posiva oy · a 3d model of the closure of the boreholes was created with gemcom surpac 3d ......

Closure of the Investigation Boreholes

POSIVA OY

Olki luoto

FI-27160 EURAJOKI, F INLAND

Phone (02) 8372 31 (nat. ) , (+358-2-) 8372 31 ( int. )

Fax (02) 8372 3809 (nat. ) , (+358-2-) 8372 3809 ( int. )

November 2014

Working Report 2012-63

Taina H. Karvonen

November 2014

Working Reports contain information on work in progress

or pending completion.

Taina H. Karvonen

Saanio & Riekkola Oy

Working Report 2012-63

Closure of the Investigation Boreholes

CLOSURE OF THE INVESTIGATION BOREHOLES ABSTRACT A spent nuclear fuel disposal facility is designed to be constructed at Olkiluoto in Eurajoki, southwestern Finland, and excavation of an underground investigation facility, ONKALO, is already close to being completed. Technology for spent fuel disposal, engineered barrier system and the natural barrier, bedrock, ensure safe long-term disposal. Investigation boreholes have been made in Olkiluoto in order to collect information of the bedrock. As a part of the closure of the disposal facility also the investigation boreholes need to be closed. Even though these boreholes do not penetrate ONKALO or the actual future repository, they reach the disposal depth, and are possibly connected to deposition tunnels through fractured zones and individual fractures. Therefore they are a potential flow route for both groundwater and surface water between disposal depth and ground surface. This report presents the conceptual design for closure of the investigation holes based on the methods developed in co-operation with SKB. The aim of this report was to define materials, techniques and requirements needed for closing investigation boreholes. Further investigations were to be defined, and a 3D model was to be created for the most significant boreholes. The closure will be implemented by restoring the natural conditions of the bedrock. Sparsely fractured rock sections with low hydraulic conductivities are closed with tight borehole backfill material, either swelling clay or a mixture of swelling clay and rock material. Sections of fractured rock and zones with larger hydraulic conductivities are closed with concrete plugs. Sections with hydraulic conductivity of 1E-8 m/s or higher, natural fracture count of 10/m or more frequent, and classification of fractured areas between RiIII and RiV were defined to be areas of fractured rock. Surface plugs made of solid rock will be placed in the upper parts of the boreholes. The uppermost borehole sections will be filled with either concrete or rock material. There are two options for installing the backfill in boreholes. Borehole backfill will be placed with the Basic Method, in which borehole backfill material is installed in place in a perforated copper tube, and the Container Method, in which borehole backfill material is transported down in a container and extruded in selected place. The division to two methods is because groundwater may cause erosion of the borehole backfill material installed with the Basic Method. Thus the Basic Method will be implemented down to 500 m of borehole length. Below this the Container Method is designed to be used. Because the method is still under development its use is limited as an alternative for the Basic Method in the deepest parts of the boreholes. Concrete utilized in the closure of the boreholes will be low-pH concrete. The concrete must not hamper the function of the borehole backfill and it should support the borehole backfill sections during the closure process. In long-term, the cement is allowed to leach from the material, as long as the grain frame remains to support the borehole and the borehole backfill below and above. A 3D model of the closure of the boreholes was created with Gemcom Surpac 3D program. Parameters to best describe rock quality were sought and interpolated to 1 m sections to place closure materials. The result is a closure design for 51 boreholes, length varying between 100 m and 1,060 m, selected according to length and site.

Keywords: Closure, closing, borehole, Olkiluoto, drill hole, plug, Basic Method, Container Method, bentonite, investigation borehole.

TUTKIMUSREIKIEN SULKEMISEN SUUNNITELMA TIIVISTELMÄ Eurajoen Olkiluotoon on suunnitteilla käytetyn ydinpolttoaineen loppusijoituslaitos, ja maanalainen tutkimustila, ONKALO, joka tulee olemaan osa maanalaista loppusijoitus-laitosta, on jo louhittu lähes valmiiksi. Tekniset vapautumisesteet yhdessä luonnollisen vapautumisesteen, kallioperän, kanssa mahdollistavat turvallisen loppusijoituksen pitkälle tulevaisuuteen. Loppusijoituspaikan valinnan ja kallionlaadun tarkastelun takia on Olkiluodon kallioperään tehty tutkimusreikiä. Loppusijoituslaitoksen sulkemisen osana myös tutkimusreiät täytyy sulkea. Vaikka reiät eivät läpäise ONKALOa tai loppusijoi-tustilaa, ulottuu osa niistä loppusijoitussyvyydelle, ja yhteys loppusijoitustunneleihin muodostuu kallioperän luonnollisen rakoilun kautta. Näin ollen reiät muodostavat mah-dollisen virtausreitin pohjavesille ja pintavesille maanpinnan ja loppusijoitustason välille. Tämä raportti esittelee konseptuaalisen suunnitelman tutkimusreikien sulkemiselle perus-tuen SKB:n kanssa kehitettyihin menetelmiin. Tämän raportin tarkoitus on määrittää materiaalit, tekniikat ja vaatimukset syvien tutkimusreikien sulkemista varten. Tarkoitus on myös määritellä jatkotutkimustarpeet ja luoda 3D malli merkittävimpien tutkimusrei-kien sulkemisesta. Sulkemisen tarkoitus on palauttaa kallion luonnolliset virtausreitit. Vä-hän rakoilleet, huonosti vettä johtavat kallioalueet suljetaan tiiviillä kairanreikien täyttö-materiaalilla, joka on joko paisuvahilaista savea tai paisuvan saven ja kiviaineksen seosta. Heikomman kivilaadun ja suuremman vedenjohtavuuden alueet suljetaan betonitulpilla. Tällaiseksi alueeksi määriteltiin kallio, jonka vedenjohtavuus on tasan tai yli 1E-8 m/s, rakoluku kairasydämissä tasan tai yli 10 kpl/m ja joka on rikkonaisuusluokitukseltaan RiIII-RiV. Tutkimusreikien yläosiin tulee kivitulppa sen tason alapuolelle, johon mahdol-lisen eroosion oletetaan yltävän. Tämän yläpuolelle tulee joko kivimateriaalia tai betonia. Täyttömateriaali asennetaan käyttäen Basic-menetelmää, jossa tiiviiksi puristettu täyttö-materiaali lasketaan reikään rei’itetyn kuparikanisterin sisällä, ja Container-menetelmää, jossa täyttömateriaali viedään alas kairanreikään säiliön sisällä ja halutulla kohdalla se työnnetään ulos säiliöstä. Menetelmiä on kaksi, sillä kairanrei’issä oleva pohjavesi voi aiheuttaa eroosiota Basic-menetelmän täyttömateriaalille asennuksen aikana. Tästä syystä Basic-menetelmää käytetään vain kairareiän pituudelle 500 m asti ja siitä pidemmälle käytetään Container-menetelmää. Koska Container-menetelmä on vielä kehitteillä, on sen käyttö rajattu vain kairanreikien syviin osiin vaihtoehdoksi Basic-menetelmälle. Betonimateriaali on matalan pH:n betonia. Betoni ei saa haitata kairanreikien täyttö-materiaalin toimintaa ja sen tulee asennuksen aikana tukea asennettavia kairanreikien täytön osia. Pitkällä aikavälillä sementti saa liueta pois betonista, kunhan raerunko jää tukemaan ylä- ja alapuolella olevia kairanreikien täytön osia. Kairanreikien sulkemisesta laadittiin 3D-malli Gemcom Surpac™ ohjelmalla. Muuttujat, jotka parhaiten kuvaavat kallion laatua sulkemiseen liittyen, määritettiin ja interpoloitiin metrin jaksoiksi sulkemissuunnitelman laatimista varten. Työn tulos on sulkemissuunnitelma 51 kairanreiälle, joista lyhin on 100 m ja syvin 1060 m pitkä. Avainsanat: Sulkeminen, sulku, Olkiluoto, kairanreikä, tulppa, Basic-menetelmä, Container-menetelmä, bentoniitti, tutkimusreikä.

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TABLE OF CONTENTS ABSTRACT TIIVISTELMÄ

TABLE OF CONTENTS .................................................................................................. 1

TERMINOLOGY AND ABBREVIATIONS ....................................................................... 3

FOREWORD .................................................................................................................. 5

1 INTRODUCTION ................................................................................................... 7

2 GEOLOGY OF OLKILUOTO ............................................................................... 11 2.1 A summary of the bedrock of Finland ........................................................ 11 2.2 Site investigations ...................................................................................... 11 2.3 Olkiluoto bedrock ....................................................................................... 11

2.3.1 General description ........................................................................ 11 2.3.2 Brittle deformation model ................................................................ 12 2.3.3 Hydrogeological conditions ............................................................. 13

3 INVESTIGATION BOREHOLES AT OLKILUOTO .............................................. 17 3.1 Borehole types and identification ............................................................... 17 3.2 Selection of boreholes ................................................................................ 19

4 REQUIREMENTS FOR BOREHOLE CLOSURE ................................................ 23

5 BOREHOLE CLOSURE METHODS AND MATERIALS ..................................... 25 5.1 Suggested specifications for borehole backfill material ............................. 26 5.2 Borehole backfill methods .......................................................................... 28

5.2.1 General description of methods ...................................................... 28 5.2.2 Previous experiments and function of methods ................................ 31 5.2.3 Evaluation on method suitability .................................................... 39

5.3 Concrete borehole plugs ............................................................................ 40 5.3.1 General design ............................................................................... 40 5.3.2 Material ........................................................................................... 41

5.4 Surface plugs ............................................................................................. 42 5.4.1 General purpose ............................................................................. 42 5.4.2 Location of the surface plug ........................................................... 43 5.4.3 Design alternatives ......................................................................... 43 5.4.4 Suggested design ........................................................................... 46

5.5 Material above the surface plug ................................................................. 48

6 CRITERIA AND DESIGN FOR THE CLOSURE OF THE DEEP INVESTIGATION BOREHOLES ...................................................................................................... 51 6.1 Criteria for closure component selection .................................................... 51 6.2 Data processing ......................................................................................... 52 6.3 Sectioning of the closure materials ............................................................ 53 6.4 Closure design ........................................................................................... 54 6.5 Material quantities ...................................................................................... 57 6.6 Borehole categories ................................................................................... 58

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7 PRODUCTION OF THE CLOSURE .................................................................... 59 7.1 General ...................................................................................................... 59 7.2 Cleaning ..................................................................................................... 59 7.3 Characterization ......................................................................................... 62 7.4 Stabilization ................................................................................................ 63 7.5 Replacing the water ................................................................................... 65 7.6 Closing the borehole .................................................................................. 66 7.7 Installing the surface plug .......................................................................... 68 7.8 Filling the upper section ............................................................................. 69 7.9 Estimation for a time schedule (OL-KR4) ................................................... 69

8 INITIAL STATE OF THE BOREHOLE BACKFILL ............................................... 73

9 CONFORMITY TO REQUIREMENTS ................................................................ 75 9.1 Requirements and specifications ............................................................... 75 9.2 Hydraulic conductivity and EMDD .............................................................. 75

10 DISCUSSION AND CONCLUDING REMARKS .................................................. 79

11 SUMMARY .......................................................................................................... 81

REFERENCES ............................................................................................................. 83

APPENDIX 1 ................................................................................................................. 93

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TERMINOLOGY AND ABBREVIATIONS Backfill material – Backfill in the context of closure refers to the materials utilized to backfill underground openings other than deposition tunnels. The following backfill materials have been identified for closure: 1) swelling clay, 2) mixture of swelling clay and rock material, and 3) rock material such as gravel, crushed rock, stones, and boulders. Basic Method – A method for installing borehole backfill material (in perforated tube). BFZ – Brittle deformation zone. Borehole – Refers to all possible holes, not depending on with what method they were made. Borehole backfill material – Material specifically meant for the backfill of the boreholes, see “backfill material”. Borehole plug - An investigation hole component located in a section intersecting water-bearing fracture zone and utilized to facilitate backfilling of the hole by supporting the surrounding rock and the backfill material above or below it. Bulk density – Density value containing both dry mass and water. Dry density – Density not containing water, only dry mass (kg) of material in 1 m3. CBI - Swedish cement and concrete research institute. Closure of the disposal facility – Refers to backfill and plugs that will be placed in access and central tunnels, shafts, miscellaneous underground openings, and boreholes. Different types of closure components may be used in different parts of the disposal facility volumes. Closure shall complete the isolation of spent fuel and support the safety function of the other barriers. Container Method – A method for installing borehole backfill material (with a container). Couronne Method – A method for installing borehole backfill material (blocks around a central rod). EMDD – Effective montmorillonite dry density. Fennoscandian shield – Exposed Precambrian crystalline rock crop out delimited in Sweden and Norway by Caledonides and plunging in south under Estonian sedimentary rocks and in east under Russian platform sediments. HZ – Hydraulically conductive zone.

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Imatran Voima, IVO – A power company that in 1998 united with Neste Oy to form Fortum Oyj, which currently owns Loviisa nuclear power plant and is a co-owner of Posiva Oy. Initial dry density – Dry density when installed in place. Original dry density divided with the new volume of the location. Initial state – Conditions and parameters of the materials immediately after placement, on-site. Nagra - National Cooperative for the Disposal of Radioactive Waste, Switzerland. ONKALO – An underground rock characterisation facility in Olkiluoto, will be a part of the planned disposal facility. Original dry density – Refers to swelling clays or mixtures containing swelling clay. Clay can be compressed to different densities. Original dry density is the density of the material after it has been manufactured and prior installing it. PFL – Posiva Flow Log, a tool for measuring hydrogeological properties of the bedrock (transmissivity) from boreholes. Pellet Method– A method for installing borehole backfill material (as pellets). Plug – The following plug types have been identified for closure: 1) mechanical plug which is a concrete or other rigid structure physically isolating installed backfill and the neighboring opening, 2) hydraulic plug which is a concrete structure with a clay component preventing water flow through the plug over the long-term, 3) inadvertent human intrusion obstructing plug which is composed of rock material, boulders, and concrete to obstruct access to the repository after closure, and 4) borehole plug which is a structure located in an investigation hole section intersecting water-bearing fracture zone and utilized to facilitate backfilling of the hole by supporting the surrounding rock and the backfill material above or below it. Posiva – An organisation responsible for the final disposal of spent nuclear fuel of the owners (Fortum Power and Heat Oy and Teollisuuden Voima Oyj). SKB – Swedish Nuclear Fuel and Waste Management Company. TDS – Total dissolved solids.

Ulkopää – A peninsula of Olkiluoto, the site of the repository for low and intermediate level waste. Water content – Mass percentage of water in a material. VLJ repository – A disposal facility for low and intermediate level nuclear waste.

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FOREWORD This work has been carried out under a contract for Posiva Oy. In addition to a Posiva Working Report, a Master’s thesis on the same subject was made. The Master’s thesis has the same technical information as the Working Report, but has a wider geological description of Olkiluoto, and a more detailed description of investigations performed there. The supervisors have been Johanna Hansen at Posiva Oy, Tapani Rämö at the University of Helsinki, and Ursula Sievänen and Antti Öhberg at Saanio & Riekkola Oy. Tauno Rautio at Geological Survey of Finland has gone through the technical aspects of the work concerning the use of borehole drilling equipment. For all of my supervisors I wish to offer my sincere thanks and appreciation. In addition help attained from Paula Keto at B+Tech Oy and Kari Försti at Saanio & Riekkola Oy is greatly appreciated.

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1 INTRODUCTION There are four operational nuclear reactors currently in Finland; two in Loviisa (owned by Fortum Power and Heat Oy, Fortum) and two in Olkiluoto (owned by Teollisuuden Voima Oyj, TVO). The fifth reactor by TVO is under construction in Olkiluoto. The Nuclear Energy Act, entered into force in 1994, states that all nuclear waste produced in Finland must be treated, stored and disposed of in Finland, and no nuclear waste from other countries shall be imported. In 1995 TVO and Fortum established Posiva Oy, which is an expert organisation responsible for the final disposal of spent nuclear fuel of the owners. A screening program of entire Finland was carried out between 1983 and 1985, preliminary site investigations for selected sites were conducted between 1986 and 1992 and between 1993 and 2000 detailed site investigations and environmental impact assessment procedures were made for four sites. A decision-in-principle that the Olkiluoto island, in Eurajoki in south-western Finland, would be the repository location, was ratified by the Finnish Parliament in 2001. An underground rock characterisation facility, ONKALO, is currently under construction at the planned disposal site. By February 2012, the excavation of ONKALO has almost been completed. In 2012 Posiva Oy will apply for a license for the spent nuclear fuel repository construction to the site (Posiva 2011). Figure 1-1 presents the location of Olkiluoto, where the spent nuclear fuel repository is designed to be and ONKALO is currently constructed. The first deep borehole, OL-KR1, in the Olkiluoto island was drilled in 1989 in order to characterize the bedrock and groundwater conditions (Rautio 1989a). Since then, a total of 55 boreholes have been drilled in Olkiluoto (by June 2011), and further ones will be drilled during the years to come. Most of these reach the disposal depth and, even though the boreholes do not enter the underground openings of ONKALO or the planned disposal facility, they connect ground surface and disposal facility through fractures in the bedrock. The disposal of the spent nuclear fuel has been designed so that it includes both a natural barrier (the bedrock) and an engineered barrier system (i.e., materials surrounding and encapsulating the spent fuel). Should barriers fail, the boreholes should not allow the dangerous radionuclides to enter the biosphere (Posiva 2009). The closure materials should also hamper the flow of surface water to the deposition level, where it could affect groundwater geochemistry. Borehole closure has been investigated for example by Posiva, SKB and Nagra1 (e.g., Pusch & Ramqvist 2006a, 2008, and Rautio 2006). The research and investigations have considered the materials and installation methods. Previously boreholes have been closed in oil industry and occasionally in mining and construction of underground spaces, but reasons and requirements for closure of such holes differ substantially from the reasons and requirements of closure of boreholes in vicinity of a spent nuclear fuel disposal facility. The latest joint operation between Posiva and SKB was the third phase of the project “Cleaning and sealing of investigation boreholes” that was carried out with SKB in 2006. The target of the project was to partly close a deep investigation borehole OL-KR24 (Rautio 2006). The installation of the borehole backfill was done with the Basic Method, in which the material is installed into a borehole in a perforated copper tube.

1 National Cooperative for the Disposal of Radioactive Waste, Switzerland

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Figure 1-1. Olkiluoto, Finland: The site for the planned disposal facility of spent nuclear fuel. Ulkopää, in Olkiluoto, is the site of the repository for low and intermediate level waste. This work gathers the information gained from previous experiments and investigations, suggests closure designs for 51 Olkiluoto boreholes, selected according to length and location, and parameters and methods used for creating the designs based on the current requirements and existing information on possible installing methods. Material requirements and suggestions for closure materials are presented and the topics needing further investigations and development are identified and discussed. This work proceeds by first introducing the most important features of Olkiluoto bedrock and how this information was obtained. This is followed by an introduction of different borehole types in the area and in detail how the boreholes were selected for this work to have a closure design. Chapter 4 then introduces the requirements for the borehole closure materials as defined in Closure Production Line Report (Sievänen et al. 2012) and Design Basis report (Posiva 2012). Chapter 5 presents borehole closure methods and materials for borehole backfill, concrete plugs, surface plugs and for borehole length above surface plugs. The created closure designs and criteria for them are presented in Chapter 6, which is followed by the production of borehole closure (Chapter 7) and an estimation of the initial state of the borehole backfill (Chapter 8).

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After the methods, materials, design and production have been introduced, the conformity to the requirements is discussed in Chapter 9, which is followed by discussion and conclusions. As the closure designs are made for several boreholes this work does not include individual consideration about the borehole cleaning procedures or closure component lengths according to curvatures. These subjects are only discussed at a general level. When the closure of the boreholes is temporally close it is necessary to update the closure designs and create individual exact plans on how the work will be implemented.

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2 GEOLOGY OF OLKILUOTO 2.1 A summary of the bedrock of Finland Finland is a part of the Fennoscandian shield in Precambrian East European craton. The bedrock of Finland can be divided into Archean and Proterozoic domains, of which Eurajoki area belongs in the latter. Bedrock of Finland comprises mostly of granitic rocks and metamorphic gneisses. 2.2 Site investigations The data to understand the regional geology of the Olkiluoto site has been collected carefully and comprehensively. The site investigations started in the 1970’s when the planning and construction of nuclear power plant started. In 1980’s the investigations of Ulkopää area in westernmost parts of Olkiluoto were carried out and the repository for low and intermediate level waste (VLJ repository) was build and commissioned in 1992. The geological, hydrogeological, and geophysical investigations of the Ulkopää area were summarized by Äikäs (1986) and pegmatitic granite dykes in the outcrops were described in detail by Lindberg (1986). Since the 1970s the investigations conducted in Olkiluoto have included geological mapping, core drilling, geophysical investigations, geochemical investigations, whole rock analyses and optical imaging. The investigations for spent nuclear fuel disposal facility began later and increased the number of investigations. In considering the borehole closure, the most important investigations have been those offering information about fractures, transmissivity, groundwater chemistry and pressure conditions. The investigations performed for a borehole depend on the borehole characteristics and the year of the investigations. (Aaltonen et al. 2010, p. 24-30). 2.3 Olkiluoto bedrock 2.3.1 General description Olkiluoto rocks are high-grade metamorphic gneisses, migmatite gneisses, tonalite-granite-granodiorote gneisses (TGG gneiss) and pegmatitic granite. These are sporadically intersected by narrow diabase dykes. The supracrustal rocks are of four different origins that can be identified, for example, according to phosphorus and calcium concentrations, their mutual ratios and their ratios to other elements. After formation the rocks have undergone several alterations and deformations, both ductile and brittle, that have left their fingerprints on the bedrock (Kärki & Paulamäki 2006). Several models of the Olkiluoto bedrock have been created with different focuses and reasons. These include for example geological, brittle deformation, ductile deformation, flow and hydrogeological models. In considering the closure of the boreholes the brittle deformation and hydrogeological models are the most relevant as they contain the data and the model of the groundwater containing fractures. These models are therefore shortly considered here.

