be hit by the experimental boreholes ● presence of advective flow in the fracture with natural or antropogenical flow ● anaerobic conditions (underground water level in the sufficient distance from the URF tunnel ● development of fracture network model in the selected rock block
The borehole system will be drilled in the selected block. The boreholes will be emplaced in the way to hit conductive fractures, identified from the tunnel wall or during drilling campaign. A detailed hydraulic testing will be proceeded to the tracer testing (see chap. 4.3.1). Hydraulic testing will result in conductive fracture identification and determination of mutual connectivity between boreholes. Such an information enable selection of suitable fractures for the experiment and moreover the selection of injection and monitoring boreholes. The boreholes on the basis of their selection will be instrumented with the multipacker systems according to their assumed function (injection borehole - monitoring borehole) Construction of borehole system depends on the experiment goal. Potential options are following 1. Multi-borehole system is suitable for determination of fracture network connectivity. Tracer advance is determined along identified fractures, altogether with tracer dispersion and diffusion in the system.
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Fig. 2 Schematic figure of borehole system for fracture network connectivity study Advective transport of the tracer in the fracture is expected, furthermore influenced by dispersion, generated by nonhomogeneous flow in the fracture, and diffusion toward undisturbed rock matrix. 2. Two boreholes system (dipole) is suitable for transport process studies (advection, diffusion) in defined fracture
Fig. 3 An example of dipole experiment instrumentation in discrete fracture (NAGRA 2000)
In such a case advective transport is expected in combination with diffusion into the undisturbed rock matrix. Basically, identification and isolation of a single fracture would be suitable to prevent tracer dispersion along other fractures. In the same time fracture flow should exhibit appropriate rate (predicted by the model) in order both processes, i.e. transport and retention, would have balanced intensity, resulting in distinctive breakthrough curve that can be evaluated using mathematical models. Multipacker system will be installed into the boreholes in order to divide the intervals of interest. Instrumentation will be realized in a way that the tracer is injected into the injection borehole, while monitoring boreholes are sampled for tracer content in the groundwater or
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probes with direct determination of defined parameters are installed directly into the system. Puls injection of the tracer into the injection borehole is presumed. Except the experimental set-up with natural fracture flow such tests can be also modified using drawing test on the selected borehole. Experiment type and instrumentation set up can be planned and decided only after thoroughly description of geological and hydrogeological situation of the site. Tracer selection 1. Fracture flow connectivity and dispersivity in the rock • dyes • non sorbing conservative tracer 2. Transport parameters • dyes • non sorbin conservative tracer • anion • redox sensitive species • mildly sorbing cation • strongly sorbing cation
Both non-active and active tracers can be used. Concentration/activity would be selected according to the predictive modelling, hydraulic conditions of the fracture system, groundwater composition and analytic method sensitivity. Tracer test is possible to repeat or modified, according to purpose and situation. If the intention of the experiment is to study fracture character (opening, flow wetted surface) resin injection with following overcoring is a suitable procedure how to withdraw the information from the real system. Impregnated fracture is then subjected to the thorough examination. In the case of radiotracer use it is convenient to use/develop a detection system for direct measurements in situ. In-situ experimental programme has to be accompanied with laboratory programme and modelling. Modelling is inevitable part of the activities, both during experiment planning (predictive modelling) and result evaluation (post-mortem modelling). An important step, utilizing modelling, is experiment dimensioning within the real hydraulic conditions. Models would enable predicting an advective flow and planning an appropriate borehole distance, altogether with injection rates or pressure size in order the experiment proceed in the selected time period and within monitoring interval. In the case of radiotracer use radioprotection measures has to be taken in order to assure both worker and visitor safety and environment protection.
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Specific requirements: ● suitable selected location for borehole system (appropriately chosen fracture network, suitable hydraulic gradient present); experiment has to be preceded not only by the hydraulic tests, but also by pressure monitoring in packed horizons ● undisturbed environment (by other experiments) ● fracture network model ● borehole drilled up to the appropriate depth ● detailed borehole description, including mutual distance ● suitable system instrumentation ● groundwater composition analyses ● appropriate selection of tracers ● 220V/380V power supply, ● lightning, switchboard ● transport of the material and equipment to the site ● internet connection ● laboratory support on the surface (solution preparation, analytical analyses) ● radiation protection in the case of radiotracer use
A zone that will be influenced by the performed experiment depends on the conductivity of the fracture. In case of low conductivity it could be several metres up to the first tens of metres Experiment duration: Duration of each experiment will depend on its purpose and complexity. Further potential use: Main purpose of the experiment is to study processes of advection and diffusion in the rock mass environment and furthermore, to also look into fracture network connectivity However, the experiments can contribute to other outcomes • description of the rock massif (including geophysical investigation of the massif) • hydrogeological description on selected site (chap. 4.1) • hydraulic parameter determination for both individual fracture and fracture network as a complex (chap. 4.1, 4.3.1) • fracture network model on the selected site (chapter 4.1) • development of measurement device • testing of transport models (chapter 4.3.5) Long-term diffusion experiment Goal of the experiment Goal of the experiment will understand of the diffusion process as a transport process from the fracture into the undisturbed rock matrix. Moreover, the experiment will be used for testing models that describing the process.
