KBS-3H - Design, Construction and Initial State of the Underground Openings POSIVA January Posiva Oy

Transcription

1 POSIVA KBS-3H - Design, Construction and Initial State of the Underground Openings Posiva Oy January 2018 POSIVA OY Olkiluoto FI EURAJOKI, FINLAND Phone (02) (nat.), ( ) (int.) Fax (02) (nat.), ( ) (int.)

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3 POSIVA KBS-3H - Design, Construction and Initial State of the Underground Openings Posiva Oy January 2018 This work has been carried out under KBS-3H System Design project co-funded by Posiva and SKB. POSIVA OY Olkiluoto FI EURAJOKI, FINLAND Phone (02) (nat.), ( ) (int.) Fax (02) (nat.), ( ) (int.)

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5 Posiva Oy Olkiluoto FI EURAJOKI, FINLAND Puh (31) - Int. Tel (31) Raportin tunnus - Report code POSIVA Julkaisuaika - Date Tammikuu 2018 Tekijä(t) Author(s) Posiva Oy Toimeksiantaja(t) Commissioned by Posiva Oy Nimeke Title KBS-3H -Design, Construction and Initial State of the Underground Openings Tiivistelmä Abstract Design basis and the methodology applied to design of the KBS-3H underground openings were presented, including their adaptation to site conditions, such that they conform to the present design basis. The underground openings as such do not contribute to the safety of the KBS-3H repository and do not have any barrier functions. However, the locations of the deposition drifts with respect to the geological, thermal, hydrogeological and mechanical properties of the rock are important for the safety of the repository. Design basis for the acceptable placement of deposition areas and deposition drifts as well as restrictions on engineered and residual materials will be provided from the assessment of the long-term safety. The underground openings shall also be designed to conform to design basis from the engineered barriers and plugs. KBS-3H is based on horizontal emplacement of canisters in long deposition drifts. The KBS-3H reference method is to drill a pilot hole that is reamed to full drift size. The reference method for excavating the deposition drifts are full-face horizontal push-reaming techniques. The site-specific basis for the reference design is geotechnical information compiled in site descriptive models (SDM) and site engineering reports (SER). The initial state of the underground openings refers to the properties of the underground openings at final installation of the buffer, supercontainer, closure and plugs. The presentation of the initial state comprises a summary of the site-adapted designs at Olkiluoto and Forsmark and the properties that can be expected based on the experiences from the reference methods. Avainsanat - Keywords Design premises, Design basis, Observational method, Site adaptation, Verification, Reference design, Reference methods, Initial state. ISBN ISSN ISBN ISSN Sivumäärä Number of pages Kieli Language 94 English

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7 Posiva Oy Olkiluoto FI EURAJOKI, FINLAND Puh (31) - Int. Tel (31) Raportin tunnus - Report code POSIVA Julkaisuaika - Date Tammikuu 2018 Tekijä(t) Author(s) Posiva Oy Toimeksiantaja(t) Commissioned by Posiva Oy Nimeke Title KBS-3H Maanalaisten tilojen suunnittelu, rakentaminen ja alkutila Tiivistelmä Abstract Raportissa esitetään KBS-3H suunnitteluperusteet sekä ne menettelytavat, joilla maanalaiset tilat suunnitellaan ja sovitetaan paikkakohtaisiin olosuhteisiin em. suunnitteluperusteet täyttäen. Maanalaiset tilojen ei sellaisenaan oleteta olevan yksi osa moniestejärjestelmää eikä näin muodoin myötävaikuttavan pitkäaikaisturvallisuuteen. Sen sijaan loppusijoitusreikiä ympäröivä kallio on yksi pitkäaikaisturvallisuuteen vaikuttavista päästöesteistä. Kallion toimintaan päästöesteenä vaikuttavat mm. sen geologiset, termiset, hydrologiset ja mekaaniset ominaisuudet. Suunnitteluperusteet loppusijoitusreikien ja -alueiden kallion ominaisuuksille sekä rajoitukset vierasaineille tullaan asettamaan pitkäaikaisturvallisuuden toimesta. Maanalaiset tilat tulee suunnitella täyttämään myös muilta päästöesteiltä (esim. tulpat) tulevat suunnitteluperusteet. KBS-3H konseptissa kapselit asennetaan peräkkäin pitkiin vaakareikiin. KBS-3H:n loppusijoitusreiän valmistuksen referenssimenetelmässä kairataan esipilottireikä, joka avarretaan lopulliseen halkaisijakokoonsa täysprofiiliporauksena. Paikkakohtaiset kalliosuunnittelun ja rakentamisen suunnitteluperusteet on koottu kallioperäolosuhteiden kuvaukseen (SER) ja loppusijoituspaikan malliin (SDM). Alkutila kuvaa loppusijoitustilojen ominaisuudet kapselipakkausten ja puskuribentoniittien asennuksen, tilojen täytön ja tulppaamisen yhteydessä. Alkutilan kuvaus muodostuu Forsmarkin ja Olkiluodon paikkakohtaisista suunnitelmista sekä näiden paikkojen odotettavissa olevista olosuhteista referenssimenetelmiin perustuen. Avainsanat - Keywords Suunnitteluvaatimukset, Suunnitteluperusteet, Asemointi, Todentaminen, Referenssisuunnitelma, Referenssiratkaisu, Alkutila ISBN ISSN ISBN ISSN Sivumäärä Number of pages Kieli Language 94 Englanti

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9 1 TABLE OF CONTEST ABSTRACT TIIVISTELMÄ PREFACE INTRODUCTION General basis This report The design of the underground openings The construction of the underground openings Purpose and delimitations Purpose Limitations Interfaces to other KBS-3H reports and aspects The report for the long-term safety analysis The design basis reports Operational safety The other 3H production reports Site descriptive reports Site descriptive model and underground design reports Structure and content Design basis Rock engineering Reference design and its conformity to the design basis The methods for construction and inspection Conclusions of the initial state DESIGN BASIS FOR THE UNDERGROUND OPENINGS General basis Identification and documentation of design basis Definitions, purpose and basic design Required functions and design considerations Functions of the underground openings in the KBS-3H repository Design considerations Design basis Design basis related to the functions in the KBS-3H repository Design basis imposed by the engineered barriers and plugs Design basis related to production and operation Design basis imposed by the underground openings Differences between Posiva and SKB ROCK ENGINEERING The Observational Method Description Monitoring... 32

10 Differences in Observational Method s application in KBS-3H Stepwise development of the underground facilities Control programme Documentation of initial as built conditions Differences between Posiva and SKB THE REFERENCE DESIGN AND ITS CONFORMITY TO THE DESIGN BASIS Repository depth Deposition area placement of deposition drifts and supercontainer sections Thermal conditions Mechanical conditions Hydrogeological conditions Pilot holes Deposition drifts and supercontainer sections Other underground openings Engineered and residual materials Rock support in underground openings Grouting measures in underground openings Quantities of engineered and residual materials Differences between Posiva and SKB REFERENCE METHODS General basis Reference methods used for the construction of deposition drifts Pilot hole drilling for reaming to full drift diameter Geometrical tolerances Water control and acceptable water inflow Development of EDZ when employing full face excavation techniques Notch for the plug in deposition drifts Methodology for accepting canister positions on the basis of a discriminating fracture Preparation of deposition drifts Reference methods associated with other underground openings Differences between Posiva and SKB CONCLUSIONS ON THE INITIAL STATE Introduction General reference design Repository depth and deposition areas Deposition drifts and supercontainer sections Geometry and properties of importance for the initial state of the engineered barriers Uncertainty and risk relative to the initial state Differences between Posiva and SKB SUMMARY Design basis for the underground openings... 63

11 3 7.2 Rock engineering The reference design and its conformity to the design basis Reference methods Initial state of the underground openings REFERENCES APPENDIX 1: KBS-3H DISPOSAL FACILITY LAYOUT 2013, POS APPENDIX 2: SUMMARY OF THE DIFFERENCES BETWEEN POSIVA AND SKB.. 87 APPENDIX 3: ABBREVIATIONS AND DEFINITIONS... 89

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13 5 PREFACE The existing KBS-3V production line reports are largely applicable to KBS-3H production line reports. In order to provide a conform description this report follows the structure and uses common text from the corresponding SKB s and Posiva s KBS-3V production line reports. The KBS-3V production line reports (produced by Posiva and SKB, respectively) have formed the basis for the organization s respective licence applications. For the construction of the KBS-3H repository SKB and Posiva have defined a set of production lines: the spent nuclear fuel; the canister; the buffer and filling components; the supercontainer; the plugs; and the underground openings. The latter four production lines are reported in separate production reports. The former two are expected to only deviate only slightly from their 3V counterparts and are incorporated in a Repository production report which also presents the common basis for the reports. This set of reports addresses primarily applicable design basis (according to the Posiva VAHA system), reference design, conformity of the reference design to the applicable design basis, production and the initial state, i.e. the results of the production. Comparison with the SKB design premises is provided in dedicated tables setting forth the differences between the two organizations and repository sites. In parallel with this process an overarching process is underway that is expected to harmonize the Posiva and SKB requirements. The preparation of the above-mentioned set of reports has been lead and coordinated by Anders Winberg (Conterra AB) with support from Antti Öhberg (Saanio & Riekkola Oy). This report has been authored by Antti Ikonen (Saanio & Riekkola Oy). The KBS-3H design has been developed jointly by SKB and Posiva since This report has been prepared within the project phase KBS-3H - System Design

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15 7 1 INTRODUCTION KBS-3H is a variant of the KBS-3 method and an alternative to the KBS-3V reference design. KBS-3H is based on horizontal emplacement of several canisters in a series in long deposition drifts whereas KBS-3V calls for vertical emplacement of the canister in individual depositions holes within a deposition tunnel, see Figure 1-1. Horizontal emplacement has been studied in parallel with the development of the KBS-3V reference design since the late 90 s. /SKB 2012/ is the report presenting the current reference design as well as the reference methods. The design basis in this report in essence is that given for KBS-3V and they are supplemented with method specific premises/ basis (see below). This has established the reference case for the KBS-3H method as well as the current status in developing design and methods. In Posiva s terminology design basis refers to the current and future environmentally induced loads and interactions that are taken into account in the design of the disposal system, and, ultimately, to the requirements that the planned disposal system must fulfil in order to achieve the objectives set for safety (i.e. the design premises). In SKB s terminology the design premises are used as input to the production reports, which present the reference design analysed in the long-term safety assessment SR-Site. The design premises correspond to the design requirements and system specifications in Posiva s terminology. Design basis is used when referring to the design premise in the following text and in the Summary. In Posiva s terminology the system design premises comprise the objectives set for the whole system, limitations set by the environment, technology and knowledge and existing operating environment (regulations, responsibilities, organisations, resources). These form the starting point for the definition of the design basis of disposal operations. Design basis (in line with this report) is provided in (Posiva 2016a). Design basis are overall shared by SKB and Posiva and exceptions are mentioned separately. Figure 1-1. Schematic drawing of the KBS-3V reference design (to the left) and KBS-3H (to the right) (SKB 2012).

16 8 1.1 General basis This report This report presents the reference design, construction and initial state of the underground openings of the KBS-3H repository for spent nuclear fuel. It is part of a set of reports presenting how the KBS-3H repository is designed, produced and inspected. The set of reports is denoted Production reports. The Production reports and their short names used as references within the set are illustrated in Figure 1-2. The reports within the set referred to in this report and their full names are presented in Table 1-1. The KBS-3H design has been developed jointly by SKB and Posiva since This report has been prepared within the project phase KBS-3H - System Design This report constitutes basis for the safety reports (Posiva 2016b) for the KBS-3H repository and the 3H Repository production report (Posiva 2016c). The present status of Posiva s long term safety related studies is presented in KBS-3H topical report /Posiva 2012e/. The long-term safety will be evaluated during the current project phase KBS-3H System Design according to the objective of the project phase (SKB 2012). The objective is to produce KBS-3H design and system understanding to such level that the preparation of a PSAR and a comparison between KBS-3V and KBS-3H is made possible. The corresponding 3V-production lines are largely applicable also to 3H. In order to provide a full description in this report, relevant sections from corresponding 3V production lines have been included. Specific commentaries with references to applicable reports related to site- and organization-specific differences are given in the end of each Chapter 2-6 and in Appendix The design of the underground openings The presented design of the underground openings presumes a repository based on the KBS-3H method with horizontal deposition of canisters in deposition drifts as outlined in the 3H Repository production report (Posiva 2016c/. The design and construction methods presented in this report constitute an approach which is technically feasible. It is, however, foreseen that the design basis, the design as well as the presented methods for construction, test and inspection will be further developed and optimised before the actual construction of the KBS-3H repository facility commences. This is especially the case for the underground openings since both the design and the methods of construction require information on the conditions at repository depth. In this context, it should be mentioned that there are alternative designs that conform to the design basis as well as alternative ways to implement (construct) the design. The safety analysis may also result in updated design basis. SKB s and Posiva s objective is to continuously develop and improve both design and production and adapt them to the specific conditions at the selected sites.

17 The construction of the underground openings The construction of the underground openings is one of the main activities included in the operation of the KBS-3H repository facility. The principal layout of the underground openings (see Appendix 1) as well as the sequence in which they are constructed are based on the planned operation of the KBS-3H repository facility presented in the layout adaptation (Appendix 1) and the Repository production report. For SKB there are no defined construction sequences for the KBS-3H repository as yet. Repository production report Spent fuel report Canister production report Supercontainer production report Buffer and filling component production report Plug production report Closure production report Underground openings construction report Figure 1-2. Reports included in the set of reports describing how the KBS-3H repository is designed, produced, tested and inspected. The dashlined Spent fuel, Canister and Closure Production reports are essentially the same for KBS-3H and for KBS-3V and hence adapted reports are not produced for KBS-3H (SKB and Posiva have produced their respective non-generic reports). Repository production report includes some information from other production reports (spent fuel, canister, closure) if there are differences between 3V and 3H. Table 1-1. The reports within the set of Production reports referred to in this report. Full title Design and production of the KBS-3H repository KBS-3H - Design, production and initial state of the supercontainer KBS-3H - Design, production and initial state of the KBS- 3H buffer and filling components KBS-3H - Design, production and initial state of the compartment and drift plug Short name used within the Production line reports 3H Repository production report Supercontainer production report Buffer and filling components production report Plug production report 1.2 Purpose and delimitations Purpose The purpose of this report is to describe how the underground openings of the KBS-3H repository are designed, constructed and inspected in a manner related to their importance for the safety of the KBS-3H repository. The report shall provide the information on the design, design basis, construction and initial state of the underground openings required for the long-term safety report, (Posiva 2016b), as well as the

18 10 information on how to construct and inspect the underground openings required for the operational safety report. With this report SKB and Posiva intend to present the design basis for the underground openings of the KBS-3H repository and demonstrate how the underground openings can be designed and constructed to conform to the stated design basis. The report presents the reference design and construction methods and summarises the research and development efforts that ensure that the underground openings can be constructed in conformity with the design basis Limitations This report includes present design basis for the underground openings related to nuclear safety and radiation protection and to the dependable construction of the KBS-3H repository. The presented reference designs of the underground openings must conform to this design basis and consequently they have governed the design. Design basis related to other aspects, e.g. environmental impact, occupational safety and utilization degree, are not included because they have not determined the design of the underground openings or the methods to construct them. The current report presents SKB s and Posiva s reference design and methods. Alternative designs and planned developments of the design and methods are not included. This report also includes the design considerations made with respect to the application of best available nuclear safety and radiation protection technique. It describes the related design basis for the design and development of methods for construction and inspection of the underground openings. Motivations of the presented reference design and methods as the best available technique are reported elsewhere. The reference design of the closure is presented in the Closure production reports, which is the same for KBS-3H as for KBS-3V. SKB and Posiva have presented their own site-specific Closure production reports SKB (SKB, 2010a) and Posiva (Posiva, 2012b). Closure of the other underground openings other than deposition drifts are not presented in this report. These matters are presented in (SKB 2010a) and (Posiva 2012a). The maximum allowed groundwater inflow to deposition drifts has been set, whereas the maximum allowable groundwater inflows for KBS-3H and KBS shafts, rock caverns and tunnels are the same as for 3V and are not repeated in this report (in Posiva s case they can be found in (Posiva 2015)). Furthermore, there are no differences between KBS-3H and KBS-3V concerning stability and rock reinforcement in underground openings (other than deposition drifts) and hence they are not presented in this report. These aspects are discussed in (SKB 2010b) and (Posiva 2012b). Uncertainties and risks will be assessed and reported later in KBS-3H project. Here only the principles are described.