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2.3.2 Brittle deformation model Brittle deformation has been investigated from core logging, surface mapping and geophysical investigations (e.g., mise-à-la-masse and seismic results). There are two groups of brittle deformation zones (BFZs), site-scale and local-scale. The geometries of majority of the modelled zones are based on a single or two brittle fault intersections and have no relevant geophysical data related to them, but the site-scale features are mainly determined by integrating mise-à-la-masse and seismic results with geological data from the brittle fault intersections in the drillholes. Where geophysical data was not available, the orientation of the BFZs is based on the orientations of slickenside fractures. The geometry of a zone has also been used as a guide in extrapolating to regions without geophysical data. Figure 2-1 presents the modelled brittle deformation zones with 0 m depth (Mattila et al. 2007, Posiva 2009). The brittle deformation model presents the orientation and consistency of fractures and fracture zones. In considering the closure of the investigation boreholes the location of the fractures and fractured zones is relevant as they form flow routes in the bedrock that, if they are not yet connected to each other, should not be allowed to remain connected through the boreholes, but should be sealed from each other.

Figure 2-1. Modelled brittle deformation zones at Z = 0 (green lines). The site-scale zones are labelled. The location of the ONKALO facility is also shown with black line (Posiva 2009, p. 118).

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2.3.3 Hydrogeological conditions A hydrogeological flow model has been created for Olkiluoto site and comprises a hydrostructure model and a flow model (Posiva 2009, p. 217-292). The objectives of the hydrogeological model were to define boundary conditions affecting deep groundwater flow, describe deep groundwater salinities, identify the most significant hydrogeological zones, and to investigate the evolution of the boundary conditions and ensuing evolutions of the groundwater pressure and salinity. The hydrostructure model provides geometries for the hydrogeological zones and the hydrogeological properties of these zones and bedrock. The flow modelling has been done based on hydrogeological structures and variable flow conditions. In considering the closure of the investigation boreholes, the structure is of a primary interest as the major fractured zones control the flow of most of the groundwater (Posiva 2009). The hydrogeological structure model of Olkiluoto is presented in Figure 2-2. This data has been used in the borehole closure design project, which was mainly carried out in 2011-2012.

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Figure 2-2. Modelling procedure applied for the hydrogeological structure model version 2008 (Vaittinen et al. 2009). The hydrogeological zones (HZ) have been identified by several geophysical and engineering geological measurements. There are several hydrogeological zones present at Olkiluoto site and their location and parameters are the subject of ongoing investigations. The larger entities (HZs) have further been subdivided into smaller sections (e.g., HZ19a-HZ19c) The most significant zones are HZ19, HZ20 and HZ21 because of their intersection with ONKALO and high transmissivities. Smaller hydrogeological zones are also present and their parameters are detected as precisely as possible (Posiva Oy 2009, p. 224-254). HZ19 and HZ20 intersections with ONKALO

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are presented in Figure 2-3. HZ21 (Figure 2-4) is below ONKALO and according to modeling it rises towards the north-western shoreline of the Olkiluoto island. The hydrogeological conditions in Olkiluoto are such that as the land uplifted from the sea level at about 2800 years BP the groundwater began to dilute from saline or brackish. The flow is mainly controlled by local topography and a network of hydrogeological zones (HZs) and the flow is directed in inland mostly downwards and near shoreline the curve is more horizontal. Near ONKALO the flow is mainly controlled by HZ19, HZ20 and HZ21. The discharge area from the repository level would be, according to the present model, near the shoreline of Olkiluoto, HZ21 being the most dominant flow route. (Posiva Oy 2009 p. 260.)

Figure 2-3. Hydraulically conductive zones HZ19 and HZ20 and ONKALO. Deposition level is approximately at the depth of -420 m. Not in scale.

Figure 2-4. Hydraulically conductive zone HZ21, Olkiluoto shoreline and ONKALO. HZ21 rises from below ONKALO towards the shoreline of the Olkiluoto island. Not in scale.

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The salinity of the Olkiluoto groundwater has, in shallow depths, probably been affected by climate changes and glacial variations, even though only the last glacial period, the Weichselian, can be traced at the surface. Glacial meltwaters from the same period can be found from the depths of Olkiluoto bedrock, but it is reasonable to presume that the salinity in deep areas is of an older origin. Due to the land uplift, which is c. 6 mm/a (Posiva 2009, p. 60), the freshwater flow from land into the bedrock is a changing variable. In the uppermost areas the salinity or total dissolved solids (TDS) is ≤1 g/l and the largest, though uncommonly high, salinity in depth has been 84 g/l (Posiva 2009, p. 545). Saline groundwater with TDS >10 g/l dominate below -400 m level. Dissolved solids are mainly CaCO3, Cl, and SO4 in varying quantities. (Posiva 2009, Pitkänen et al. 2004, Pitkänen & Partamies 2007 and Andersson et al. 2007a and 2007b.)

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3 INVESTIGATION BOREHOLES AT OLKILUOTO 3.1 Borehole types and identification Olkiluoto and ONKALO boreholes, describing the type of the hole with prefixes used for identification and their quantities (by June 2011), are listed in Table 3-1 according to borehole database maintained by Posiva Oy. In Table 3-2 are the shallower holes and trenches, and prefixes used in their identification. By June 2011 there were 55 core drilled boreholes at Olkiluoto done in order to characterize the bedrock and groundwater conditions. For some of them a shorter adjacent borehole was core drilled to gain more information of the uppermost part of the bedrock. The core drilled boreholes are named OL-KR and have the number of the hole; for the short adjacent boreholes the letter b is added. The drilling of borehole and its mapping and properties are described in drilling reports (published as Posiva working reports). The investigations conducted in the boreholes are also reported in Posiva working reports. By June 2011 there were also 15 core drilled boreholes drilled from ONKALO (labeled ONK-KR). Table 3-1. Olkiluoto and ONKALO boreholes according to Posiva borehole database (by June 2011).

Borehole type Prefix Quantity

Core drilled (Olkiluoto, ground surface) OL-KR 55

Core drilled (ONKALO, underground) ONK-KR 15

Pilot hole (Olkiluoto, ground surface) OL-PH 1

Pilot hole (ONKALO, underground) ONK-PH 17

Percussion drilled (Olkiluoto, ground surface) OL-PR 10

Multilevel piezometric (Olkiluoto, ground surface) OL-EP 8

Shallow core drilled (Olkiluoto, ground surface) OL-PP 69

Shallow core drilled (ONKALO, underground) ONK-PP 288

Table 3-2. Other holes and trenches in Olkiluoto and ONKALO.

Other holes and trenches Prefix

Core drilled (Ulkopää, ground surface) SK

Standpipes in overburden PVP

Shotholes or -points (seismic measuring) L, PA, H

Control points KP

Groundwater monitoring holes PVA

Test pits KK

Investigation trenches P, TK

Grouting INJ

Control holes (grouting) IC

Probe hole TR

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Pilot holes were drilled to where ONKALO access tunnel was later excavated. Pilot holes have a PH prefix. Only one pilot hole, OL-PH1, was drilled from the ground surface. It was drilled towards the access tunnel of ONKALO (Niinimäki 2004a, p. 3) and has hence been excavated. The other pilot holes, in total 17 by June 2011, were drilled in ONKALO before proceedings of the excavations, and indicated by an ONK-PH prefix. Pilot holes are excavated of and locations become tunnels, but if some locations remain unexcavated in future they will need to be closed also. Core drilled holes were made by Imatran Voima Oy in the 1970’s in the Ulkopää area. These holes had SK prefix and they are in TVO control and will possibly be closed by TVO in future. There were 10 percussion drilled boreholes at Olkiluoto by June 2011. They have a prefix PR and a maximum length is 253.5 m (OL-PR10). The method for the PR holes is described for example by Niinimäki & Rautio (2004). There were eight multilevel piezometer holes (OL-EP1 – OL-EP8) at Olkiluoto by June 2011. The maximum length of these is approximately 103 m. By June 2011 there were 69 shallow core drilled holes (OL-PP1 – OL-PP69). The lengths reach the maximum of approximately 80 m and often only few tens of meters. The shallow core drilled holes drilled in 2006 were described by Rautio (2007) and mentioned here to provide an example of a report where the method is described. The latest shallow core drilled holes drilled in 2008 were described by Kuusirati and Tarvainen (2009). PP holes have also been drilled in ONKALO and they have an ONK-PP prefix. All together 288 ONK-PP holes were drilled by June 2011. Closure schedule and a decision on whether and how these will be closed in future are to be done later at the end of operative phase of the disposal facility and they are for now excluded from this work. Other holes at Olkiluoto are for perforated standpipes in overburden (prefix PVP), shotholes or -points used in seismic measurements (prefixes L, PA and H), control points (prefix KP), groundwater investigation holes (prefix PVA) and test pits (prefix KK). These are all less than 40 m long, some are in ONKALO, and some were made from ground surface. Investigation trenches (prefix P and TK) have also been made at Olkiluoto. Results from them are considered together with borehole information when applicable. Closure schedule and a decision on whether and how these will be closed in future are to be done later at the end of operative phase of the disposal facility and they are for now excluded from this work. In ONKALO there are also drillholes made for grouting that have slightly deviated from the ONKALO tunnel or shaft profiles. It is possible that some of them will also be closed during the closure of the facility in future. The investigations of the site conditions are ongoing and new holes are made almost yearly. Each and every one of these holes needs to be considered when the deposition is completed and the closure of the repository begins. Some will be made from ground surface, but most from ONKALO. Most of these will probably be rather short, about 20-40 m. Deposition tunnel pilot holes could theoretically penetrate unexpected fracture zones, which would cause discarding of the site for the intended use, and require closure of this kind of borehole remaining at the repository.

19

3.2 Selection of boreholes Boreholes at Olkiluoto have been made using different techniques and for different reasons throughout the history of site investigations and characterization of the bedrock and its parameters. The holes have different diameters, lengths and curvatures, and have been made from both ground surface and underground (from ONKALO). The quantity of holes is large and new holes are drilled almost on yearly basis to increase the information of the area. For this work a selection was made that only holes that could have a long term safety effect and that are reaching deep in the bedrock (borehole length of more than approximately 100 m is used here as including limit) are included. Furthermore only holes extending from ground level and in proximity of disposal area are included. The reasons exclude for now for example the EP holes done for piezometric investigations. Three boreholes are excluded because they were in present shaft locations, as is pilot hole done for access tunnel (Figure 3-1). The included 51 boreholes handled in this report are listed in Table 3-3 and presented in Figure 3-2.

Figure 3-1. ONKALO and the excluded boreholes. Access tunnel is in the location of OL-PH1 and shafts in the locations of OL-KR24, OL-KR38 and OL-KR48.

20

Table 3-3. OL-KR boreholes (by June 2011) and OL-PR10. Holes made after June 2011 are not considered. OL-KR holes are deep core drilled investigation boreholes and OL-PR refers to percussion drilled holes.

Hole id Length

(m) Diameter

(mm) Azimuth

(degrees) Inclination (degrees)

References

OL-KR1 1001,05 56 340,7 75 Rautio 1989a

OL-KR2 1051,89 56 359,3 76,2 Rautio 1989b, Rautio 1995c

OL-KR3 502,00 56 306 67,5 Rautio 1989c

OL-KR4 901,58 56 0 77 Rautio 1990a, Rautio 1995b

OL-KR5 558,85 56 340 65 Rautio 1990b

OL-KR6 600,77 76 35,9 50 Rautio & With 1991, Rautio 2000

OL-KR7 811,05 56 43,1 69,5 Jokinen 1994, Niinimäki 2000b

OL-KR8 600,59 56 154,6 64,4 Rautio 1995a, Niinimäki 2002f

OL-KR9 601,25 56 360 70 Rautio 1996b

OL-KR10 614,40 76 0 89,8 Rautio 1996a

OL-KR11 1002,11 56 310 70 Rautio 1999

OL-KR12 795,34 56 90 69,7 Niinimäki 2000a

OL-KR13 500,21 76 285 55,6 Niinimäki 2001a

OL-KR14 514,10 76 0 69,9 Niinimäki 2001b

OL-KR15 518,85 76 321 89,4 Niinimäki & Rautio 2002, Niinimäki 2002d

OL-KR16 170,20 76 0 90 Niinimäki 2002a

OL-KR17 157,13 76 0 90 Niinimäki 2002b

OL-KR18 125,49 76 0 90 Niinimäki 2002c

OL-KR19 544,34 76 306,5 76,4 Niinimäki 2002e

OL-KR20 494,72 76 290 50,4 Rautio 2002b

OL-KR21 301,08 76 40 29,6 Niinimäki 2002g

OL-KR22 500,47 76 271 59,1 Niinimäki 2002h

OL-KR23 460,25 75,7 289,7 59,7 Niinimäki 2002i, Niinimäki 2004b

OL-KR242 551,11 75,7 0 90 Niinimäki 2003b

OL-KR25 604,87 75,7 43,4 70,1 Niinimäki 2003a

OL-KR26 103,00 75,7 300,2 44,9 Rautio 2003a

OL-KR27 550,84 75,7 285 54 Niinimäki 2003c

OL-KR28 656,33 75,7 325,4 54,5 Rautio 2003b

OL-KR29 870,18 75,7 314,6 70,2 Rautio 2004a

OL-KR303 98,28 75,7 359,5 75 Rautio2004b

OL-KR31 340,15 75,7 180 65,4 Rautio 2004c, Pussinen & Niinimäki 2006b

OL-KR32 191,81 75,7 352 54,8 Rautio 2005a

OL-KR33 311,02 75,7 320,5 55,3 Rautio 2005b

OL-KR34 100,07 75,7 283,1 83,3 Rautio 2005d

The table continues to the next page.

2 Not considered in this report, shaft location/borehole plug experiment location 3 Not considered in this report, borehole length less than 100 m

21

Hole id Length

(m) Diameter

(mm) Azimuth

(degrees) Inclination (degrees)

References

The table continues from the previous page.

OL-KR35 100,87 75,7 280,6 85,7 Rautio 2005e

OL-KR36 205,17 75,7 105,5 59,8 Niinimäki & Rautio 2005

OL-KR37 350,00 75,7 18,3 47,9 Niinimäki 2005a

OL-KR384 530,60 75,7 0 90 Rautio 2005f

OL-KR39 502,97 75,7 309,6 65,4 Niinimäki 2005b

OL-KR40 1030,56 75,7 270,3 70,3 Pussinen & Niinimäki 2006a

OL-KR41 401,42 75,7 269,7 70 Pussinen & Niinimäki 2006c

OL-KR42 400,85 75,7 269 71 Pussinen & Niinimäki 2006d

OL-KR43 1000,26 75,7 357,3 60,9 Niinimäki 2006

OL-KR44 900,47 75,7 99,9 61,2 Pohjolainen 2007

OL-KR45 1023,30 75,7 100,1 59,3 Toropainen 2007b

OL-KR46 600,10 75,7 180 70,1 Toropainen 2007a

OL-KR47 1008,76 75,7 44,8 54,8 Toropainen 2008a


OL-KR49 1060,22 75,7 11,5 59,2 Toropainen 2008c



OL-KR52 427,35 75,7 299,7 79,8 Toropainen 2009c

OL-KR53 300,48 75,7 330,2 54,8 Toropainen 2009d



OL-PR10 153,50 115 318,1 88,7 Hjärtsrtöm 2007

4 Not considered in this report, shaft location 5 Not considered in this report, shaft location

22

Figure 3-2. The location of the 51 boreholes considered in this report and listed in Table 3-3. The closure design of this work is composed for boreholes presented in the figure, except PR10.

23

4 REQUIREMENTS FOR BOREHOLE CLOSURE As the closing of investigation boreholes can be considered as a part of the closure of the disposal facility, the overall requirements are in this work kept similar. The requirements for closure of a disposal facility are presented and justified in the Design Basis report (Posiva 2012) and the Closure Production Line report (Sievänen et al. 2012). Posiva’s requirement system is in five levels starting from the Finnish legislation and proceeding to more details as levels go up. Level 1 is stakeholder requirements, Level 2 is system requirements, Level 3 is subsystem requirements, Level 4 is design requirements and Level 5 is design specifications. Table 4-1 shows the performance targets, design requirements, and design specifications concerning closure. Because the requirements have been made for the closure of the entire disposal facility, and all of them are not directly applicable for the closure of the boreholes, some simplifications and/or interpretations were necessary. Specifications for how requirements can be met are presented in Chapter 5.1.

24

Table 4-1. Performance targets and design requirements affecting the closure of the investigation holes as stated in the Design Basis report and Closure Production Line report (Sievänen et al. 2012).

ID Level 3 - Performance targets - Closure

L3-CLO-13

Unless otherwise stated, the closure materials and structures shall fulfill the performance targets listed below over hundreds of thousands of years in the expected repository conditions except for incidental deviations.

L3-CLO-5 Closure shall complete the isolation of the spent nuclear fuel by reducing the likelihood of unintentional human intrusion through the closed volumes.

L3-CLO-6 Closure shall restore the favourable, natural conditions of the bedrock as well as possible.

L3-CLO-7 Closure shall prevent the formation of preferential flow paths and transport routes between the ground surface and deposition tunnels/deposition holes.

ID Level 4 - Design Requirements - Closure

L4-CLO-7 Structures and materials that considerably obstruct unintentional intrusion shall be utilized in the closure of the uppermost parts of the facility and investigation holes extending to the ground surface.

L4-CLO-8 Structures and materials of the closure components shall be selected in such a way that the isolation functions of closure can be provided despite possible loadings related to glacial cycles, such as permafrost or changing groundwater chemical conditions.

L4-CLO-10

Closure as a whole shall be so designed that the hydraulic connections from the disposal depth to the surface environment through the closed tunnels, shafts, and investigation holes are not better than through existing natural fractures and fracture zones.

ID Level 5 - Design Specifications - Closure

L5-CLO-6 Glacial erosion shall be taken into account in the design of the intrusion obstructing structures and materials.

L5-CLO-7 Grain size distribution and mineralogy of the rock materials utilized in the backfilling shall be chosen so as to resist erosion.

L5-CLO-8 The water conductivities of backfill in different parts of the facility and investigation holes shall be sufficiently low to enable natural ground water flow characteristics to be restored after closure.

L5-CLO-9 Compaction of backfill shall be taken into account in design for instance by using sufficiently uncompressible materials in underground openings.

L5-CLO-14

The amount of organics, oxidizing compounds, sulfur, and nitrogen compounds in the closure components shall be limited.

L5-CLO-15

Low pH concrete mix is used in the closure components composed of concrete and located below HZ20.

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5 BOREHOLE CLOSURE METHODS AND MATERIALS The borehole closure concept presented here aims at restoring the natural flow paths of the bedrock as well as possible and seal the areas of intact rock to prevent flow between fractures that would not be connected otherwise. A closed borehole will contain borehole backfill sections, concrete plugs, a surface plug and a section above it. Sectioning is explained in more detail in Chapter 6.3. Figure 5-1 presents an illustration of a closed borehole.

Figure 5-1. An illustration of a closed borehole containing altering sections of borehole backfill and concrete plugs, a surface plug and a section above it.

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5.1 Suggested specifications for borehole backfill material The maximum hydraulic conductivities that are accepted in backfill materials of the disposal facility are suggested in Sievänen et al. 2012 based on the characteristic hydraulic conductivities of the surrounding bedrock and the targeted performance. In areas requiring tight backfill the hydraulic conductivities accepted for backfill material are at three different levels. The uppermost backfill down to 200 m is planned to have a hydraulic conductivity of 1E-7 m/s or lower, section in the depth between 200 m and hydraulically conductive structure HZ20 (at approximately 300 m) a hydraulic conductivity of 1E-8 m/s or lower, and the section below that a hydraulic conductivity of 1E-9 m/s or lower. In the closure of the boreholes the requirements for the borehole backfill are the same, and to simplify the selection of borehole backfill material and the borehole closure process itself the smallest allowed hydraulic conductivity, 1E-9 m/s or lower, is for now kept as a reference for all depths. It is reasonable to uniform the requirements also based on the different depths at which the boreholes intersect the main hydraulically conductive structures, taking into account at which depth the same structures intersect ONKALO (Figure 5-2). For example HZ20 in ONKALO is approximately at depth 300 m but when OL-KR14 is considered the borehole and HZ20 intersect at a borehole length of approximately 200 m. OL-KR40 and HZ20 intersect, on the other hand, at depths of 500 m and 600 m. The mentioned boreholes were selected randomly to display the differences in intersection depths.

Figure 5-2. The intersections of HZ19 and HZ20 with OL-KR14, OL-KR40 and ONKALO.

27

Effective montmorillonite dry density (EMDD) (Dixon et al. 2012) offers a numerical value that presents a materials swelling-clay proportion and can be used as a limiting factor, also when the initial dry density is considered. Figure 5-3 presents the relationship between hydraulic conductivity and EMDD with different salinities of groundwater. The total mass, mass of non-swelling minerals, and unit weight of non-swelling minerals are needed for calculating the EMDD for a material (Equation 5-1): EMDD = (mt - mns) / (1-mns/Gns) (5-1) mt = Total mass (for 1 tonnes, derived from dry density) mns = Mass of non-swelling minerals (calculated from montmorillonite content) Gns = Unit weight of non-swelling minerals (particle density of non-swelling minerals) Because the maximum hydraulic conductivity for a borehole backfill material is here set at 1E-9 m/s, the corresponding EMDD should be more than 0.5 Mg/m3 with 3.5% salinity of groundwater (total dissolved solids, TDS). To be conservative in the selection of the material, this EMDD value is kept as a guideline for all depths. Material that has a higher EMDD value, than 0.5 Mg/m3, has desired (or lower) hydraulic conductivity.

Figure 5-3. Generic hydraulic conductivity (K) behavior predicted using EMDD parameter showing effects of clay type and ground water salinity (Dixon et al. 2011).