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Conceptual proposal: The basic concept of the experiment is based on the presumption of tracer injection to the undisturbed crystalline rock massif. Tracer solution will be then kept in the contact with the rock matrix along defined time period. Diffusion process will be described using concentration/activity decrease in the injection borehole, concentration/activity increase in the monitoring boreholes, altogether with evaluation of diffusion profiles in the rock itself after borehole overcoring. The controlled zone in Rožná mine brings an inevitable advantage of possibility to use radioactive tracers for such experimental activities, namely utilizing maximal approximation toward reality and high sensitivity of radioanalytical methods. Stud of diffusion as a retention process would be also possible in the short term period (hours to days), using the experiments in the fracture system (see chap. 4.3.3.). Technical solution: The undisturbed rock block has to be identified within Bukov URF, located in the way the following preconditions are fulfilled: ● undisturbed rock massif ● absence of advective flow ● anaerobic conditions (under groundwater level in sufficient distance from the tunnel) An exploration borehole will be drilled, being subsequently characterized in detail (geology, hydrogeology, and geochemistry). Following that, hydrodynamic tests in the borehole will proceed (see chap. 4.3.1). The goal of the test will be characterization of hydraulic properties of the rock massif. All the results will be directed towards determination of the experimental injection interval in the borehole. The basic presumption is to drill one single borehole (monopole) instrumented with a multipacker system that would enable to leave the experimental interval open to the contact with experimental solution. The circulation system will be implemented in order to allow tracer solution injection and sampling of the solution in the contact with the massif. The experimental system can also consist of multi-borehole system, i.e. an injection borehole and system of one or several monitoring boreholes. Each borehole has to be carefully characterized (see above). In such a case exact distance between boreholes has to be determined. Monitoring boreholes, aimed to observe approaching diffusion front from the injection borehole, would be also instrumented with a packer system in the depth matching the interval of the injection. When it is proved that the system is hydraulically stable, i.e. no advection flow takes place in the observed rock block, and the tracer solution can be implemented into the experimental reservoir. Experimental solution is than left in the contact with the rock mass for defined time period. According to the experimental plan all the selected boreholes are sampled in defined time periods. Furthermore, hydrochemical parameters of tracer solution are measured. All the analyses should be performed as soon as possible after sampling. In case of radiotracer application it is possible to use or to develop in-situ detection system directly in the borehole. Radiotracer selection has to be done with the respect to expected outcome of the experiment. The most effective choice is a combination of conservative non-sorbing tracer, anion, and finally mildly and strongly sorbing cations. Concentration/activities have to be
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chosen according to the URF and experimental conditions (groundwater chemical compositions, sensitivity of analytical measurement etc.) When the experiments are finalized, the packer is removed and the solution is stabilized in the rock (e.g., resin injection). Following that, the injection borehole will be overcored. The experimental interval will be removed, divided according to the analytical method requirements and send for analyses of diffusion profiles. However, determination of diffusion profiles is suitable only for sorbing tracers. Multiple borehole system when the diffusion front is determined in the monitoring boreholes is more efficient for observation of nonsorbing tracer. Their diffusion profile can suffer from any sample preparation that enters high uncertainty into the system. In-situ activities have to be complemented with laboratory programme and modelling. In case of radiotracer use the radioprotection measures has to be undertaken in order to assure workers´, visitors´ and environmental safety. Specific requirements ● suitable selected site for the borehole system (undisturbed rock, stabile and infected hydraulic field, anaerobic conditions) ● undisturbed environment (by other experiments) - highly needed! ● fracture network model ● borehole drilled up to appropriate depth ● detailed borehole description, including mutual distance ● suitable system instrumentation ● groundwater composition analyses ● appropriate selection of tracers ● electro power 220V/380V, ● lightning, switchboard ● transport of the material and equipment to the site ● internet connection ● laboratory support on the surface (solution preparation, analytical analyses) ● radiation protection in the case of radiotracer use Experiment duration: According to need; the best would be 2 - 4 years. Further potential use: The basic assumption is to employ the experiment for study of diffusion in the rock environment. Within the experiment it is possible to gain data on: • description of the rock massif (including geophysical investigation of the massif) • hydrogeological description on selected site (chap. 4.1) • hydraulic parameter determination for both individual fracture and fracture network as a complex (chap. 4.1, 4.3.1) • fracture network model on the selected site (chapter 4.1) • development of measurement device • testing of transport models (chapter 4.3.5)
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Tracer tests monitoring connectivity of the fracture network Goal of the experiment: The experiment will be focused on verification of velocity and character of groundwater flow in the fracture network in crystalline rock environment at the DGR depth. Moreover, it enables detailed exploration / verification of connectivity of the fracture network studied Conceptual proposal: A horizontal borehole, heading parallel to the tunnel wall or at the angle of approximately 30° to the tunnel wall will be injected by a tracer solution. Arrival of the tracer solution to the tunnel wall will be monitored in time and space using cameras or other monitoring technique. Technical solution: In the tunnel beyond the URF, a horizontal borehole of about 15-30 m length will be drilled, parallel to the selected wall. Possible direction is also at an angle of approx. 30 ° to the wall. A suitable tracer solution, which is not significantly adsorbed to the rock or to the fracture infill, will be injected into this borehole. Constant injection pressure of several bars will be used, or more according to local conditions, to overcome local hydraulic gradients and ensure migration of the injected fluid to all directions from the borehole, incl. direction to the tunnel wall. The tunnel wall will be illuminated by a light of suitable wavelength (e.g., long wave UV), that will induce good visibility of the tracer (e.g., fluorescent). Such effect will be monitored by a system of cameras. Those will record images of fracture network on the tunnel wall in the constant time steps. Such a procedure will document gradual penetration of the tracer from injection borehole through fractures in the undisturbed rock matrix and through the EDZ nearby tunnel wall. A prerequisite is the occurrence of appropriate fracture network in the location where the injection borehole could be drilled. Length of the borehole and its distance from the tunnel must be proportional to the average length of fractures in the rock massif between the borehole and the tunnel. The rear part of the injection borehole must be located in the rock massif at a depth several times higher than is a length of the individual fractures encountered by the borehole, in order to be capable of revealing relatively complex fluid migration along crosscutting fractures etc., and not only to exhibit different permeability of individual single fractures between borehole and tunnel. After penetration of the tracer through at least part of fractures on the tunnel wall, the injected tracer can be exchanged for a different one (with different fluorescence colour etc.), to e.g. allow monitoring its penetration into the structures already saturated with the first tracer or to perform semi-quantitative evaluation of mixing fluids with the two tracers. Specific requirements: ● 230V power supply; ● network for data transfer; ● installation of specialized light sources of a suitable wavelength to induce visibility of the tracer (e.g., long wave UV); ● possibility to transport material and equipment into the underground; ● supply of technical water; ● horizontal borehole;
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● borehole logging before start of the experiment – especially acoustic TV, cavernometry, resistivity; ● hydrodynamic tests of the experimental injection borehole before start of the experiment – tests to quantitatively characterize individual parts of the borehole. Experiment duration: At least two years including the preparation. If the results will be beneficial for SURAO, it can be easily extended to the entire period of operation of the underground laboratory (preliminary plan for 10 years). Further potential use: The existing field and laboratory tests clearly show that groundwater in brittle structures usually does not migrate along the entire surface of the structure, but it rather migrates along irregular preferential paths which often follow crossing of brittle structures, inhomogeneities of fracture infill etc. This is especially true in the case of mesoscopic structures, such as fractures, fracture zones and minor faults. Therefore, the brittle structures cannot be confidently characterized by a homogeneous hydraulic conductivity in numerical simulations. It is eligible to test and refine methodologies how to most precisely characterize the fracture environment and related preferential fluid migration paths in numerical simulations of groundwater flow, using field data from a particular example of well described rock environment. Application will be mainly in these subjects: • testing and verification of the structural-geological models incl. DFN models, mathematical models of groundwater flow and the possibility of complementing detailed fracture models using bulk anisotropy of hydraulic conductivity of the rock massif. • testing of transport simulations.