19 Interfaces to other KBS-3H reports and aspects The role of the Production Line reports in the safety evaluation of a KBS-3H repository at Olkiluoto is presented in the 3H Repository production report (Posiva 2016c). A summary of the interfaces to other reports is given below The report for the long-term safety analysis By providing a basic understanding of the repository performance over different timeperiods and by the identification of scenarios that can be shown to be especially important from the standpoint of risk the long-term safety assessment provides feedback to the design of the engineered barriers and underground openings. The methodology used for deriving design basis from the long-term safety assessment is introduced in the 3H Repository production report (Posiva 2016c) The design basis reports A thorough description as well as the resulting design basis are given in the report design basis (Posiva 2016a) for a KBS-3H repository, hereinafter referred to as design basis for long-term safety. This design basis constitutes a basic input to the design of the underground openings. The report (SKB 2012) presents the current main reference design as well as the reference methods. The design basis is in essence that given for KBS-3V and it is supplemented with method specific design basis. This has established the reference case for the KBS-3H method as well as the current status in developing design and methods Operational safety No specific operational safety report has been prepared during this project phase. The current report, however, provides information to the operational safety report on the design of the underground openings and the technical systems used to construct and inspect them as well as instructions on where and when inspections shall be performed The other 3H production reports The 3H Repository production report presents the context of the set of production reports and their supporting role in relation to the safety report. It also includes definitions of some central concepts of importance for the understanding of the Production reports. The Repository production report also set out the laws and regulations set forth by regulators and presents demands from the nuclear power plant owners that are applicable to the design of a repository for spent nuclear fuel. In addition, it describes the functions of a KBS-3H-repository and how the safety is maintained by the barriers and their barrier functions. The report also describes how design basis are derived and

20 12 developed from laws and regulations, owner demands and the stepwise processes of design and safety assessment and design and technique development, respectively. The design and production of the different engineered barriers and underground openings are inter-related. An overview of the design and production interfaces will be provided in the 3H Repository production report. The design basis imposed by the engineered barriers for the underground openings stated in each of the engineered barrier production reports are repeated in this report. The conformity of the reference designs of the underground openings to this design basis are considered in this report. 1.4 Site descriptive reports Site descriptive model and underground design reports Posiva has performed surface-based and underground site investigations with the purpose to develop site descriptive models (SDM). A SDM is an integrated model for geology, thermal properties, rock mechanics, hydrogeology, hydrogeochemistry, bedrock transport properties and a description of the surface system. The SDM concluding the surface-based investigations at Olkiluoto are presented in (Posiva 2011). This report presents the integrated understanding of the site considering the aforementioned information. The SDM is comprehensive and serves the needs of many users. To abstract data in the form of relevant parameters required for the design and layout of the underground openings a Site Engineering Report (SER) has been developed. The SER provides geological constraints and engineering guidelines for design issues related to the longterm safety of the repository as well as to operational requirements. Posiva s SER for the Olkiluoto site is presented in (Posiva 2012d) and is based on interpretation and evaluation of information in (Posiva 2011). The corresponding documentation of the SDM based on surface based site investigation at Forsmark and the associated Forsmark SER is presented in (SKB 2008) and (SKB 2009a), respectively. 1.5 Structure and content Design basis The design basis sets out the information required for the design. The current KBS-3H design basis for the underground openings are presented in Chapter 2 of this report. The chapter starts with the definition of the underground openings and their purpose. After that follows a presentation of the functions the underground openings shall provide to contribute to the safety of the repository and the considerations that shall be made in the design with respect to the application of a well tried out and reliable technique. Finally, the detailed design basis for the underground openings is given. They state the properties the reference design shall have to maintain the functions.

21 Rock engineering Chapter 3 outlines the objectives of rock engineering and the methodology to be applied in the design work. The design methodology providing the framework for the design and construction of the underground openings as well as for adapting their layout to the conditions at the repository site is presented Reference design and its conformity to the design basis Chapter 4 presents the reference design of the underground openings for Forsmark and Olkiluoto. It is based on the currently completed design stage for the repository. The conformity of the reference design to each of the design basis presented in Chapter 2 is discussed and concluded upon the basis of the current knowledge of the site The methods for construction and inspection In Chapter 5 the reference methods for construction and inspection of the underground openings are presented. The presentation includes the current state of development and results from demonstrating the performance of the reference methods relative to the design basis Conclusions of the initial state The concluding Chapter 6 presents the expected initial state of the underground openings and the conformity of the constructed underground openings to the design basis related to the long-term safety of the repository. The chapter also provides conclusions regarding the layouts and their adaptation to the site conditions and the projected capability of the reference methods to result in underground openings that conform to the specifications.

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23 15 2 DESIGN BASIS FOR THE UNDERGROUND OPENINGS The KBS-3 method is the method proposed in Finland and Sweden for geological disposal of spent nuclear fuel. Therefore, requirements on the host rock related to longterm performance of engineered barriers will, to a large extent, be similar in the two countries. Still there are site-specific features and differences in available site data to be considered in development of the Rock Suitability Classification (RSC). The RSC system has been developed by Posiva to define suitable volumes for repository design and construction (McEwen et al. 2012). The RSC system includes criteria for defining volumes of rock suitable for the repository areas, and a forthcoming procedure to assess the suitability of deposition drifts or supercontainer sections and for the acceptance of supercontainer sections for emplacement. The aim is to avoid features of the host rock that may be detrimental to the favourable conditions for the safety either initially or in long term. There are, however, differences in the definitions and the terminology applied which are partly arising from the differences in the regulations in Sweden and Finland. There is a difference in the basic starting point for defining the requirements in the regulations by the Finnish and Swedish authorities. Whereas the focus in the Finnish regulations is in the expected scenarios of future evolution, the Swedish regulations point out the scenarios that can be shown to be especially important from the standpoint of risk. There are no differences between KBS-3H and KBS-3V concerning regulatory requirements and guidance and these issues are further discussed in (SKB 2012). In this chapter the present design basis for the underground openings are presented. They comprise the functions and properties the underground openings shall sustain in the KBS-3H repository and design basis for their design. The required functions and design basis are written in italics, being in parity with the 3H Design basis report (Posiva 2016a). 2.1 General basis Identification and documentation of design basis The methodology to derive, review and document design basis is presented in the Repository production report and is detailed for KBS-3H in (Posiva 2016a). The design basis is based on: international treaties, national laws and regulations; the functions of the KBS-3H repository; the safety analysis; technical feasibility; and the planned production. The repository production report includes a presentation of the laws and regulations applicable for the design of a repository. Based on the treaties, laws and regulations, SKB and Posiva have substantiated functions and considerations as a specification of the KBS-3H repository, and as guidelines for the design of its engineered barriers and

24 16 underground openings. In the repository production report the functions and properties that the underground openings shall provide in order to contribute to the functions of the KBS-3H repository are presented. The repository production report also presents the design considerations to be applied in the design work. The applicable functions of the underground openings and the considerations that shall be applied in the design work are presented in Section 2.2. The design basis related to the functions of the underground openings in the KBS-3H repository are based on the results from the latest long-term safety analyses (Posiva 2016b). This design basis for the underground openings is presented in Section Design basis related to technical feasibility refer to the properties the underground openings shall have to accommodate, and work, together with the engineered barriers and other parts of the repository during the production. The general approach to substantiate this kind of design basis and the interfaces to the engineered barriers and other parts in the production are presented in the Repository production report. Here this design basis related to interfacing with the engineered barriers and plugs are presented in Section Finally, design basis related to the operation of the KBS-3H repository facility and construction of the underground openings are presented in Section The methodology to substantiate these kinds of design basis is presented in the Repository production report Definitions, purpose and basic design The underground openings are the cavities constructed in the rock that are required to accommodate the sub-surface part of the repository facility. The underground openings comprise: the actual location and geometry (space) of the cavities; the rock surrounding the openings that is affected by the construction works; and engineered materials for sealing and rock reinforcement, and residual materials from performance of activities in the repository facility, which remain in and on the rock bounding the openings at deposition or closure. The underground openings as such do not contribute to the safety of the KBS-3H repository and do not have any barrier functions. However, the locations of the deposition areas and deposition drifts with respect to the geological, thermal, hydrological, mechanical and chemical properties of the rock are important for the utilisation of the rock as a barrier and thus for the safety of the repository. Furthermore, damage and disturbances on the rock surrounding the drifts and tunnels, i.e. the excavation damaged zone (EDZ 1 ), and engineered and residual materials that remain in 1 EDZ = Damage not including disturbance (stress redistribution, chemical precipitates etc) according to SKB definition. Section of the rock that is irreversibly damaged by the excavation of the tunnel according to Posiva definition.

25 17 the rock may affect the barrier functions of the rock and/or the engineered barriers, and must therefore be established when assessing the safety of the repository. The underground openings shall accommodate the sub-surface part of the repository facility, cf. Chapter 4. The principal layout of the KBS-3H repository facility and the nominal dimensions of the underground openings have been decided considering operational requirements, activities in the KBS-3H repository facility and the dimensions of the engineered barriers and plugs (see Appendix 1). 2.2 Required functions and design considerations In this section, the functions and design considerations applicable to the underground openings are presented. They are based on the functions of the KBS-3H repository in the 3H Repository production report and have been divided into: functions and properties that the underground openings shall sustain in order for the repository to maintain its safety (Section 2.2.1); and issues that shall be considered when developing the layout and design of the underground openings and methods for excavation, grouting, rock reinforcement and inspection (Section 2.2.2) Functions of the underground openings in the KBS-3H repository In order for the KBS-3H repository to be able to accommodate all spent nuclear fuel from the currently approved Swedish and Finnish nuclear power programmes the underground openings shall: accommodate the sub-surface part of the repository facility with the number of approved supercontainer sections that are required to deposit all canisters with spent nuclear fuel (from the approved programme). In order for the repository to contain, prevent or retard the dispersion of released radioactive substances, the rock shall provide stable and favourable conditions for the engineered barriers so that their barrier functions can be sustained for as long as necessary bearing in mind the radiotoxicity of the spent nuclear fuel. Should the containment provided by the canister be breached, the rock will contribute to the safety of the repository by preventing or retarding the dispersion of radioactive substances. In order for the rock to sustain its barrier functions and to maintain the multi-barrier principle (the containment of radioactive substances can be sustained over a long period of time), the underground openings shall be adapted to the conditions at the repository site so that: thermally favourable conditions are provided; mechanically stable conditions are provided; favourable hydrogeologic and transport conditions are provided; and chemically favourable conditions are provided.

26 18 In order for the KBS-3H repository to maintain the multi-barrier principle and have several barriers which individually and together contribute to maintaining the barrier functions, the underground openings shall: be designed so that they do not significantly impair the barrier functions of the rock (for example through development of EDZ) or the engineered barriers (for example water flow affecting the buffer erosion). In the design of the KBS-3H repository unintentional intrusion shall be considered so that the repository site after closure of the repository facility can be utilised without compromising the freedom of action, needs and aspirations of future generations. With respect to this and the fact that the repository shall isolate the spent fuel from the environment at the surface: the repository depth shall be selected with respect to the human activities which, based on present living habits and technical prerequisites, may occur at the repository site. In order for the barrier system of the repository to withstand conditions, events and processes that may impact their functions, the underground openings shall: allow the deposition of canister, buffer and plugs to the drifts with the desired barrier functions; and allow the installation of closure to the other underground openings with the desired barrier functions. For the nuclear operation of the repository facility to be safe, the underground openings shall: be designed so that breakdowns and mishaps (e.g. caving in and flooding) in conjunction with the nuclear operations are prevented. The underground openings shall also be designed so that other activities, e.g. maintenance in the repository facility, can be carried out in a safe way. In Posiva s case the disposal timing (order) shall allow one responsible organization to withdraw from the repository earlier than the other. This is possible according to the Finnish law, if the organization in question has disposed and plugged acceptable all waste of it and the remaining responsible organization takes also the total responsibility of closing the shared part of the facility (technical rooms, access routes etc.). This could be reasonable if the remaining responsible organization has a need to operate the facility decades longer than the other. This timing issue does not have any effect on the underground opening construction methods used and hence it is not dealt more in this report Design considerations In this section the design considerations that shall be regarded in the design of underground openings and the development of construction methods as well as the methods for monitoring and inspections of the underground openings are presented.

27 19 The system of barriers and barrier functions of the repository shall withstand failures and conditions, events and processes that may impact their functions. Hence the following shall be considered. Excavation, sealing and rock reinforcement shall be based on well-tried or tested techniques. The construction and inspections of the underground openings shall be dependable, and the following shall be considered. The underground openings shall be designed and constructed using methods so that they, with reliability, provide the desired rock conditions. The properties of the underground openings shall be possible to inspect against specified criteria. Further, environmental impact such as noise and vibrations, emissions to air and water, impact on groundwater and consumption of material and energy shall also be considered in the design. Methods to construct and inspect the underground openings must also conform to regulations for occupational safety. Requirements related to these aspects can generally be met in a number of alternative ways for designs that conform to the safety and radiation protection requirements. Design basis related to these other aspects, e.g. environmental impact, workers safety and cost-effectiveness (like utilization degree), are not included here because they have not determined the design of the underground openings or the methods to construct them. 2.3 Design basis In this section the design basis for the underground openings are given. The design basis constitutes specifications for the design of the underground openings. The design basis comprises the properties to be designed and design basis for the design such as quantitative information on features, performance, events, loads, stresses, combinations of loads and stresses and other information, e.g. regarding environment or adjacent systems, which form a necessary basis for the design. The design basis is based on the functions the underground openings shall have in the repository as presented in Section and the design considerations as presented in Section The design basis given as feedback from the long-term safety analyse will be compiled in Design basis report. Initial state properties of the as built repository in the production line reports is a starting point for the safety analysis. The design basis given as feedback from the technical development are based on the reference designs of the other parts of the KBS-3H repository and the plans for the main activities and operation of the KBS-3H repository facility (SKB 2012).

28 Design basis related to the functions in the KBS-3H repository The design basis for the underground openings related to their functions in the KBS-3H repository (see also Figure 2-1) are compiled in Table 2-1 (divided in sub tables A-C). In the left column of the table the functions which form the basis for the design basis as presented in Section are repeated, the middle column contains the underground opening property or condition to be designed and adapted to the site and the right-hand column gives the design basis as stated from the long-term safety point of view. Figure 2-1 The deposition drift and its main components. The deposition drift is excavated from the niche with a slight inclination upwards enabling drainage during installation (based on Posiva 2013). A) SKB s disposal facility design with only one central (main) tunnel. B) Posiva s design with two parallel central tunnels.

29 21 Table 2-1. The functions, the related properties and parameters to be designed and the design basis for the underground openings. A. Repository depth and deposition areas Function Property to be designed Design basis long-term safety The underground openings shall accommodate the sub-surface part of the repository facility with the number of approved deposition holes that are required to deposit all canisters with spent nuclear fuel. Deposition areas utilised rock domains, distances between supercontainers and loss of supercontainer sections. Repository depth The repository volumes and depth need to be selected where it is possible to find large volumes of rock fulfilling the specific requirements on supercontainer sections. The requirements on supercontainer sections include acceptable thermal, mechanical, rock stress, hydrological and transport conditions. The repository shall have sufficient capacity to store 6,000 canisters (SKB) and 4,500 canisters/ (Posiva). 2 The underground openings shall be adapted to the rock so that thermally favourable conditions are provided and the containment of radioactive substances can be sustained over a long period of time. The repository depth shall be selected with respect to the human activities which, based on present living habits and technical prerequisites, may occur at the repository site. Repository depth With respect to potential freezing of buffer and backfill, surface erosion and inadvertent human intrusion, the depth should be considerable. Analyses in the SR-Site and Posiva s Safety Case portfolio corroborate that this is at least 400 m. The minimum temperature of the rock at the repository level is set -4 C to avoid freezing of the buffer (SKB 2011). The underground openings shall be adapted to the rock so that chemically favourable conditions are provided and containment, prevention or retardation of dispersion of radioactive substances can be sustained over a long period of time. Deposition areas utilised rock domains, hydrogeochemical conditions. Repository depth The design basis is presented in (SKB 2009a) and (Posiva 2012c). (KBS-3H has the same design basis for chemical conditions as KBS-3V). 2 These are not a design basis from the long-term safety. They are estimations based on the number of spent fuel assemblies to be encapsulated and deposited.