1.E-15

1.E-14

1.E-13

1.E-12

1.E-11

1.E-10

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

0.30 0.50 0.70 0.90 1.10 1.30 1.50 1.70 1.90 2.10

Hyd

rau

lic C

on

du

cti

vit

y (

m/s

)

Effective Montmorillonite Dry Density (Mg/m3)

Deionized water

1 % TDS

3.5 % TDS

7 % TDS

10 - 35 % TDS

Deionized Water

3.5 % TDS7 % TDS

10 - 35 % TDS

28

The hydraulic conductivity of a material depends mostly on the dry density of the material (e.g., swelling clay) (Pusch et al. 2012). As the exact material selection will be done only in temporal proximity of the closure implementation, the dry density has not been defined here, but instead it should be confirmed prior to selection that the material conforms to the set requirements. The set parameters can be met with several materials. The following Chapter presents the borehole backfill installation methods and the results that have been obtained from the experiments. The problems and suitability are also discussed. The conformity to requirements presented here is discussed in Chapter 9 after the methods and production have been presented. The borehole backfill will, in addition to the given parameters (hydraulic conductivity and EMDD), have to be homogeneous and resist piping, although defining parameters for them have not been set. Further requirements for the borehole backfill material may in future arise from the installation point of view. 5.2 Borehole backfill methods Posiva Oy and the Swedish Nuclear Fuel and Waste Management Company (SKB) have examined four different methods for installing borehole backfill to the sparsely fractured rock sections (i.e. Rautio 2006; Pusch & Ramqvist 2007 and 2008). These are the Pellet Method, Couronne Method, Basic Method, and Container Method. Independent of the method, the borehole backfill will be under certain circumstances; the boreholes are filled with groundwater that has varying salinity (0-7%) and produces an increasing hydrostatic pressure highest 10 MPa in the depth of 1,000 m. The fractures, some with elevated hydraulic conductivities, occur sporadically in the boreholes. The maturation and homogenization processes of the borehole backfill are affected by hydraulic conductivity, water pressure, and initial water composition as well as density and composition of the borehole backfill material. Geometrical conditions of the borehole and of the borehole backfill are also important factors (Pusch & Ramqvist 2008, p. 10-11). 5.2.1 General description of methods In the Pellet Method, a section of the rock that is sparsely fractured would be filled with pellets or granules manufactured of swelling clay. In the Couronne Method, dense annular blocks manufactured of swelling clay are installed into a borehole by a central rod (Figure 5-4). Both the rod and the blocks remain in the hole (Pusch & Ramqvist 2006a, p. 39-42 and 2008, p. 25-29). In the Basic Method, a dense block of borehole backfill material in a perforated tube is installed into a borehole (Figure 5-5). As the clay comes in contact with water it swells from inside the tube through the holes on the sides into the borehole (Figure 5-6). Both the tube and the borehole backfill material remain in the hole. In the Container Method, a dense block of borehole backfill material is lowered inside a container into a borehole and then pushed out in the selected place in the borehole by piston. Figure 5-7 presents the idea of the Container Method when material is installed in a groundwater-filled borehole. In the Container Method, both the

29

borehole backfill material and a bottom plate remain in the borehole and the container is removed (Pusch & Ramqvist 2008, p. 8-25).

Figure 5-4. The Couronne Method blocks are being set to the central rod (Pusch & Ramqvist 2008, p. 27).

Figure 5-5. Basic Method tubes with MX-80 bentonite, pictures from the closure of the OL-KR24 (Rautio 2006, p. 38).

30

Figure 5-6. Growth of soft clay through the perforation of a copper tube confining a dense MX-80 clay core in an 80 mm diameter oedometer. Appearance at removal of the lid 8 hours after start. The larger part of the core is still unaffected by water (Pusch & Ramqvist 2008, p. 18).

31

Figure 5-7. Illustration of the Container Method, not in scale. 5.2.2 Previous experiments and function of methods The methods and materials for borehole backfill have been experimented on since the 1980s. The experiments concern the installation methods, erosion (the Basic Method), perforation rate (the Basic Method), swelling, saturation, maturation, and piping. The behavior of the materials is dependent on the installation method and the borehole conditions.

32

Basic Method Several field experiments (below; Experiments 1-4) concerning borehole closure have been done in the 1980’s, including some conducted in the Stripa mine in Sweden and one at sea (Pusch 1981, Pusch & Ramqvist 2004, p. 43-47). Field experiment 5 was done at Olkiluoto site (Rautio 2006). Experiment 1 was a Stripa mine pilot project on borehole closure, in which a cylindrical MX-80 block with a 10% water content and a bulk density of 2,150 kg/m3 was installed in a perforated (50% perforation degree) copper tube into a vertical 6 m long and 56 mm diameter hole. The copper tube had a length of 2.5 m, an outer diameter of 35 m and an inner diameter of 32 mm. The diameter of the MX-80 block was 30 mm. The ultimate density would have been 1,780 kg/m3 at 43% water content, but when borehole was over cored 6 months later the water content was between 35% and 37% and the estimated degree of saturation from 75% to 85%. The clay had swelled from the tube and the water had been uniformly distributed in the clay. The reason for unsaturation was poor access to water (Pusch 1981, Pusch & Ramqvist 2004, p. 43). Experiment 2 was performed in a horizontal 56 mm diameter and a 100 m long hole, with copper tubes that were 2.5 m long, 50% perforated with 11 mm holes, had a 54 mm diameter and were 39 pieces jointed together with connecting copper pieces. Cylindrical MX-80 with 11% water content was compressed with 120 MPa to a bulk density of 2,110 kg/m3. The outer diameter of these blocks was 48.7 mm and they had a central hole with a 18.3 mm diameter for a copper pipe installed for experimental reasons. After 2.5 years the clay section was extracted with a hydraulic jack. It was completely saturated and had a water content of approximately 33% and a density of 1,950 kg/m3 (Pusch & Ramqvist 2004, p. 44). Experiment 3 was in vertical 76 mm diameter hole that was 14 m long. The perforated copper tube had an outer diameter of 68.6 mm and an inner diameter of 65 mm. Perforation rate was 50% and hole diameter 11 mm. MX-80 bentonite was again compacted with 120 MPa and 11% water content to a bulk density of 2,110 kg/m3. The cylindrical blocks had a diameter of 65 mm and a central hole of 20 mm diameter for investigation purposes. The water content in saturation should have been 40% and the density 1,820 kg/m3. The force required to extrude the materials at the end of the test was an axial force of 9 tons, corresponding to an adhesive strength of 100-120 kPa. From this it was estimated that the density was 1,750-1,800 kg/m3 and the water content between 35-45% (Pusch & Ramqvist 2004, p. 44-45). Experiment 4 conducted at sea and comprised of five 76 mm-diameter holes with a length up to 160 m that were closed using concrete and the Basic Method perforated copper tubes. Concrete was cast below and above the Basic Method tubes that were installed to sections with lengths varying between 10 and 15 m. Materials were not retrieved (Pusch & Ramqvist 2004, p. 45). Experiment 5 was carried out when installation of the Basic Method borehole backfill was field tested at Olkiluoto. The closure experiment was conducted for OL-KR24, which is 551 m deep, and the process was successful (Rautio 2006). The tubes were

33

2.5 m long and they were inserted as a 7.5 m long section, in which three tubes were jointed together with connection pieces, and as an additional single tube. The thickness of the tube wall was only 1 mm and the outer diameter of the tubes was 72 mm. The diameter of OL-KR24 is 76 mm. The weight of one 2.5 m long tube was 25 kg (Rautio 2006, p. 38). Pusch and Ramqvist (2006a, p. 30) examined the erosion rate of the Basic Method borehole backfill material and found out that when the material was MX-80 bentonite with 6% water content and a 2,050 kg/m3 density, the erosion rate was ranging from 6% to 9% when transportation down to 1,000 m was simulated. This would lower the initial dry density to approximately 1,800 kg/m3. It is possible to compress MX-80 to a larger density, approximately 2,100 kg/m3, and this could decrease the erosion rate between 4% and 5%. Regardless of whether rotation during installation occurs, the erosion rate can increase up to 15% (Pusch & Ramqvist 2006a, p. 32). Figure 5-8 presents a series of MX-80 dry densities acquired when samples with varied water contents were compressed with different compaction pressures. A suitable grain size distribution of the clay powder was found to be 20% 2-8 mm, 20.4% 1-2 mm, 42.4% 0.1-1 mm and 17.2% <0.1 mm (Pusch & Ramqvist 2006a, p. 30). To prevent too rapid expansion and erosion of swelling clay gel around the tube, the water in the boreholes needs to be poor in electrolytes. In practice this means that saline groundwater must be replaced by fresh water. This procedure is considered in Chapter 7.5. In electrolyte-poor water the installation of the Basic Method borehole backfill can take up to 5-10 hours but if the water is saline the corresponding time is only one hour (Pusch & Ramqvist 2008, p. 17). Again, too rapid installation can increase the erosion rate. According to Pusch & Ramqvist (2006a, p. 32) an installation time to the borehole length of 1,000 m should be 3-8 hours.

Figure 5-8. MX-80 dry densities with altering water contents and compaction forces. The black line presents the maximum dry density for a certain water ratio corresponding to complete water saturation. (Modified from Sandén & Börgesson 2006.)

34

In the Basic Method the clay embeds the tube as it swells through the holes in it, and even though the density between the tube and the rock is very low in the beginning of maturation, it raises as the clay homogenizes. According to Pusch & Ramqvist (2008, p. 17) the homogeneous paste, “clay skin”, forms around a tube in no less than 8 hours and after a few weeks it becomes dense, but it takes several months for the clay section to homogenize and reach the required density and water conductivity. After this time has passed the Basic Method borehole backfill meets the set requirements. An optimal perforation degree of a Basic Method tube is 50% and the holes should have a 10 mm diameter and half hole shift. This provides a symmetrical structure and makes all holes equal in considering migration of clay and final maturation. The experiments and calculations were performed with a copper tube with 2 mm thickness (Pusch & Ramqvist 2006a, p. 16). Figure 5-9 shows a perforation process of a Basic Method tube. The long-term laboratory tests of the Basic Method demonstrated complete swelling and saturation of bentonite MX-80 after 10-20 days. Mean swelling pressure against the rock was 2.8 MPa for fresh water and 0.6 MPa for saline water. After 20 days of maturation the hydraulic conductivities for the clay segment between the tube and rock were ranging from 5E-13 m/s to 9E-13 m/s for fresh water and 2E-12 m/s for saline water. These meet well the requirements set for borehole backfill material. Laboratory studies indicate that permanent density differences may remain in the Basic Method borehole backfill (Pusch & Ramqvist 2008, p. 9). The water inserting fractures are sporadically in the boreholes and the maturation and homogenization will thus take longer than in the laboratory conditions, about 3 months (Pusch & Ramqvist 2008, p. 10-11).

Figure 5-9. Copper tube being perforated in a lath (Liwinstone) (Pusch & Ramqvist 2006a, p. 33).

35

The maturation rate of a Basic Method borehole backfill has been investigated by observing time-dependent growth of the shear resistance. This was investigated by extruding a 3 m long Basic Method borehole backfill section from a 5 m long borehole with a hydraulic jack, which was operated from another borehole that reached the bottom of the test borehole. Diameter of the test borehole was 80 mm, the diameter of the tube was 76.1 mm and the thickness 4 mm. The main observation was that the tube slowed the formation of “clay skin” around the tube and caused microstructural heterogeneity in the first days. However, the force to move a 10 m Basic Method borehole backfill section would be approximately 300 kN, which is a good result (Pusch & Ramqvist 2006b, p. 36 and 39-40 and 2008, p. 15-17). If there is a pressure gradient in a borehole, borehole backfill can suffer from piping. Laboratory tests gave results that pointed how the passing time increased the piping resistance. When tested, the Basic Method borehole backfill material was kept under 500 kPa for 8 hours and critical pressure for piping was observed to be 700 kPa. After 19.5 hours it was 900 kPa and after 41.5 hours 1,700 kPa (Pusch & Ramqvist 2006a, p. 26-27). In this work the material for the Basic Method tube is suggested to be copper but titanium has also been considered and it can be kept as an alternative. Container Method The borehole backfill material does not suffer erosion when installed with the Container Method. It will have a narrower diameter than it would if the Basic Method was used, as the container and the space between the container and rock wall create an empty volume when the borehole backfill is pushed out. The borehole backfill will have to be able to fill this space as it expands and achieves required hydraulic conductivity. Pusch and Ramqvist (2006, p. 35) used powdered MX-80 with a 6% water content and a compression force of 250 MPa. This provided backfill blocks with 72 mm diameter, a 1,700 kg/m3 dry density and an ultimate saturated density of 1,950 kg/m3 when installed into a borehole with 80 mm diameter. The formation of “clay skin” around the Container Method borehole backfill is quicker than in the Basic Method, as there is more surface and no restricting tube around the material. The limited water quantity and uneven maturation would result in heterogeneity as sections in vicinity of water feeding fractures maturate better at an early stage. The borehole backfill would, nevertheless, mature and homogenize more as time passes (Pusch & Ramqvist 2006a, p. 36). Experiments by Pusch & Ramqvist (2006b, p. 37) show that even though the density and shear strength increase rapidly in the Container method borehole backfill, microstructural heterogeneity and coagulation prevailed during the first days. The shear strength grew twice as fast as in the Basic Method borehole backfill during the first days, but slowed to nearly same after that. Average shear stress after 96 hours was 159 kPa. Piping of the Container Method borehole backfill was experimented with similar method as for the Basic Method. As the Container Method equipment was not yet available the blocks were inserted manually. After 6 hours the critical pressure was

36

already 1,700 kPa, after 18 hours 1,800 kPa and finally rose to 115 kPa or higher as the backfill could not be extruded anymore with the hydraulic jack (Pusch & Ramqvist 2006a, p. 36-37). In theory and according to laboratory investigations the Container Method appears to function well. It must be considered, though, that the installation equipment is yet to be manufactured and field tested and the Container Method should not be selected as the only installation method. The small volume of the backfill material may also act as an inhibiting factor for its use, as the container wall and gap between the container and borehole wall diminish the diameter of the actual borehole backfill. The material of the bottom plates of the Container Method is here assumed to be copper, but it can as well be of another material that has been accepted (e.g., titanium). The container itself is not left in the borehole and can thus be made for example of stainless steel. Pellet Method The Pellet Method has in several occasions been used in oil fields by Texas/Chevron to close abandoned holes drilled for oil or gas production, and also NAGRA 6 has conducted many experiments on them. The pellets or granules have been rather large, 4-10 mm in diameter, sometimes a mixture of two different sizes, and they have, in some instances, been coated with a degradable agent that slows the onset of the swelling to allow installation into desired depth (Pusch & Ramqvist 2006a, p. 43). When the pellets are installed, the water will initially flow fast to fill the voids between them and this creates quick saturation. The clay swells and soft paste forms to fill the voids, but the uneven distribution of water-conducting fractures along a borehole could lead to uneven densities and expansion. Permeable flow paths and heterogenic densities remain even after complete water saturation (Pusch & Ramqvist 2008, p. 32). The swelling clay that pellets are manufactured from should have potassium, rather than calcium, as the major adsorbed cation, as calcium bentonite has given much more heterogenic microstructural density results (Pusch & Ramqvist 2008, p. 37). The loading experiments performed on the Pellet Method borehole backfills demonstrated compression of the material instead of displacement (Pusch & Ramqvist 2006b, p. 36). According to Pusch & Ramqvist (2006a, p. 43) the highest densities for the Pellet Method borehole backfill are acquired by blowing the pellets into a hole. Dropping them into steep holes gives only moderate densities and maturation, and mechanical compaction would be difficult. When considering the shape of the pellets, the best densities were acquired by using pillow-shaped pieces of compacted bentonite (Figure 5-10). The borehole would have to be drained before the installation of the pellets, to assure the best possible compaction and resulting density. The production of a Pellet Method borehole backfill is possible for short holes, the maximum borehole length being some tens of meters. Below this the compaction would

6 National Cooperative for the Disposal of Radioactive Waste, Switzerland

37

be problematic. The blowing of pellets would not be enough to reach desired densities and the compaction would demand vibration and load. Keeping the borehole dry during the installation of a Pellet Method borehole backfill could result in higher densities, but it would be difficult, if not impossible, to do so for a borehole deeper than 100 m (Pusch & Ramqvist 2008, p. 36-37). An average bulk density of 1,650 kg/m3 with saturation and percolation with tap water gives pellet borehole backfill hydraulic conductivity of 2E-12 m/s and approximately E-10 m/s when the water has a 1% salinity (Pusch & Ramqvist 2006a, p. 47). This demonstrates that the densities are adequate for shallow length boreholes. Figure 5-11 shows a picture of a Pellet Method borehole backfill saturated and extruded in laboratory circumstances.

Figure 5-10. Pillow-shaped pellets with 10% water content in 30 mm cell (Pusch & Ramqvist 2008, p. 32).

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Figure 5-11. Picture of a Pellet Method borehole backfill after extruding it from investigation circumstances simulating realistic backfill conditions (Pusch & Ramqvist 2006a, p. 47). Couronne Method In the Couronne Method, the density of the swelling clay would be adequate as the blocks around the central rod can be compressed to the desired density. The swelling clay should have potassium as the major adsorbed cation as calcium interacts too rapidly with saline water (see above, Pellet Method). The metal of the rod should be chemically compatible with the selected swelling clay. If the rod is composed of material that does not degrade, the volume of the borehole is lowered. If the central rod degrades, the ultimate density will suffer as the volume to fill would be larger. In the Couronne Method the gap between the borehole backfill and rock surface is very narrow, about 3 mm, and this is beneficial to the resulting ultimate density of the swelling clay (Pusch & Ramqvist 2006a, p. 39-42 and 2008, p. 25-29). In the Couronne Method a borehole should be drained, as in the Pellet Method; this is not feasible in boreholes deeper than 100 m. With the Couronne Method, density presents no problems, because the blocks around the rod can be compressed to desired density, but the groundwater erodes the borehole backfill material as the assembly is being installed downwards. If a Couronne Method borehole backfill can be installed in dry conditions it performs well. After the installation the groundwater will start to flow back into the drained and closed hole from fractures and it begins the dispersion of the clay and a soft, heterogeneous and permeable clay gel forms to fill the void between the rock and the backfill. As time passes the “clay skin” becomes denser as the expanding clay consolidates it (Pusch & Ramqvist 2006a, p. 39-42 and 2008, p. 25-29).

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5.2.3 Evaluation on method suitability The Basic Method can be used in the closure of the investigation boreholes considered in this report. In the light of the present knowledge it may be necessary to limit its usage to borehole lengths less than 500 m. The method has been reported to be usable up to lengths of 1,000 m, but the erosion degree and verification of function need more investigations. The Basic Method was successfully implemented to OL-KR24 (Rautio 2006) but the Borehole backfill has not yet been extracted and investigated. Replacing the water and verifying the success of it may, on the other hand, hinder the use of the Basic Method (Pusch & Ramqvist 2008). The Container Method is in this report considered to be an alternative for the Basic Method to install borehole backfill material in holes longer than 500 m. As it has never been used to install swelling clay it should be thoroughly experimented on beforehand. Laboratory tests and a field test should be performed before the method can be accepted for general use. In this report it is, however, assumed to be used in the deepest areas that need to be backfilled, in boreholes longer than 500 m, because of the potential erosion problems in the Basic Method. The Pellet and Couronne Methods have been discarded as possible installation methods for deep boreholes in accordance with, i.e., Pusch & Ramqvist (2008). This is due to the need to drain dry of groundwater the to-be-closed boreholes, should the mentioned methods be used. This is not feasible according to present knowledge. In the Pellet Method also the problematic compaction and possible remaining heterogeneities exclude it from being accepted. It is possible, though, to use the Pellet Method or the Couronne Method to backfill short holes from ONKALO, as the experiments give adequate water conductivities (see Chapter 5.2.2). Table 5-1 presents the pros and cons of the installation methods and their suitability for deep boreholes considered in this work. Table 5-1. The pros and cons of the different borehole backfill installation methods and suitability for borehole closure. Method + - Suitabilitity for borehole closure

Basic Field tested (OL-KR24) Good compaction

Erosion Replacing the water

Suitable in boreholes 1,000 m long. In this work use restricted to the boreholes with length of 500 m due to erosion risk.

Container Good compaction No erosion

Instrumentation undeveloped Small volume

Suitable, but due to possible future problems considering undeveloped instrumentation the use in this work is restricted to be as an alternative to the Basic Method in boreholes longer than 500 m.

Couronne Good compaction Erosion risk in long holes Requires draining of the hole

Suitable for holes with length less than 100 m. Not suitable for boreholes considered in this work.

Pellet Implemented in oil industry

Erosion Heterogeneity (flow routes) Poor compaction Requires draining of the hole

Suitable for short holes less than few tens of meters long. Not suitable for boreholes considered in this work.

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In the Container Method, even though there is no erosion, some water leakage into the container may occur and this should be investigated thoroughly before implementation. If water leakage does occur and the installation is delayed, the swelling clay may get stuck in the tube. Small water leakage may be allowed if the installation can be done swiftly and the borehole is stable. The Container Method has not been used in placing swelling clay but a similar method was successfully utilized in Posiva field test at Olkiluoto to lower cement/quartz concrete (Rautio 2006, p. 37). The problem is that, as the container needs to be lowered into very long distances into a borehole with a narrow diameter, the walls of the container need to have an adequate thickness. This, added to the needed space between the tube and the rock, eventually lead to a relatively large space between the out-pushed borehole backfill material and the rock. Because of these reasons the borehole backfill material must have a high density and a good swelling and homogenization capacity. The replacement of groundwater that is in the boreholes is not needed but is recommended to diminish sedimentation of the large aggregates that result from the dispersion of the borehole backfill material (Pusch & Ramqvist 2008, p. 24). Should better installation methods be discovered in the future, they can replace the ones suggested here. It could be possible to coat the borehole backfill material with an abrasion-durable and erosion-slowing substance, which could offer new possibilities for closure methods. A composite coating material could also be applied. If this kind of method is found applicable, the use of coating materials will need to be accepted before it can be considered as a reference, due to material restrictions at site. The best results, i.e., the largest volume of borehole backfill in comparison to the borehole volume are obtained in boreholes with largest diameters, if it is assumed that the space between the tube and the rock (in the Basic Method) remains the same. The same applies if the space required by the gap between the container and the rock and the thickness of the container wall remain the same (in the Container Method). It is, however, likely that the boreholes will not be drilled to a larger uniform dimension, but closure is implemented for different diameter holes. This means that equipment must be obtained for different-size boreholes and borehole backfill sections must be manufactured in different sizes. In all investigations made for borehole backfill, the material has been MX-80 bentonite from Wyoming. There is, however, no reason to consider this material the only alternative. The material choice is discussed more in Chapter 9, where it is considered how borehole backfill conforms to the requirements. 5.3 Concrete borehole plugs 5.3.1 General design In sections where transmissivity or fracture frequency is higher and requirements for the closure material are thus different than in the sparsely fractured regions of the bedrock, the suggested material is concrete. There is no long term need for the cement to stay in the borehole as long as the physical grain frame will remain to support the borehole backfill material. Rock material with grain distribution similar to moraine may be adequate even without the cement and admixtures. It is likely, though, that the use of

41

cement and admixtures would be beneficial when considering the installation and short time stability of the closure structures. A concrete plug must be hard enough to support the backfill atop it (Pusch & Ramqvist 2008, p. 41). If rock material is used instead of concrete, a concrete section may be needed below borehole backfill to ensure the stability during installing phase. 5.3.2 Material Requirements for the closure of the disposal facility requires the use of low pH type concrete at disposal depth (see requirements, Chapter 4). Closure of the boreholes would allow the use of standard concrete closer to ground surface, above the depth of approximately -300 m. Considering the small volumes of concrete involved, the low pH material will be used through the whole length of the hole if applicable. Examples of theoretical borehole volumes are presented in Table 5-2. The actual volume is slightly larger, because rock material will be eroded from the areas of fractures or fracture zones (water flow, drilling equipment etc.). Any notches deviating from the theoretical caliber increase the volume of the hole. Concrete volume may also rise due to its flow into fractures, which can be diminished by proper choice of ballast material. If needed, these sections can be stabilized prior to casting the concrete plug. Such need may arise, e.g., from constant erosion of the rock from the wall. Stabilization of a borehole section will be described in Chapter 7.4. The reactions between concrete and bentonite have been monitored and these reactions do not reach far distances from the contact surfaces but only affect the closest centimeters of the bentonite. The transportation of the concrete admixtures in the rock fractures is not very far reaching (Lehikoinen 2009). A low-pH concrete that could be an alternative, was designed by Vogt et al. (2009, p. 15). To lower pH the quantity of binder was lowered and the off-taken quantity was replaced with silica fume. This composition is here suggested to be borehole closure low-pH concrete (Table 5-3). Pusch & Ramqvist (2006a, p. 49) presented another composition, CBI7 silica concrete, which could also be considered as an alternative (Table 5-4). Minor changes are expected to be made to the concrete mix. Table 5-2. Theoretical borehole volumes.