4.3.4 Determination of groundwater age and origin
Goal of the experiment: The aim of the research will be assessment of the groundwater residence time in geological environment and determination of the GW mixing degree o from various sources around the URF. The residence time of groundwater in the rock environment is an important indicator of the fluid migration rate. Origin of groundwater suggests the possibility of communication of deep groundwater with the subsurface zone or biosphere. These factors would significantly affect the DGR safety. Conceptual proposal Samples of groundwater will be collected in the URF and its vicinity. Age of groundwater and its isotopic composition will be determined by the means of geochemical methods.
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Technical solution Origin and mixing of groundwater will be determined based on the groundwater chemical composition and their physical and chemical properties (Eh, pH, temperature) and on observation of stable isotopes of D, 18O, 34S and 13C in groundwater and surface water. Age 3 3 14 of groundwater will be defined using the methods of H, He, C, SF6 and CFCs. The most appropriate method will be those mentioned above, based on the conditions found in Bukov URF and according to the GW chemical composition. The results of individual methods will complement mutually, resulting in precise information about GW age. Samples will be collected from the main inflows with high recharge in the URF and its surroundings, from the upper and lower parts of the Rožná mine and from the surface water resources in the infiltration area above the facility. Geochemical interaction processes of groundwater with rocks and the residence time of water, which is inflowing into the facility, will be determined subsequently. Specific requirements: ● a sufficient amount of water needed for each analysis – some elements may be present in very small amounts in the groundwater and subsequently a large amount of the solution must be collected in order to separate a sufficient amount of analyte (tens to hundreds of litres); ● transportation of the required material for the collection of bulk samples of water; ● precise analytical procedures.
Experiment duration Determination of the GW age will take place mainly in the first years after the construction of the underground facility. Stable isotope analyses should be performed in the period at least three years in order to catch up their seasonal variability. Further potential use of the experiment • mathematical models of groundwater flow; • long-term hydrogeological monitoring; • transport simulations.
4.3.5 Transport model testing
Goal of study: The aim of this part of work is (a) to verify the potential use of various conceptual models for solute transport in the rock with fracture permeability (b) to directly use the models as a part of the migration experiments data evaluation (4.3.3). The result should be evaluation of the importance of individual processes in dependence on the conditions (experiment configuration), on rock parameters (to certain extent), on scale effect etc.
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Conceptual proposal: The model concepts should be based preferably on the real configuration of the particular types of migration experiments (see 4.3.3). For a more detailed understanding, additional models with “synthetic” configuration can be included, e.g., for demonstration of relations among the phenomena and among various conceptual models (dimension, continuum / discrete fracture network). The transport models will be closely linked with hydraulic models (see section 4.3.2), both due to the geometry used and due to the use of particular hydraulic parameters determining the velocity field for the advection calculation. The results of the transport model calibration based on the migration experiments can eventually contribute to the further improvement of the hydraulic models (data, fracture configuration) and vice versa. Technical solution: Several computer programs are suggested to be used in order to cover the appropriate extent of various conceptual models, physical phenomena, and available numerical schemes. The models will be mainly concentrated on the following principal transport phenomena: ● Advection in the velocity field, determined by the hydraulic models (in fractures) ● Hydrodynamic dispersion in the mobile water volume ● Matrix diffusion (as both transport and retention process) ● Sorption The use of models will be possible in several regimes: ● Inverse modelling, i.e. determination of model parameters (evaluation the rock properties) with the optimal fit of the model outputs to the measurements, for particular selected conceptual models. ● Verification of mutual relations between different conceptual models, expressing a combination of the transport and the retention. ● Comparison of the inverse modelling results between different scales, which could be seen as a model validation using the parameters identified from the experiment in another configuration or another spatial/temporal scale. ● Identification of uncertainties in the conceptual model selection and in the rock parameter determination (as a result of equivalent data fit by different models) The use of various conceptual models can include: ● Various spatial dimensions (1D, 2D, 3D, axisymmetric) ● Representation by either the equivalent continuum or the discrete fracture network ● Various representations of the matrix diffusion in connection with the advection
Specific requirements: ● A suitable set of software allowing a use of more different solutions (link/comparison) and a direct connection to the hydraulic models (geometry, data) ● Schedule coordination with planning and interpretation of the migration experiments
Experiment duration: Over the entire time of the underground facility operation.