30 22 B. Deposition drifts and supercontainer sections Function Property to be designed Design basis long-term safety The underground openings shall be adapted to the rock so that desired temperature conditions are provided and the containment of radioactive substances can be sustained over a long period of time. Deposition drifts distances between supercontainer sections and deposition drifts. The buffer geometry (e.g. void spaces), water content and distances between supercontainer sections and deposition drifts should be selected such that the temperature in the buffer is <100 C. The horizontal deviation of the pilot hole and deposition drift shall be < 2 m from the nominal position at a distance of 300 m. Nominal (centre to centre) horizontal distance from deposition drift to another is alternative 30 m or 40 m at Forsmark and 25 m in Olkiluoto (SKB 2012). The underground openings shall be adapted to the rock so that mechanically stable conditions are provided and the containment of radioactive substances can be sustained over a long period of time. Supercontainer sections respect distance to deformation zone (SKB) / layout determining features (LDFs), hydrogeological zone, brittle deformation zone (Posiva). Deposition drifts respect distance to layout determining features (LDFs) (Posiva). supercontainer sections are tentative not allowed to be placed closer than 100 m to deformation zones with a trace length longer than 3 km (SKB) (SKB 2010b). Tentatively supercontainer sections shall not intersect the respect volumes of LDF, hydrogeological zone or brittle deformation zone (Posiva) (SKB 2012). Tentatively deposition drifts shall not intersect the respect volumes of LDFs (Posiva) (SKB 2012). SKB has not defined a corresponding requirement. Canister intersecting fractures (mechanical properties). Canister positions should, as far as reasonably possible, be selected so that they do not have potential for shear larger than the canister can withstand. Criterion to be applied in selecting supercontainer sections from this point of view will be addressed later. The underground openings shall be adapted to the rock so that favourable hydrologic and transport conditions are provided and the containment, prevention or retardation of dispersion of radioactive substances can be sustained over a long period of time. Supercontainer sections inflow The total volume of water flowing into a supercontainer section (a drift section containing one supercontainer and two halves of distance blocks, one half on both sides of the supercontainer), for the time between when the buffer is exposed to inflowing water and saturation, should be limited to less than or equal to 0.1 l/min (SKB 2012). Grouting is not allowed in a supercontainer section (10 m) (SKB 2012). The underground openings shall be designed so that they do not significantly impair the barrier functions of the rock or the engineered barriers. Deposition drifts transmissivity of EDZ (includes result from the excavation method and the redistribution of stresses). Before supercontainer emplacement, the connected effective transmissivity integrated along the full length of the deposition drift and as averaged around the drift will be addressed.

31 23 C. Other underground openings and engineered and residual materials Function Property to be designed Design basis long-term safety The underground openings shall be designed so that they do not significantly impair the barrier functions of the rock or the engineered barriers. Shafts and ramp/ access tunnel, rock caverns and tunnels other than deposition drifts transmissivity of EDZ. Grouting, outbrake filling and rock reinforcement in deposition drifts extent/design, leaching product of grouting material. Grouting and rock reinforcement in drill holes, shafts and ramp /access tunnel, rock caverns and tunnels other than deposition drifts leaching product of grouting material. Engineered and residual materials in all underground openings amounts and composition. SKB has set limits for the integrated effective connected hydraulic conductivity of the backfill in tunnels, ramp/ access tunnel and shafts and the EDZ surrounding them (SKB 2010b). Posiva has set limits for the EDZ depth (in floor mm, rest of the profile mm) (Posiva 2012c). Only clay-based materials (see Section 2.5) for outbreak filling and no cement based grouts for possible rock bolting (mechanical bolts) No shotcrete is allowed No grouting (SKB 2012) nor bolting is allowed in supercontainer section (i.e. a drift section containing one supercontainer and two halves of distance blocks, one half on both sides of the supercontainer) Only non-cementitious post grouts (silica-based) are allowed with Mega-Packer technique for deposition drifts Low ph based grouts (See Section 2.5) shall be used as primary grouting material below 300 m depth at Olkiluoto (Posiva 2012a). In the case of SKB only low ph materials are allowed below the level of the top seal at Forsmark at 200 m depth (SKB 2010b). Use of other residual materials must be limited Design basis imposed by the engineered barriers and plugs In this section the design basis for the underground openings imposed by the engineered barriers and plugs related to technical feasibility are presented. Note that interdependencies between the underground openings and other parts of the repository occurring after the initial state are considered in the design basis related to the functions of the underground openings in the repository, as presented in Table 2-1. Buffer and filling component A background to the design basis imposed on the deposition drifts by the buffer is given in the Buffer and filling components production report. The deposition drift shall allow reliable installation of the buffer and filling components according to specification. To achieve this, the design basis presented in Table 2-2 and illustrated in Figure 2-1 is imposed on the deposition drifts. Supercontainer A background to the design basis imposed on the deposition drifts by the supercontainer is given in the Supercontainer production report. The deposition drifts shall allow reliable installation of the supercontainer according to specification. To achieve this, the

32 24 design basis presented in Table 2-3 is imposed by the supercontainer on the deposition drifts. Plugs in deposition drifts A background to the design basis imposed on the deposition drifts by the plugs (drift plug and compartment plug) is given in the Plug production report. The deposition drifts shall allow reliable installation of the plugs in deposition drifts according to specification. To achieve this, the design basis presented in Table 2-4 are imposed on the deposition drifts by the plugs. The deposition drifts shall conform to this design basis during the operational phase of the repository facility. The type of plug/-s and their positioning are presented in Figure 2-1. Table 2-2. Design basis imposed by the buffer and filling components on the deposition drifts. Required property Design basis The diameter of the deposition drift shall allow sufficient room to accommodate the buffer. Variations in deposition drift geometry must not be larger than to allow deposition of buffer according to specification Nominal dimensions of the supercontainer affect to the dimensions of the buffer and filling components Resulting diameter of the drift is allowed to vary between to m (See also Section 5.2.2). Table 2-3. Design basis imposed by the supercontainer on the deposition drifts. Required property Design basis The inflow into deposition drifts during supercontainer installation must not prevent supercontainer installation. The diameter of the deposition drift shall allow sufficient room to accommodate the supercontainer. Variations in deposition drift geometry must not be larger than to allow deposition of supercontainer according to specification. Based on current experiences the maximum inflow to the deposition drift after post grouting is set to be less than or equal to 10 l/min in a 300 m long deposition drift /SKB 2012/ related to the performance of the deposition machine. A positive 2 +1 inclination (pilot hole and deposition drift) is needed for drainage (SKB 2012). Resulting diameter to m (See also Section 5.2.2). The emplacement equipment can move properly in the drift for steps of up to 5 mm (SKB 2012) (See also Section 5.2.2). The emplacement equipment functions properly for a roughness up to 5 mm (SKB 2012) (See also Section 5.2.2). The centre line waviness (deviation) must be kept within ± 10 mm (in vertical direction) over a length of 6000 mm (SKB 2012) and + 20 mm (in horizontal direction) to prevent the supercontainer from contacting the rock surface during transport in the drift.

33 25 Table 2-4. Design basis imposed by the plug on the deposition drifts. Required property Design basis Inflow of water to the part of the deposition drift where the plug shall be installed must be limited since excessive water inflow may impact the properties of the finished plug. The compartment plug and drift plug shall be installed in sound rock with no open fractures to prevent water flow around the plug A notch for foundation of the plug shall be prepared in the rock. The strength and properties of the rock in the area of the location of the plug shall be suitable for construction of the notch for the plug. The accepted inflow is not determined at this stage of development. Excellent/good rock quality (to be quantified). Geometry of the reference plug. The forces transmitted from the plug to the rock. The distance between the intersection of the central tunnel wall and the drift plug The distance between the intersection of the central tunnel wall and the drift plug shall be at least 10 m in order to limit unfavourable rock mechanical effects, see Appendix 1, Section 2.4 (central tunnel diameter related variable). Closure The reference design of the closure is presented in the closure production report, which is the same for KBS-3H as for KBS-3V. SKB (SKB 2010a) and Posiva (Posiva 2012a) have prepared their own non-generic closure production reports. Closure of the other underground openings, other than deposition drifts are not presented in this report. These aspects are discussed in (SKB 2010a) and (Posiva 2012a). In addition, in order to limit the probability that closed (filled) investigation drillholes will form water conductive channels that may jeopardize the barrier functions of the rock, the locations of the drill holes have to be considered in the layout of the repository facility. Drillholes collared at the surface which intersect underground openings must be avoided. Further, deposition drifts must not be intersected by any investigation drillholes. There will be plugs also in (transport, main and central) tunnels, ramp/ access tunnel and shafts. The objectives of these plugs are to separate filled and closed underground openings from underground openings that remain to be closed, to isolate conductive features in the rock or to facilitate the installation of the closure. These plugs will impose similar design basis on the underground openings as the plugs in deposition drifts Design basis related to production and operation In this section the design basis for the underground openings related to their construction and the operation of the KBS-3H repository facility are given. In addition to the functions and design considerations presented in Section 2.2, they are based on how the main activities in the repository facility are planned to be carried out and on

34 26 SKB s and Posiva s objective to minimize radiation doses during the operation of the KBS-3H repository facility. The layout of the underground openings, the grouting and rock reinforcement shall be designed so that breakdowns and mishaps in conjunction with the nuclear operation are prevented. Further, the design of the underground openings shall allow activities in the repository facility to be carried out in a safe and cost-effective way with acceptable impact on the environment and on groundwater levels. With respect to this, limits for the maximum allowed inflow to shafts, rock caverns and tunnels other than deposition drifts have been set, and they are the same for KBS-3H and KBS-3V and are not presented in this report (in Posiva s case they can be found in (Posiva 2016a)). Furthermore, there are no differences between KBS-3H and KBS-3V concerning stability and rock reinforcement in underground openings (other than for deposition drifts) where the canister or supercontainer is handled and hence it is not presented in this report. These matters are presented in (SKB 2010b) and (Posiva 2012b). Design basis related to nuclear operations are given in Table 2-5. Table 2-5. Design basis for the underground openings related to the nuclear operation of the final repository facility. Design consideration or function Required property Design basis The underground openings shall be designed so that breakdowns and mishaps in connection with the nuclear operations are prevented. The underground openings shall allow the deposition of supercontainer and installation of buffer and filling components with desired barrier functions. The underground openings shall be designed so that breakdowns and mishaps in connection with the nuclear operations are prevented. The placement of the deposition drift within the deposition niche shall allow deposition of buffer, filling components and supercontainers. Underground opening stability, rock reinforcement in underground openings where the canister is handled. Deposition drift length needs to be feasible from a construction point of view. Deposition niche geometry. Installation equipment for buffer, filling components and supercontainer. The frequency of the event: Rock falling on the canister and damaging it so it is no longer fit for deposition. must not exceed 10 3 (SKB) (SKB 2010b). Posiva has not yet determined a corresponding frequency; will be addressed later. Deposition drift length < 300 m (SKB 2012). 2.4 Design basis imposed by the underground openings The underground openings do not impose any design basis for the engineered barriers or other parts in the repository. The construction of the underground openings will, due to the occurrence of vibrations, impose that there shall be a respect distance between construction works and completed parts of the repository, i.e. deposition drifts where installation of the buffer, supercontainer and plugs are completed. Tentatively a vibration respect distance is in the order of 50 m from excavation to the canister are considered (Saanio et al. 2007).

35 Differences between Posiva and SKB The differences related to site and organization-specific differences in design basis are following: Nominal (centre to centre) horizontal distance from deposition drift to another (drift spacing) is alternative 30 m or 40 m in Forsmark and 25 m in Olkiluoto (SKB 2012). The repository shall have sufficient capacity to store 6,000 canisters (SKB) and 4,500 canisters (Posiva). There are no differences between KBS-3H and KBS-3V concerning chemically favourable conditions; only minor differences between the sites are evident, as shown by /SKB 2009a/ and (Posiva 2012c). Tentatively deposition drifts shall not intersect the respect volumes of layout determining features (LDFs) (Posiva) (SKB 2012). SKB has not yet set a corresponding requirement. Supercontainer sections are tentatively not allowed to be placed closer than 100 m to deformation zones with a trace length longer than 3 km (SKB) (SKB 2010b). Tentatively supercontainer sections shall not intersect the respect volumes of either LDF, hydrogeological zones or brittle deformation zone (Posiva) (SKB 2012). SKB has set limits for the integrated effective connected hydraulic conductivity of the backfill in tunnels, ramp/ access tunnel and shafts and the EDZ surrounding them (other than deposition drifts) (SKB 2010b). Posiva has set limits for the EDZ depth around the peripheries (for other underground openings than deposition drifts) (Posiva 2012c). Low ph (long term ph<10 (Posiva 2012g)) based grouts shall be used primary grouting material below 300 m depth at Olkiluoto /Posiva 2012a/. Correspondingly for Forsmark only low ph (long term ph<11) materials are allowed below the level of the top seal of Forsmark (at 200 m depth) (SKB 2010b).

36 28

37 29 3 ROCK ENGINEERING 3.1 General The design basis for the underground openings is presented in Chapter 2. The objectives of rock engineering are to ensure that the site-adapted layout of the repository facility, as well as the construction and as-built underground openings, conform to this design basis. Engineering projects are divided into design and construction. The design is carried out successively as more detailed descriptions/models of conditions at the sites become available. The reference layout design document for Olkiluoto (see Appendix 1) includes the design for the underground part of the repository facility based on the site conditions given in (Posiva 2011 and Pere et al. 2012). The current designs are presented in Figures 3-1 and 3-2 for Forsmark and Olkiluoto, respectively. The design preceding the construction, i.e. the detailed design, will produce the specifications and engineering drawings for the layout and underground openings that will constitute the repository. Figure 3-1. Illustration of the 3H-layout for a repository facility in Forsmark (with alternative 30 m drift spacing, another option is 40 m). A to D stand for different main tunnels. Section at 470 m depth (SKB 2012).

38 30 Figure 3-2. Illustration of the 3H-layout for a final repository facility in Olkiluoto (see Appendix 1). During all phases of underground design and construction, uncertainties with regard to site conditions must be anticipated and addressed. In order to establish a final layout for deposition drifts, a large volume of rock will have to be characterised, see Figures 3-1 and 3-2. The uncertainties that will influence the final layout are the spatial location, geometry and variability of the geological setting and its constituents, the rock mass response to excavation, rock support and grouting measures. These uncertainties and the size of the repository volume emphasize that the methodology used to adapt the final layout of the repository to the site conditions must be integrated with the construction activities required to develop the repository. The methodology that SKB and Posiva will use for adapting the layout of the repository to the site conditions is based on the observational method (Peck 1969). 3.2 The Observational Method The observational method is a risk-based approach to underground design and construction that employs adaptive management, including monitoring and measurement techniques and modelling (SKB 2009b and Posiva 2012d). The observational method was developed for large scale infrastructure projects where the complexity and spatial variability of the geological setting prohibits knowing the detailed site conditions prior to construction. Consequently, the observational method must provide for the collection of site information in conjunction with construction.