Theoretical borehole diameter (mm)

Volume of 1 m (m3)

Volume of 10 m (m3)

Volume of 100 m (m3)

Volume of 1,000 m (m3)

56 0.00246 0.0246 0.246 2.463

75.7 0.00450 0.0450 0.450 4.501

76 0.00454 0.0454 0.454 4.536

7 Swedish cement and concrete research institute

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Table 5-3. An example for low-pH silica concrete for borehole plugs (Vogt et al. 2009, p. 15). The mix can be replaced in future as material investigations proceed.

Material Kg/m3

CEM I 42.5 MH/SR/LA 120

Silica fume 80

Water 165

Limestone filler 369

Sand 0-8 1,037

Gravel 8-16 558

Glenium 51 6.38

water/cement 1.375

water/binder 0.825

water/powder 0.29

Table 5-4. Alternative low-pH silica concrete for borehole plugs (Pusch & Ramqvist 2006a, p. 49).

Material Kg/m3

White cement 60

Water 150

Silica fume 60

Fine ground α-quartz 200

Fine ground cristobalite quartz 150

Superplasticizer 4.38 (dry weight)

Aggregate 0-4 mm 1,679

Organic material must be washed off of the ballast before use in order to avoid problems in installation and hardening (Rautio 2006, p. 37 and 40-41). The minerals should be as inert as possible, i.e. quartz. 5.4 Surface plugs 5.4.1 General purpose A surface plug is needed in the uppermost part of the boreholes as a mechanical lock. This keeps the borehole backfill material in the boreholes and diminishes the possibilities of interaction between the closure materials below and anything above this plug. In considering possible future glaciations, the surface plug should endure stress caused for example by flowing glacial waters that contain a lot of debris. Other requirements for the surface plugs are similarity with the surrounding rock and durability over hundreds of thousands of years.

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5.4.2 Location of the surface plug Påsse (2004) concluded that the last glacial cycle in Scandinavia caused an erosion of approximately 1 m with a local maximum of 4 m. In the Canadian shield, erosion caused by glaciations has been estimated at approximately 20-35 m per 100,000 years (McMurry et al. 2003). An ideal site for the surface plug would be just below the erosion level but the exact erosion depth is impossible to predict. In view of the studies mentioned above the plug should be at the depth of 25-30 m or deeper. Material that will be installed above surface plug will endure erosion during next glaciations. Possible material choice could be concrete or rock material. 5.4.3 Design alternatives The material considerations for borehole surface plug have previously been concrete, copper, and rock (Pusch & Ramqvist 2007, 2008, Pusch et al. 2012). In most of the boreholes the uppermost part of the boreholes has a wider diameter than the lower part (e.g., Niinimäki & Rautio 2002, p. 5 and 35). Originally, the upper sections were drilled larger to place pumps below groundwater surface to facilitate hydraulic investigations (Öhberg 2006, p.8). When boreholes are made a casing, which is a steel pipe that is grouted to the bedrock, is installed to the wider upper section. Examples of upper borehole structures can be seen from any of the borehole reports listed in Table 3-3. When considering a rock plug this makes it feasible to insert a rock plug to the bottom of the wider part. The location and diameter of the uppermost parts where a casing is vary, as do the length and diameter of the holes. The majority of the boreholes have a 140/134 mm casing for which a 165 mm hole was made with a DTH-hammer. These casings are grouted into the bedrock. The narrower casings have diameters between 64 mm and 90 mm (Table 5-5). The dimensions of the rock plug are here considered only according to installation possibilities. Considering installation a plug should be approximately 6 mm narrower than the borehole. A tool to insert a plug is yet under consideration, but it is assumed that installation can be done by using drilling equipment. The length of a plug could be something between 0.3 m and 1.9 m in line with the lengths of the examined plugs; copper and concrete. A rock plug has not been tested during the borehole project.

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Table 5-5. Dimensions of the upper parts of the boreholes in comparison to the lower hole diameter.

Hole id (OL-KR)

Nominal hole diameter below

the casings (mm)

Diameter of the upper part of the

hole (mm)

Outer diameter of the casing (mm)

Inner diameter of the casing (mm)

1, 2, 5, 7, 9, 11,12 56 165 140 130

3, 4 56 165 140 134

23, 25, 27, 28, 29, 31, 33, 37, 39, 40, 41, 42, 43, 44, 45, 46, 47, 49, 50, 51, 52, 53, 54, 55

75.7 165 140 134

10 76 165 140 130

13, 15, 16, 17, 18, 19, 20, 22

76 165 140 134

6, 14, 21 76 90 90 77

32, 34, 35, 36 75.7 89 89 78

26 75.7 84 84 77

8 56 64 64 57

Pusch & Ramqvist (2007) examined the function of a copper plug and a concrete plug. A copper plug was lowered into a borehole and expanded with 20 t pulling force to assure intact contact with rock surface. The borehole had a diameter of 200 mm and it was reamed 6 cm wider in the section where the plug was set. The recess was 300 mm high. Concrete was inserted below and on top of the plug. The plug was then slot-drilled and sawed in to two halves to visually inspect the contact and expansion. A copper plug is presented in Figure 5-12 and slot-drilled section with a copper plug and concrete in a borehole in Figure 5-13. The copper plug can resist an axial pressure of more than 30 MPa. A reamed section was also prepared for concrete plug. The ballast was selected to be rather large, approximately 1 cm. The result was a solid concrete plug that, after approximately three weeks, can yield more than a 30 MPa pressure. Punching tests on a similar plug with added quartzite give an axial force of 12 t, which corresponds to a 40 MPa axial pressure. Leaking of excess water did not significantly decrease the function of this concrete plug (Pusch & Ramqvist 2007). Concerning the concrete plug option, the cement fraction of the concrete will dissolve but, then again, the requirements for surface plug do not have specific hydraulic conductivity values. The concrete plug could be cast in a section reamed larger and selecting a suitable ballast material will add shear strength. Copper is also well studied and tested, and it benefits from a possibility to expand the plug mechanically against the walls. Rock is a good material as it is similar to surrounding material (bedrock) and relatively stable no matter the future circumstances. The rock plug could be manufactured as wedge-shape pieces, which are pressed against the rock wall when placed, but the function of the plug does not necessarily require this. The surface plug does not have a sealing requirement. Its function is to hamper inadvertent entry below (in borehole case meaning either drilling and burrowing of small animals) and filling the hole.

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Figure 5-12. A surface plug manufactured of copper (Pusch & Ramqvist 2007, p.14).

Figure 5-13. A slot drilled copper plug sliced in half, concrete fill above and below (Pusch & Ramqvist 2007, p. 21).

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5.4.4 Suggested design In this report it is suggested that the surface plug is a solid rock plug. When the casing dimensions are 140/130 mm or 140/134 mm the casing is left in place and a rock plug is lowered to the bottom of the casing, up to where concrete then already reaches. An illustration is presented in Figure 5-14. If this depth is above the estimated erosion level, the hole is widened until it reaches the desired depth and the rock plug is lowered there. When the casing is narrower than needed, it is overcored off with a wide drill bit and the hole is extended down to desired depth below the estimated erosion level. The hole is cleaned after overcoring or deepening and a rock plug is installed.

Figure 5-14. Illustration of a surface plug at the bottom of a casing. Not in scale.

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The casings are manufactured of steel and thus they will break and decay in the far future. As they are near the ground surface and their removal is challenging (they are grouted to the bedrock) they are for now considered to be left in the holes. If surface plugs are produced in the manner introduced here, the plug quantities and sizes are as presented in Table 5-6. This report does not take a stance on whether one of the presented diameters would be used for boreholes that need widening and deepening. The 1 m length is selected due to factors depending on sectioning the material for the 3D model and should be reconsidered separately before manufacturing and production of the closure. If the surface plug is constructed of rock it can be manufactured in a quarry. The plug must be chemically and physically as stable as the surrounding rock or have a higher strength. Granite, for example, is a good alternative as it composes of quartz, plagioclase and K-feldspar with only minor quantities of accessory minerals. Other rocks (e.g., diorite or granodiorite) can be considered if need be. As the function of the surface plug in the closure of the boreholes is to keep the closure materials in place, the pressure provided by all closure materials above the uppermost borehole backfill section should be larger than the pressure of the borehole backfill. Radial swelling pressure of MX-80 bentonite in a Basic Method tube was examined by Börgesson & Sandén (2006) to be 2.8 MPa in fresh water and 0.6 MPa in saline water (3.5% salinity). In natural circumstances, when the backfill material swells its dry density falls and ability to swell decreases. A quantity of borehole backfill material can only expand to a certain volume defined by initial dry density. In addition, the concrete plugs between borehole backfill sections inhibit swelling. When the closure implementation is at hand the pressures can be calculated to ensure that the materials do not extrude at any circumstances. Calculated in a simplified manner, so that swelling pressure is compared to pressure directed downwards by a 1 meter rock plug and concrete above that, the first backfill sections should be approximately at a borehole length of 123 m. This calculation has not taken into consideration the effect of multiple overlying sections of concrete and borehole backfill, friction, dip angle or other variants, but has only considered the weights of overlying materials directed straight down.

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Table 5-6. A suggestion for dimensions and quantities of surface plugs.

Suggestions for surface plug dimensions

Hole id (OL-KR) Number of holes

124 mm x 1 m 1, 2, 5, 7, 9, 10, 11, 12 8

128 mm x 1 m

3, 4, 13, 15, 16, 17, 18, 19, 20, 22, 23, 25, 27, 28, 29, 31, 33, 37, 39, 40, 41, 42, 43, 44, 45,46, 47, 49, 50, 51, 52, 53, 54, 55

34

Overcoring (widening and deepening of the hole)

6, 8, 14, 21, 26, 32, 34, 35, 36 9

5.5 Material above the surface plug The material above the surface plug will be placed to the uppermost section of the boreholes (from ground level to 30 m - 41 m of borehole length), which is most often fractured and will erode during future glacial events, the selection of material is not as demanding. The material should be such that it can be allowed to erode and that it acts as a barrier between the closure materials installed deeper. The material could be concrete, crushed rock, or solid-rock cylinders (e.g., core samples). At this depth there are no pH-restrictions for concrete. The concept of filling a borehole above surface plug is presented in Figure 5-15.

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Figure 5-15. An illustration of upper section of closed borehole.

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6 CRITERIA AND DESIGN FOR THE CLOSURE OF THE DEEP INVESTIGATION BOREHOLES

6.1 Criteria for closure component selection The borehole closure components are concrete plugs and borehole backfills. The Basic Method will be implemented down to 500 m along borehole length and below this the Container Method is assumed to be used. A surface plug will be installed into each borehole. Suggested materials and descriptions of the sections they will be placed into are presented in Table 6-1. Several parameters have been monitored and measured from the boreholes. To determine sections needing backfill or plugs it was necessary to select the parameters that best indicate the need of each closure material. The most crucial factor is the flow of groundwater in fractures. This has been measured from all of the boreholes considered in this report. The water flow has been published as transmissivities in fractures by Tammisto et al. (2009), Palmén et al. (2010) and Tammisto & Palmén (2011). It was decided that a concrete plug was needed in sections with hydraulic conductivity ≥1E-8 m/s. This is justified as it is on the same scale as the hydraulic conductivity when the grouting need arises, should such flow occur in the ONKALO access tunnel. If the value would be lower, the vast majority of the borehole volume would end up being filled with concrete, which is not suitable in the far future (only grain frame remains). If the hydraulic conductivity would be larger, there is a risk that groundwater could erode clay from borehole as the flow would go directly through a borehole backfill section. Thus ≥1E-8 m/s is considered to be the best threshold value. The second factor selected was fracture frequency. Sections with 10 fractures or more per meter were considered to need a concrete plug (not depending on measured flow of the fractures). Source for fracture counts were those from the original drilling reports (Table 3-3). Fractured zones from core loggings were also used to indicate sections needing stabilization. Fractured zones were classified according to Korhonen et al. (1974) and Gardemaister et al. (1976) in the original drilling reports (Table 3-3); the logged RiIII - RiV zones were interpolated to one meter sections and considered to need a concrete plug. The selected parameters dictate that backfill material can be installed into sections with hydraulic conductivity less than 1E-8 m/s, natural fracture count less than 10 per meter, and sections being only sparsely fractured. Table 6-2 presents the criteria for sectioning.

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Table 6-1. Closure materials.

Closure component Suggested material Description of section

Borehole backfill Swelling clay/ swelling clay and ballast mixture

Intact rock with low hydraulic conductivities, the Basic Method above 500 m and the Container Method below 500 m

Concrete plug Low-pH silica concrete Fractured rock and/or elevated hydraulic conductivities

Surface plug Rock Depth of 25-42 m

Material above surface plug Undefined concrete/ rock material

Elevated hydraulic conductivities, section above surface plug

Table 6-2. Parameters used in sectioning the closure materials and depths for surface plug and material above it.

Closure component K (m/s) Fractured zones Natural fractures/m

Borehole backfill < 1E-8 none, RiI-RiII < 10

Concrete plug ≥ 1E-8 RiIII-RiV ≥ 10

Closure component Depth (m)

Surface plug 25-41

Material above surface plug 0-Surface plug

6.2 Data processing In this work, the database reports for hydraulically conductive fractures by Tammisto et al. (2009), Palmén et al. (2010) and Tammisto & Palmén (2011) are used as sources for transmissivities (T). To be conservative the maximum T value was used for each borehole if there were several measurements for a same borehole length site in a borehole. The T values were interpolated into sections of 1 m starting from the top of the borehole. T values within the same 1 m section were added. As the T values were then in 1 m sections, they can be modified into hydraulic conductivities (K value) using Equation 6-1. The K value data was then changed into maximum K logarithms (Max Log K) in 1 m intervals. This interval data is as an excel table and as a database file (Microsoft Access™) that can be viewed with Gemcom Surpac™ program. The use of a 3D program (Gemcom Surpac™) facilitates better visualization of the structures and creates an easy method to keep and update the data. For the length of casings the Max K Log was set at -17, for sparsely fractured rock at -16. Sparsely fractured rock is a rock section with hydraulic conductivities so low that they could not be measured with used methods. K = T/l (6-1) K= The hydraulic conductivity (m/s) T= The transmissivity (m2/s) l= The length of a section (m).

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6.3 Sectioning of the closure materials As the error in flow measurements was observed to be approximately 1 m at a borehole length of 1,000 m and the data from the database reports (Tammisto et al. (2009), Palmén et al. (2010) and Tammisto & Palmén (2011) were already corrected, the lengths were considered to be accurate. A plug section should have a concrete plug with a length that exceeds the interpolated length with 1 m both below and above due the possible error influence in length. This gives a three meter minimum length for a concrete section. Backfill is inserted into areas of intact rock, but with a minimum length of 2.5 m with the Basic Method (borehole length less than 500 m) or 2 m with the Container Method (borehole length more than 500 m). The lengths of backfill are multiples of 2.5 m with the Basic Method (borehole length less than 500 m) or multiples of 2 m with the Container Method (borehole length more than 500 m). These lengths were selected for the Basic Method tubes with a length of 2.5 m were used successfully in closing OL-KR24 (Rautio 2006) and a recommended minimum section length for the Container Method is 2 m (Pusch & Ramqvist 2008, p. 25). It was decided that no backfill will be installed above a surface plug, which, if the width of the borehole must be enlarged or the depth increased, is here systematically placed approximately to the depth of 30 m from the ground surface (the borehole length may vary depending on the angle of the borehole). It is suggested that concrete will be placed in contact with surface plug instead of bentonite even if the set criteria would approve backfill material directly below it. If there is already concrete in a certain section of a hole, only concrete is assumed to be placed there. These sections are presented in Table 6-3. Table 6-3. Boreholes with cemented sections.

Borehole id Cemented sections

OL-KR1 40.20 - 100.20 m

OL-KR2 40.35 - 100.20 m 878.5 - 883.5 m

OL-KR3 40.58 - 104.50 m

OL-KR4 40.00 - 100.20 m

OL-KR5 40.15 - 109.70 m

OL-KR6 5.25 - 26.25 m

OL-KR10 140 - 310.36 m

OL-KR40 41 - 125 m

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6.4 Closure design The closure designs for selected 51 boreholes can be found in Appendix 1. An example of a closure design (OL-KR1) is shown in Figure 6-1 and Figure 6-2. The closure designs display a borehole in four parallel figures that present the chosen criteria parameters and closure components: hydraulic conductivity, natural fractures, fractured zones and closure materials (see Chapter 6.1).

55

500

450

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

1_a

≥ 10 per meter

< 10 per meter

Not determined

OL-KR10 - 500 m

≥ -8

< -8

Not determined

Max log K

Natural fractures

Fractured zones

RiIII

Sparsely fractured

Not determined

Closure materials

Casing and/or upper material

Concrete plug

Basic Method borehole backfill

Max log K Fractured zones Closure

materials

Natural fractures

Surface plug

Figure 6-1. The closure components and criteria for their sectioning in borehole OL-KR1, between groundlevel and -500 m. The borehole figures are not in scale but are all viewed from south to north.

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1000

950

900

850

800

750

700

650

600

550

500

Not in scale

OL

-KR

1_b

OL-KR1

≥ 10 per meter

< 10 per meter

≥ -8

< -8

Max log K

Natural fractures

Closure materials

Concrete plug


Container Methodborehole backfill

Max log KNatural fractures Fractured

zones Closure materials

500 - 1001.05 m

Fractured zones

RiIII

Sparsely fractured

Figure 6-2. The closure components and criteria for their sectioning in borehole OL-KR1, between 500 m and 1,001.05 m. The borehole figures are not in scale but are all viewed from south to north.

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6.5 Material quantities The design presented in this work leads to closure of 51 boreholes with a total length of 29,457 m. Total of 6,376 m are filled with low-pH concrete (plug material), 20,833 m with borehole backfill material, 51 m with surface plugs and 1,913 m with a material above the surface plugs (Table 6-4). When considering only the borehole backfills, the quantity of materials is presented in Table 6-5. These were counted according to diameters and borehole backfill installation methods. The total mass of borehole backfill is presented in Table 6-6. The mass is calculated assuming a bulk density of 2,050 kg/m3. The weight of the copper tube of the Basic Method was not considered in the weight calculations. The Basic Methods bottom and top lid are estimated to be 5 mm and so is the thickness of the Container Methods bottom plate. A further assumption is that the Basic Method’s tube and the Container Method’s container are 3 mm thick and the gap between the tube/container and the rock is 3 mm. Table 6-4. Lengths of closure components and their percentage quantities of the length of selected 51 boreholes.

Material Total length (m) Percentage of total borehole length (%)

Borehole length 29,457 100

Concrete plug 6,376 21.6

Material above surface plug 1,913 6.5

Surface plug 51 0.2

Basic borehole backfill 14,043 47.7

Container borehole backfill 6,79 23.1

Borehole backfill, total 20,833 70.7

Table 6-5. Lengths of borehole backfill sections of selected 51 boreholes and the quantities of minimum length sections if inserted one by one.

Backfill method Borehole diameter 56 mm 75,7 – 76 mm


Length (m) 3,395 10,647.5

Quantity of 2,5 m long sections 1,358 4,259

Container Method borehole backfill

Length (m) 2,328 4,462

Quantity of 2 m long sections 1,164 2,231

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Table 6-6. The weight of the borehole backfill if the bulk density is 2,050 kg/m3. Tube and bottom plate are not considered.

Basic method borehole backfill,

2.5 m Container method borehole

backfill, 2 m

Borehole diameter (mm) Volume

(m3/2,5 m) Mass (kg/2.5 m)

Volume (m3/2 m)

Mass (kg/2 m)

56 0.00380 7.8 0.00304 6.2

75.7 - 76 0.00804 16.5 0.00643 13.2

Total backfill mass of backfill in all (51) considered boreholes according to suggestion in this report (kg)

56 10,583 7,257

75.7 - 76 70,218 29,426

Total backfill mass (kg) 117,484

6.6 Borehole categories The 51 boreholes can be considered in groups according to matters concerning the closure. There are different possibilities in dividing the groups. The first dividing factor, tied to the borehole backfill installation methods, is length of the hole; boreholes are either less or more than 500 m long. The second differentiating factor is the diameter of the borehole, which is either 56 mm or 75.7-76 mm. The third factor is the inner diameter of the casing in the uppermost parts of the boreholes. Considering the third factor, the boreholes can be divided into three groups: casing diameter of 134 mm, 130 mm or those with such small casing diameters and casing depths that they need to be over cored and deepened if a rock plug is to be placed as the surface plug. Table 6-7 presents one grouping of the boreholes, based on the selection for a surface plug. For borehole lengths, see Table 3-3. Table 6-7. The boreholes with different calibers and examples for surface plugs.