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Further potential use of the experiment The research area is in reversible link with the migration experiments (sec. 4.3.3) and offers potential for the interpretation improvement in further areas – the hydraulic models (sec. 4.3.2), the hydraulic tests (4.3.1), and water age determination (4.3.4). In the latter case, the relation between the transports in different scales is concerned (units of metres for migration tests between boreholes and hundreds of metres and more for 4.3.4). The determined rock parameters could be also studied in relationship to the geophysical measurement
4.4 Testing of rock mass influence on changes of potential engineering barrier properties
The aim of proposed experiments is to determinate the effect of host rock conditions, corresponding to the DGR depth, on behaviour of potential engineering barrier materials. The experiments set-up should be complex in order to allow evaluation of influence of several processes at the same time (as e.g., corrosion itself, effect of corrosion products on bentonite, effect of microbial activity in system etc.).
4.4.1 Corrosion experiments under anaerobic conditions in granitic host rock
The proposed experiments will reflect real system as much as possible. They will be performed with Czech candidate SNF canister materials. Technical and experimental design will reflect Czech DGR concept and will allow performing complex experiments in order to use more materials in one experiment. Obtained results will be compared with the result from the laboratory experimental programme and furthermore will be implemented into the DGR safety assessment.
Corrosion experiments under anaerobic conditions Goal of the experiment: The main aim of the experimental work is to determine corrosion rate of the candidate materials from the SNF canister outer shell under DGR conditions. The experimental results would provide data for the development of canister outer shell technical design and also will be used in evaluation of canister performance and safety assessment. The main aim of the experiments will be to determine the corrosion rate of the proposed materials for the outer part of the container. The corrosion rate has to be considered for the conditions in the expect DGR environment. Conceptual proposal: The experimental equipment containing the samples of candidate metal materials, surrounded by compacted bentonite of appropriate dry density, will be emplaced into URF Bukov. The experimental apparatus will allow the sample temperature regulation and will also prevent oxygen intrusion into boreholes.
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Technical solution The equipment technical solution will be based on the experience, used within international and Czech projects, focused on in-situ corrosion experiments. Experimental activities has to be in accordance with the SÚRAO project, focused on canister technical design Research and development of disposal canister for spent nuclear fuel until the specimen development (SO2013-088). Equipment technical design has to involve regulation of sample temperature as a simulation of SNF heat flux. Metal samples have to be in direct contact with compacted bentonite of specific dry density. The compacted bentonite will be of Czech origin. It is presumed that bentonite swelling pressure would reduce microbial activity inside the bentonite. However, testing of microbial activity should be involved in the experimental programme as well. During the experiments is necessary to reach anaerobic condition and to reduce the penetration of the oxygen into system through drilling boreholes. After borehole drilling boreholes it is recommended to close them by the packer systems in order to prevent oxygen penetration. Moreover, during the experiment preparation the system of bentonite – metal samples will be prepared under anaerobic conditions in order to eliminate oxidizing effects. Technical solution of the apparatus should be modular to easily replace metal samples with new ones. During the sampling bentonite will be also taken, that will be analyzed according to the research requirements. After the dismantling determinate corrosion rate will be done and analysis of corrosion product will be performed etc. During sampling process will be reduced the oxygen contamination of corrosion system and boreholes. Equipment technical design should be modular in order to replace removed samples with a new set of the samples. Altogether with metal sampling bentonite samples will be taken in order perform specific analyses (mineral composition, corrosion product content, CEC, microbial content etc.). Oxygen intrusion should be minimized during sampling. Technical design can also allow installation of equipment for continuous corrosion rate measurement in order to determine corrosion rate decrease at the beginning of the experiments. Equipments will also contain a groundwater sampler around the corrosion system. The sampler prohibits oxygen penetration into systems and will be easy to manipulate. The water samples will be provided for chemical and microbial analysis. Specific requirements: ● Heat flux can affect other experimental activities (rock stress etc.), therefore specific emplacement should be considered for such activities; ● Saturated zone for emplacement of the equipments; ● 230V/16A power supply; ● Data connection; ● Specific techniques of boreholes drilling (to minimize intrusion of oxygen to the boreholes); ● Detailed borehole characterization; ● Technical support from DIAMO; ● Protection of equipment against damage.
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Duration of the experiment Time scale for the experiment duration: 1, 3, 5, 7 and 10 years (duration of the longest experiments depends on Bukov URF operation time). Further potential use of the experiment The corrosion rates will be used for specification the lifetime of the SNF canister materials under DGR conditions and in order to produce required input to the corresponding safety case analysis. Sampled ground water will be provided for chemical and microbial analysis (see 4.4.2). There can be also analyzed the effect of the corrosion product on bentonite etc. On the other hand the experiments can be used for determination of the effect of heat flux on parameters of host rock stress etc. (see 4.3.2., 4.2.2 etc.).
Experiment of Mock-Up type Goal of the experiment: The experiment will be focused mainly on study of compacted bentonite long-term stability during long-term heat exposure in real host-rock conditions. Corrosion of steel samples and microbiological processes will be also investigated. Conceptual proposal: Physical model assembled as a supercontainer will be inserted into the vertical borehole. The experimental borehole containing supercontainer will be closed in order to the swelling pressure will increase gradually due to bentonite saturation by groundwater. Artificial heat generation will be controlled to reach and maintain 90 °C on contact of heater-bentonite barrier. Sampling will be possible both after dismantling and during experiment operation. Technical solution The experiment should be built in a short, dead-end gallery, close to its face. The rock disrupted during gallery excavation should be removed in the model vicinity. Then concrete platform should be constructed to enable fixing the drilling machine. The borehole with 380mm diameter to depth of approx. 1200mm is proposed. The low pH concrete layer will fill the base of the drill. Low pH concrete layer (thickness approx. 7 cm) will also cover supercontainer and its bentonite blocks. Due to sufficient amount of available data about bentonite swelling behaviour the instrumentation of such a kind will not be needed inside the experiment. Thermometers will be emplaced into the network of monitoring boreholes around the experiment. It is expected that temperature in surrounding rock will increase roughly of about 1 °C in a distance of 1.5 m from the borehole. The 350kg heavy physical model will be assembled as a supercontainer (SC) at the ground laboratory and then transported to the testing well in Bukov URF. The model will be equipped with protective cover during transport. The supercontainer body will consist of heater in the centre, surrounded with compacted bentonite blocks around it. A sheet of steel (container candidate material) may cover the heater and could be used as a "super" sample for corrosion study. Moreover, further corrosion samples will be incorporated into or between the bentonite blocks during SC manufacturing and assembling.