39 Description The formal requirements of the observational method are found in the European standard for construction and geotechnical design, Eurocode 7 (EN :2004, c.f. Section 2.7 therein). The main elements of the observational method are: 1. acceptable limits of behaviour shall be established; 2. the range of possible behaviour shall be assessed and it shall be shown that there is an acceptable probability that the actual behaviour will be within the acceptable limits; 3. a plan for monitoring the behaviour shall be devised, which will reveal whether the actual behaviour lies within the acceptable limits; 4. the response time of the monitoring and the procedures for analysing the results shall be sufficiently rapid in relation to the possible evolution of the system; and 5. a plan of contingency actions shall be devised which may be adopted if the monitoring reveals behaviour outside acceptable limits. SKB and Posiva will apply the observational method for adaptation of the repository to the site conditions, so that the as-built layout and underground openings conform to the design basis. Application of the observational method requires the following: (1) An action plan must be defined to cater for possible unfavourable conditions. This implies that the method cannot be applied if a predictive model for the behaviour cannot be developed, i.e. one must be able to establish a model that can calculate the parameters that will later be observed during construction. (2) One must be able to monitor the parameters that can predict behaviour. This is not a trivial task as often we can measure what we cannot calculate and vice versa. This means that the monitoring plan must be chosen very carefully with a good understanding of the significance to the problem at hand. Incorrect preconceptions about the dominant phenomena that control the behaviour can lead to choosing irrelevant observational parameters. The detailed design for Olkiluoto is based on Posiva s SDM presented in the Site Report (Posiva 2011) and considers the most likely ground conditions as well as possible deviations ranging from most favourable to worst conceivable conditions. The application of the observational method is based on identification of hazards, i.e. uncertainties that may contribute to the risk of nonconformity of the layout and underground openings to the design basis. The current design identified the uncertainties in the site geological conditions, termed geohazards, which could impact on the design and repository layout. The observational method is a formal design procedure requiring a formal comparison, at designated milestones, of the design assumptions and actual encountered ground conditions. The comparisons shall assess if the layout used to accommodate the site conditions satisfies the design basis. If deviations from the design should occur a formal review is required. This implies that parameters used to monitor the conformance of the layout to the design basis must be clearly identified and acceptance criteria (threshold

40 32 levels) quantified beforehand. Examples of applications of the observational method are presented in (SKB 2010b and Posiva 2012d), respectively Monitoring The monitoring activities required for implementing the observational method are dependent on the repository functional requirements and the particular geohazard being monitored. The details of the monitoring programme will be developed successively. For example, the groundwater inflows to the access ramp/ access tunnel and the associated drawdown of the groundwater head around the excavation require monitoring. In addition to verifying the SDM, an assessment of the orientations of fractures where inflows occur and their spatial distribution are also required. The groundwater conditions encountered will be documented using formal as-built reporting guidelines. The as-built conditions will be compared with the predictions made prior to the beginning of construction. The comparison must be carried out using criteria developed during the detailed design preceding the construction and will take place once the repository access reaches a particular milestone or checkpoint. If the comparison shows that the actual site conditions deviate outside the predicted variability, and that the consequence of such deviation is significant, the as-built conditions are reported for review and possible mitigating measures. Clearly the criteria for comparing the as-built conditions with the predicted conditions must be developed in detail and fully specified. In this example, such criteria can only be specified once the expected ground conditions for the repository access excavations have been established. Hence investigations will be required before hand to establish the ground conditions in sufficient detail to establish the criteria. Posiva has devised a monitoring programme (Posiva 2012f). In case the geohazard is groundwater inflow, it can be predicted and it can be measured directly. However, in other situations the geohazard cannot be measured directly. For example, while in situ stress is recognized as a geohazard, the maximum horizontal stress is measured indirectly using either hydraulic fracturing, overcoring or convergence methods. In this case the criteria for comparing the as-built conditions encountered with the predictions, must also specify the methodology used to interpret the indirect measurement. Regardless of the measuring and monitoring requirements, procedures and guidelines must be developed with the understanding that a main purpose of the investigations and monitoring is to assess site conditions that were used as the basis for the detailed design and to quantify the deviations from those conditions, should they occur Differences in Observational Method s application in KBS-3H The main differences in the Observational Method s application for the full-face deposition drifts compared with traditional drill and blast tunnelling are: Only one 76 mm pilot hole is available for characterisation of the drift profile ahead instead of a pilot hole and several (batches of) probe holes. (The reference method in KBS-3H is to drill a pilot hole that is subsequently reamed to full drift size, with an additional intermediate reaming step to pilot hole size (diameter c. 300 mm) (SKB 2012).

41 33 On the other hand it could be argued that the pilot hole in the case of KBS-3H can be regarded as being more representative since the deposition drift s cross section area is smaller (compared to the drill and blast tunnel cross section of the KBS-3V deposition tunnel). This is however related to mode and degree of heterogeneity of the rock. Feedback during full face boring is rarely available (e.g. in conjunction with change of full face crown) compared to drill and blast rounds every 3-5 metres The KBS-3H deposition drift provides an ideal shape to observe the occurrence of excavation induced spalling and leakages (compared to rough tunnel profile). In all above-mentioned differences are not fundamental: the observational method can be applied to deposition drifts. 3.3 Stepwise development of the underground facilities The development of the underground facilities is carried out in stages. Initially the accesses to repository depth are developed, followed by the central area/ technical rooms and the deposition drifts and rooms for the test (SKB) and demonstration (Posiva) operations. Finally, during routine operation, the repository will be developed in stages, focussing on a particular deposition area. During each stage deposition works and rock construction works are carried out in parallel separated by a partition wall. Each stage comprises the construction of deposition drifts required for a given number of supercontainers/ canisters. During each development stage deposition works are carried out in the area completed during the previous stage, and detailed site investigations are performed for the deposition drifts to be constructed in the next stage. Thus, there are three separate activities associated with a stage in the development of deposition areas: 1. investigation of the detailed site conditions and adaptation of the layout to those conditions; 2. investigation and construction of deposition drifts with control programme; and 3. deposition works including deposition of supercontainers and installation of buffer, filling components and plugs. The stepwise development of the deposition areas will enable systematic auditing of the design and construction activities. 3.4 Control programme The control programme shall ensure, using standard quality control and assurance procedures, that the construction works and constructions methods conform to the reference methods. The main objective of the control programme is to secure that the reference methods perform in such a way that the design basis, quality and efficiency are fulfilled. With respect to long-term safety the control programme embraces, but is not limited to: inspection of delivered material in terms of quantity and quality;

42 34 control and inspection of construction works e.g. grouting and excavation activities; and inspection and quantification of the results of the construction works e.g. inflow, geometry and excavation damage zone. The control programme and its quality documentation constitute the basis for the evaluation whether the performance of the reference methods is acceptable with respect to long-term safety. The quality documentation comprises, but is not limited to: documentation of the performance of material and reference methods; documentation of quality related to the design basis, and any non-conformity and related correcting measures; and as-built drawings containing positions, geometry and material. The overall requirements on, and objectives of the control programme will be defined before the start of the construction. Experiences will be obtained successively during the excavation of the repository, which may result in modification to the reference methods in order to meet the design basis. 3.5 Documentation of initial as built conditions The formal documentation of the in situ conditions and the layout adopted to those conditions are provided in an as-built documentation. The formal requirements for the content of the as-built documentation will be developed in conjunction with the requirements for the test with spent nuclear fuel (SKB) and demonstration without spent fuel (Posiva) operation. The documentation will provide information on the initial state of the deposition drifts completed during the development stage and will tentatively include the following contents: 1. The location of the boundaries of the given deposition area; 2. The location of surface and remaining underground investigation drillholes; 3. The location and geometry of the deposition drifts; 4. The location of the accepted and rejected supercontainer sections; 5. Documentation of inspections and inspection-results that demonstrate conformity to the design basis; 6. Documentation of any non-conformity related to long-term safety and related mitigating measures; and 7. Documentation of all engineered materials left in the rock mass (types of, positions and amounts). In parallel to the development of the main (SKB) and central (Posiva) tunnels and deposition drifts the rock mass conditions are documented as part of the development of the site descriptive modelling for the given deposition area.

43 Differences between Posiva and SKB SKB s design differ from that of Posiva in that SKB employs a single main tunnel where as Posiva employs a system with dual central tunnels (20 m nominal rock mass between). In the SKB s concept the niche is excavated between the main tunnel and the drifts whereas in Posiva s case the niche is excavated between the dual tunnels so that the drift starts from the bounding central tunnel. Other differences related to site and organization-specific differences in rock engineering are minor. They mainly relate to equivalence in non KBS-3H specific items like terminology (e.g. Posiva s central tunnel vs. SKB s main tunnel, Posiva s technical rooms vs. SKB s central area) and the sitespecific layout adaptation to Olkiluoto / Forsmark. In its stepwise development SKB will test operations with spent fuel. Posiva do not plan such test operations apart from demonstrations employing for example non-radioactive dummy canisters.

44 36

45 37 4 THE REFERENCE DESIGN AND ITS CONFORMITY TO THE DESIGN BASIS This chapter presents the reference design of the underground part of the KBS-3H repository facility and the conformity of the underground openings to the design basis as stated in Section 2.3. The reference design is called DAWE (Drainage Artificial Watering and air Evacuation) and it is the result of the KBS-3H design stage Complementary studies. The most significant results are presented in (SKB 2012), which constitutes the main reference for this chapter and it presents the KBS-3H reference design applicable to both organisations. The reference design reflects the current level of detail and the current status of rock engineering for the underground facilities. The conceptual layout and nominal dimensions of the underground openings for Olkiluoto are given in Appendix 1. The reference design represents one possible layout of the underground facilities at Forsmark and at Olkiluoto, see Figures 3-1 and 3-2, respectively. It also provides an estimation of material quantities required for rock support and grouting. The sitespecific basis for the reference design is site characterisation data, site descriptive models and geotechnical information, which have been interpreted and evaluated in a SER (site engineering report) (SKB 2009a and Posiva 2012d). It is important to point out that the verification of the conformity of the reference design to the design basis as stated in Section 2.3 is restricted by the currently anticipated uncertainties related to the SDM and SER. The reference design established in the current design stage will thus be the basis for the next design stage. The successive excavation of underground openings will provide information that is expected to reduce (or eliminate) uncertainties with regard to the SDM and SER, and the reference design will gradually be developed and refined and converge in accordance with the overall design methodology presented in Chapter 3. In Section 2.3 the design basis for the underground openings are divided into design basis: related to the functions in the KBS-3H repository; from the engineered barriers and plug; and related to the production and operation. In the following sections the reference design and its conformity to the design basis is presented. The design basis related to the functions of the repository is presented under the headers: repository depth; deposition areas; pilot holes; deposition drifts and supercontainer sections; other underground openings; and engineered and residual materials.

46 38 Issues related to design basis from engineered barriers and production and operation are also included in the above headers. The EDZ (excavation damaged zone), dimensions and tolerances of underground openings as well as grouting, are further discussed in Chapter 5 which deals with reference methods. 4.1 Repository depth The following design basis is stated for the repository depth and deposition areas in Section (Table 2-1A). The repository volumes and depth need to be selected where it is possible to find large volumes of rock fulfilling the specific requirements on supercontainer sections. With respect to potential freezing of buffer and backfill, surface erosion and inadvertent human intrusion, the depth should be considerable. Analyses in the SR- Site and Posiva s Safety Case portfolio corroborate that this is at least 400 m. The minimum temperature of the rock at the repository level is set -4 C to avoid freezing of the buffer (SKB 2011). The reference depth was established considering the design basis and the constructability of the tunnels and deposition drifts. The main influence of the design basis stated in Section on the reference depth is the hydrogeology of the site, i.e. frequency and occurrence of transmissive fractures and their correlation to depth, while the influence on depth from constructability is mainly related to rock mechanical and stress issues, e.g. the likelihood and extent of spalling in deposition drifts prior to emplacement. A rationale for identifying suitable rock volumes for deposition as well as depth intervals for the repository facility has been employed to establish a depth interval where it is possible to find rock volumes that conform to the specific design basis for deposition drifts with regard to: in situ temperature; fracture frequency (conductive fractures); hydrogeology considerations; spalling considerations; available space site adaptation; construction costs and environmental impact; and other considerations. Application of the above rationale resulted (already in (SKB2010b)) in a depth range of 450 m to 500 m according to SKB (SKB 2009a) and in minimum depth 400 m according to Posiva (Posiva 2012c). The in situ stress magnitude and the fracture frequency of water-bearing fractures were the governing conditions.

47 Deposition area placement of deposition drifts and supercontainer sections Thermal conditions The layout of the deposition drifts shall conform to the following design basis for thermal conditions stated in Section (Table 2-1B). The buffer geometry (e.g. void spaces), water content and distances between supercontainer sections (canister spacing) and deposition drifts (drift spacing) should be selected so that the temperature in the buffer is <100 C. Nominal (centre to centre) horizontal distance from deposition drift to another (drift spacing) is alternatively 30 m or 40 m in Forsmark and 25 m in Olkiluoto (SKB 2012). Deviation of the pilot hole and deposition drift shall be < 2 m from the nominal end position at a distance of 300 m (SKB 2012). Relative positioning of a supercontainer section and deposition drifts in rock with a lower thermal conductivity can be optimised and individual drift and canister spacing calculated (compared to nominal values). According to current knowledge, volumes of rock with a very low thermal conductivity are sparse as well as detectable Mechanical conditions The following design basis for the mechanical conditions in deposition drifts and supercontainer sections are stated in Section 2.3.1: Supercontainer sections are tentatively not allowed to be placed closer than 100 m to deformation zones with a trace length longer than 3 km (SKB) /SKB 2010b/. Tentatively supercontainer sections shall not intersect the respect volumes of LDF, hydrogeological zone or brittle deformation zone (Posiva) (SKB 2012). Tentatively deposition drifts shall not intersect the respect volumes of LDFs (Posiva) /SKB 2012/. SKB has not a corresponding requirement. Canister positions should, as far as reasonably possible, be selected so that they do not have potential for shear larger than the canister can withstand. This design basis together with predefined boundaries of the repository footprint governs the gross capacity of the repository. A tentative methodology for verifying the conformity of the reference design to this design basis has been established by Posiva (Pere et al. 2012) and SKB (Munier 2006, 2007, 2010). In order to mitigate the impact of potential future earthquakes, canister positions are selected so that they do not intersect discriminating fractures, so-called large fractures. Criteria and conformity to design basis to be applied in selecting canister positions from this point of view will be addressed later.