Borehole diameter (mm)

Inner diameter of the casing (mm)

Boreholes (OL-KR)

Surface plug (diameter x length) or procedure

56

57 8 Overcoring (widening and deepening of the hole)

130 1, 2, 5, 7, 9, 11, 12 124 mm x 1 m

134 4 128 mm x 1 m

75.7 - 76

77 6, 14 Overcoring (widening and deepening of the hole)

130 10 124 mm x 1 m

134 15, 19, 25, 27, 28, 29, 40, 43, 44, 45, 47, 49, 50, 51, 55

128 mm x 1 m

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7 PRODUCTION OF THE CLOSURE 7.1 General The production of the closure has seven phases: 1. Cleaning the borehole 2. Re-characterization of the borehole 3. Stabilizing the weak sections 4. Replacing the borehole water 5. Closing the borehole 6. Installing the surface plug 7. Installing the material above surface plug, Some stages may have to be repeated several times during the closure production; for example the replacing of the water may need to be repeated before the installation of each borehole backfill section. 7.2 Cleaning Prior to stabilizing, the boreholes must be cleaned of debris and erosion products that may have gathered to the walls and the bottoms of the holes. This material might hamper the function of the closure materials and complicate the installation of the closure materials. In some cases parts of the drilling equipment or investigation devices have gotten stuck in the boreholes and these need to be extracted before the closure can commence. The boreholes are groundwater-filled to varying depths. The cleaning can be performed with a brush bit and rinsing water, which should be marked with fluorescent marker according to instructions concerning Olkiluoto borehole investigations. According to Rautio et al. (2004), the best cleaning results are obtained with a steel brush that has a slightly larger diameter than the borehole. For example an 80 mm or a 90 mm brush is compatible with a 76 mm borehole. Steel is better than nylon, as it has a better durability. A brush connected to a drill string with an adapter is inserted into a borehole and rotated slowly as it is moved downwards. Flushing should be performed simultaneously through holes either in the adapter or the brush itself. At the end of the cleaning procedure the borehole should be flushed thoroughly to remove any muck that was rinsed downwards when brushed. According to Rautio et al. (2004, p. 24-25) the form of a brush remains unaltered and though small weight reduction occurs no visual difference in the brush is noticeable. A steel brush is presented in Figure 7-1. A cleaning procedure, implemented for OL-KR10, has been described by Rautio (2002a, p. 5-8) and cleaning of OL-KR4 and OL-KR14 by Pussinen (2006).

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Figure 7-1. A 125 mm steel brush before and after use (Rautio et al. 2004, p. 25). In cases of stuck equipment, the pieces must be retrieved. Extraction can be done by using recovery equipments that are commercially available, although in cases of measuring equipment the rescue tools may have to be designed and manufactured for an individual rescue mission. Some equipment should be recovered undamaged due to their importance and cost. Any materials endangering the environment of the borehole should be extracted unharmed (e.g., batteries). Rescue equipments can be maneuvered with a drill rig and, if necessary, a jack lift may be used. The stuck equipment can be retrieved using recovery taps or recovery bell taps, or drilled through or overcored. Metal pieces that fall off from the recovery rig or stuck equipment, when being recovered, can be flushed up or lifted with a magnet (Rautio et al. 2004, p. 3-23). The removal of any stuck equipment or measuring instruments or materials left behind are always individual procedures. There are several tools for this, but in some cases it may be necessary to design and construct equipment for a single removal. The methods for removing objects from boreholes are described by Rautio et al. (2004) and Rautio (2005c) described the removal of stuck measuring equipment from OL-KR4. Sections to be stabilized due to mentioned reasons, special notifications and stuck equipment are presented in Table 7-1. This data may be incomplete and complementary information gathering on this subject may be needed.

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Table 7-1. Sections, special notifications and stuck equipment in considered boreholes. Data may be lacking and verification of openness of holes should be validated prior to production of the closure. Borehole id Remarks Special sections

OL-KR1 Centralizer (length about 60 cm) at the bottom of the hole. Groundlevel Z measured from top of ground slab.

Cemented section 40.20 - 100.20 m.

OL-KR2 Length of the funnel/cone 0.20 m. Below 1039 m weak section. Cemented

section 40.35 - 100.20 m. Cemented section 878.5 - 883.5 m. Steel wedge cemented at 879.70 m.

OL-KR3 Length of the funnel/cone 0.20 m. Groundlevel Z measured from top of ground slab.


OL-KR4 Length of the funnel/cone 0.20 m. 758 - 762 m weak section. Cemented section 40.00 - 100.20 m.

OL-KR5 Length of the funnel/cone 0.20 m. Groundlevel Z measured from top of ground slab.


OL-KR6 Cemented section 5.25 - 26.25 m.

OL-KR7

Length of the funnel/cone 0.076 m. Drill string (42 m) stuck in the borehole (borehole section c. 715 - 755 m). Weak section 690.5 - 692 m.

c. 375 m, core barrel was cut at this depth.

OL-KR9 Length of the funnel/cone 0.07 m.

OL-KR10 Centralizer at the bottom of the borehole.

Section 40.46 - 100.00 m reamed with down-the-hole percussion drilling (diam.115 mm).

Section 100 - 177.63 m

diam. 86 mm.

Cemented section 140 - 310.36 m.

OL-KR11 Weak fracture zone 624.8 - 626.4 m.

OL-KR12 Good spooling water recovery.

Length of the funnel/cone 0.07 m.

OL-KR13 Weak section 451.04 - 459.23 m.

OL-KR14

Core barrel (length 3.95 m) and pressure sensor (length 0.20 m) left at the bottom of the hole.

Borehole cemented below 508 m.

OL-KR21 Flowmeter equipment (length c. 7.25 m) at the borehole bottom.

OL-KR25 Casing extended 0.9 m (12.10.2006).

OL-KR26 Cement at the depth of about 6 m.

OL-KR29 Drill cuttings and loose rock material and 0.5 m long dummy sond at the bottom of the hole.

The table continues to the next page.

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The table continues from the previous page.

Borehole id Remarks Special sections

OL-KR34 Borehole filled with grout.

OL-KR36 Grout in the borehole

OL-KR37

Upper wedge/top of wedge at the depth of 94.56 m.

Lower wedge/top of wedge at the depth of 228.22 m.

Total length of the wedge is 4339 mm.

OL-KR40 Unstable section 74 - 110 m. Cemented section 41 - 125 m.

OL-KR42 A new cone was installed on the top at the old cone. See Working Report-2007-41.

OL-KR44 Deviation measured from casing top (+6.71).

OL-KR46 Length (columns "length" and "hole openess") measured from top of casing. Deviation measured from cut casing top (+5.10).

OL-KR47 EMS-survey tool could not pass the section at the depth of 920 m.

Hole section 40.14 - 41.40 m

core drilled (diam. 86 mm).

OL-KR49 Hole section 40.32 - 40.86 m

core drilled (diam. 86 mm).

OL-KR50 During drilling loose rock fragments from hole section 384 - 444 m fell into the drillhole.

Hole section 40.15 - 40.89 m

core drilled (diam. 86 mm). Weak section 384.26 - 387.10 m.

7.3 Characterization After cleaning and prior to installation of any closure materials the caliber of the borehole must be measured, the borehole should be optically examined and dummy probing must be implemented. The initial characterization for each borehole has been done during the drilling phase and investigations have been carried out during the years they have been open, but as the boreholes will be of substantial ages when the closure is implemented, they may have suffered erosion and gathered material on the walls and on the bottom. Some may be clogged by eroded material from fractures above or fractured zones. The cleaning of a borehole should remove any dirt, clogs and excess material, but the caliber may nevertheless have changed in eroded sections. Caliber measurement is done for example by using a caliper tool that has three connected hard metal arms. The angle of the opening arms produces the primary signal. It is lowered to the borehole with a cable and a motorized winch. The length measurement is triggered by pulses of sensitive length encoder installed on a pulley wheel. The cable is marked with a minimum of 10 m intervals. The tool must be tested before and after use by using approximately four different-diameter metal rings. The measurement of the caliber is applied upwards from the bottom of the hole. Recording spacing of the device is approximately 0.01 m. Caliber values provide data for the actual volumes that need to be closed with selected materials (Rautio 2006, p. 13-14). The caliber of a hole could also be acquired from acoustic televiewer measurements (Pusch et al. 2012).

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Optical imaging of the borehole is used for visual examination. Optical imaging has been done for boreholes deeper than 100 m but if substantial time has passed between the optical imaging and the closure procedure, it may be necessary to repeat it in some holes and compare the results in case a fracture, or fracture zone, that was initially unnoticed has emerged with time by the flow of groundwater. The optical imaging device is lowered with similar cable as the caliber device (Rautio 2006, p. 13). Dummy probing is done to ensure that the curvature of the borehole is large enough for insertion of closure material of selected lengths. It is done with a wire line cable of the drill rig. There are dummy probes of different lengths and they should be used every time before a backfill section is installed. Consideration to use dummy probing to ensure openness and the straightness of a borehole should also be done before longer devices are inserted into the boreholes (Rautio 2006, p. 17). 7.4 Stabilization Pusch and Ramqvist (2008, p. 39) considered that boreholes should be stabilized in sections, governed by, e.g., fractures or fractured zones, which may cause closure equipment to get stuck or the borehole wall to crumble. The fractured zones or individual fractures may also displace closure material into the surrounding rock before the setting, and this should be prevented. Minor water flow into the borehole can in some cases also be diminished, or even temporarily ceased. The stabilizing is implemented by first reaming the section wider. Stabilization concrete is then installed into the borehole to the reamed section. The setting takes approximately 24 h and after this the section can be drilled through. This leaves a concrete “pipe” to support the section and closure can be implemented through and inside it. The concrete should be of a low-pH type, because it should have a minimal effect to the closure materials and minerals in the fractures. Later the cement may be transported further off into the bedrock, as long as the aggregate material remains physically intact and acts as support for the closure materials. The experience from closing the borehole OL-KR24 was that the stabilizing material did not stay where it was cast and several problems emerged as stabilizing was attempted (Rautio 2006, p. 19-33). Therefore stabilization will need further development and demonstration before implementation begins. The stabilization is carried out in three phases: reaming of the selected section, installation of stabilizing material, and redrilling. Drill rig and equipment needed for reaming, stabilization and redrilling have specific demands that were in the case of the stabilizing process of borehole OL-KR24 (Rautio 2006, p. 20-21): - Minimum lifting capacity of the rig 560 m of NT drill rods - ability to ream upwards with a force of 10,000 N - controlled and recorded penetration rate of the drilling rig - flush pump able to regulate the pressure up to 70 bars - flow capacity of the pump 50 l/min - flow can be regulated down to 5 l/min.

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These demands are borehole specific and depend on the diameter of the borehole and the operation depth as borehole length. The drill rods need to be checked. Both impregnated and corborit bits are reserved for redrilling. The flush pump for the reaming tool needs to be equipped with two accumulators with different sizes to manage the constant water flow and pressure needed for the function. For the installation of the stabilizing material drill rigs, pistons and barrel cores are required depending on the selected installation method (Rautio 2006, p. 21). The reaming tool is connected to the drill rods and tested on the surface before lowering it to the chosen section. The reaming is performed upwards. Borehole OL-PR10 drilled for geophones required stabilization of a water-conducting zone at the borehole length from -53 m to -60 m. The stabilization was made by pumping cement slurry down the hole and increasing the pressure up to 20 bar. The slurry had a water/cement ratio of 0.5 and was kept in constant movement to prevent separation. Pumping was conducted with a rotating drill string for the length of the hole. After the slurry had solidified, which took about three days, the hole was redrilled. The stabilization process was considered successful (Hjärtström 2007, p. 7). The stabilization of borehole OL-KR24 was attempted with “the inner tube method” (Rautio 2006, p. 23). A bottom packer was lowered into the borehole below the reamed section and inflated with water pressure. Then an outer core barrel with drill bit was lowered some 3 m above the bottom packer. Another core barrel was inserted and a lower piston was placed inside it, then a chosen volume of concrete, and an upper piston. Before the insertion of the inner core barrel a special barrelhead was applied below the bottom piston. The inner core barrel was then inserted through the drill bit to some 0.5 m above the lower packer. With the pressure applied to the upper piston the concrete was pushed outside through the barrelhead that had opened by overshot. The lower piston, which remained in the bottom above the lower packer, and the concrete were pushed out by applied pressure and the upper piston. As the concrete was supposed to be pumped out the drill rods were supposed to be lifted upwards accordingly, and the upper piston should also have extruded into the borehole above the reamed section. This method did not succeed and the concrete got stuck in the equipment even with several attempts. Eventually concrete was installed by attaching the concrete truck to drilling equipment and feeding the material down straight through the drill rods (Rautio 2006). Redrilling can start when samples of the installed concrete are hardened. There should be at least two cup samples, one in dry cup and one preserved in the conditions (temperature, groundwater salinity) of the borehole. The redrilling can be done as example by using a corborit tungsten carbide bit as it cuts easier through aluminum and plastic of the packers, but is less prone for deviation (Rautio 2006, p. 24). It was conservatively thought that stabilization should be done to several sections of a borehole. In considering the materials that would be placed in these sections, there would be no definite need to stabilize them beforehand, as both stabilizing material and closure material would be concrete. Nevertheless, investigation and drilling equipment are constantly moved up and down in the boreholes and stability is occasionally a

65

problem. The washing will in most cases be enough to facilitate the closure without stabilization, but as stuck equipment is challenging to remove, especially considering there might also be swelling bentonite during the closure procedure, stabilization should be considered where there are outbreaks in the borehole walls. The concrete mix for the stabilization process is another than for the concrete plugs. The requirements are somewhat different. The stabilization concrete is cast to stop crumbling of a borehole wall into a borehole and to fill spaces that deviate from the wall line, as well as to minimize water flow from the fractures or into them. An additional concrete ingredient can be fiberglass used for reinforcement. Fiberglass concrete was used in stabilizing attempt of borehole OL-KR24. The result was unsuccessful partially due to leaching of the material into fractures and partially due to problems with delays and equipment (Rautio 2006, p. 19-33). The composition of the concrete used in stabilizing borehole OL-KR24 is the suggested mix for stabilization concrete (Table 7-2). Some changes to it can be expected to be made, or if a mix that functions better is developed, it can replace the one mentioned in this work. A careful selection and washing of the ballast is imperative. Table 7-2. Fiberglas concrete used for stabilizing attempt of OL-KR24 (Rautio 2006, p. 22).

Material Kg/m3

White cement 514.26

Microsilica grade 940/silica fume 342.84

Fine ground α-quartz M300 133.2

Fine ground α-quartz M500 107.5

Glenium 51 8 (dry content)

Fine quartz sand <250 µm 325.4

Coarse quartz sand <500 µm 488.1

Glass fiber, 6 mm 53.6

7.5 Replacing the water Concrete is not as sensitive to the salinity of the water as bentonite is. In fact, concrete hardens faster in saline water. Thus replacing the water should be done prior only to installing a borehole backfill section. The replacement of saline groundwater with fresh water can be implemented by using drilling equipment. The change will have to be made by pumping tap water to the bottom of the hole to dilute the saline groundwater, while the excess water is pushed out of the borehole. In theory, salinity should be measured from the bottom of the borehole before any clay material is inserted into selected section using the Basic Method. Replacing of the water may have to be repeated several times as the closure proceeds. If future field tests reveal that the replacing of the water is not efficient, the installation of especially the Basic Method borehole backfills need to be exact, fast and with no

66

delays, as there is a risk that the clay will swell too rapidly and equipment may get stuck during the installation or that dispersion of clay is too excessive. There is no quick test to measure groundwater salinity from the boreholes in field conditions. A common laboratory technique is to evaporate the water and measure salt content, but in field circumstances this may not work. One method is to measure electric conductivity (EC) of the water, as it is a direct indicator of salt content once other affecting impurities are filtered off (Öhberg 2006, p. 11). Also the temperature of the water affects the EC value. In considering the EC, a label agent is added to the flushing water and this water is directed to flow to the bottom of the borehole via drill string. The EC of the water is measured after adding the label agent. The saline groundwater is slowly diluted as water is pushed upwards in the hole. Fractures may add saline water to the hole but flushing water may also be pushed into the fractures. It is optimistic to consider that the salinity would be completely removed, even momentarily, in the deepest holes, but it may be lowered for a short time. When the flushing is performed the EC of overflowing water can be monitored. The salinity changes during the flushing could perhaps be monitored from the changing EC of the out-flowing water. For checking salinity, a sample from the bottom of the borehole can be collected and EC value measured from it. The practical problem in performing this operation is that as moving the equipment up and down a hole takes time and if flushing is stopped momentarily, the prevailing flow of groundwater returns. As measuring is conducted the conditions in the bottom of the hole may change. During drilling of the boreholes EC has been monitored (after the label agent has been added) and subsequently from the overflowing water as the drilling proceeds (for example Rautio 2005f, p. 16). The monitored differences have been small. The label agent quantity in the water flowing from the hole could also possibly be used to determine the success of water replacement. When the label agent concentration in overflowing water is similar to the concentration in the inflowing water it may be justifiable to presume that the salinity is also similar in both (not saline). If it is not possible to measure this consistency in field circumstances, preliminary investigations should be made for each hole on how long it takes to flush it fresh. This can be performed for example by flushing a hole and collecting overflowing water samples at constant intervals, also from the bottom of the hole. This preliminary investigation should not take place until in the temporal proximity of the closure, because as the years pass the flow into a borehole may go through some alterations. 7.6 Closing the borehole In this report it is assumed that the Basic Method and the Container Method are used to install the borehole backfills into the selected investigation boreholes. The Basic Method will be applied to borehole lengths less than 500 m and after this, in deep parts of the hole the Container Method will be used. These are selected according to present knowledge of the materials, techniques concerning installation, and experiments performed on different methods. If better closure methods were discovered in future, they could surpass these selected techniques.

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The Basic Method tubes can be jointed together by pressing a connection piece around a connection, by screw mechanism or by a bayonet clutch. The length of the section is defined by the length demanded by the rock characteristics and also by the curvature and stability of the borehole. Jointed sections can be up to about 24 m long, but shorter sections and single tubes can also be used, as the weight of the tubes presses them firmly on top of each other after they are installed. The thickness of the tube wall should be 2-3 mm and the outer diameter of the tube about 6 mm less than the diameter of the hole. A transport instrument designed by LiwInStone AB can be used to lower the tubes into a borehole, to the bottom of the borehole, or on top of the previous tube or plug section (Rautio 2006, p. 38, Pusch & Ramqvist 2008, p. 8-19). Replacing the water is to be performed before installing the Basic Method borehole backfill sections. In using the Container Method the container will be filled with borehole backfill material. A bottom plate, which will extrude as enough pressure is applied from above, will be set to the bottom of the container. A piston will situate above the borehole backfill material, and an adapter will be placed between the piston and the drilling equipment to facilitate the applying of the pressure. The container is then lowered to the selected location: down to the bottom of the borehole, above a previously installed borehole backfill section or on top of a concrete plug. When the bottom is slightly above the desired lower border of the selected site the pressure is applied and the borehole backfill and the bottom plate are extruded of the container. The container is simultaneously lifted upwards. When the backfill has been pushed out, it will maturate and swell when affected by groundwater in the hole, and after some hours another section of borehole backfill or other material can be installed on top of it. The length of a Container Method borehole backfill that can be inserted at one time is regulated by the curvature of the borehole and technical reasons deriving from the force needed to extrude the borehole backfill material out off the tube. The sections should be approximately 2-5 m long (Pusch & Ramqvist 2008, p. 19-25). The curvature of a hole is the main attribute on as how long sections the borehole backfill can be installed. The narrowness of the boreholes leaves very little room for a curvature of the hole. The edges of the borehole backfill, either a Basic Method tube or a Container Method container, as it is moved down, might hit the walls and this could jam the instrument or harm the borehole backfill. The length of borehole backfill sections that can be lowered simultaneously should be planned in detail before the implementation of the closure (Pusch et al. 2012). The concrete can be manufactured on site prior to installation, because the required volumes are very small (see Table 5-2). Samples of the concrete monitored during casting indicate the desired properties and hardening. For each monitoring interval, one sample should be stored in dry conditions but the other should be kept in conditions similar to the length of the borehole (temperature, water, salinity of the water). The concrete can be placed, for example, by inserting a bottom packer to the bottom of the borehole or, as closure proceeds, over a borehole backfill section. The bottom packer will open as the pressure arises to a desired level and concrete is pushed out. The drill rods would have to be filled with concrete prior to inserting them to ensure that a desired volume of concrete is installed. Another way to install the concrete is the inner

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tube method which was described with selective stabilization (Chapter 7.3). The emplacement of borehole plug material is an ordinary procedure but it needs to be tested and demonstrated before actual operations. A special care should be taken in ensuring that air pockets do not form in the concrete and that sorting of the material is as minimal as possible. When the chosen upper level has been reached and the concrete has hardened, it will be tested with drilling equipment to assure the correct location and to ensure that it is hard enough to hold the weight of the upper closure materials that will be placed on top of it. Suggested low-pH concrete takes about one to three days to harden enough to support borehole backfills. Strength development of low-pH concrete from Table 5-3 is presented in Figure 7-2 (modified from Vogt et al. 2009, p. 17). According to Pusch et al. (2012) the strength of 1 MPa is enough to support the section to be placed on the concrete. It takes one day for the alternative concrete presented in Table 5-4 to achieve this desired strength (Pusch et al. 2012).

Figure 7-2. Strength development of low-pH silica concrete, mix presented in Table 5-3. (Modified from Vogt et al. 2009, p. 17.) 7.7 Installing the surface plug The dimensions of the casings constructed in the upper sections of the boreholes vary. If the outer casing has an outer diameter of 140 mm and it reaches the depth of at least 25-30 m, it will not be removed, but the surface plug will be placed to the bottom of the casing. If the casing is narrower and/or does not reach desired depths, it can be removed by overcoring it with selected drilling equipment. The new wider section should reach to at least the depth of 25-30 m. The surface plug will be placed to the bottom of this new section.

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7.8 Filling the upper section The upper section above the surface plug will be filled with either concrete or rock material. It is here presumed that the section will be filled with concrete, because it will sort less than aggregate material during the installation. Sorting might generate flow paths and this should be restricted. Standard concrete may be used, as there are no requirements for this shallow depth, as long as the material is durable even after the cement is leached off via fractures (i.e., the grain frame is of a varying grain distribution). Concrete can be pumped from a truck or installed by other methods. Uppermost volumes of this section will erode during the next glacial cycles. 7.9 Estimation for a time schedule (OL-KR4) An estimation for a time it takes to close a borehole is here considered by examining borehole OL-KR4. This borehole was selected as it is in the proximity of ONKALO and intersects the most important hydrogeological zone. Table 7-3 shows at what borehole length downwards from the ground surface HZ19, HZ20 and HZ21 intersect the borehole. The zones are also presented in Figure 7-3. Preparatory phases (characterization, cleaning, removing possible stuck objects and stabilization) are not taken into consideration, only the time it takes to install the materials. Here it is assumed that the insertion down to 1,000 m takes three hours and thus the installation speed for borehole backfill (not depending on the method) is assumed to be constantly 330 m/h. In reality the installation may occur faster, but in some instances it can also take longer. The mentioned speed is selected as an example because it is the highest recommended speed for installing borehole backfill with the Basic Method when regarding erosion of the material (see Chapter 5.2.2). It is assumed that it takes approximately 1 hour to lift the equipment before another sections installation and one day for the concrete to set. Further assumption is that installation of a surface plug takes 4 hours. For concrete, the time for casting a section of 2 m is estimated to take four hours and after this additional 20 minutes are added for a meter of concrete fill (e.g., 6 meters would take 5 hours 20 minutes). Pusch & Ramqvist (2012) were concerned on the effect of curvature on the length of borehole backfill, in as long jointed sections could be lowered without impact to walls. Even though it was previously described that the Basic Method tubes could be jointed to a maximum length of 24 m it is in these calculations assumed that a maximum length of 15 m is used. Maximum length for the Container Method was previously set as 5 m, but because the sections in this work are created in manner that the Container Method sections are multiples of 2 m, the maximum length is here considered to be 4 m at a time. The curvature itself is not considered here. The intersections with HZ19, HZ20 and HZ21 were checked to have concrete plug sections in the design.