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The design of SC will allow core sampling (core drilling) of the bentonite barrier during operation of the experiment. The samples will provide information on saturation progress and may be used for corrosion and microbiological investigations. The dismantling of the experiment (sampling procedures, number and size of samples etc.) will be managed with respect to demands of studies on mineralogy, microbiology, corrosion, geochemistry and geotechnics. Thermal influence of the surrounding experiment will be low; however it still has to be taken into account. Water flow around the experiment can be relatively high (e. g. due to drainage of the gallery). Potential erosion and transport of colloids should be taken into account and possibly monitored in boreholes around the experiment. On the other hand, transport of water (colloids) could be controlled (driven) by artificial pressure field. Specific requirements: ● The experiment, due to its size and heating, might influence other experimental work in the URF (esp. due to modified stress and hydraulic field around). Therefore the experiment should be in sufficient distance from other tests, ● Suitable place should have height min. 2.5 m; width min. 2.5 m; separate ventilation (if dead-end gallery is more than 10 m in a length) ● Access to technological water ● Suitable known hydraulic conditions ● Light, electric board and 230V/400V power supply with a backup ● Data network (Ethernet) with EMI filter and connection into the internet (or other wide network); could be replaced by regular manual download of data from dataloggers ● Optical network ● Possibility to transport of material and equipment to experiment construction site (drilling machine, concrete mixer, electrical winch etc.) ● Possibility to transport the supercontainer to the site
Duration of the experiment: As long as needed for intended studies, at least 4 years (sampling expected twice per year). Further potential use of the experiment: Key research area of the experiment is long term behaviour and stability of bentonite – its mineralogy, geo-chemistry and geotechnical parameters. Microbiology and corrosion studies represent bonus potential, being based on the main experimental aim. On the other hand the results can be used to study rock stress field and material interactions within the SC - see chap.4.2.2 or 4.4. The results can be also used for THMC modelling. .
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4.4.2 The influence of microbes on degradation of engineered barriers and the penetration of microorganisms in bentonite
Goal of the experiment: The aim is the indication of corrosion active microorganisms and their potential impact on the corrosion of waste package materials or their potential impact on engineering barriers materials. Conceptual proposal: In the underground facility, several experiments (4.4.1, 4.4.3) will be operated, which allow providing suitable samples for verifying of the microbial activity, having an impact on microbial corrosion of the waste package materials and/or causing changes in the structure of the bentonite and its properties. During the experiments, the particular samples will be taken to verify the activity of microbial communities and for the characterization of the studied construction materials (metal, bentonite, cement). These samples will be taken either continuously (see Mock-up experiment) or after the termination of the experiment. It is also possible (as an alternative solution in the preparation phase of the experiments) to use targeted inoculation of some parts or components of the experiment by the well defined particular microbial communities. Then the comparison of such altered and unaltered material samples (of the waste package and/or bentonite) can be made. After performing of all planned analyzes, the potential impact of microbial communities to waste package and engineering barrier material properties will be evaluated.
Technical solution Methodically, all activities will be supported by in-situ sampling, intact sampling, DNA extraction, Next-generation sequencing (NGS), development of biomarkers, and providing of reference taxons Project will monitor following areas: • Creation of a matrix of functional groups of potentially dangerous microorganisms; • Development of appropriate biomarkers and validation of their impact; • Monitoring the dynamics in microbial community structure; • Isolation of microbial DNA from bentonite samples; • Estimation of the secondary contamination level; • Continuous sampling and data collection; • Evaluation and creation of comprehensive reports. For experiments (4.4.1, 4.4.3), a plan will be created in order to acquire of key construction materials (samples of bentonite, cement) at different times. This material will be subject of microbiological and molecular testing.
Apart from the sampling of originally microbiologically non-activated material, there is an opportunity in the Mock-up experiment (4.4.1) to consider the implementation of the specifically defined construction materials, inoculated by previously known microbial contamination. After experiment dismantling, a comparative analysis of indigenous and inoculated samples for microbial vitality, viability and proliferation could be carried out.
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However, such an implementation should endanger in any way the progress of any other experiments. An integral part of the result evaluation must be a feedback towards the results of the experimental section 4.2.6. Specific requirements: ● long-term monitoring of changes in the underground facility and subsequent laboratory analysis (microbial colonization of bentonite); ● experience with intact sampling; ● infrastructure for molecular biology; ● preparation of technical solutions; ● overview in biomarkers; ● experience with biomarker preparation according to the experiment needs; ● ability to analyze the vitality and viability of microbial colonization; ● time demanding ● close cooperation with research teams (challenging technical and methodological cooperation); ● economic demands - modulated. Experiment duration: The entire period of the underground facility operation Further potential use of the experiment: ● - Identification of the extent of container material corrosion ● - Monitoring of bentonite long-term stability.