48 Hydrogeological conditions The following design basis for the hydrological conditions in deposition drifts and supercontainer sections are stated in Chapter 2.3.1: Based on current experiences the maximum inflow to the deposition drift after grouting is set to be less than or equal to 10 l/min in a 300 m long deposition drift (SKB 2012) (related to the performance of the deposition machine). The total volume of water flowing into a supercontainer section (a drift section containing one supercontainer and two halves of distance blocks, one half on both sides of the supercontainer), for the time between when the buffer is exposed to inflowing water and saturation, should be limited to less than or equal to 0.1 l/min (SKB 2012). A method for verifying the conformity of the reference design to the design basis is inflow measurements. Most of these non-accepted supercontainer sections are likely to be screened out by the potential earthquake criterion, and the most likely situation is that very few additional sections will be lost due to high inflow. 4.3 Pilot holes Pilot holes are drilled with directional (steered) core drilling. The reference method is to drill a pilot hole (diameter 76 mm) that is reamed to full drift size, by way of an intermediate reaming step to pilot hole size (diameter c. 300 mm) (SKB 2012). Acceptable geometrical tolerances for deposition drifts are imposed by the buffer, filling components and the supercontainer. The design basis concerns the straightness, inclination, waviness, diameter, steps and roughness. The three first criteria need to be fulfilled already when establishing the pilot holes. The following design basis for the pilot holes (and deposition drifts) is stated in Section (Table 2-1B): The horizontal deviation of the pilot hole and deposition drift shall be < 2 m from the nominal end position at a distance of 300 m (SKB 2012); A positive 2 +1 inclination (pilot hole and deposition drift) is needed for drainage (SKB 2012); and The centre line waviness (deviation) must be kept within ± 10 mm (in vertical direction) over a length of 6,000 mm (SKB 2012) and + 20 mm (in horizontal direction) to prevent the supercontainer from contacting the rock surface during transport in the drift. 4.4 Deposition drifts and supercontainer sections The following design basis for the excavated damaged zone (EDZ) in deposition drifts are stated in Section 2.3.1:

49 41 Before supercontainer emplacement, the connected effective transmissivity integrated along the full length of the deposition drift and as averaged around the drift will be addressed. Damage related to the excavation resulting in increased transmissivity along deposition drifts can be either the result of the applied method to excavate the drifts, or a process governed by the mechanical properties of the rock and the redistribution of stresses around the excavated deposition drifts (spalling). The EDZ induced by the excavation activities is related to the performance and execution of the reference method, and is discussed in Section The likelihood of spalling in deposition drifts could be significantly reduced if not eliminated by aligning the deposition drifts near parallel to the maximum horizontal stress (Bäckblom 2008). A complete description of spalling and the methodology used to assess the spalling potential can be found in (Bäckblom 2008). The deposition drifts shall be aligned within ±30 degrees of the orientation of the maximum horizontal stress to significantly reduce the risk of spalling in deposition drifts. Spalling in deposition drifts due to excavation-induced stresses is permitted, but the final deposition drift geometry must conform to the tolerances specified in the design basis imposed by the buffer. Uncertainties related to the in situ stress conditions, rock properties and the capability to model the extent of spalling and related changes in transmissivity, restrict a verification of the reference design at this stage. Means of reducing the remaining uncertainties related to spalling must be developed in the next design phase, something which is facilitated by the design methodology presented in Chapter 3. The contingency measure for reducing or eliminating spalling in deposition drifts is to align the deposition drifts near parallel to the maximum horizontal stress. In the event that spalling occurs on the periphery of deposition drifts, mitigation measures would need to be taken in effect to increase the likelihood of achieving conformity to the above design basis. Loose rock debris from localized spalling on rock walls in deposition drifts would be scaled off. Scaling or rock fall-out will affect the dimensions of deposition drifts. Possible ways to adapt the installation of the buffer to the resulting geometry are discussed in Section The issue is thermal spalling which will take place after the drift has been closed with no access. One of the potential ways to mitigate or resolve the issue is establishment of sufficient counter pressure from the swelling bentonite. The design basis imposed on the deposition drifts by the buffer, filling components and supercontainer are given in Tables 2-2 and 2-3. The depositions drifts must conform to the design basis to achieve the required buffer density and a reliable installation of the buffer and filling components. The specified acceptable deviations in radii include all possible causes discussed in Section The design basis imposed on the deposition drifts by the plug is given in Table 2-4. They comprise the construction of a notch for foundation of the plug, as well as acceptable inflow and strength of the rock mass in the area where the plug shall be installed. The rock should be of excellent/good quality with no fractures (to be quantified). The construction of the notch is discussed in Section For the other

50 42 design basis imposed by the plug there are no specifications so far. For rock reinforcement and grouting the approaches discussed in Sections and are applied. 4.5 Other underground openings The following design basis for the excavated damaged zone in the underground openings in the ramp/ access tunnel, shafts and tunnels other than deposition drifts are stated in Section SKB has set limits for the integrated effective connected hydraulic conductivity of the backfill in tunnels, ramp/ access tunnel and shafts and the EDZ surrounding them (SKB 2010b). Posiva has set limits for the EDZ depth (in floors mm, rest of the profile mm) (Posiva 2012c). The EDZ induced by the excavation activities is related to the performance and execution of the corresponding reference method. This has no differences between KBS-3H and KBS-3V and hence it is not presented in this report. These matters are presented in (SKB 2010b) and (Posiva 2012b). 4.6 Engineered and residual materials The following design basis for engineered and residual materials left in the repository, when the installation of buffer is performed or the underground openings are closed, are stated in Section For deposition drifts: Only clay-based materials (see Section 2.5) for outbreak filling and no cement based grouts for possible rock bolting (mechanical bolts); No shotcrete is allowed; No grouting (SKB 2012) nor bolting is allowed in supercontainer sections (i.e. a drift section containing one supercontainer and two halves of distance blocks, one half on either side of the supercontainer); and Only non-cementitious post grouts (silica-based) are allowed with Mega-Packer technique for deposition drifts. For drillholes, shafts and ramp/ access tunnel, rock caverns and tunnels other than deposition drifts: Only low ph (See Section 2.5) materials are allowed below the level of the top seal (200 m) at Forsmark (SKB 2010b); and Low ph based grouts shall be used as primary grouting material below 300 m depth at Olkiluoto (Posiva 2012a). Engineered materials left in the repository consist of materials for sealing by grouting and rock reinforcement. Cement is used in shotcrete, for embedding various support elements and in grout mixes for sealing purposes. In addition, there are residual

51 43 materials from the operation of the repository facility that will remain after decommissioning and preparations for installation of buffer, supercontainer or closure. For these the following design basis is stated in Section 2.3.1: Other residual materials must be limited. The assessed amounts of remaining engineered materials from rock support and grouting activities and the amounts of residual materials are discussed in Section Rock support in underground openings To facilitate estimates of quantities of ground support for the reference design, guidelines are given in (SKB 2009a) and (Posiva 2012d). They are based on extensive underground construction experience and outline which categories of rock support, e.g. rock bolts (and shotcrete in other underground openings than deposition drifts) that are considered suitable for use in the foreseen ground types. The possible rock bolts in the drifts are grouted in with no cement based materials (mechanical bolts) (See Section 2.5). The ends of rock bolts will be cut off or sunk below the surface of the drift wall e.g. by chamfering the rock surface. Rock bolts will be used only if needed, which should be very seldom given the circular drift geometry which together with the small drift radius and the excavation method promotes rock stability. Furthermore, rock quality is foreseen to be good in the drifts. The rock support in other underground openings than deposition drifts are practically the same for KBS-3H and KBS-3V and hence they are not presented or discussed in this report. This subject is handled in (SKB 2010b and Posiva 2012b) Grouting measures in underground openings The design basis for acceptable inflow imposed on the deposition drifts by the supercontainer is given in Table 2-3. The deposition drifts must conform to the design basis to enable and achieve a reliable installation of the supercontainer. The leaking sections will be post-grouted with colloidal silica. The grouting measures in other underground openings than deposition drifts are practically the same for KBS-3H and KBS-3V and hence they are not presented in this report. These issues are dealt with in (SKB 2010b and Posiva 2012b). Water inflow and grouting in underground openings are considered to cause disturbance that should be avoided. Constructing access routes (ramp or shaft) in such a way that they would be located above or near the potential location of the deposition drift should be avoided according (STUK 2003). Mega-Packer test results (Eriksson and Lindström 2008) indicate that the sealing efficiency of post-grouting will be sufficient and that the reference design conforms to the specified inflow limits.

52 Quantities of engineered and residual materials Engineered materials originating from rock support and grouting activities will remain in the repository after decommissioning and closure of the repository facility. Residual materials from the operation of the repository facility will also remain in the repository. The structural reinforcement elements included in the rock support of deposition drifts are possible rock bolts and no cement based grouts for bolt installation/ mechanical bolts and clay-based material filling of the outbreaks. Spray/ drip shields and grouting materials are employed in connection with water leakages. The former objects are not allowed to be left in the drift so that they may give rise to a hydraulic connection between canister positions (SKB 2012). For all excavation methods there will be spills of materials; e.g. steel, hard metal and hydraulic oils. Using a horizontal push-reaming for the drift excavation would minimize use of construction material in the drift. Spills of hydraulic oil could occur, but mainly at the drill rig that is located outside the drift during this process. It is assumed that spill of oil is around 0.01 L/m 3. The minute amounts of grease for drill rods and for cutters are thought to be effectively flushed out of the drift due to the mucking method selected for reaming (Bäckblom and Lindgren 2005). The amounts of engineered and other residual materials in KBS-3H repository for Olkiluoto have been evaluated by (Hagros 2007). The evaluation includes also above mentioned materials. There is however a need to update that evaluation for the current layouts and volumes. 4.7 Differences between Posiva and SKB The difference related to site and organization-specific differences is the resulted depth range of 450 m to 500 m according to SKB (SKB 2009a) and minimum depth 400 m according to Posiva (Posiva 2012c). Differences in design basis are presented in Section 2.5 and they need to conform to the reference design. In this report term residual materials (SKB) is a synonym for term foreign materials (Posiva). Posiva s regulator has stated, that constructing access routes (ramp or shaft) in such a way that they would be located above or near the potential location of the deposition drift should be avoided according (STUK 2003).

53 45 5 REFERENCE METHODS 5.1 General basis The design basis introduced by long-term safety and the design basis imposed by the buffer and backfill together with the design considerations presented in Section result in design basis for a number of methods used for the construction of the underground openings. This chapter presents the proposed reference methods for the construction. SKB and Posiva regard the reference methods as technically feasible. However, some methods need to be further developed before the construction of the repository facility commences. Given that the other underground openings (ramp, shafts, transport and central/main tunnels etc) of KBS-3V and KBS-3H are produced in the same way, only the production of the KBS-3H deposition drift is handled here. The used technology, the operational aspects and the environment in which the reference methods are applied, are all possible sources of uncertainty relative to the ideal performance of the reference methods. The conformity to the design basis will be handled as part of the observational method and the development of quality control and assurance procedures as outlined in Section 3.4. Within the framework of the observational method the predicted performance of the reference methods need to be fully established before they are put in operation to construct the underground openings of the repository facility. Moreover, before a reference method can be considered as operational, parameters and criteria (threshold levels) that shall be used to predict the performance must be established. Observable and quantifiable parameters with potential for predicting the performance of the reference methods are outlined in the following sections. 5.2 Reference methods used for the construction of deposition drifts The reference method for excavating the deposition drifts is the full-face horizontal push-reaming technique. The design basis for deposition drifts related to their function in the KBS-3H repository are found in Table 2-1and the design basis imposed by the buffer, filling components and supercontainer are expressed in Tables 2-2 and 2-3. Prior to the installation of the buffer the conformity to the criteria set forth in relation to size of fractures intersecting the deposition drift deposition position, groundwater inflow, connected transmissivity of the EDZ and geometrical tolerances applicable to the design basis including e.g. the Rock Suitability Classification shall be verified and the deposition drift prepared for installation of the distance blocks, supercontainer and filling components. Reaming of the pilot hole to full drift diameter will be made by using slightly adapted equipment for conventional raise boring, where the cutter head is pushed and rotated. Stabilisers are necessary to stabilise the bore string, Figure 5-1.

54 46 Figure 5-1. Principal illustration of horizontal push-reaming. From the left: pilot hole, reamer head and two stabilizers in the already excavated drift. Courtesy: Atlas Copco. Horizontal push-reaming generates substantial volumes of fragmented rock and muck at a high rate (up to some 3 m 3 /h) and the rock cuttings need to be removed from the almost horizontal drift using flushing water. Effective mucking was considered at an early stage to be vital for efficient excavation, and several options were successively tested and rejected during the excavation of the test drifts. The removal of the debris using re-circulated water (flow rate 3,000 litres/min) was found to be sufficient to clean the drift at a 2 upward inclination (Bäckblom and Lindgren 2005) Pilot hole drilling for reaming to full drift diameter The reference method is to drill a pilot hole (diameter 76 mm) that is reamed to full drift size, with an intermediate reaming step to a hole diameter of c. 300 mm. Pilot holes are drilled with directional (steered) core drilling. Guided directional drilling requires two main controls, one that establishes the position of the drill bit in space and a second system that guides the direction of the pilot hole based on the error in the bit position relative to the planned theoretical trajectory of the pilot hole (SKB 2012). Verification that the geometrical requirements have been met constitutes an important part of the drift/ pilot hole excavation process. If the drift for some reason does not fulfil the requirements it may imply that deposition is not possible. The measurements should be done stepwise (pilot hole, intermediate reaming, full drift size) and using proven technology to the extent possible. Special measurement devices cannot be ruled out in future applications (SKB 2012). A 300 m long surface testing facility for pilot hole deviation equipment with a dedicated 60 m long section tailored to the KBS-3H geometrical demands has been constructed at the SKB Äspö HRL (Hard Rock Laboratory). Plans are to test the candidate deviation methods/instruments prior to be used when establishing a new KBS-3H underground test facility at the 410 m level at the Äspö HRL. Drift inclination and direction can be measured by use of conventional deviation techniques. During the excavation of the 95 metres drift at Äspö HRL in 2005, conventional survey techniques were used. There are a number of commercial systems available on the market, each with its own limitations and special characteristics. Calibration of the tool is very important. Inclination and direction of the drift is best measured during the drilling of the preceding pilot hole, where mitigating efforts also can be made early on to correct deviations that might lead to the ensuing drift not fulfilling the set-up requirements (SKB 2012). Also, the intermediate reaming step (say

55 47 to 300 mm diameter) is expected to further smoothen out irregularities and undulation seen in the initial pilot borehole Geometrical tolerances Acceptable geometrical tolerances for deposition drifts are imposed by the buffer, filling components and supercontainer. The design basis concerns the 1) straightness (See Table 2-1B) and 2) diameter, inclination, waviness/undulation, steps and roughness (See Table 2-3). This will impose constraints on the performance of the reference method in terms of the resulting dimensions of the deposition drift. The tests at the Äspö Hard Rock Laboratory, successfully demonstrated the feasibility of push-reaming technology (Bäckblom and Lindgren 2005). For a 300 m long drift, however, fulfilment of the geometrical criteria is yet to be demonstrated. With respect to the geometrical requirements (see Section 2.3), a diameter change (reduction) is anticipated during the course of the reaming due to wear of the periphery cutters. For a 300 m long drift, it is envisaged that the demands placed on the minimum and maximum diameter of the drift will result in the need of careful monitoring of the wear of the cutters, and timely exchange of cutters during the course of reaming (that is likely to introduce steps). Reversed reaming can be done if the diameter is found to be too small. When reaming in reversed mode, centralizing the back reaming should be controlled. Concerning the smoothness of the drift, the reamer head manufacturers have no documented experience how it may be affected by the reamer head design, e.g. using six instead of four peripheral cutters. Furthermore, there are no data available on the marginal extra overbreak that is

56 48 Figure 5-2. The end of the 95 m drift at the Äspö HRL showing the final shape of the drift face and occasional grooves /SKB 2012/. generated beyond the periphery cutter. The reaming may also generate grooves and steps but it is not fully clear how to design the reamer head and how to operate the equipment to minimize generation of grooves and steps. Figure 5-2 illustrates the end of the 95 metres full diameter drift at Äspö after reaming (SKB 2012). Control programme Requirements on the drift s mantel surface in terms of roughness, steps, diameter changes etc., need to be addressed by measurement. Laser scanning of the drift has been tested in Äspö and found feasible. The method generates huge amounts of data from which the surface geometry can be imaged and analysed (SKB 2012). There are other suitable methods and instruments for inspecting the dimensions of deposition drifts, e.g. geodetic methods. SKB and Posiva will develop a procedure for verifying that the geometrical tolerances of deposition drifts conform to the design basis. Primarily quality control and assurance procedures will be applied to inspect pilot holes (pilot holes and deposition drifts) through proper positioning, fastening and alignment of the drill rigs as well as the conditions related to the drilling operations, e.g. checking cutter conditions. The resulting geometry after drilling will be inspected by one or a combination of measurement methods. A visual inspection of the completed deposition drift is also necessary in order to assess the occurrence of spalling prior to deposition. Any deposition drift that do not conform to the geometrical tolerances shall be rejected and backfilled.