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Table 7-3. OL-KR4 intersection locations as borehole lengths with hydraulically conductive zones HZ19, HZ20 and HZ21.

HZ Borehole length (m)

from to

19a 81 82

19b 141 143

19c 115 118

20a 307 317

20b 365 368

21a 757 764

21b 862 865

Figure 7-3. OL-KR4 intersections with HZ19, HZ20 and HZ21. Not in scale. If the work is done without delays and in shifts, the total installation time is approximately 38 days with the assumptions made here (Table 7-4). The most time consuming effort is waiting for the concrete to set. Setting of concrete always takes at least 24 hours, which is here assumed to be a resting period for installation crew and a possibility to prepare the ongoing work. On the other hand, the time of the day is not considered here and it is not likely that if the concrete is ready in the middle of the night, the crew would then in that hour continue the work. In addition to such breaks in work dummy probing and replacing of water will need time too. In reality, the time may well double to be e.g., 75-80 days, which is approximately 2.5 months. The quantities of different material sections are presented in Table 7-5. If it turns out that while the concrete sets there are long periods without work, two or more holes could be closed at the same time. This would demand individual equipment for each borehole, but would save working hours.

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Table 7-4. The estimated time for installation of closure materials to OL-KR4. The preparative phases are not considered (characterization, cleaning, replacing the water, dummy probing and stabilization). The time it takes to install concrete plugs is additionally presented divided to actual installation time and time it takes for the concrete to set (theoretically).

Closure material Time (h)

Material above surface plug 16

Surface plug 4

Concrete plugs 571

Borehole backfill (Container) 266

Borehole backfill (Basic) 52

Total time (h) 909

Total time (d) 38

Concrete Time (h)

concrete installation 131

concrete setting 440

Table 7-5. Quantities of different length borehole backfill sections for OL-KR4.

Lengths Quantity

Basic Method

2.5 m 3

5 m 2

7.5 m 1

10 m 4

12.5 m 1

15 m 19

Container Method

2 m 3

4 m 85

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8 INITIAL STATE OF THE BOREHOLE BACKFILL In the initial state a borehole will contain concrete, borehole backfill, and rock material (the ballast in concrete and the surface plug). The initial state of the borehole backfill refers to the state of the material immediately after installation. Here also some further attributes are presented. Table 8-1 presents different phases of the borehole backfill material using MX-80 bentonite with a compressed bulk density of 2,050 kg/m3 and a water content of 6% (Pusch & Ramqvist 2006a, p. 30), calculated for 1 m sections. The material may also be other than MX-80, and this will be further discussed in Chapter 9. Table 8-1 presents the volume of water that surrounds the borehole backfill in the borehole, in the gap between the borehole backfill and rock wall. It gives the initial dry density of the material (in theoretical borehole volumes), the initial water saturation degree, the water saturation degree after the surrounding water has been adsorbed and corresponding bulk density, and the bulk density at 100% saturation degree. These are given for both the Basic Method and the Container Method for all borehole sizes. Calculations are made assuming that the thickness of a Basic Method tube is 2 mm and the gap between the tube and the rock wall is 3 mm wide. With the Container Method it is assumed that the container wall is 2 mm and the gap between the container and the rock wall is 3 mm, and thus a 5 mm void gap between the extruded borehole backfill and the rock wall. The Basic Method tube and the Container Method container are both dimensioned according to 76 mm diameter for boreholes with diameters 75.7 mm and 76 mm, because the difference between these two is only 0.3 mm. This reduces the gap in 75.7 mm diameter holes to 2.85 mm. Erosion or caliber deviations are not taken into account in the calculations. The MX-80 grain density in the calculations is 2,775 kg/m3 (Kumpulainen & Kiviranta 2011, p. 29). The results for a 9% erosion rate for the Basic Method are presented in Table 8-2.

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Table 8-1. The state of the borehole backfill immediately after installation, after the surrounding water is adsorbed and at 100% saturation. MX-80 grain density is 2,775 kg/m3 (Kumpulainen & Kiviranta 2011, p. 29).

Basic Method (1 m section of borehole backfill)

Hole diameter

(mm)

Initial dry density (kg/m3)

Water mass (initially surrounding installed

backfill) (kg)

Bulk density when surrounding water has been absorbed (kg/m3)

Density at full saturation

(kg/m3)

56 mm 1,473 0.65 1,837 1,942

75.7 mm 1,621 0.90 1,921 2,037

76 mm 1,622 0.90 1,922 2,038

Container Method (1 m section of borehole backfill)

Hole diameter

(mm)



backfill) (kg)



(kg/m3)

56 mm 1,383 0.80 1,786 1,885

75.7 mm 1,544 1.11 1,877 1,988

76 mm 1,546 1.12 1,879 1,989

Table 8-2. The state of the Basic Method borehole backfill immediately after installation, after the surrounding water is absorbed and at 100% saturation, when assumed that 9% of the original material has eroded during installation. MX-80 grain density is 2,775 kg/m3 (Kumpulainen & Kiviranta 2011, p. 29).

Basic Method (1 m section of borehole backfill, 9% erosion )

Hole diameter

(mm)



backfill) (kg)



(kg/m3)

56 mm 1,341 0.80 1,762 1,858

75.7 mm 1,475 1.20 1,838 1,943

76 mm 1,476 1.21 1,839 1,944

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9 CONFORMITY TO REQUIREMENTS 9.1 Requirements and specifications Requirements concerning borehole closure were presented in Chapter 4. Specifications for achieving the requirements were made for the borehole backfill material in Chapter 5.1. Degree of conformity is here presented by comparing variables (hydraulic conductivity according to dry density, EMDD) of possible materials to the requirements. 9.2 Hydraulic conductivity and EMDD The borehole backfill parameters that were specified to fulfill the requirements (hydraulic conductivity, specified by EMDD) depend on the dry density and the swelling clay proportion. According to Pusch et al. (2011), the hydraulic conductivities are primarily affected by the initial density of the selected material. Table 9-1 provides the dry densities for different diameter boreholes when the Basic Method tube is 2 mm thick and the tube is 6 mm narrower than the hole, and when the Container Method container is 2 mm thick and 6 mm narrower than the hole. The original dry density of borehole backfill material is 1,800 kg/m3. The tube remains in the hole in the Basic Method. Because of material of choice (copper) it is extremely slow to degenerate. In calculating the initial densities the volume of the copper tube can be subtracted from the volume of the borehole. Should copper corrode, the end materials are here assumed to stay embedded in the clay and the borehole volume remains the same as with the copper tube. The backfill calculations are made for 1 m sections of boreholes and possible bottom plate volumes are not included in the calculations. The perforation ratio of a Basic Method tube is 50%. Because it is possible to compress bentonite clay to high densities (Pusch & Ramqvist 2006a), the initial dry densities for borehole backfill with both methods and dimensions for installation devices given above are also calculated for material with original dry density of 2,000 kg/m3 (Table 9-2). The calculated initial dry densities (Tables 9-1 and 9-2) can be compared to material tests and calculations made for swelling clays. For example Karnland et al. (2006, p. 39 and 45) published data for MX-80 bentonite and the resulted hydraulic conductivities are according to the specifications made to achieve the requirements. The results from Karnland et al. (2006, p. 39 and 45) that are necessary for evaluating the conformity to the requirements are presented in Table 9-3, with also swelling pressures. Table 9-1. Initial dry densities with the Basic Method and the Container Methods for 1 m section of a borehole. Original dry densities according to Pusch & Ramqvist (2006a, p. 30).

Hole diameter

(mm)

Tube/ container

diameter (mm)

Backfill diameter

(mm)

Dry density (kg/m3)

Initial dry density (kg/m3) in 1 m of borehole

Basic backfill Container backfill

56 mm 50 46 1,800 1,294 1,215 75.7 mm 69.7 65.7 1,800 1,423 1,356 76 mm 70 66 1,800 1,425 1,357

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Table 9-2. Calculated initial dry density (kg/m3) after installation with the Basic Method and the Container Method for 1 m sections of a borehole if the original dry density is 2,000 kg/m3.

Hole diameter

(mm)

Tube/ container

diameter (mm)

Backfill diameter

(mm)

Dry density (kg/m3)

Initial dry density (kg/m3) in 1 m of borehole

Basic backfill Container backfill

56 mm 50 46 2,000 1,438 1,349 75.7 mm 69.7 65.7 2,000 1,582 1,506 76 mm 70 66 2,000 1,583 1,508

Table 9-3. Examples of swelling pressures (Ps) and hydraulic conductivities (K) for MX-80 bentonite with different dry densities and water salinities (modified from Karnland et al. 2006, p. 39 and 45).

Water Dry density (kg/m3) Pressure (kPa) K (m/s)

H2O 517 61 5,00E-12

0.1 M 517 35 6,00E-12

H2O 761 156 2,00E-12

0.1 M 761 123 1,00E-12

0.3 M 761 68 3,00E-13

1 M 761 37 3,00E-12

H2O 1,202 1,02 3,00E-13

0.1 M 1,202 1 2,00E-13

0.3 M 1,202 800 3,00E-13

1 M 1,202 550 6,00E-13

H2O 1,461 4,19 5,00E-14

0.1 M 1,461 4,24 5,00E-14

0.3 M 1,461 4 6,00E-14

1 M 1,461 3,15 5,00E-14

3 M 1,461 1,24 1,00E-13

H2O 1,539 7,59 4,00E-14

0.1 M 1,539 7,59 3,00E-14

0.3 M 1,539 7,38 2,00E-14

1 M 1,539 6,34 2,00E-14

3 M 1,539 4,55 4,00E-14

H2O 1,641 12,47 2,00E-14

0.1 M 1,641 12,35 2,00E-14

0.3 M 1,641 12,17 2,00E-14

1 M 1,641 11,52 2,00E-14

3 M 1,641 10,22 2,00E-14

The EMDD for final dry densities of 1 m sections were calculated using 0.187 fraction of non-swelling minerals and grain density of 2,775 kg/m3 (Kumpulainen & Kiviranta 2011, p. 32 and 29, respectively). The EMDD values range between 1.075 Mg/m3 and

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1.281 Mg/m3, which are well above the specified level of 0.5 Mg/m3 (Table 9-4). These values provide lower than desired hydraulic conductivities (Figure 5-3) even with groundwater having 10-35% total dissolved solids (TDS). When the material is as dense as described in initial state (Tables 8-1 and 8-2) both EMDD and dry density are higher. Based on the comparison between calculated initial dry densities (Tables 9-1 and 9-2) and hydraulic conductivities (Table 9-3), in addition to the EMDD values (Table 9-4), the set requirements are achievable with the available materials and methods. The material used in almost all of the borehole experiments has been bentonite MX-80 from Wyoming, but it can as well be another smectite-rich swelling clay, or a mixture containing swelling clay and ballast that has been approved for the use. It might be beneficial to use a mixture, because if the clay fraction would be diluted off the borehole backfill for some reason, the grain frame would remain. If one considers the demands for the borehole backfill material, which are solely based on hydraulic conductivity and EMDD, it can be seen that several other materials besides MX-80 meet them as well, even though they have not been experimented on as borehole backfills. The reason why all borehole experiments and investigations have been done using MX-80 is not clear. Table 9-5 presents some materials that have higher than required hydraulic conductivities and EMDD values and could be considered for closure of boreholes. Table 9-4. Calculated EMDD values for 1 m initial dry density materials from Table 9-1. Material in calculations is MX-80 bentonite clay from Wyoming.

MX-80 bentonite installed with the Container Concept

Diameter / length 56 mm / 1 m 75.7 mm / 1 m 76 mm / 1 m

Initial dry density (kg/m3) 1,215 1,356 1,357

EMDD (Mg/m3) 1.075 1.213 1.215

MX-80 bentonite installed with the Basic Concept

Diameter / length 56 mm / 1 m 75.7 mm / 1 m 76 mm / 1 m

Initial dry density (kg/m3) 1,294 1,423 1,425

EMDD (Mg/m3) 1.152 1.280 1.281

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Table 9-5. Swelling pressures (PS), hydraulic conductivities (K) and effective montmorillonite dry density (EMDD) values of samples of four different swelling clays (MX-80, Deponit CaN, Asha and Friedland clay). The dry densities were determined from water ratios (w) of samples measured after finishing the swelling pressure and hydraulic conductivity measurements (modified from Kumpulainen & Kiviranta 2011, p. 32).

Sample PS (MPa) Dry density

(kg/m3) w (%)

K at 20 °C (m/s)

Volume fraction of non-swelling

minerals

EMDD (Mg/m3)

MX-80 ref.1 7.17 1,547 28.61 7.08E-14 0.187 1.404

MX-80 ref.2 5.66 1,533 29.21 - 0.187 1.390

MX-80 ref.2 11.30 1,631 25.28 - 0.187 1.490

Dep-CaN ref.1 5.54 1,448 32.86 1.17E-13 0.279 1.223

Dep-CaN ref.2 7.75 1,505 30.26 9.60E-14 0.279 1.279

Dep-CaN ref.3 7.08 1,489 31.00 - 0.279 1.263

Asha ref.1 6.50 1,612 - 1.35E-13 0.329 1.324

Asha ref.2 6.08 1,525 31.elo - 0.329 1.238

Asha ref.3 6.42 1,531 30.82 - 0.329 1.243

Friedland ref.1 2.66 1,821 19.10 8.74E-13 0.682 1.043

Friedland ref.2 3.17 1,837 18.63 8.15E-13 0.682 1.059

Friedland ref.3 1.00 1,718 22.39 - 0.682 0.941

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10 DISCUSSION AND CONCLUDING REMARKS The aim of this work was to create a closure design for deep investigation boreholes in Olkiluoto. Previous experiments and investigations were compiled and designs were created accordingly. Requirements were identified and specifications as how to comply with them were acquired. Individual closure designs were done using Gemcom Surpac™ 3D modelling program and Microsoft Access™ as a supporting program. The data were derived from Olkiluoto investigation results and parameters were selected after careful consideration of how they respond to the required information. Hydraulic conductivity of the bedrock and the number of natural fractures and fractured zones were used in sectioning the boreholes for different closure materials. For closure materials, hydraulic conductivity and EMDD were considered to respond to the requirements. The closure designs suggest that low-pH concrete plugs should be placed where the bedrock is marked as a fractured zone (RiIII-RiV), fractured (with ≥10 fractures per meter) or water conducting (hydraulic conductivity ≥1E-8 m/s). For other sections the material should be borehole backfill material, either swelling clay or a mixture of swelling clay and rock material. The backfill material should be installed with the Basic Method down to approximately 500 m and below this with the Container Method. A surface plug should be installed to a borehole length between 30 m and 41 m (the exact depth depends on the borehole) and above the surface plug only material that can be allowed to erode in the far future will be placed (rock or concrete). A closure design for 51 investigation boreholes has been introduced in this work. The designs conform to the requirements in that it supports restoration of the original flow routes in the bedrock and isolates well-conducting zones from each other. Material suggestions are in correlation with the materials allowed and recommended to be used in the closure of the facility. In the current design the division between borehole backfill and borehole plug varies often causing in some parts of the hole very short backfill sections. It might be more feasible to combine the longer sections of concrete material as a long unit. It would not have a significant change to the hydraulic properties of the surrounding rock. It can also be considered that as the rock near ground level is more fractured and conductive, the first borehole backfill section could be for example below approximately 80-100 m. A discussion could also be raised on the necessity to fill sections far below the disposal depth with borehole backfill, or would it be sufficient to use other material, e.g. concrete if the performance requirements still are fulfilled. A discussion can be raised on a topic that is it necessary to use borehole backfill material in the entire sections of sparsely fractured rock. As the borehole backfill produces low conductivity sections as short units, is it necessary to use such quantities? The sectioning used in this report is based on the original agenda: to restore the original flow paths and hydraulic conductivities of the bedrock of Olkiluoto. This is done with the designs presented here and with materials meeting the requirements by conforming

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to the achieved specifications. The material quantities are low and the main cost for the operation comes from man hours. In all, it is clear that even though this report holds suggestions for general closure designs for 51 investigation boreholes, more detailed individual designs are needed as the closure of each borehole is at hand. Even though the design as a whole appears to function, as has been indicated by laboratory investigations and the field tests (both in Stripa mine and in Olkiluoto), the function and performance have not been comprehensively verified. The following steps should be considered: 1. The Container Method needs developing. The container itself should be obtained

and installation should be tested in laboratory conditions and, after this, in field circumstances.

2. More erosion tests on the Basic Method would be beneficial to ensure the remaining of the material as the tube is installed.

3. Retrieving the closure materials from OL-KR24 could give valuable information about the performance of the materials and techniques.

4. Replacing of the borehole water should be verified to be possible for the duration of the borehole backfill installation (the Basic Method).

5. The curvatures of each individual hole must be observed to define as how long sections the borehole backfill can be installed.

6. A surface plug should be manufactured and it should be considered what instrument can be used in lowering it down, or should a new one be designed.

7. The swelling pressure of the borehole backfill should be considered to verify there is no danger it could extrude material off the borehole.

8. Installing methods of the borehole backfill should be further investigated. Retrieval of the borehole backfill from borehole OL-KR24 should be done in the near future, as the work is done from ONKALO shaft connection, which can be used for such a drilling operation only until constructions there begin. As it comes to the other mentioned steps it would be best to first consider coating the borehole backfill. According to results acquired from these two operations the methods and materials can be developed further.

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11 SUMMARY This report offers information on the borehole closure materials and techniques, and a design for closure of 51 boreholes in Olkiluoto. The suggestion presents that the boreholes are to be closed using concrete plugs to sections that are fractured and borehole backfill to sections of intact rock. The borehole backfill should be installed with the Basic Method down to 500 m and below this using the Container Method. In the Basic Method the borehole backfill is in a perforated copper tube and in the Container Method the material is transported in place in a container and then pushed out. A surface plug would be placed in the bottom of the upper casings in the boreholes and it is suggested to be a rock plug. If the bottom of the casing is at too high a level considering the estimated erosion level, the borehole can be reamed or over cored larger and deeper to facilitate the plugging. The borehole section above the surface plug can be filled with either concrete or a rock material that is yet to be defined. Future investigations on the topic of borehole closure should be made to verify the function of the suggested surface plug design, to confirm the function of borehole backfill with ensued laboratory investigations and installation methods, to further develop the techniques to install the borehole backfill, and to field test the production of the closure.

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REFERENCES Safety case portfolio main reports: Design Basis Safety case for the disposal of spent nuclear fuel at Olkiluoto 2012 - Design Basis. Eurajoki, Finland: Posiva Oy. POSIVA 2012-03. ISBN 978-951-652-184-1. Other references: Aaltonen, I. (ed.), Lahti, M., Engström, J., Mattila, J., Paananen, M., Paulamäki, S., Gehör, S., Kärki, A., Ahokas, T., Torvela, T. & Front, K. 2010. Geological model of the Olkiluoto site, version 2.0. Eurajoki, Finland: Posiva Oy. Working Report 2010-70. 580 p. Äikäs, T. 1986. The geology and hydrological conditions on the Ulkopää investigation site in Olkiluoto. Helsinki, Finland: Teollisuuden Voima Oy. TVO/VLJ Repository, Work Report 86-03. 57 p. Andersson, J., Ahokas, H., Hudson, J., Koskinen, L., Luukkonen, A., Löfman, J., Keto, V., Pitkänen, P., Mattila, J., Ikonen, A.T.K. & Ylä-Mella, M. 2007a. Olkiluoto Site Description 2006 – Part 1. Eurajoki, Finland: Posiva Oy. Report 2007-3. 229 p. Andersson, J., Ahokas, H., Hudson, J., Koskinen, L., Luukkonen, A., Löfman, J., Keto, V., Pitkänen, P., Mattila, J., Ikonen, A.T.K. & Ylä-Mella, M. 2007b. Olkiluoto Site Description 2006 – Part 2. Eurajoki, Finland: Posiva Oy. Report 2007-3. 313 p. Börgesson, L. & Sandén, T. 2004. Design of borehole plugs of Basic Type. In: Pusch, R. and Ramqvist, G. 2006a. Cleaning and sealing of borehole – Report on sub-project 1 on design and modeling of the performance of borehole plugs. Stockholm, Sweden: Swedish Nuclear Fuel and Waste Management Co. (SKB). Report IPR-06-28. 103 p. Dixon, D., Sandén, T., Jonsson, E. & Hansen, J. 2011. Backfilling of deposition tunnels: Use of bentonite pellets under repository conditions. Stockholm, Sweden: Swedish Nuclear Fuel and Waste Management Co. (SKB). Report P-11-44. 52 p. Follin, S. & Svensson, U. 2003. On the role of mesh discretisation and salinity for the occurrence of local flow cells – Results from a regional-scale groundwater flow model of Östra Götaland. Stockholm, Sweden: Swedish Nuclear Fuel and Waste Management Co. (SKB). Report R-03-23. 51 p. Gardemaister, R., Johansson, S., Korhonen, P., Patrikainen, P., Tuisku, T. & Vähäsarja, P. 1976. The application of Finnish engineering geological bedrock classification (in Finnish). Espoo, Finland: Technical Research Centre of Finland, Geotechnical laboratory. Research note 25. 38 p.