4.4.3 Material interaction experiments (cement, bentonite)
Goal of the experiment: The main aim of the experiments will be evolution of long-term interaction of engineering barrier materials, considered to be used during the DGR construction. Conceptual proposal: The experiment will be composed of thoroughly characterized samples of engineering barrier materials (bentonite, concrete, cement or other materials) that will be inserted into drilled boreholes in order to simulate their mutual interaction under DGR conditions, namely under anaerobic conditions below the water table. Except individual "interaction" borehole material as well the Mock-Up experiment arrangement could be as well used as its components (concrete, bentonite) would be in direct contact. Technical solution: Direct interaction of materials in the borehole The basic arrangement of the experiment is simple. It consists of material sample emplacement into the borehole with sufficient depth and water inflow. The samples will represent selected materials – bentonite, cement (low-pH, ordinary-pH) or other materials such as a backfill material. Then the borehole will be closed using a suitable plug (e.g., resin one etc.) and all the materials will be left to interact mutually under DGR conditions for the
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defined period of time. All materials will be thoroughly characterized before being emplaced to the borehole (chemical analyses, mineralogy, microstructure, and physical and mechanical properties). In the case that the water chemistry influence is studied, the experimental borehole/monitoring borehole assembly can be used. The samples would be inserted into the experimental borehole into defined depth. The observation interval in the monitoring borehole/s will be separated by the packer system from the rest of the borehole and groundwater samples, determining changes in groundwater chemistry due to the material interaction with the groundwater, will be collected in defined periods. Such samples will be analyzed in detail (electrochemical parameters, chemical composition). Experimental borehole will be overcored after the end of the experiment duration. It means that the new borehole will be made with significantly larger diameter in order to obtain a core containing the original samples and surrounding rock in sufficient thickness. The materials inside the original borehole will be removed and, as well as surrounding rock, will be analyzed in detail (chemical analyzes, mineralogy, microstructure, physical and mechanical properties). Changes of aged materials, altogether with mutual influence and influence on the surrounding system will be described, heading toward description of the processes of material mutual interaction Any material, used as a buffer, sealing and construction material within DGR can be used in such an experiment.
Mock-Up arrangement (see 4.4.1) Materials (bentonite, cement) will originate in the experimental set up described in chap. 4.4.1. The experiment would be modified, enabling regular sampling of bentonite samples. Technical and methodical measures will be prepared, allowing also sampling of low-pH cement parts during bentonite sampling campaign (these measures will be used also during the respective sampling). The created hole in bentonite mass (as a result of the sampling) will be filled using bentonite cylinders with identical parameters (e.g., density). Samples taken from the experiment will be analyzed in detail (identical analyses as for the samples taken from "interaction borehole"). It has to be noted here that sampling points in the experiment can be used only once because of the nature of long term interaction study. Thus the careful planning of sampling campaigns is necessary. Results of analyzes will be compared with results obtained from the borehole experiments and from the parallel laboratory research. Laboratory research enables also to study different boundary conditions (e.g., temperature, oxygen content).
Specific requirements: Material interaction in the borehole ● chemistry (alkaline plume) coming from the borehole may affect surrounding groundwater chemistry. Therefore the location of the experiment has to be considered carefully, being potentially expelled from any areas of groundwater chemistry sampling and long-term monitoring points, sampling points used for other monitoring (tracers, colouring tests);
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● appropriate choice of borehole location (e.g., in the case of borehole cluster in water- filled fissure with water drainage); ● knowledge of groundwater chemistry; ● construction of boreholes in appropriate assembly (experimental borehole, monitoring borehole); ● borehole characterization; ● ensuring sufficient amount of water in the borehole, altogether with anaerobic conditions (sufficient depth); ● technical support from the DIAMO company during installations; ● ensuring groundwater sampling and sample analyzes in the case of monitoring boreholes network; ● ensuring the protection of equipment from damage; ● appropriate choice of technology used during overcoring; ● appropriate sampling and consecutive sample analyzes. Mock-up ● technical effectiveness of bentonite and concrete sampling; ● readiness of concrete plateau (part of the experiment) for concrete/bentonite interface sampling; ● methodological concept of sampling (the interface must not be damaged); ● appropriate choice of sampling schedule
Experiment duration: It is possible to drill several assemblies of boreholes and to terminate the experiments therein after 3, 5, 7 and 10 years. Further potential use of the experiment Determined rates of material degradation during mutual interaction will be used for their stability specification under DGR conditions and for subsequent safety assessments. Groundwater sampled in the vicinity of boreholes will be provided for chemical and microbiological analyzes (see chap. 4.4.2). Bentonite and other materials used in the experiment can be used for consecutive analyzes for identification of microbial activity impact on the processes (see chap. 4.4.2).
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4.5 Testing of EDZ and EdZ formation and development in metamorphic rock in DGR depth
EDZ and EdZ property determination methodology has to be based on hydraulically and mechanical measurements. However, it will be adjusted into the small scale during survey of parameter distribution from the tunnel wall (with a resolution of tenths of cm). Furthermore, geophysical methods can be used, including new methods and equipment, developed for this purpose only. Periodical survey of EDZ/EdZ extent is expected in defined time periods in order to described EDZ/EdZ evolution in the context of different parameters (massif rheology, thermal load, massif dehydration changes in the rock stress, caused by excavation etc.)