57 49 Detailed information regarding the measurement techniques can be found in (Bäckblom and Lindgren 2005) as well (Autio et al. 2008). As mentioned previously, a surface testing facility for pilot hole deviation equipment has recently been constructed at the SKB Äspö HRL Water control and acceptable water inflow Acceptable inflow to the deposition drift is stated in Table 2-3 and to a supercontainer section in Table 2-1 B. Grouting of deposition drifts can be considered as long as the results are compatible with the long-term safety design basis. This implies that neither grouting nor intersection of fractures in which grouting material has been observed or in which there are indications of grouting material is allowed in a supercontainer section (supercontainer + two halves of distance blocks). No grouting holes are allowed to be drilled outside the drift profile (Anttila et al. 2008). The grouting agent employed need to be approved. The groundwater flow out of the deposition drift during its operational period must not be so high that it affects the installation of engineered components. Either pre-grouting in the pilot hole or Mega-Packer post grouting will be used to limit substantial water inflow into the drift where required (See Table 2-1B). The leaking drift sections will be post-grouted with colloidal silica which will have a longevity equivalent to the operational time only (SKB 2012). The same grout agent selection applies to pregrouting in the pilot hole. Full-scale tests of the Mega-Packer were initiated at Äspö HRL during the Demonstration phase in 2007 and have been reported in (Eriksson and Lindström 2008). The Mega-Packer, Figure 5-3, is an equipment consisting of a large tube of 48 mm thick steel, 1,970 mm long (with a grouting length of 1,590 mm) and a diameter of 1,820 mm, only slightly smaller (30 mm) than the nominal drift (e.g. 15 mm annular gap between the Mega-Packer and the drift wall when centred). It has packers sealing off at both ends. The packers are inflated with water at a pressure required to resist grout penetrating out between the packers and the rock wall during grouting. The steel tube has connections for valves, so that the hoses for grouting and measurement equipment can be connected. Silica-sol is used as grouting material and the residual layer of grout on the drift wall is removed after the grouting. To grout fracture zones of more substantial thickness, two Mega-Packers can be connected in a series and used simultaneously. The current design allows for this connection but the function has not been included in the tests that have been carried out (SKB 2012).

58 50 Figure 5-3. The Mega-Packer positioned outside the 95 m drift at Äspö HRL (SKB 2012). There are several parameters and associated criteria that have potential for predicting the performance of a reference method for the selection of deposition drift sections with acceptable inflows. For example, hydrogeological characterisation can be carried out and inflows can be measured in the pilot hole that will be drilled at the planned deposition drift position. Additional modelling and measures are required to predict/estimate the inflow situation of the drift section. Monitoring and control programmes A procedure for verifying that the inflow in deposition drift will conform to the design basis will be developed. The planned locations of deposition drifts will be decided in the detailed design (thermo optimal drift spacing etc.) according to the Rock Suitability Classification protocol. Input to adjusting or verifying the detailed design will be obtained within the framework of the observational method and the detailed site investigation programme, i.e. by combining results from characterisation in drillholes and underground openings and modelling at different scales. The model that refers to deposition drift -scale (tunnel scale) is based on geological and hydrogeological mapping of the drift, measurement of groundwater inflow to the drift and the preceding geological and hydrogeological characterisation of the pilot hole for the deposition drift. It is foreseen that the inflow to excavated deposition drifts and supercontainer sections will be monitored as long as possible i.e. until the installation of the drift components starts. If a deposition drift or supercontainer section does not conform to the design basis it will be rejected.

59 Development of EDZ when employing full face excavation techniques It is stipulated that the contribution from EDZ to the connected effective transmissivity in deposition holes (3V) and deposition drifts (3H) must be limited. This is achieved by employing full face reaming techniques combined with a careful drilling procedure. No quantitative measure for a limiting transmissivity of the EDZ has been proposed for the KBS-3H deposition drifts. In underground openings excavated with mechanical excavation methods it is possible to achieve a EDZ that is limited to a few centimetres into the rock surrounding the excavation and with a hydraulic conductivity that is in the order of m/s (Bäckblom 2008). These properties are valid in rock conditions where spalling has not occurred. Hence the full-face drilling method can be expected to create only minor damage to the surrounding rock walls. The resulting connected effective transmissivity after excavation will therefore largely be governed by the connected transmissivity of natural fractures that intersect the deposition drifts and the less likely occurrence and intensity of spalling. Control programme Currently there is no reliable method that can quantify the connected effective transmissivity of the annular zone of EDZ along the drifts. Geophysical techniques have been used to characterise EDZ, however, none of these are by themselves sufficient for assessing the intensity and extent of the EDZ, nor for characterizing its hydraulic properties. Tentatively it is foreseen that the deposition drifts conform to the design basis for the connected effective transmissivity if they conform to the conditions for acceptable inflow (SKB 2010b). A visual inspection of the completed deposition drift is necessary in order to rule out the occurrence of spalling. Should localised spalling occur, the potential to conform to the design basis for connected effective transmissivity can be improved by removing loose rock debris on the drift walls (SKB 2010b). This mitigation measure requires that outbreaks are levelled with clay-based material. The final contingency action in case of non-compliance would be to reject and backfill the deposition drift Notch for the plug in deposition drifts The design basis for deposition drifts imposed by the compartment and drift plugs are found in Table 2-4. The related rock engineering work includes the excavation of a notch for fastening of the plug. The required notch can be prepared by applying sawing techniques. The two types of plugs have slightly different rock notch profile, but the same technique can be applied (SKB 2012). In Figure 5-4 the mounted saw and the resulting V-shaped notch profile are illustrated.

60 52 Figure 5-4. The rock notch is excavated with parallel-cut sawing. Several cuts are made and the slabs broken away creating a V-shaped notch. The method has been proved to be functional. The top image shows the saw mounted in the drift, the resulting notch profile is shown to the bottom (SKB 2012) Methodology for accepting canister positions on the basis of a discriminating fracture In Table 2-1 B it is stated that: Canister positions should, as far as reasonably possible, be selected so that they do not have potential for shear larger than the canister can withstand. At the scale of a deposition drift and disposal location within the drift, the criteria for avoiding fractures with potential for large shear displacements are defined in Appendix C of Posiva (2016a). In order to avoid unnecessarily discarding canister positions in case they are intersected by an FPI (Full Perimeter Intersection) fracture that in reality is of limited size and thus is unlikely to experience damaging shear movements, the criteria are defined so that not all FPIs are avoided, but only those observed in three or more adjacent drifts, as well as those observed in two boundary drifts (Posiva 2016a, c.f. Appendix C and Section therein).

61 53 Monitoring and control programmes SKB and Posiva will develop a procedure for maximising the probability of detecting discriminating fractures (and deformation zones), so-called large fractures. Primarily this includes tailoring the detailed investigation programme that precedes drift excavation. Geological mapping of drift and core samples will provide detailed characterisation of the fractures that intersect the drift, and neighbouring drifts. Core sample, pilot hole logs and investigations will provide information on the location and the orientation of potentially discriminating (large) fractures. Any fracture, that would intersect an adjacent deposition drift or tunnel by extrapolation, should be investigated. The reliability of the methods used for matching fractures (and deformation zones) between deposition drifts and pilot holes remains to be assessed. These methods include cross-hole correlation (exploiting kinematic indicators), hydraulic and cross-hole geophysical techniques such as drillhole radar and seismics, also involving measurements between developed drifts which would provide good indications of the location and geometry (potentially also extent) of the fracture/zone in the rock around the hole. Hence application of the criterion requires results from geological characterisation, geophysical techniques and integrated modelling. A large fracture experiment involving these techniques (including resistivity (mise-ala-masse)) is currently being carried out at Äspö at the 410 m level (SKB 2016). All supercontainer sections that do not fulfil the criterion shall be rejected Preparation of deposition drifts Before installation of the drift components e.g. bentonite blocks and supercontainers, preparation of the deposition drift is carried out. The preparation of deposition drifts comprises: cleaning of the deposition drift; inspection of inflow to and its distribution along the deposition drift (see Section 5.2.3); inspection of potentially discriminating fractures intersecting the deposition drift (and neighbouring drifts) (see Section 5.2.6); installation of drip/ spray shields if necessary; inspection to determine the true/actual dimensions and geometrical tolerances of the deposition drift (see Section 5.2.2); levelling of possible rock outbreaks with clay-based infill materials; supplementary post grouting if leakages have increased to exceed the limits (during the time between the primary post grouting and drift component installation); excavation of rock notches for the plugs employing parallel-cut sawing; and installation of parts of the DAWE system The spraying, dripping, and squirting of groundwater onto the buffer material during the installation phase is prevented by placing metal spray shields over inflow points, see Figure 5-6. At single inflow points the shielding can be implemented through the use of stud type nipples (e.g. penny shaped disk attached on the rock surface in the centre of the inflow point). Inflow coming from the roof of the deposition drift will be redirected towards the lower hemisphere of the circular drift (Anttila et al. 2008).

62 54 The material alternatives for the shields are copper, titanium or steel, where titanium is the preferred material. The drip shield shown in Figure 5-6 was tested in the KBS-3H demonstration drift at Äspö HRL (Anttila et al. 2008). Figure 5-5. Principle of using drip shields (Anttila et al. 2008). Figure 5-6. Drip shield as attached to the demonstration drift at Äspö. Photo by H. Wimelius.

63 55 Outbreaks in the deposition drift will be levelled according to design basis with claybased material and only titanium plates can be used to cover such clay levellings. The titanium plates are not allowed to protrude from the drift profile so that they hinder the installation of drift components. For the most likely in situ stress conditions the excavation of the deposition drifts will not induce spalling, neither at Forsmark nor at Olkiluoto (spalling study) (Lönnqvist and Hökmark 2007 and 2009). After a few years of heating spalling is likely to occur without the support pressure induced by the swelling of buffer. There will be a significant mechanical counter pressure acting on the rock surface which would indicate that the issue of thermally induced spalling could be mitigated/ avoided for the reference design with artificial watering (SKB 2012). The spalling study results referenced should be considered as being indicative, because no adjoining thermo-mechanical calculations were carried out. To confirm the preliminary results and to minimize the uncertainties, full 3D thermo-mechanical analyses for the KBS-3H design should be carried out. 5.3 Reference methods associated with other underground openings The bentonite buffer (rings and blocks) will be transported from the SKB s intermediate storage at ground level down to the repository level through the shaft (with the skip). The buffer is placed in sealed containers in the storage (facility/room). Handling and transport are facilitated by conventional overhead cranes, grapple units and load carriers. From the storage, the buffer containers will be transported to the reloading station where the container will be opened and the buffer components are lifted and moved to the handling cell. The bentonite buffer that is placed in sealed containers will be transported down to the Posiva s storage area at the upper floor of the reloading station at repository depth through the (canister) shaft. From the storage, the buffer containers will be transported to the reloading station where the container will be opened for assembly of the supercontainer (Posiva 2016d). Canisters are transferred to the disposal level through the canister shaft in Olkiluoto and via the ramp at Forsmark. At the reloading station, See Figure 5-7, at the disposal level the canisters are packed in supercontainers. The supercontainer consists of a perforated protective cylinder (with solid end plates), bentonite buffer blocks and a copper canister. The supercontainers are transported in a transport shielding tube via the central tunnel (Olkiluoto) or ramp (Forsmark) to the disposal area and deposition niche by a transport vehicle. The transport vehicle is based on a self- propelled modular transporter, which are widely used all over the world in very large and heavy transportation operations (Kirkkomäki and Rönnqvist 2011).

64 56 Figure 5-7. Reloading station at the disposal depth at Olkiluoto is part of the technical rooms system (Figure by Fortum). After completing the drift a docking flange will be built to act as a drift entrance, see Figure 5-8. A transport shielding tube is docked to the docking flange steering ring (Kirkkomäki and Rönnqvist 2011). Concrete collar Steering ring Adjustment ring Adjustment bracket Figure 5-8. A docking flange between main/central tunnel and the deposition drift. The drift entrance is levelled with a concrete collar (Kirkkomäki and Rönnqvist 2011).

65 57 At the disposal area, the supercontainers are installed from the deposition niche, see Figures 2-1 and 5-9, into the deposition drift with a deposition machine. Installation operation requires a free space length of 23 m or more in front of the deposition drift (Kirkkomäki and Rönnqvist 2011). Deposition niches are situated between central tunnels in Olkiluoto (Figure 5-9) and on either side of a main tunnel in Forsmark (Figure 2-1). The supercontainers are moved with the deposition machine employing water cushion technique on top of a very thin water film with a lift pallet. The force needed to push them forward in the deposition drift is relatively small compared with the weight of the supercontainer. Figure 5-9. Deposition niche, transfer vehicle (with wheels) and deposition machine (yellow) at Olkiluoto (Kirkkomäki and Rönnqvist 2011). The supercontainers cannot be installed into the deposition drifts immediately after the other because of the thermal dimensioning, implying need of bentonite distance blocks between the supercontainers. The distance blocks are installed into the deposition drifts with the deposition machine in a similar manner as for the supercontainers. 5.4 Differences between Posiva and SKB The differences related to site and organization-specific differences in reference methods are following: Deposition niches are situated between central tunnels in Olkiluoto and at either side of a main tunnel in Forsmark; and Canisters are transferred to the deposition niche through the canister shaft and via central tunnel in Olkiluoto and via ramp in Forsmark.

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67 59 6 CONCLUSIONS ON THE INITIAL STATE 6.1 Introduction The initial state of the underground openings refers to the properties and states of the underground openings at the time of final installation of the buffer, closure or plugs. For the assessment of the long-term safety it needs to be confirmed that the underground openings at the initial state conform to the design basis related to the functions in the repository. There may be a time lag between completion of a given deposition drift and when it is actually taken in use. For example, drift geometry and groundwater inflow have possible time-dependent effects like spalling. 6.2 General reference design The reference design for a KBS-3H repository at the Forsmark and Olkiluoto sites has been developed in accordance with the design basis related to the functions of the underground openings in the repository, Table 2-1. The repository facility layouts that are part of the reference design are based on current knowledge of the sites and are adapted to the properties of the sites (by way of the site engineering reports (SER), (SKB 2009a) and (Posiva 2012d). The reference design and its conformity to the design basis are presented in Chapter 4 and is summarized in the following subsections Repository depth and deposition areas The repository depth shall be selected with respect to potential freezing of the buffer, surface erosion and unintentional human intrusion. Deposition areas and depth shall be selected with respect to Rock Suitability Classification (for example hydrogeochemical conditions) and the possibility to find large enough volumes to host the required number of deposition drifts, Table 2-1. The determination of repository depth and the basis for the utilisation of deposition areas is presented in sections 4.1 and 4.2 and are summarized below. The repository depth shall according to SKB be located at elevations ranging between 450 m and 500 m and at a minimum depth 400 m according to Posiva. The current reference design has been established according to these elevation intervals. Thereby the risk for intersecting water bearing fractures without significantly increasing the risk for spalling is reduced. The layout and the utilisation of deposition areas are significantly influenced by the design basis for deposition drifts and supercontainer sections, Table 2-1. The primary design constraints are: - (1) deformations zones requiring a respect distance, - (2) groundwater inflow and

68 60 - (3) thermal properties of the rock mass as well as the approach used in the thermal dimensioning. Tentatively deposition drifts shall not intersect the respect volumes of LDFs (Posiva) (SKB 2012). SKB has not defined a corresponding requirement. The reference design layouts are based on a fixed distance between deposition drifts. The specified minimum centre-to-centre spacing is alternative 30 m or 40 m in Forsmark and 25 m in Olkiluoto (SKB 2012). The minimum distance between deposition drifts (drift spacing) can be determined with respect to the maximum allowed temperature in the buffer, Table 2-1. The thermal conductivity of the different rock domains is the basis for determining the distance between deposition drifts and the associated typical distance between supercontainers in the individual deposition drifts. The justification of the fact that the rock volumes selected for deposition areas in the reference design have favourable chemical conditions for deposition drifts is found in (SKB 2009a and Posiva 2012d). The reference design does not verify favourable chemical conditions in individual deposition drifts Deposition drifts and supercontainer sections With respect to the functions in the repository the deposition drifts and canisters shall be placed so that the potential for shear displacements (large fractures), water inflow and connected transmissivity are limited, Table 2-1. The design basis for supercontainer sections that significantly influence the loss of supercontainer sections are defined in Rock Suitability Classification (for example minor deformation zones or fracturing). The location of structures with potential for shear displacements, i.e. discriminating fractures and deformation zones, cannot be determined deterministically at this stage, Section While it is very likely that some canister positions will be rejected due to discriminating factures, it is unlikely that this will impose a risk on the design basis to accommodate about 6,000 canisters (SKB) and 4,500 canisters (Posiva). Very few additional supercontainer sections will be lost due to high inflows (for criterion, c.f. Table 2-1B) as most of these positions are likely to be screened out by the criterion for discriminating fractures. 6.3 Geometry and properties of importance for the initial state of the engineered barriers The expected geometry and other properties of importance for the reliable installation of the engineered barriers according to specification and the extent of the EDZ will mainly depend on the performance of the methods for excavation (reference methods). The results that were used when determining the initial state of the engineered barriers are based on experiences and results presented in Chapter 5 and are summarized in the following.