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Gehör, S., Karhu, J., Kärki, A., Löfman, J., Pitkänen, P., Ruotsalainen, P. & Taikina-aho, O. 2002. Fracture calcites at Olkiluoto: evidence from Quaternary infills for paleohydrogeology. Eurajoki, Finland: Posiva Oy. Posiva Report 2002-03. 118 p. Hjärtström, I. 2007. Installation of geofones in borehole OL-PR10 at Olkiluoto, Finland. Eurajoki, Finland: Posiva Oy. Working Report 2007-9. 16 p. Jokinen, J. 1994. Core drilling of the borehole OL-KR7 at Olkiluoto in Eurajoki, 1994 (in Finnish with an English abstract). Helsinki, Finland: Teollisuuden Voima Oy. Työraportti PATU-94-38. 26 p. Kärki, A. & Paulamäki, S. 2006. Petrology of Olkiluoto. Olkiluoto, Finland: Posiva Oy. Posiva Report 2006-02. 77 p. Karnland, O., Olsson, S. & Nilsson, U. 2006. Mineralogy and sealing properties of various bentonites and smectite-rich clay materials. Stockholm, Sweden: Swedish Nuclear Fuel and Waste Management Co. (SKB). Report TR-06-30. 112 p. Kasa, S. 2011. Results of monitoring at Olkiluoto – Foreign materials. Eurajoki, Finland: Posiva Oy. Working Report 2010-46. 35 p. Korhonen, K.-H., Gardemaister, R., Jääskeläinen, H., Niini, H. & Vähäsarja, P. 1974. Engineering geological bedrock classification (in Finnish). Espoo, Finland: Technical Research Centre of Finland, Geotechnical laboratory. Research note 12. 78 p. Korsman, K., Korja, T., Pajunen, M. & Virransalo, P. 1999. The GGT/SVEKA transect: structure and evolution of the continental crust in the Paleoproterozoic Svecofennian orogen in Finland. International Geology Review 41 (4). pp. 287-333. Kumpulainen, S. & Kiviranta, L. 2011. Mineralogical, chemical and physical study of potential buffer and backfill materials from ABM test package 1. Eurajoki, Finland: Posiva Oy. Working Report 2011-41. 50 p. Kuusirati, J. & Tarvainen, A.-M. 2009. Core drilling of drillholes OL-PP66-69 at Olkiluoto 2008. Eurajoki, Finland: Posiva Oy. Working Report 2009-13. 62 p. Lehikoinen, J. 2009. Bentonite-cement interaction – Preliminary results from model calculations. Eurajoki, Finland: Posiva Oy. Working Report 2009-37. 35 p. Lindberg, A. 1986. Petrographic and mineralogical study at the Ulkopää site (in Finnish with an English abstract). Helsinki, Finland: Teollisuuden Voima Oy. Work Report 9071/86/HHä. 26 p. Lindberg, A. 2009. Geochemical and mineralogical study of selected weathered samples from Olkiluoto site. Eurajoki, Finland: Posiva Oy. Working Report 2009-19. 52 p.

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McMurry, J., Dixon, D.A., Garroni, J.D., Ikeda, B.M., Stroes-Gascoyne, S., Baumgartner, P. & Melnyk, T.W. 2003. Evolution of a Canadian deep geologic repository. Atomic Energy of Canada Limited Report 06819-REP-01200-10092-R00. Niinimäki, R. 2000a. Core drilling of deep borehole OL-KR12 at Olkiluoto in Eurajoki 2000 (in Finnish with an English abstract). Helsinki, Finland: Posiva Oy. Working Report 2000-28. 192 p. Niinimäki, R. 2000b. Extension core drilling of deep borehole OL-KR7 at Olkiluoto in Eurajoki 2000 (in Finnish with an English abstract). Helsinki, Finland: Posiva Oy. Working Report 2000-31. 121 p. Niinimäki, R. 2001a. Core drilling of deep borehole OL-KR13 at Olkiluoto in Eurajoki 2001 (in Finnish with an English abstract). Helsinki, Finland: Posiva Oy. Working Report 2001-19. 179 p. Niinimäki, R. 2001b. Core drilling of deep borehole OL-KR14 at Olkiluoto in Eurajoki 2001 (in Finnish with an English abstract). Helsinki, Finland: Posiva Oy. Working Report 2001-24. 146 p. Niinimäki, R. 2002a. Core drilling of deep borehole OL-KR16 at Olkiluoto in Eurajoki 2001. Helsinki, Finland: Posiva Oy. Working Report 2002-09. 99 p. Niinimäki, R. 2002b. Core drilling of deep borehole OL-KR17 at Olkiluoto in Eurajoki 2001. Helsinki, Finland: Posiva Oy. Working Report 2002-12. 94 p. Niinimäki, R. 2002c. Core drilling of deep borehole OL-KR18 at Olkiluoto in Eurajoki 2001. Helsinki, Finland: Posiva Oy. Working Report 2002-13. 90 p. Niinimäki, R. 2002d. Extension core drilling of deep borehole OL-KR15 at Olkiluoto in Eurajoki 2002. Olkiluoto, Finland: Posiva Oy. Working Report 2002-35. 92 p. Niinimäki, R. 2002e. Core drilling of deep borehole OL-KR19 at Olkiluoto in Eurajoki 2002. Olkiluoto, Finland: Posiva Oy. Working Report 2002-49. 220 p. Niinimäki, R. 2002f. Extension core drilling of deep borehole OL-KR8 at Olkiluoto in Eurajoki 2002. Olkiluoto, Finland: Posiva Oy. Working Report 2002-53. 108 p. Niinimäki, R. 2002g. Core drilling of deep borehole OL-KR21 at Olkiluoto in Eurajoki. Olkiluoto, Finland: Posiva Oy. Working Report 2002-56. 131 p. Niinimäki, R. 2002h. Core drilling of deep borehole OL-KR22 at Olkiluoto in Eurajoki. Olkiluoto, Finland: Posiva Oy. Working Report 2002-59. 199 p. Niinimäki, R. 2002i. Core drilling of deep borehole OL-KR23 at Olkiluoto in Eurajoki. Olkiluoto, Finland: Posiva Oy. Working Report 2002-60. 137 p.

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Niinimäki, R. 2003a. Core drilling of deep borehole OL-KR25 at Olkiluoto in Eurajoki 2003. Olkiluoto, Finland: Posiva Oy. Working Report 2003-44. 197 p. Niinimäki, R. 2003b. Core drilling of deep borehole OL-KR24 at Olkiluoto in Eurajoki 2003. Olkiluoto, Finland: Posiva Oy. Working Report 2003-52. 137 p. Niinimäki, R. 2003c. Core drilling of deep borehole OL-KR27 at Olkiluoto in Eurajoki 2003. Olkiluoto, Finland: Posiva Oy. Working Report 2003-61. 209 p. Niinimäki, R. 2004a. Core drilling of pilot hole OL-PH1 at Olkiluoto in Eurajoki 2003-2004. Olkiluoto, Finland: Posiva Oy. Working Report 2004-05. 95 p. Niinimäki, R. 2004b. Extension core drilling of deep borehole OL-KR23 at Olkiluoto in Eurajoki 2004. Olkiluoto, Finland: Posiva Oy. Working Report 2004-41. 102 p. Niinimäki, R. 2005a. Core drilling of deep borehole OL-KR37 at Olkiluoto in Eurajoki 2005. Olkiluoto, Finland: Posiva Oy. Working Report 2005-62. 144 p. Niinimäki, R. 2005b. Core drilling of deep borehole OL-KR39 at Olkiluoto in Eurajoki 2005. Olkiluoto, Finland: Posiva Oy. Working Report 2005-68. 161 p. Niinimäki, R. 2006. Core drilling of deep borehole OL-KR43 at Olkiluoto in Eurajoki 2006. Olkiluoto, Finland: Posiva Oy. Working Report 2006-115. 250 p. Niinimäki, R. & Rautio, T. 2002. Core drilling of deep borehole OL-KR15 at Olkiluoto in Eurajoki 2001. Posiva Oy, Helsinki, Finland. Working Report 2002-01. 106 p. Niinimäki, R. & Rautio, T. 2004. Drilling of shallow core drilling holes, percussion drillings, video recordings of boreholes and installing ground water monitoring pipes at Olkiluoto in Eurajoki in winter and spring of 2004 (in Finnish with an English abstract). Olkiluoto, Finland: Posiva Oy. Working Report 2004-37. 59 p. Niinimäki, R. & Rautio, T. 2005. Core drilling of the deep borehiole OL-KR36 at Olkiluoto in Eurajoki 2005. Olkiluoto, Finland: Posiva Oy. Working Report 2005-38. 103 p. Öhberg, A. 2006. Investigation equipment and methods used by Posiva. Olkiluoto, Finland: Posiva Oy. Working Report 2006-81. 115 p. Palmén, J., Tammisto, E. & Ahokas, H. 2010. Database for hydraulically conductive fractures – Update 2009. Eurajoki, Finland: Posiva Oy. Working Report 2010-13. 64 p. Påsse, T. 2004. The amount of glacial erosion of the bedrock. Stockholm, Sweden: Swedish Nuclear Fuel and Waste Management Co. (SKB). TR-04-25. 39 p. Paulamäki, S. 1989. Geological bedrock and joint mapping of the Olkiluoto study site, Eurajoki, western Finland. Helsinki, Finland: Teollisuuden Voima Oy. TVO/Site investigations, Work Report 89-25. 63 p.

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Paulamäki, S. & Koistinen, T.J. 1991. Interpretation of the geological structures of the Olkiluoto area, Eurajoki, Western Finland (in Finnish with an English abstract). Helsinki: Teollisuuden Voima Oy. TVO/Site investigations, Work Report 91-62. 34 p. Pitkänen, P., Partamies, S. & Luukkonen, A. 2004. Hydrogeochemical interpretation of baseline groundwater conditions at the Olkiluoto site. Eurajoki, Finland: Posiva Oy. Working Report 2003-07. 159 p. Pitkänen, P. & Partamies, S. 2007. Origin and implications of dissolved gases in groundwater at Olkiluoto. Eurajoki, Finland: Posiva Oy. Posiva 2007-04. 57 p. Pohjolainen, E. 2007. Core Drilling of Deep Borehole OL-KR44 at Olkiluoto in Eurajoki 2007. Olkiluoto, Finland: Posiva Oy. Working Report 2007-84. 170 p. Pöllänen, J. 2009. Difference flow and electrical conductivity measurements at the Olkiluoto site in Eurajoki, drillholes OL-KR44, OL-KR44B, OL-KR45, OL-KR45B, OL-KR46, OL-KR47 and OL-KR48. Eurajoki, Finland: Posiva Oy. Working Report 2009-81. 238 p. Posiva 2009. Olkiluoto site description 2008 – Part 1 and 2. Eurajoki, Finland: Posiva Oy. Posiva Report 2009-01. 714 p. Posiva 2011. Final disposal of spent nuclear fuel in Olkiluoto. Brochure. Eurajoki, Finland: Eura Print Oy. 20 p. Pusch, R. 1981. Borehole sealing with highly compacted Na bentonite. Stockholm, Sweden: Swedish Nuclear Fuel and Waste Management Co. (SKB). TR 81-09. 53 p. Pusch, R. & Ramqvist, G. 2004. Borehole sealing, preparative steps, design and function of plugs – basic concept. Stockholm, Sweden: Swedish Nuclear Fuel and Waste Management Co. (SKB). Report IPR-04-57. 166 p. Pusch, R. & Ramqvist, G. 2006a. Cleaning and sealing of borehole – Report on sub-project 1 on design and modeling of the performance of borehole plugs. Stockholm, Sweden: Swedish Nuclear Fuel and Waste Management Co. (SKB). Report IPR-06-28. 103 p. Pusch, R. & Ramqvist, G. 2006b. Cleaning and sealing of borehole – Report on sub-project 2 on plugging of 5 m boreholes at Äspö. Stockholm, Sweden: Swedish Nuclear Fuel and Waste Management Co. (SKB). International Progress Report IPR-06-29. 76 p. Pusch, R. & Ramqvist, G. 2007. Cleaning and sealing of borehole – Report on sub-project 4 on sealing of 200 mm boreholes at Äspö. Stockholm, Sweden: Swedish Nuclear Fuel and Waste Management Co. (SKB). International Progress Report IPR-06-31. 74 p. Pusch, R. & Ramqvist, G. 2008. Borehole project – Final report of phase 3. Eurajoki, Finland: Posiva Oy. Working Report 2008-06. 73 p.

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Pusch, R., Ramqvist, G., Bockgård, N. & Ekman, L. 2012. Sealing of investigation boreholes, phase 4 – final report (publication pending). Stockholm, Sweden: Swedish Nuclear Fuel and Waste Management Co. (SKB). Pussinen, V. 2006. Clearing of the deep boreholes OL-KR4 and OL-KR14 at Olkiluoto inEurajoki (in Finnish). Olkiluoto, Finland: Posiva Oy. Työraportti 2006-46. 16 p. Pussinen, V. & Niinimäki, R. 2006a. Core drilling of deep borehole OL-KR40 at Olkiluoto in Eurajoki 2005-2006. Olkiluoto, Finland: Posiva Oy. Working Report 2006-49. 255 p. Pussinen, V. & Niinimäki, R. 2006b. Extension core drilling of deep borehole OL-KR31 at Olkiluoto in Eurajoki 2006. Olkiluoto, Finland: Posiva Oy. Working Report 2006-50. 85 p. Pussinen, V. & Niinimäki, R. 2006c. Core drilling of deep borehole OL-KR41 at Olkiluoto in Eurajoki 2006. Olkiluoto, Finland: Posiva Oy. Working Report 2006-84. 143 p. Pussinen, V. & Niinimäki, R. 2006d. Core drilling of deep borehole OL-KR42 at Olkiluoto in Eurajoki 2006. Olkiluoto, Finland: Posiva Oy. Working Report 2006-97. 173 p. Rautio, T. 1989a. Core drilling of deep borehole OL-KR1 at Olkiluoto in Eurajoki (in Finnish with an English abstract). Helsinki, Finland: Teollisuuden Voima Oy. TVO/paikkatutkimukset työraportti 89-38. 17 p. Rautio, T. 1989b. Core drilling of deep borehole OL-KR2 at Olkiluoto in Eurajoki (in Finnish with an English abstract). Helsinki, Finland: Teollisuuden Voima Oy. TVO/paikkatutkimukset työraportti 89-43. 16 p. Rautio, T. 1989c. Core drilling of deep borehole OL-KR3 at Olkiluoto in Eurajoki (in Finnish with an English abstract). Helsinki, Finland: Teollisuuden Voima Oy. TVO/paikkatutkimukset työraportti 89-45. 16 p. Rautio, T. 1990a. Core drilling of deep borehole OL-KR4 at Olkiluoto in Eurajoki (in Finnish with an English abstract). Helsinki, Finland: Teollisuuden Voima Oy. TVO/paikkatutkimukset työraportti 90-24. 17 p. Rautio, T. 1990b. Core drilling of deep borehole OL-KR5 at Olkiluoto in Eurajoki (in Finnish with an English abstract). Espoo, Finland: Teollisuuden Voima Oy. TVO/paikkatutkimukset työraportti 90-26. 17 p. Rautio, T. 1995a. Core drilling of the borehole OL-KR8 at Olkiluoto in Eurajoki (in Finnish with an English abstract). Helsinki, Finland: Teollisuuden Voima Oy. Työraportti PATU-95-22. 24 p.

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Rautio, T. 1995b. Extension drilling of deep borehole OL-KR4 at Olkiluoto in Eurajoki 1995 Eurajoki (in Finnish with an English abstract). Helsinki, Finland: Teollisuuden Voima Oy. Työraportti PATU-95-46. 20 p. Rautio, T. 1995c. Extension drilling of deep borehole OL-KR2 at Olkiluoto in Eurajoki 1995 (in Finnish with an English abstract). Helsinki, Finland: Teollisuuden Voima Oy. Työraportti PATU-95-62. 22 p. Rautio, T. 1996a. Core drilling of deep borehole OL-KR10 at Olkiluoto in Eurajoki (in Finnish with an English abstract). Helsinki, Finland: Posiva Oy. Työraportti PATU-96-02. 27 p. Rautio, T. 1996b. Core drilling of deep borehole OL-KR9 at Olkiluoto in Eurajoki (in Finnish with an English abstract). Helsinki, Finland: Posiva Oy. Työraportti PATU-96-32. 28 p. Rautio, T. 1999. Core drilling of deep borehole OL-KR11 at Olkiluoto in Eurajoki(in Finnish with an English abstract). Helsinki, Finland: Posiva Oy. Työraportti 99-50. 171 p. Rautio, T. 2000. Extension core drilling of deep borehole OL-KR6 at Olkiluoto in Eurajoki 2000 (in Finnish with an English abstract). Helsinki, Finland: Posiva Oy. Working Report 2000-33. 105 p. Rautio, T. 2002a. The cleaning of boreholes OL-KR10 and OL-KR7 at Olkiluoto in Eurajoki in 2000 (in Finnish with an English abstract). Olkiluoto, Finland: Posiva Oy. Working Report 2002-40. 11 p. Rautio, T. 2002b. Core drilling of deep borehole OL-KR20 at Olkiluoto in Eurajoki 2002. Olkiluoto, Finland: Posiva Oy. Working Report 2002-50. 178 p. Rautio, T. 2003a. Core drilling of deep borehole OL-KR26 at Olkiluoto in Eurajoki 2003. Olkiluoto, Finland: Posiva Oy. Working Report 2003-41. 89 p. Rautio, T. 2003b. Core drilling of deep borehole OL-KR28 at Olkiluoto in Eurajoki 2003. Olkiluoto, Finland: Posiva Oy. Working Report 2003-57. 186 p. Rautio, T. 2004a. Core drilling of deep borehole OL-KR29 at Olkiluoto in Eurajoki 2004. Olkiluoto, Finland: Posiva Oy. Working Report 2004-50. 221 p. Rautio, T. 2004b. Core drilling of deep borehole OL-KR30 at Olkiluoto in Eurajoki 2004. Olkiluoto, Finland: Posiva Oy. Working Report 2004-50. 83 p. Rautio, T. 2004c. Core drilling of deep borehole OL-KR31 at Olkiluoto in Eurajoki 2004. Olkiluoto, Finland: Posiva Oy. Working Report 2004-55. 111 p. Rautio, T. 2005a. Core drilling of deep borehole OL-KR32 at Olkiluoto in Eurajoki 2004. Olkiluoto, Finland: Posiva Oy. Working Report 2005-01. 106 p.

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Rautio, T. 2005b. Core drilling of deep borehole OL-KR33 at Olkiluoto in Eurajoki 2004. Olkiluoto, Finland: Posiva Oy. Working Report 2005-02. 131 p. Rautio, T. 2005c. The cleaning of borehole OL-KR4 at Olkiluoto in Eurajoki in 2004 (in Finnish with an English abstract). Olkiluoto, Finland: Posiva Oy. Working Report 2005-21. 9 p. Rautio, T. 2005d. Core drilling of deep borehole OL-KR34 at Olkiluoto in Eurajoki 2005. Olkiluoto, Finland: Posiva Oy. Working Report 2005-36. 88 p. Rautio, T. 2005e. Core drilling of deep borehole OL-KR35 at Olkiluoto in Eurajoki 2005. Olkiluoto, Finland: Posiva Oy. Working Report 2005-37. 86 p. Rautio, T. 2005f. Core drilling of deep borehole OL-KR38 at Olkiluoto in Eurajoki 2005. Olkiluoto, Finland: Posiva Oy. Working Report 2005-58. 143 p. Rautio, T. 2006. Borehole plugging experiment in OL-KR24 at Olkiluoto, Finland. Olkiluoto, Finland: Posiva Oy. Working Report 2006-35. 45 p. Rautio, T. 2007. Core drilling of short drillholes at Olkiluoto in Eurajoki 2006. Olkiluoto, Finland: Posiva Oy. Working Report 2007-40. 12 p. Rautio, T., Alaverronen, M., Lohva, K. & Teivaala, V. 2004. Cleaning of boreholes. Olkiluoto, Finland: Posiva Oy. Working Report 2004-39. 29 p. Sandén, T. & Börgesson, L. 2006. Manufacturing of bentonite plugs with very high density. In: Pusch, R. & Ramqvist, G. 2006a. Cleaning and sealing of borehole – Report on sub-project 1 on design and modeling of the performance of borehole plugs. Stockholm, Sweden: Swedish Nuclear Fuel and Waste Management Co. (SKB). International Progress Report IPR-06-28. 103 p. Tammisto, E. & Palmén, J. 2011. Database for hydraulically conductive fractures – Update 2010. Eurajoki, Finland: Posiva Oy. Working Report 2011-12. 54 p. Tammisto, E., Palmén, J. & Ahokas, H. 2009. Database for hydraulically conductive fractures. Eurajoki, Finland: Posiva Oy. Working Report 2009-30. 110 p. Toropainen, V. 2007a. Core drilling of deep borehole OL-KR46 at Olkiluoto in Eurajoki 2007. Eurajoki, Finland: Posiva Oy. Working Report 2007-74. 146 p. Toropainen, V. 2007b. Core drilling of deep drillhole OL-KR45 at Olkiluoto in Eurajoki 2007. Eurajoki, Finland: Posiva Oy. Working Report 2007-95. 175 p. Toropainen, V. 2008a. Core drilling of deep borehole OL-KR47 at Olkiluoto in Eurajoki 2007-2008. Eurajoki, Finland: Posiva Oy. Working Report 2008-13. 208 p. Toropainen, V. 2008b. Core drilling of deep borehole OL-KR48 at Olkiluoto in Eurajoki 2007. Eurajoki, Finland: Posiva Oy. Working Report 2008-13. 102 p.

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Toropainen, V. 2008c. Core drilling of deep borehole OL-KR49 at Olkiluoto in Eurajoki 2008. Eurajoki, Finland: Posiva Oy. Working Report 2008-80. 186 p. Toropainen, V. 2009a. Core drilling of deep borehole OL-KR50 at Olkiluoto in Eurajoki 2008. Eurajoki, Finland: Posiva Oy Finland. Working Report 2009-09. 194 p. Toropainen, V. 2009b. Core drilling of deep borehole OL-KR51 at Olkiluoto in Eurajoki 2009. Eurajoki, Finland: Posiva Oy. Working Report 2009-73. 134 p. Toropainen, V. 2009c. Core drilling of deep borehole OL-KR52 at Olkiluoto in Eurajoki 2009. Eurajoki, Finland: Posiva Oy. Working Report 2009-107. 132 p. Toropainen, V. 2009d. Core drilling of deep drillhole OL-KR53 at Olkiluoto in Eurajoki 2009. Eurajoki, Finland: Posiva Oy. Working Report 2009-111. 114 p. Toropainen, V. 2010a. Core drilling of deep drillhole OL-KR54 at Olkiluoto in Eurajoki. Eurajoki, Finland: Posiva Oy. Working Report 2010-82. 137 p. Toropainen, V. 2010b. Core drilling of deep drillhole OL-KR55 at Olkiluoto in Eurajoki. Eurajoki, Finland: Posiva Oy. Working Report 2010-82. 246 p. Väisäsvaara, J., Kristiansson, S., Pöllänen, J. & Sokolnicki, M. 2008. Monitoring measurements by the difference flow method during the year 2007, Drillholes OL-KR2, -KR7, -KR8, -KR14, -KR22, KR22B, -KR27 and -KR28. Eurajoki, Finland: Posiva Oy. Working Report 2008-40. 140 p. Vogt, C., Lagerblad, B., Wallin, K., Baldy, F. & Jonasson, J.-E. 2009. Low pH self compacting concrete for deposition tunnel plugs. Stockholm, Sweden: Swedish Nuclear Fuel and Waste Management Co. (SKB). R-09-07. 78 p.