4.5.1 Different EDZ behaviour due to use of different excavation methods - I.
Goal of the experiment The experiment will be aimed on detection of the rock massif property changes, further on phenomena related to the origin and evolution of the EDZ. Such a survey will be performed using the geophysical methods. The purpose of the experiment is to prepare an advanced monitoring system, which will allow predicting disturbance of the rock massif, both as a result of natural rock processes and as a result of unfavourable influences of mining-technical activities (repository excavation, EDZ stability). Conceptual proposal: The concept is based on use of an apparatus for the electrical resistivity measurement, for effects of the induced polarization and for the seismic properties, with application of high frequencies in the order of thousands Hz for detection even a small fractures. Observation of the spatial distribution (tomography) together with the temporal changes is the principal issue. Technical solution: The experiment will proceed in several phases: Phase 1: Equipment preparation and commissioning. The measured quantities are the electrical resistivity, effects of the induced polarization, and the rock seismic properties. The electrical resistivity is observed in a configuration of the resistivity tomography; however the data evaluation is performed also by other sophisticated procedures (statistics). The seismic measurements are based on excitation of high frequency elastic waves (thousands Hz). It implicates a high sensitivity even during creation of thin fractures. Besides the applied (or even basic) research results, the operation of the apparatus will be able to warn in case of unfavourable rock massif behaviour, related to e.g., mining operation in the surrounding area. Phase 2: Examination of the testing tunnel walls by geophysical methods. It is possible to do especially the following measurements: ● Seismic measurement in frequencies of tens to hundreds Hz; ● Resistivity tomography; ● Spontaneous polarization method; ● Stray currents observation method;
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● Radar measurements. The purpose of the measurement is to find out the physical (or geotechnical) conditions in the testing tunnel vicinity. The aim is especially to detect a presence and a character of fault zones crossing the testing tunnel or going parallel close to the tunnel. Based on the processed results, the reasons of the rock massif behaviour changes could be more precisely interpreted and the rock massif could be described in a larger context. If some of the tested methods will be found and confirmed as useful and appropriate, they will be then added to the monitoring system Phase 3: Research of the EDZ properties. The following parameters will be observed: ● Thickness of the EDZ; ● Changes in the EDZ behaviour; ● Relation between the EDZ thickness and the geotechnical rock parameters (Poisson ratio, elastic modulus, rock fracturing). This phase can be referred as an applied research work. The excitation and interpretation of the seismic waves of various frequencies (tens to hundreds Hz) is the expected main testing method. The measurement results will be interpreted in cooperation with other methods studying the EDZ in the testing site. Specific requirements: ● Electricity supply 230V with a backup ● Ethernet for online transmission (regular manual download of recorded data is also possible) ● Protection against electromagnetic interference Experiment duration: Throughout the entire operation time of the underground facility (ideally – longer recorded data sequence). Further potential use of the experiment Geotechnics, fracture displacements, hydrogeology, geochemistry, preparation of mining/excavation technologies
4.5.2 Different EDZ behaviour due to use of different excavation methods - II.
Goal of the experiment Using geophysical methods can enable to obtain very valuable information about the geological structure, properties and behaviour of the rock mass, including the EDZ. The use of geophysical methods in the underground at the stage of the current knowledge can be divided into two essential groups, i.e. the methods already tested (group A) and the methods in which it is necessary to test their application and to develop the required measurement equipment, processing and interpretation software and methodologies for measurement (group B) – similar as in 4.2.5.
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Conceptual proposal
Group A – the methods already tested Electrical resistivity tomography, seismic refraction using hammer blows, and seismic tomography can bring both quantitative and qualitative information about the EDZ. Group B – the methods under development It is known from the geophysical work performed before that a certain knowledge about the EDZ can be obtained using the seismic refraction using hammer blows, applied to the wall of a mine tunnels. Furthermore use of the electrical resistivity tomography, measured on the side of a crosscut or a tunnel, is possible. In the future it would be appropriate to develop and test new methods or measurement methodologies. The following methods can be used as major techniques: • Seismic radiography in beams, parallel to the wall of a mine tunnel (a modified “cross hole” method); • Use of land-based radar (GPR) with antennas of high frequencies; and • Use of vertical electrical micro-sounding. Technical solution The following methods are proposed, choosing from a wide selection of methods: Parallel seismic radiography The application of this method requires drilling of three lines of boreholes (fans), located three to ten metres apart. The boreholes of the first fan are used to generate a seismic signal. Further two fans are used to measure the arrival time of the seismic signal. Using this differential measurement, the uncertainty of precise detection of the origin of a seismic disturbance is excluded. The number of boreholes in the fan is governed by the requirement for the precision to identify the shape of the EDZ. It appears to use four to six boreholes in one fan as the most suitable method. Boreholes 10 to 20 metres long can be drilled coreless and their minimum diameter should be at least 50 mm. The boreholes in the measuring fans can also be used for other measurements, but only for the ones that will not require a permanent installation of measuring systems in boreholes. Using repeated measurement it is possible to detect the time development of the EDZ. These measurements do not affect the rock mass in their surroundings. Use of land-based radar (GPR) for the EDZ In order to identify the EDZ state, it would be appropriate to test the possibilities of land- based radar. For measurement it will be necessary to use an antenna with a higher frequency, probably 500 MHz It would also be suitable to test antennas with a higher and a lower frequency. All antennas should be shielded. The radar record should show the thickness of the loosened rock mass, and, if possible, also the top of the zone of concentrated stress. Groundwater could have an adverse effect in the rock mass. However, it is likely that the first EDZ on the sides and ceiling of a crosscut tunnel will be without dry. If groundwater occurs in the further zone, then it is likely that the boundary between the first zone and the second zone will become a better reflective surface for electromagnetic radiation. A very clear negative effect can be expected from any metal objects. This method
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could be applied only on the place where no solid metal lining occurs in the mine working. However, it can be assumed that if a timber support is behind the props, then GPR can be used. This method of measurement will not require any mining preparatory work carried out. Any place where the measurement can get into the conflict with other measurements is appropriate for the survey. The measuring equipment will be installed always only for the time of our measurements. The only condition is that no other activity will take place over the duration of geophysical measurements at the site. Duration of the experiment Over the entire time of the underground facility operation. Further potential use of the experiment Monitoring of the state of stress, seismic monitoring, and progress of geotechnical, hydraulic and thermal experiments.
4.5.3 Different EDZ behaviour due to use of different excavation methods - III.
Goal of the experiment The aim of the experiment is to investigate the changes in rock mass and other phenomena in connection with EDZ formation/development caused by different blasting methods. Conceptual proposal: The solution will use the combination of the following methods:
• Geophysical methods (see chapter 4.5.1) • Hydraulic testing of permeability (and its changes) in the borehole (water, air) • Instrumented rock bolts • Monitoring by additional geophysical methods in chosen localities 1. Monitoring in campaigns (at least once a year; preferably every half year or quarterly): • Using geophysical methods (detail description in 4.5.1), adjusted to determination of original EDZ extent and selection of locations for further experimental phases • Hydraulic testing of permeability: gradually prolonged borehole of 10-15 m length and 76 mm diameter (diameter could be adjusted according to the available drilling rig) will be tested using single and double packer system in short sections by water and air. It would be helpful to know stress conditions in advance in order to select appropriate pressure for fissure opening.