69 61 The buffer and supercontainer impose design basis (Tables 2-1, 2-2 and 2-3) for the - straightness, - diameter, - inclination, - waviness, - steps and - roughness of the deposition drifts In addition, the potential for occurrence of EDZ due to the excavation method must also be considered. The results from excavating the deposition drifts (15 m and 95 m long drifts) at the 220 m level at the Äspö HRL (Bäckblom and Lindgren 2005) showed that the boring accuracy is acceptable and that the dimensions of the deposition drifts conforms to the current design basis, Section The horizontal push-reaming method, which is the reference method, creates very little damage to the surrounding rock walls, Section A reasonable value for the hydraulic conductivity of the EDZ, which is limited to a few centimetres in extent, is in the order of m/s (Bäckblom 2008). This magnitude is valid for rock conditions where spalling has not occurred. 6.4 Uncertainty and risk relative to the initial state There are three general categories of uncertainties which may contribute to the risk that the initial state of the underground openings in the repository facility does not conform to the design basis. These uncertainties are related to: 1. site conditions (geohazards); 2. adequacy of design methodologies; and 3. performance of reference methods. The objective here is to assess the risk of nonconformity to the functions, geometry and other properties of importance for the repository. The risk of rejecting underground openings for which the initial state conforms to the design basis is not analysed. Uncertainties and risks will be assessed and reported later in KBS-3H project. The principles that can be used are described for KBS-3V in (SKB 2010b). 6.5 Differences between Posiva and SKB Differences in design basis like in initial state of the underground openings are presented in Section 2.5 and the resulted depth range in Section 4.1 (see also Appendix 2).

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71 63 7 SUMMARY This report is included in a set of KBS-3H specific production reports, presenting how the KBS-3H repository is to be designed, produced and inspected. The set of reports will form the basis for the safety reports for the KBS-3H repository and repository facility. The report also provides input on the initial state of the underground openings for the assessments of the long-term safety. In addition, the report provides input to the operational safety report, on how the underground openings shall be constructed and inspected. The report presents the design basis and the methodology applied to design the underground openings and their adaptation to the site conditions so that they conform to the present design basis. It presents the reference design mainly at Olkiluoto (Finland) and partly for Forsmark (Sweden) and its conformity to the design basis. It also describes the reference methods to be applied to the construction and inspection of the different types of underground openings. Finally, the initial state of the underground openings and its conformity to the present design basis is presented. 7.1 Design basis for the underground openings The design basis for the underground openings is based on applicable regulations; the functions of the KBS-3H repository; the design basis cases from the assessment of the long-term safety; the design basis events from the assessment of the operational safety; technical feasibility of the planned construction. The underground openings shall accommodate the sub-surface part of the KBS-3H repository facility. The underground openings as such do not contribute to the safety of the KBS-3H repository and do not have any barrier functions. However, the locations of the deposition drifts with respect to the geological, thermal, hydrogeological and mechanical properties of the rock are important for the utilisation of the rock as a barrier and thus for the safety of the repository. Furthermore, irreversible changes in the rock surrounding the rock excavation, i.e. the excavation damaged zone (EDZ), and engineered and residual materials that remain in the rock may impair the barrier functions of the near-field rock and/or the engineered barriers. Design basis for the acceptable placement of deposition areas and deposition drifts as well as restrictions on engineered and residual materials are provided from the assessment of the long-term safety. The underground openings shall also be designed to conform to design basis from the engineered barriers and plugs, and to design basis related the development and operation of the repository facility. 7.2 Rock engineering The objectives of rock engineering are to ensure that the site-adapted layout as well as the construction and as-built underground openings, conform to the design basis. Posiva and SKB will apply the so called Observational Method for adapting the layout of the repository and construction of the underground openings to the successively developed understanding and description of the site. The design will always be based on the most

72 64 recent site descriptive model at applicable scale and will consider the most likely ground conditions as well as possible deviations ranging from the most favourable to the worst conceivable conditions. Application of the Observational Method implies that hazards that contribute to the risk for nonconformity to the design basis are identified beforehand, that models predicting the hazard and calculating parameters that will be observed during construction are established, and also that action plans for handling of possible adverse conditions are defined beforehand. At designated milestones, formal comparisons of the predicted design assumptions and the encountered ground conditions are performed and corrective/remediating actions are taken in relation to the defined action plans where required. 7.3 The reference design and its conformity to the design basis KBS-3H is based on horizontal emplacement of several canisters in a series in long deposition drifts (whereas KBS-3V employs vertical emplacement of the canister in individual depositions holes within a deposition tunnel). The KBS-3H reference method is to drill a pilot hole that is reamed to full drift size, with one or more additional intermediate reaming step. The reference method for excavating the deposition drifts are full-face horizontal push-reaming techniques. The spent nuclear fuel is introduced in the deposition drift by way of a supercontainer which consists of an outer perforated protective cylinder (with solid end plates), bentonite buffer blocks and a copper canister. At the disposal area, the supercontainers, distance blocks and filling components are installed from deposition niches into the drifts. The supercontainers are introduced using the deposition machine with water cushion technique on top of a very thin water film with a lift pallet. The reference design is the result of the present completed design step. The site-specific basis for the reference design is geotechnical information compiled in site descriptive models (SDM) and site engineering reports (SER). The information in the SER builds on the surface-based site investigations carried out at the both sites. ONKALO underground investigations at the Olkiluoto site are presented in the site descriptive model. The verification of the conformity of the reference design to the design basis is restricted by uncertainties expressed in the SDM and SER reports. The reference design is presented under the subtitles; - repository depth - deposition area - pilot holes - deposition drifts and supercontainer sections - other underground openings - engineered and residual materials The repository depth is selected to conform with the design basis to find large enough volumes fulfilling the specific requirements on deposition drifts (for example rock stresses) and to avoid freezing of buffer by permafrost during future glaciations and inadvertent human intrusion. The deposition areas and positioning of the deposition drifts shall conform to design basis for favourable and stable thermal, mechanical and hydrogeological conditions. The deposition drifts as well as other tunnels, ramp/access

73 65 tunnel and shafts are designed to conform to design basis regarding limitation of the EDZ. Finally, the amounts of engineered and residual materials in different parts of the underground facilities are estimated and compared with the acceptable amounts. 7.4 Reference methods The reference method for excavating the deposition drifts is full-face boring techniques. Grouting with Mega-Packer will be used for post-grouting the deposition drifts. Experiences from mechanical excavation methods and post-grouting with Mega-Packer show that it is possible to achieve an EDZ and sealing result in conformity with the design basis. Based on experiences from Äspö HRL (the SKB Hard Rock Laboratory) the geometrical variations will lie within the acceptable tolerances, notably the experiences are from 15 and 95 m long drifts at 220 m depth. The reference methods also comprise methods for inspection. The method and criterion applied in selecting deposition drifts and canister positions will be impacted by the conformity to the design basis to avoid shear displacements larger than the canister can withstand and water inflows larger than the buffer can withstand. More detailed criteria for positioning are provided by the forthcoming Rock Suitability Classification adapted for KBS-3H. 7.5 Initial state of the underground openings The initial state of the underground openings refers to the properties of the underground openings at final installation of the buffer, supercontainer, closure and plugs. The presentation of the initial state comprises a summary of the site-adapted designs at Olkiluoto and Forsmark and the properties that can be expected based on the experiences from the reference methods. An assessment of the risk that the initial state of the underground openings does not conform to the design basis will be done later in KBS-3H project.

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75 67 REFERENCES SKB s (Svensk Kärnbränslehantering AB) publications are available at Posiva s publications are available at Anttila P., Autio J., Berghäll J., Börgesson L., Eriksson M., Hagros A., Halvarsson B., Johansson E., Kotola R., Parkkinen I., Rönnqvist P-E, Sandén T., KBS-3H Design Description Posiva Report Posiva Oy. Autio J., Börgesson L., Sandén T., Rönnqvist P.-E., Berghäll J., Kotola R., Parkkinen I., Johansson E., Hagros A., Eriksson M., Design Description Posiva Working Report Posiva Oy. SKB R Svensk Kärnbränslehantering AB. Eriksson M., Lindström L KBS-3H post-grouting. Mega-Packer test at -220 m level at Äspö HRL. SKB R and Posiva Working report Svensk Kärnbränslehantering AB and Posiva Oy. Bäckblom G., Lindgren E., KBS-3H - Excavation of two horizontal drifts at the Äspö Hard Rock Laboratory during year Work description, summary of results, and experience. SKB R Svensk Kärnbränslehantering AB. Bäckblom G, Excavation damage and disturbance in crystalline rock results from experiments and analyses. SKB TR-08-08, Svensk Kärnbränslehantering AB. EN :2004. Eurocode 7. Geotechnical design Part 1: General rules. European Committee for Standardization. Brussels. Hagros, A, Estimated quantities of residual materials in a KBS-3H repository at Olkiluoto. Posiva Working report and SKB R Posiva Oy, Svensk Kärnbränslehantering AB. Kirkkomäki, T. and Rönnqvist, P-E., KBS-3H Technology, layout and Stepwise implementation. Posiva Working Report (in Finnish), Posiva Oy. Lönnqvist M, Hökmark H, Thermo-Mechanical Analyses of a KBS-3H Deposition Drift at Olkiluoto Site. Posiva Working Report Lönnqvist, M., Hökmark, H., Assessment of Thermally Induced Spalling at Forsmark. Draft version April 2009, Svensk Kärnbränslehantering AB. McEwen T., Aro S., Kosunen P., Mattila J., Pere T., Käpyaho A., Hellä P. Rock Suitability Classification RSC Eurajoki, Finland. Posiva Oy. Posiva Report (ISBN ) Munier R, Using observations in deposition tunnels to avoid intersections with critical fractures in deposition holes. SKB R-06-54, Svensk Kärnbränslehantering AB.

76 68 Munier R, Demonstrating the efficiency of the EFPC criterion by means of sensitivity analyses. SKB R , Svensk Kärnbränslehantering AB. Munier R, Full perimeter intersection criteria. Definitions and implementations in SR-Site. SKB TR-10-21, Svensk Kärnbränslehantering AB. Peck R B, Advantages and limitations of the observational method in applied soil mechanics. Geotechnique, 19, pp Pere, T., Mattila, J., Wikström, L., Aro, S., Vaittinen, T. and Ahokas, H Layout determining features, their influence zones and respect distances at the Olkiluoto site. Posiva report Posiva Oy. ISBN Posiva, Olkiluoto Site Description Posiva report , Posiva Oy. ISBN Posiva, 2012a. Design, production and initial state of the underground disposal facility closure. Posiva report , Posiva Oy. ISBN Posiva, 2012b. Underground Openings Production Line Design, production and initial state of the underground openings. Posiva report , Posiva Oy. ISBN Posiva, 2012c. Safety Case for the disposal of spent nuclear fuel at Olkiluoto - Design basis Posiva report , ISBN Posiva Oy. Posiva, 2012d. Site Engineering report. Posiva report , Posiva Oy. ISBN Posiva 2012e. Description of KBS-3H design variant. Eurajoki, Finland: Posiva Oy. POSIVA p. ISBN Posiva 2012f. Monitoring at Olkiluoto - a Programme for the Period Before Repository Operation. Eurajoki, Finland. Posiva Report Posiva, 2012g. Design Basis report, DB Eurajoki, Finland. Posiva Oy. POSIVA Report Posiva YJH-2012 Nuclear waste management at Olkiluoto and Loviisa power plants: Review of current status and future plans for Eurajoki, Finland: Posiva Oy. YJH p. Posiva, 2016a. Safety Evaluation for a KBS-3H spent nuclear fuel repository at Olkiluoto Design Basis, Posiva Report , Posiva Oy. Posiva 2016b. Safety Evaluation for a KBS-3H spent nuclear fuel repository at Olkiluoto Performance Assessment, Posiva Report , Posiva Oy

77 69 Posiva 2016c. Design and production of the KBS-3H repository. Posiva Report , Posiva Oy. Posiva 2016d. KBS-3H Design, production and initial state of the supercontainer, Posiva Report , Posiva Oy. Saanio, T., Kirkkomäki, T., Keto, P., Kukkola, T., and Raiko, R., Preliminary design of the repository, stage 2. Posiva Working Report Posiva Oy. SKB, Site description of Forsmark at completion of the site investigation phase. SDM-Site Forsmark. SKB TR-08-05, Svensk Kärnbränslehantering AB. SKB, 2009a. Site engineering report Forsmark. Guidelines for underground design. Step D2. SKB R-08-83, Svensk Kärnbränslehantering AB. SKB, 2009b. Underground design Forsmark. Layout D2. SKB R , Svensk Kärnbränslehantering AB. SKB, 2010a. Design, production and initial state of the closure. SKB TR-10-17, Svensk Kärnbränslehantering AB. SKB, 2010b. Design, construction and initial state of the underground openings. SKB TR 10-18, Svensk Kärnbränslehantering AB. SKB, Long term safety for the final repository for spent nuclear fuel at Forsmark. Main report of the SR-Site project. VOL 1-3. SKB TR 11-01, Svensk Kärnbränslehantering AB. SKB KBS-3H Complementary studies Stockholm, Sweden: Swedish Nuclear Fuel and Waste Management Co. (SKB). Technical Report TR p. ISSN (Also published as POSIVA ) STUK Posiva Oy:n selvitykset kapselointilaitoksen ja ONKALOn maanpintayhteyksien vaihtoehdoista. (Posiva Oy clarifications on alternatives for encapsulation plant and access routes for ONKALO.) Y811/37, , Finnish Radiation and Nuclear Safety Authority, Helsinki. In Finnish.

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79 71 Memo Writer: Timo Kirkkomäki (Fortum Number: POS Power and Heat Oy) Organisation: Development Version: 1 Written: Page(s) 0 (14) Issued: Information of the document Headline: KBS-3H Disposal Facility Layout 2013 Written by / Date: Timo Kirkkomäki (Fortum Power and Heat Oy) / Checked by / Date: Palomäki Jaana / Approved by / Date: Vuorio Petteri / Issued Dated document number: Organization Development Project - Distribution: Printed out of an electronic original: / OlkiRendSrv Please, check the validity of the document Posiva Oy Approved by: Vuorio Petteri /

80 72 Memo Writer: Timo Kirkkomäki (Fortum Number: POS Power and Heat Oy) Organisation: Development Version: 1 Written: Page(s) 1 (14) Issued: KBS-3H DISPOSAL FACILITY LAYOUT Introduction This memorandum describes the changes made in 2013 to the layout of the KBS-3H variant for the repository. The memorandum was drafted based on an assignment by Petteri Vuorio / Posiva Oy. The previous layout for the KBS-3H alternative in the Olkiluoto bedrock was completed at the end of 2010 (Kirkkomäki & Rönnqvist 2010) (Figure 1-1). After this, the quantity of spent nuclear fuel to be deposited has increased due to the addition of the spent nuclear fuel from OL4, the layout direction of the deposition drifts has been changed, and the geological model has been updated. The layout proposals presented in this memorandum have been created with 3D design. Figure 1-1. Underground repository according to the 2010 plan at the disposal depth (Kirkkomäki & Rönnqvist 2010). The direction of deposition drifts at 90/270 degrees. Printed out of an electronic original: / OlkiRendSrv Please, check the validity of the document Posiva Oy Approved by: Vuorio Petteri /