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APPENDIX 1 Closure designs for investigation boreholes at Olkiluoto in Eurajoki, southwestern Finland. A closure design was made for boreholes OL-KR1 – OL-KR55. Of those originally planned, four were excluded: OL-KR24, OL-KR38 and OL-KR48. They are in locations where shafts have been excavated and thus they need not to be closed. OL-KR30 is less than 100 m long, and thus a closure for it was not designed. Only parameters presented in the figure are mentioned in the legends. Figures are not in scale, as the narrow diameters of the boreholes would make it demanding to view the figures. All figures are viewed from south to north.

94

500

450

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

1_a

≥ 10 per meter

< 10 per meter

Not determined

OL-KR10 - 500 m

≥ -8

< -8

Not determined

Max log K

Natural fractures

Fractured zones

RiIII

Sparsely fractured

Not determined

Closure materials


Concrete plug


Max log K Fractured zones Closure

materials

Natural fractures

Surface plug

95

1000

950

900

850

800

750

700

650

600

550

500

Not in scale

OL

-KR

1_b

OL-KR1

≥ 10 per meter

< 10 per meter

≥ -8

< -8

Max log K

Natural fractures

Closure materials

Concrete plug





500 - 1001.05 m

Fractured zones

RiIII

Sparsely fractured

96

500

450

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

2_a

≥ 10 per meter

< 10 per meter

Not determined

OL-KR20 - 500 m

≥ -8

< -8

Not determined

Max log K

Natural fractures

Fractured zones

Closure materialsCasing and/or upper material

Concrete plug


Fractured zones

Closure materials

Natural fractures

Max log K

Container Method borehole backfill

Surface plug

RiIII

Not determined

Sparsely fractured

97

1050

1000

950

900

850

800

750

700

650

600

550

500

Not in scale

OL

-KR

2_b

OL-KR2

≥ 10 per meter

< 10 per meter

≥ -8

< -8

Max log K

Natural fractures

500 - 1051.89 m

Fractured zones

RiIII

Closure materials

Concrete plug

Basic Methodborehole backfill

Container Method borehole backfil

Max log KNatural fractures

Fractured zonesClosure materials

Sparsely fractured

98

5 00

45 0

40 0

35 0

30 0

25 0

2 0 0

1 50

1 00

5 0

0

Not in scale

OL

-KR

3

OL-KR30 - 502 m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Fractured zones

Closure materials


Concrete plug

Basic Methodborehole backfill


Fractured zones

Closure materials

Surface plug

RiIII

Not determined

Sparsely fractured

99

500

450

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

4_a

OL-KR40 - 500 m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Fractured zones

Closure materials


Concrete plug


Max log K Natural fractures

Fractured zones

Closure materials

Surface plug

RiIII

Not determined

Sparsely fractured

100

900

850

800

750

700

650

600

550

500

450

Not in scale

OL

-KR

4_b

OL-KR4500 - 901.58 m

≥ 10 per meter

< 10 per meter

≥ -8

< -8

Max log K

Natural fractures

Fractured zones

RiIII

Sparsely fractured

Closure materials

Concrete plug





RiIV

101

550

500

450

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

5

OL-KR50 - 558.85 m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Fractured zones

Closure materials


Concrete plug


Max log K Natural fractures Fractured



Surface plug

RiIII

Sparsely fractured

Not determined

102

60 0

5 5 0

5 00

45 0

4 00

35 0

3 00

2 50

2 00

150

10 0

50

0

Not in scale

OL

-KR

6

OL-KR60 - 600.77 m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Fractured zones

Closure materials


Concrete plug


Max log K

Natural fractures

Fractured zones

Closure materials


Surface plug

RiIII

Sparsely fractured

Not determined

103

450

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

7_a

OL-KR70 - 450 m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Fractured zones

Not determined

Closure materials


Concrete plug


Max log K

Natural fractures

Fractured zones

Closure materials

RiIII

Sparsely fractured

RiIV

Surface plug

104

800

750

700

650

600

550

500

450

400

350

300

Not in scale

OL

-KR

7_b

OL-KR7450 - 811.05 m

≥ 10 per meter

< 10 per meter

≥ -8

< -8

Max log K

Natural fractures

Fractured zones

Closure materials

Concrete plug




Fractured zones

Closure materials

RiIII

Sparsely fractured

RiIV

105

600

550

500

450

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

8

OL-KR80 - 600.59 m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Fractured zones

Not determined

Closure materials


Concrete plug


Max log K

Natural fractures

Fractured zones

Closure materials

RiIII

Sparsely fractured

RiIV


Surface plug

106

600

550

500

450

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

9

OL-KR90 - 601.25 m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Fractured zones

Closure materials


Concrete plug



Fractured zones

Closure materials


Surface plug

RiIII

Sparsely fractured

Not determined

107

600

550

500

450

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

10

OL-KR100 - 614.40 m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Closure materials


Concrete plug



Fractured zones

Closure materials

Fractured zones

Not determined

RiIII

Sparsely fractured

RiIV


Surface plug

108

500

450

400

350

30 0

250

200

150

100

50

0

Not in scale

OL

-KR

11_a

OL-KR110 - 500 m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Closure materials


Concrete plug



Fractured zones Closure

materials

Fractured zones

Not determined

RiIII

Sparsely fractured

RiIV


Surface plug

109

1000

950

900

850

800

750

700

6 50

600

550

500

450

Not in scale

OL

-KR

11_b

OL-KR11500 - 1002.11 m

≥ 10 per meter

< 10 per meter

≥ -8

< -8

Max log K

Natural fractures

Closure materials

Concrete plug



Max log K

Natural fractures


materials

Fractured zones

RiIII

Sparsely fractured

RiIV

110

450

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

12_a

OL-KR120 - 400 m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Fractured zones

RiIII

Sparsely fractured

Not determined

Closure materials


Concrete plug


Max log K

Natural fractures

Fractured zones

Closure materials

Surface plug

111

750

700

650

600

550

500

450

400

Not in scale

OL

-KR

12_b

OL-KR12400 - 795.34 m

≥ 10 per meter

< 10 per meter

≥ -8

< -8

Max log K Natural fractures Closure materials

Concrete plug




Fractured zones

Closure materials

Fractured zones

RiIII

Sparsely fractured

RiIV

112

OL-KR130 - 500.21 m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Closure materials


Surface plug

Concrete plug


Max log K

Natural fractures

Fractured zones

Closure materials

Fractured zones

Not determined

RiIII

Sparsely fractured

RiIV500

450

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

13

113

500

450

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

14

OL-KR140 - 514.10 m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Closure materials


Concrete plug



Fractured zones

Closure materials

Fractured zones

Not determined

RiIII

Sparsely fractured

RiIV

RiV


Surface plug

114

500

450

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

15

OL-KR150 - 518.85 m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Closure materials


Concrete plug



Fractured zones

Closure materials

Fractured zones

Not determined

RiIII

Sparsely fractured

RiIV


Surface plug

115

150

1 00

50

0

Not in scale

OL

-KR

16

OL-KR160 - 170.20 m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K Natural fractures Fractured zones

Sparsely fractured

Not determined

Closure materials


Concrete plug



Fractured zones

Closure materials

Surface plug

116

1 50

100

50

0

Not in scale

OL

-KR

17

OL-KR170 - 157.13 m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined


RiIII

Sparsely fractured

Not determined

Closure materials


Concrete plug



Fractured zones

Closure materials

Surface plug

117

1 00

50

0

Not in scale

OL

-KR

18

OL-KR180 - 125.49 m

< 10 per meter

Not determined

≥ -8

< -8

Not determined


RiIII

Sparsely fractured

Not determined

Closure materials


Concrete plug



Fractured zones

Closure materials

Surface plug

118

5 00

45 0

4 00

35 0

3 00

25 0

2 00

15 0

10 0

5 0

0

Not in scale

OL

-KR

19

OL-KR190 - 544.34 m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Closure materials


Concrete plug




Fractured zones

Not determined

RiIII

Sparsely fractured

RiIV


Surface plug

119

450

400

350

300

25 0

200

150

100

5 0

0

Not in scale

OL

-KR

20

OL-KR200 - 494.72 m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Closure materials


Concrete plug


Fractured zones

Not determined

RiIII

Sparsely fractured

RiIV

Max log K

Natural fractures

Fractured zones

Closure materials

Surface plug

120

300

250

200

150

1 00

50

0

Not in scale

OL

-KR

21

OL-KR210 - 301.08 m

< 10 per meter

Not determined

≥ -8

< -8

Not determined


RiIII

Sparsely fractured

Not determined

Closure materials


Concrete plug


Surface plug

Max log K

Natural fractures

Fractured zones

Closure materials

121

5 00

45 0

40 0

35 0

300

250

2 00

15 0

100

5 0

0

Not in scale

OL

-KR

22

OL-KR220 - 500.47 m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Closure materials


Concrete plug


Fractured zones

Not determined

RiIII

Sparsely fractured

RiIV

Surface plug

Max log K

Natural fractures

Fractured zones

Closure materials

122

4 50

400

350

300

250

20 0

1 50

100

50

0

Not in scale

OL

-KR

23

OL-KR230 - 460.25 m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Closure materials


Concrete plug


Fractured zones

Not determined

RiIII

Sparsely fractured

RiIV

Surface plug

Max log K

Natural fractures

Fractured zones

Closure materials

123

OL-KR250 - 604.87 m

600

550

500

450

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

25

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Fractured zones

Not determined

RiIII

Sparsely fractured

RiIV

Max log K

Natural fractures

Fractured zones

Closure materials

Closure materials


Concrete plug



Surface plug

124

100

50

0

Not in scale

OL

-KR

26

Fractured zones

Closure materials

Max log K

Natural fractures

≥ 10 per meter

< 10 per meter

≥ -8

< -8

Max log K

Natural fractures

Closure materials


Concrete plug


Fractured zones

RiIII

Sparsely fractured

RiIV

Surface plug

OL-KR260 - 103 m

125

5 50

50 0

4 50

4 00

3 50

3 0 0

25 0

20 0

1 50

10 0

5 0

0

Not in scale

OL

-KR

27

Fractured zones

Closure materials

Max log K

Natural fractures

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

OL-KR270 - 550.84 m

Fractured zones

Not determined

RiIII

Sparsely fractured

RiIV

Closure materials


Concrete plug



Surface plug

126

650

600

550

5 0 0

4 50

4 00

3 50

30 0

2 50

2 00

15 0

10 0

50

0

Not in scale

OL

-KR

28

Fractured zones

Closure materials


≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Fractured zones

Not determined

RiIII

Sparsely fractured

RiIV

OL-KR280 - 656.33 m

Closure materials


Concrete plug



Surface plug

127

500

450

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

29_a

Fractured zones

Closure materials


≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Closure materials


Concrete plug


Fractured zones

Not determined

RiIII

Sparsely fractured

RiIV

Surface plug

OL-KR290 - 500 m

128

850

800

750

700

650

600

550

500

450

400

Not in scale

OL

-KR

29_b


materials


≥ 10 per meter

< 10 per meter

≥ -8

< -8

Max log K

Natural fractures

OL-KR29500 - 870.18 m

Fractured zones

RiIII

Sparsely fractured

RiIV

RiV

Closure materials

Concrete plug



129

3 00

250

20 0

15 0

100

50

0

Not in scale

OL

-KR

31

OL-KR310 - 340.15 m Max log K

Natural fractures

Fractured zones

Closure materials

≥ -8

< -8

Not determined

Max log K

≥ 10 per meter

< 10 per meter

Not determined

Natural fractures Fractured zonesNot determined

RiIII

Sparsely fractured

RiIV


Concrete plug


Surface plug

130

150

1 00

50

0

Not in scale

OL

-KR

32

OL-KR320 - 191.81 m



≥ 10 per meter

< 10 per meter

≥ -8

< -8


RiIII

Sparsely fractured

RiIV


Concrete plug


Surface plug

131

300

250

200

150

100

50

0

Not in scale

OL

-KR

33

OL-KR330 - 311.02 m

Max log K

Natural fractures

Fractured zones

Closure materials

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K Natural fractures Closure materialsFractured zones

RiIII

Sparsely fractured

RiIV

RiV

Not determined Casing and/or upper material

Concrete plug


Surface plug

132

100

50

0

Not in scale

OL

-KR

34

OL-KR340 - 100.07 m



≥ 10 per meter

< 10 per meter

≥ -8

< -8


RiIII

Sparsely fractured

RiIV


Concrete plug


Surface plug

133

OL-KR350 - 100.87 m



≥ 10 per meter

< 10 per meter

≥ -8

< -8


RiIII

Sparsely fractured

Closure materials

100

50

0

Not in scale

OL

-KR

35


Concrete plug


Surface plug

134

200

150

100

50

0

Not in scale

OL

-KR

36

OL-KR360 - 205.17 m

Max log K

Natural fractures

Fractured zones

Closure materials

≥ 10 per meter

< 10 per meter

≥ -8

< -8


RiIII

Sparsely fractured

RiIV


Concrete plug


Surface plug

135

300

250

200

150

100

50

0

Not in scale

OL

-KR

37

OL-KR370 - 350 m

Max log K

Natural fractures

Fractured zones

Closure materials

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined


Not determined

RiIII

Sparsely fractured

RiIV

Closure materials


Concrete plug


Surface plug

136

500

450

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

39

OL-KR390 - 502.97 m Max log K

Natural fractures

Fractured zones

Closure materials

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Fractured zones

Not determined

RiIII

Sparsely fractured

RiIV

Closure materials


Concrete plug


Surface plug

137

550

500

4 50

4 00

35 0

30 0

25 0

200

15 0

10 0

50

0

Not in scale

OL

-KR

40_a

OL-KR400 - 550 m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Fractured zones

RiIII

Sparsely fractured

Not determined

Closure materials


Concrete plug


Surface plug


Max log K

Natural fractures


materials

138

1 000

950

90 0

8 50

800

7 50

7 00

65 0

600

55 0

50 0

Not in scale

OL

-KR

40_b

OL-KR40550 - 1030.56 m

≥ 10 per meter

< 10 per meter

≥ -8

< -8

Max log K

Natural fractures

Closure materials

Concrete plug



Fractured zones

RiIII

Sparsely fractured

RiIV

Max log K

Natural fractures

Fractured zones

Closure materials

139

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

41

OL-KR410 - 401.42 m

Max log K

Natural fractures

Fractured zones

Closure materials

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Fractured zones

Not determined

RiIII

Sparsely fractured

RiIV

Closure materials


Concrete plug


Surface plug

140

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

42

OL-KR420 - 400.85 m

Max log K

Natural fractures

Fractured zones

Closure materials

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Fractured zones

Not determined

RiIII

Sparsely fractured

RiIV

Closure materials


Concrete plug


Surface plug

141

550

500

450

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

43_a

OL-KR430 - 500 m Max log K Natural

fracturesFractured zones

Closure materials

Fractured zones

Closure materials


Concrete plug


Surface plug


≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Not determined

RiIII

Sparsely fractured

RiIV

142

1000

950

900

850

800

750

700

650

600

550

500

450

Not in scale

OL

-KR

43_b

OL-KR43500 - 1000.26 m



Closure materials

Concrete plug



Fractured zones

RiIII

Sparsely fractured

RiIV

≥ 10 per meter

< 10 per meter

≥ -8

< -8

Max log K

Natural fractures

143

450

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

44_a

OL-KR440 - 300 m

Max log K

Natural fractures

Fractured zones

Closure materials

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Fractured zones

RiIII

Sparsely fractured

Not determined

Closure materials


Concrete plug


Surface plug

144

800

750

700

650

600

550

500

450

400

350

300

Not in scale

OL

-KR

44_b

OL-KR44300 - 600 m

Max log K

Natural fractures

Fractured zones

Closure materials

Closure materials

Concrete plug



Fractured zones

RiIII

Sparsely fractured

RiIV

≥ 10 per meter

< 10 per meter

≥ -8

< -8

Max log K

Natural fractures

145

900

850

800

750

700

650

600

Not in scale

OL

-KR

44_c

OL-KR44600 - 900.47 m

Max log K

Natural fractures

Fractured zones

Closure materials

Closure materials

Concrete plug



Fractured zones

RiIII

Sparsely fractured

RiIV

≥ 10 per meter

< 10 per meter

≥ -8

< -8

Max log K

Natural fractures

146

550

500

450

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

45_a

OL-KR450 - 400m

Max log K

Natural fractures

Fractured zones

Closure materials

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Fractured zones

Closure materials


Concrete plug


Surface plug

Not determined

RiIII

Sparsely fractured

RiIV

147

9 00

850

800

750

700

650

600

550

500

450

400

Not in scale

OL

-KR

45_b

OL-KR45400 - 750 m

Max log K

Natural fractures

Fractured zonesClosure m

ateria ls

Closure materials

Concrete plug



Fractured zones

RiIII

Sparsely fractured

RiIV

≥ 10 per meter

< 10 per meter

< -8

Max log K

Natural fractures

148

1 000

95 0

9 00

850

800

750

700

OL-KR45_c

OL-

KR

45_c

OL-KR45700 - 1023.30 m

Max log K

Natural fractures

Fractured zones

Closure materials

Closure materials

Concrete plug



Fractured zones

RiIII

Sparsely fractured

≥ 10 per meter

< 10 per meter

< -8

Max log K

Natural fractures

149

600

550

500

450

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

46

OL-KR460 - 600.10 m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Fractured zones

Closure materials


Concrete plug


Surface plug


Not determined

RiIII

Sparsely fractured

RiIV


Fractured zones

Closure materials

150

550

500

450

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

47_a

OL-KR470 - 500m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Fractured zones

Closure materials


Concrete plug


Surface plug


Not determined

RiIII

Sparsely fractured

RiIV

Max log K

Natural fractures

Fractured zones

Closure materials

151

100 0

950

900

850

800

750

70 0

650

600

550

500

450

Not in scale

OL

-KR

47_b

OL-KR47500 - 1008.76m

Closure materials

Concrete plug



Fractured zones

RiIII

Sparsely fractured

RiIV

≥ 10 per meter

< 10 per meter

Natural fractures

Max log K

Natural fractures

Fractured zones

Closure materials

≥ -8

< -8

Max log K

152

600

550

500

450

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

49_a

OL-KR490 - 550m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Fractured zones

Closure materials


Concrete plug


Surface plug


Not determined

RiIII

Sparsely fractured

RiIV

Max log K

Natural fractures

Fractured zones

Closure materials

153

1050

1000

950

900

850

800

750

700

650

600

550

500

Not in scale

OL

-KR

49_b

OL-KR49550 - 1060.22 m

Closure materials

Concrete plug



Fractured zones

RiIII

Sparsely fractured

RiIV

≥ 10 per meter

< 10 per meter

≥ -8

< -8

Max log K

Natural fractures


Fractured zones

Closure materials

154

500

450

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

50_a

OL-KR500 - 450 m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Closure materials


Concrete plug


Surface plug

Fractured zones

RiIII

Sparsely fractured

RiIV

RiV

Not determined



155

900

850

800

750

700

650

600

550

500

450

Not in scale

OL

-KR

50_b

OL-KR50450 - 939.33 m

Closure materials

Concrete plug



Fractured zones

RiIII

Sparsely fractured

RiIV

≥ 10 per meter

< 10 per meter

≥ -8

< -8

Max log K

Natural fractures

Max log K

Natural fractures


materials

156

650

600

550

500

450

400

350

300

250

200

150

100

50

0

Not in scale

OL-

KR

51

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Closure materials


Concrete plug


Surface plug


Fractured zones

RiIII

Sparsely fractured

RiIV

RiV

Not determined

Max log K

Natural fractures

Fractured zones

Closure materialsOL-KR51

0 - 650.55 m

157

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

52

OL-KR520 - 427.35 m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Fractured zones

Closure materials


Concrete plug


Surface plug

Not determined

RiIII

Sparsely fractured

RiIV



158

300

250

200

150

100

50

0

Not in scale

OL

-KR

53

OL-KR530 - 300.48 m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K Natural fractures Fractured zones Closure materials


Concrete plug


Surface plug

Not determined

RiIII

Sparsely fractured

RiIV

Max log K

Natural fractures

Fractured zones

Closure materials

159

500

450

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

54

OL-KR540 - 500.18 m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Fractured zones

Closure materials


Concrete plug


Surface plug

Not determined

RiIII

Sparsely fractured

RiIV


zonesClosure materials

160

400

350

300

250

200

150

100

50

0

Not in scale

OL

-KR

55_a

OL-KR550 - 400 m

≥ 10 per meter

< 10 per meter

Not determined

≥ -8

< -8

Not determined

Max log K

Natural fractures

Fractured zones

Closure materials


Concrete plug


Surface plug


Not determined

RiIII

Sparsely fractured

RiIV

Max log K

Natural fractures

Fractured zones

Closure materials

161

600

550

500

450

400

350

300

250

200

150

Not in scale

OL

-KR

55_b

OL-KR55400 - 600 m

Closure materials

Concrete plug



Fractured zones

RiIII

Sparsely fractured

RiIV

≥ 10 per meter

< 10 per meter

≥ -8

< -8

Max log K

Natural fractures

Max

log

K

Nat

ural

frac

ture

sFr

actu

red

zone

sClo

sure

mat

eria

ls

162

950

900

850

800

750

700

650

600

550

500

450

Not in scale

OL

-KR

55_c

OL-KR55600 - 998.40 m

Closure materials

Concrete plug


Fractured zones

RiIII

Sparsely fractured

RiIV

≥ 10 per meter

< 10 per meter

< -8

Max log K

Natural fractures

Max log K

Natural fractures

Fractured zones

Closure materials

posiva oy · a 3d model of the closure of the boreholes was created with gemcom surpac 3d ......

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