2. Continuous monitoring • Multipoint (up to 9 measurement points) instrumented rock bolts will be installed into selected places to monitor rock mass deformation and rock bolt loads. It has been shown in other locations (e.g. Skalka) that stabilization of load on rock bolts takes several years. • In chosen location the boreholes will be drilled and equipped with multi packer system. These boreholes will be used for monitoring of hydrogeology (water inflow, water pressure, etc.). • Continuous geophysical monitoring in selected locations
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Specific requirements: • 230V/400V Power supply with a backup • Data network (Ethernet) with EMI filter and connection into the internet (or other wide network). • Optical network Experiment duration: Over the entire time of the underground facility operation. Further potential of the experiments: Geotechnics, fissure movements, hydrogeology, geochemistry, development of excavation methods
4.5.4 Influence of internal rock structure and present structural domains on the URF behaviour and stability
In terms of URF behavior, geomechanical deformation and strength properties of rock and rock blocks in the vicinity of the construction (including the impact of their direction dependencies - anisotropy) in the interaction with the stress state and geometric arrangement of fracture structures in a given location are essential. It can be assumed that, for example, the orientation of mineral grains in metamorphic rocks can be the source of anisotropy of specific deformation properties. That means that the stability and behavior of the URF can be significantly influenced by mutual geometrical relation between the anisotropy direction, URF geometry and its course. Ductile deformation of these rocks causes directional changes in anisotropy related to the character of deformation. It can result in changes in stability in different parts of the URF. This phenomenon can be expected in case of deformations of the size of the profile of the URF or greater. Therefore, mutual geometric arrangement of individual affecting factors, e.g. ductile anisotropy of rocks, direction of fracture systems, anisotropy of material properties, hydraulic situation, stress and deformation states and influence of the URF itself on them, should be considered. At this point, the research should consist of both laboratory activities, focusing on the study of material properties especially in relation to any material anisotropy and present ductile anisotropy, and in-situ research, taking into account rock deposition in the vicinity of the URF (transfer of properties from microscale used in the laboratory to the scale of massif blocks). Methodology of geotechnical classification of rock mass should be used. Finally, even the mining technology and the influence of planned experiment operation have to be considered. The study can be complemented with systematic qualification of intensity and orientation of microfractures in relation to different types of blasting activities and distances from the blasting point. In order to evaluate the location in terms of its long-term stability and the URF behavior, the obtained results should be verified by means of mathematical modelling.
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5 General requirements for ensuring implementation of monitoring, research and experimental work at the Bukov URF
Construction of Bukov underground research facility and implementation of the selected monitoring, research and experimental activities represents an important step towards transfer to conditions that resemble presumed conditions in the SNF and HLW deep geological repository depth. For such a reason only the activities that will bring appropriate data and argument for DGR safety has being assessed. Moreover, it could significantly support development of procedures and methodologies that can be later used during the construction and performance of DGR itself. However, the implementation of research activities is dependent on many factors that need to be taken into account even before starting the activities and planning of the experimental program. Following are the activities that the authors consider as the important ones: • development of the supporting ground workplace that would help to organize the department for preparation, construction and/or maintenance of experimental equipment for the activities. Moreover, supporting analytical procedures or measurements can be performed as well. The main reason originates from the fact that some activities cannot be easily to perform under difficult conditions of the mine The workplace should consist of o mechanical workshops o laboratory of samples, equipment and arrangement preparation o geotechnical laboratories o chemical laboratories with equipment and instrumentation technique according to the performed activities o radiochemical labs with corresponding equipment and analytical devices in the case of radiotracers use, at least on the level of supervised area, • development of local supporting team that would ensure activities in the mine, preparation and course of some of the experimental activities and monitoring activities if needed • assuring of the operation system activities within the mine (planning, system of transfer within the mine, ensuring of the transfer through Bukov mine etc. • planning of all the activities, experimental works, measurements etc. • ensuring that the experiments do not get disturbed (planning, sitting, progress of the activities etc.) • compilation of the comprehensive and skilled team of contractors • active cooperation of DIAMO company • supporting laboratory and modelling programme (mentioned many times above)
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6 Conclusions
Construction of Bukov underground facility enables to perform scientific and experimental activities under conditions close to the conditions of the deep geological repository. Until the final site is selected and a confirmation laboratory will be built within this site, Bukov facility will be used as a test site for evaluation of host rock in the depth that is relevant to the considered depth of deep geological repository. A selection of monitoring, research and experimental work is presented. Those will enable to survey events and processes, relevant to DGR safety assessment, under conditions that will resemble DGR conditions in the 500 m depth. All the proposed activities should lead to the above mentioned goals as close as possible. However, it is clear that the experimental programme cannot include all the presented experiments. Except the proposal of the experimental activities, conditions and requirements for implementation of each activity are mentioned. Similarly, general conditions for the experimental programme are presented in the last chapter. It is necessary to remember that the work in the mine is difficult, concerning both technical activities and requirements towards the workers. Simultaneously, it is also necessary to take into account the activities of the own uranium mine and adjust the planning and preparation work. Moreover, supporting laboratory and modelling programme has to be inevitable part of the experimental program.
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7 References
ONDŘIK, J. ET AL. Hydrogeologická charakteristika jižní části uranového ložiska Rožná a uranového ložiska Olší se zřetelem na umístění hlubinného úložiště VJP a RAO na lokalitě Kraví hora. Výzkumná zpráva č. 1. Dolní Rožínka: DIAMO s. p. závod GEAM, 2010. 78 s. Dvořáková M., Vencl M., Kříž P. (2014): Budování podzemního výzkumného pracoviště Bukov. Tunel č. 2/2014, 18 – 22. NAGRA (2000): Grimsel Test Site Investigation Phase IV (1994 – 1996): The Nagra-JNC in situ study of safety relevant radionuclide retardation in fractured crystalline rock II: The RRP project methodology development, field and laboratory tests. NAGRA Technical Report NTB 00-06.
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