81 73 Memo Writer: Timo Kirkkomäki (Fortum Number: POS Power and Heat Oy) Organisation: Development Version: 1 Written: Page(s) 2 (14) Issued: Initial data 2.1 Quantities of spent nuclear fuel, canisters and canister positions 2.2 Layout direction The total accumulation of spent nuclear fuel from the Olkiluoto and Loviisa power plants estimated in 2011 is 5,440 tu (Saanio et al. 2012). This quantity is distributed into disposal canisters so that there will be 1,170 OL1/2 canisters, 646 LO1/2 canisters and 954 OL3 canisters. The total number of disposal canisters is 2,770. According to the decisions-in-principle received by Posiva, the maximum quantity of spent nuclear fuel to be deposited can be 9,000 tu (Saanio et al. 2012). The corresponding number of disposal canisters is 4,500. Of these, 1,400 are OL1/2 canisters, 750 LO1/2 canisters, and 2,350 in total are OL3 and OL4 canisters. Separate layout alternatives have been created for both amounts of canisters. When preparing the alternatives, it has been assumed that due to currently unknown fractured zones in the disposal area or due to deposition drifts potentially failing during drilling, 20 % more canister positions at the specified minimum canister spacings will be needed in proportion to the number of disposal canisters. The margin to be used is based on estimates on the utilisation degree of the Olkiluoto bedrock made on the basis of results from Rock Suitability Classification (RSC) work (Posiva 2012c). As mentioned, layout proposals for the repository will be created for both 3,324 and 5,400 canister positions. In the 2010 layout, the direction of the deposition drifts was east and west (90 /270 ) (Kirkkomäki & Rönnqvist 2010). The latest research information obtained on the Olkiluoto bedrock and the model based on it (Posiva 2012a and 2012b) have been used as the basis for this work. The direction of the principal stress in the rock at the disposal level is 112 degrees, i.e. approximately east-west (stress state model 1), or 144 degrees, i.e. approximately south-east to north-west (stress state model 2) (Posiva 2012b). However, these directions are not necessarily optimal for the repository facilities, because the direction of bedrock fractures may also affect the stability of rock spaces. The final layout direction of the facilities will be optimized during the construction of the facilities as the amount and quality of data increases. In this memorandum, the layout direction of the deposition drifts has been chosen as 126 degrees, which is the same as in the plan for the KBS-3V variant (Kirkkomäki 2012). This means that the direction chosen is nearly mid-way between the principal stress directions of the above-mentioned stress state models. Printed out of an electronic original: / OlkiRendSrv Please, check the validity of the document Posiva Oy Approved by: Vuorio Petteri /

82 74 Memo Writer: Timo Kirkkomäki (Fortum Number: POS Power and Heat Oy) Organisation: Development Version: 1 Written: Page(s) 3 (14) Issued: Disposal area Layout-determining features (LDFs) and their respect areas at the disposal level of m are shown in Figure 2-1. The combined ranges of zones HZ21, HZ21B, BFZ021, HZ099 and BFZ099, zones BFZ020A, BFZ020B, HZ20A and HZ20B, and zones BFZ146 and HZ146 are referred to as zones R21, R20 and R146 in this memorandum. The ONKALO facilities are located between zones R21 and R20 (Figure 2-2). The primary disposal area is located between zones R20 and R21. East of this lies the other, eastern disposal area. It is delimited by zones R20 and R146. The layout of the disposal facilities is also restricted by the border of the planning area, boreholes and the shoreline. Disposal facilities will not be located under the sea. A safety zone of 10 metres will be left for the boreholes, and another margin of 1.25 % of the borehole length will be added to this for the inaccuracy of the borehole location information. A land use plan is in force at the area under Posiva's management on the island of Olkiluoto which only allows disposal in the planning area (Figure 2-2). However, it can be assumed that this area can be extended during future decades to the west and south-west of the ONKALO facilities so that disposal facilities can be located between zones R20 and R21 and zones R20 and R146 up to the shoreline. For this reason, this memorandum presents layout alternatives for the spent nuclear fuel quantities of both tu and tu, considering the current planning area and assuming that it will be extended in the future. Printed out of an electronic original: / OlkiRendSrv Please, check the validity of the document Posiva Oy Approved by: Vuorio Petteri /

83 75 Memo Writer: Timo Kirkkomäki (Fortum Number: POS Power and Heat Oy) Organisation: Development Version: 1 Written: Page(s) 4 (14) Issued: Figure 2-1. The Layout Determining Features at Olkiluoto. The respect volumes cover all LDF zones (Posiva 2012a). Figure 2-2. Hydrogeological and brittle fault zones of the Olkiluoto bedrock with the related respect volumes, the border of the planning area, boreholes and the shoreline restricting the layout of the disposal facilities. The location of ONKALO has been marked in green. Printed out of an electronic original: / OlkiRendSrv Please, check the validity of the document Posiva Oy Approved by: Vuorio Petteri /

84 76 Memo Writer: Timo Kirkkomäki (Fortum Number: POS Power and Heat Oy) Organisation: Development Version: 1 Written: Page(s) 5 (14) Issued: Deposition and safety distances In the KBS-3H variant, disposal canisters are installed in drifts with a maximum length of 300 metres, which are approximately 2 degrees upward-drilled, nearly horizontal. The drifts have a diameter of approximately 1.85 m. The minimum drift spacing measured from centre to centre is 25 m. Disposal canisters are installed in the drifts inside Supercontainers. The minimum canister spacing is 7.2 m for LO1/2 canisters, 9.0 m for OL1/2 canisters and 10.6 m for OL3 and OL4 canisters. The distance between the central tunnel and the closest canister is assumed to be the same as in KBS-3V i.e m in this document. In fact this distance can be shorter in 3H. The current estimate of the distance needed between the central tunnel and the centre of the closest canister is about 27 m. This is based on rock mechanics calculation according to which the drift plug can be placed at a distance of times the diameter of the central tunnel. An additional space for a 0.5 m thick bentonite slice of distance block type is added between the drift face and the adjacent distance block. In a deposition drift, the length of one compartment can be at most 150 m (Kirkkomäki & Rönnqvist 2010). As a result, if the total length of a deposition hole is more than m, it is assumed that a 24-metre-long space is left in the drift for the compartment plug and the transition zones on both sides of the plug. The disposal canisters are installed in the deposition drift inside a Supercontainer. For the installation of the canister, there is a deposition niche in front of the drift opening between the two parallel central tunnels. The width of the deposition niche shall be at least 10 m and the length approximately 26 m. The angle between the drift and the central tunnel shall be at least 75 degrees (Kirkkomäki 2010). The safety distance between the deposition drifts and parallel central tunnels has been assumed to be 50 metres. Similarly, a safety distance of 50 metres will be left between the disposal facilities and the technical facilities and the vehicle access tunnel. No disposal facilities will be located directly under the vehicle access tunnel. 3 Layout 3.1 Alternative 1 Figure 3-1 shows a layout proposal for an underground repository for a spent nuclear fuel quantity of 5,440 tu. The layout assumes that the current planning area can be extended in the future to the west and south-west of the ONKALO facilities between zones R20 and R21 all the way to the shoreline. Printed out of an electronic original: / OlkiRendSrv Please, check the validity of the document Posiva Oy Approved by: Vuorio Petteri /

85 77 Memo Writer: Timo Kirkkomäki (Fortum Number: POS Power and Heat Oy) Organisation: Development Version: 1 Written: Page(s) 6 (14) Issued: The reach of the facilities in the east-west direction is approximately 2.2 km, and in the north-south direction approximately 1.5 km. The facilities are located entirely within the primary disposal area between zones R20 and R21. There are a total of 141 deposition drifts. Their total length is 37.6 km. The average length of a deposition drift is 267 m. There are altogether 80 drifts of the maximum length (300 m). There are 14 deposition drifts less than m in length, which will not include a compartment plug. Figure 3-1. Underground repository for a spent nuclear fuel quantity of 5,440 tu positioned in the Olkiluoto bedrock. There are altogether 90 deposition niches. Of these, 39 are for one drift only. The other 51 can be used to deposit canisters in two opposite drifts. The total length of all deposition niches is approximately 1.8 km. The total length of the central tunnels without the deposition niches is 7.4 km. The total volume of the underground repository is approximately 1.0 million m 3 (Table 3-1). The central tunnels comprise 43 % of the total volume and the deposition niches 7 %. The volume of deposition drifts is approximately 101,000 m 3, which is 10 % of the total volume. Printed out of an electronic original: / OlkiRendSrv Please, check the validity of the document Posiva Oy Approved by: Vuorio Petteri /

86 78 Memo Writer: Timo Kirkkomäki (Fortum Number: POS Power and Heat Oy) Organisation: Development Version: 1 Written: Page(s) 7 (14) Issued: Table 3-1. Volumes of the underground repository. Spent nuclear fuel quantity 5,440 tu. Facility Volume (m 3 ) % Vehicle access tunnel and shaft connections 193,000 19% Shafts 29,000 3% Technical facilities 152,000 15% Disposal facility for low- and intermediate-level waste 25,000 2% Central tunnels, total length 7,360 m 432,000 43% Deposition niches, 90 in total / 1,790 m 71,000 7% Deposition drifts, total length 37,590 m 101,000 10% Total 1,003, % 3.2 Alternative 2 Figure 3-2 shows a layout proposal for an underground repository for a spent nuclear fuel quantity of 9,000 tu. The layout assumes that the current planning area can be extended in the future to the west and south-west of the ONKALO facilities between zones R20 and R21 as well as zones R20 and R146 all the way to the shoreline. The reach of the facilities in the east-west direction is approximately 2.5 km and in the north-south direction approximately 1.8 km. The primary disposal area between zones R20 and R21 has been used completely in the layout. In addition, facilities have been positioned to the east of zone R20. There are a total of 233 deposition drifts. Their total length is 63.2 km. The average length of a deposition drift is 271 m. There are altogether 125 drifts of the maximum length (300 m). There are 20 deposition drifts less than m in length, which will not include a compartment plug. There are altogether 144 deposition niches. Of these, 55 are for one drift only. The other 89 can be used to deposit canisters in two opposite drifts. The total length of all deposition niches is approximately 2.9 km. The total length of the central tunnels without the deposition niches is 11.4 km. The total volume of the underground repository is approximately 1.35 million m 3 (Table 3-2). The central tunnels comprise 49 % of the total volume and the deposition niches 8 %. The volume of deposition drifts is approximately 170,000 m 3, which is 13 % of the total volume. Printed out of an electronic original: / OlkiRendSrv Please, check the validity of the document Posiva Oy Approved by: Vuorio Petteri /

87 79 Memo Writer: Timo Kirkkomäki (Fortum Number: POS Power and Heat Oy) Organisation: Development Version: 1 Written: Page(s) 8 (14) Issued: Figure 3-2. Underground repository for a spent nuclear spent nuclear fuel quantity of 9,000 tu positioned in the Olkiluoto bedrock. Table 3-2. Volumes of the underground repository. Spent nuclear fuel quantity 9,000 tu. Facility Volume (m 3 ) % Vehicle access tunnel and shaft connections 193,000 14% Shafts 29,000 2% Technical facilities 152,000 11% Disposal facility for low- and intermediate-level waste 25,000 2% Central tunnels, total length 11,420 m 668,000 49% Deposition niches, 144 in total / 2, ,000 8% Deposition drifts, total length 63,170 m 170,000 13% Total 1,351, % Printed out of an electronic original: / OlkiRendSrv Please, check the validity of the document Posiva Oy Approved by: Vuorio Petteri /

88 80 Memo Writer: Timo Kirkkomäki (Fortum Number: POS Power and Heat Oy) Organisation: Development Version: 1 Written: Page(s) 9 (14) Issued: Alternative 3 Figure 3-3 shows a layout proposal for an underground repository for a spent nuclear fuel quantity of 5,440 tu considering the current planning area. Facilities have not been positioned to the west and south-west of ONKALO all the way to the shoreline. The reach of the facilities in the east-west direction is slightly less than 1.8 km, and in the north-south direction slightly more than 1.8 km. The primary disposal area between zones R20 and R21 has been used completely in the facility layout up to the border of the planning area. In addition, facilities have been positioned to the east of zone R20. There are a total of 143 deposition drifts. Their total length is 37.8 km. The average length of a deposition drift is 265 m. There are altogether 69 drifts of the maximum length (300 m). There are 17 deposition drifts less than m in length, which will not include a compartment plug. There are altogether 93 canister deposition niches. Of these, 43 are for one drift only. The other 50 can be used to deposit canisters in two opposite drifts. The total length of all deposition niches is approximately 1.9 km. The total length of the central tunnels without the deposition niches is 8.8 km. Figure 3-3. Underground repository for a spent nuclear fuel quantity of 5,440 tu positioned in the Olkiluoto bedrock in the current planning area. Printed out of an electronic original: / OlkiRendSrv Please, check the validity of the document Posiva Oy Approved by: Vuorio Petteri /

89 81 Memo Writer: Timo Kirkkomäki (Fortum Number: POS Power and Heat Oy) Organisation: Development Version: 1 Written: Page(s) 10 (14) Issued: The total volume of the underground repository is approximately 1.1 million m 3 (Table 3-2). The central tunnels comprise 47 % of the total volume and the deposition niches7 %. The volume of deposition drifts is approximately 108,000 m 3, which is 10 % of the total volume. Table 3-3. Volumes of the underground repository. Spent nuclear fuel quantity 5,440 tu. The facilities have been positioned within the current planning area. Facility Volume (m 3 ) % Vehicle access tunnel and shaft connections 193,000 17% Shafts 29,000 3% Technical facilities 152,000 14% Disposal facility for low- and intermediate-level waste 25,000 2% Central tunnels, total length 8,790 m 521,000 47% Deposition niches, 93 in total / 1,890 m 77,000 7% Deposition drifts, total length 37,890 m 108,000 10% Total 1,105, % 3.4 Alternative 4 Figure 3-4 shows a layout proposal for an underground repository for a spent nuclear fuel quantity of 9,000 tu considering the current planning area. Facilities have not been positioned to the west and south-west of ONKALO all the way to the shoreline. The reach of the facilities in the east-west direction is approximately 2.6 km and in the north-south direction approximately 1.8 km. The primary disposal area between zones R20 and R21 has been used completely in the facility layout up to the border of the planning area. In addition, the area between zones R20 and R146 has been utilised in full. There are a total of 237 deposition drifts. Their total length is 60.7 km. The average length of a deposition drift is 256 m. There are altogether 92 drifts of the maximum length (300 m). There are 31 deposition drifts less than m in length, which will not include a compartment plug. Section 2.1 (Spent nuclear fuel quantity) of this memorandum states that the disposal facilities will be designed with minimum canister spacings so that there will be 20 % more canister positions than there are disposal canisters. This means that with a spent nuclear fuel quantity of 9,000 tu for disposal, the layout should include 5,400 canister positions. This layout only includes 5,027 canister positions, which is approximately Printed out of an electronic original: / OlkiRendSrv Please, check the validity of the document Posiva Oy Approved by: Vuorio Petteri /

90 82 Memo Writer: Timo Kirkkomäki (Fortum Number: POS Power and Heat Oy) Organisation: Development Version: 1 Written: Page(s) 11 (14) Issued: % more than the actual number of canisters (4,500). No more canister positions would fit in the space available. There are altogether 146 deposition niches. Of these, 55 are for one drift only. The other 91 can be used to deposit canisters in two opposite drifts. The total length of all deposition niches is approximately 3.0 km. The total length of the central tunnels without the deposition niches is 12.8 km. The total volume of the underground repository is approximately 1.4 million m 3 (Table 3-2). The central tunnels comprise 52 % of the total volume and the deposition niches 8 %. The volume of deposition holes is approximately 165,000 m 3, which is 12 % of the total volume. Figure 3-4. Underground repository for a spent nuclear fuel quantity of 9,000 tu positioned in the Olkiluoto bedrock in the current planning area. Printed out of an electronic original: / OlkiRendSrv Please, check the validity of the document Posiva Oy Approved by: Vuorio Petteri /

91 83 Memo Writer: Timo Kirkkomäki (Fortum Number: POS Power and Heat Oy) Organisation: Development Version: 1 Written: Page(s) 12 (14) Issued: Table 3-4. Volumes of the underground repository. Spent nuclear fuel quantity 9,000 tu. The facilities have been positioned within the current planning area. Facility Volume (m 3 ) % Vehicle access tunnel and shaft connections 193,000 14% Shafts 29,000 2% Technical facilities 152,000 11% Disposal facility for low- and intermediate-level waste 25,000 2% Central tunnels, total length 12,790 m 738,500 52% Deposition niches, 146 in total / 2,990 m 117,000 8% Deposition drifts, total length 60,670 m 164,500 12% Total 1,419, % 4 Stepwise implementation The rate of disposal will vary between 26 and 56 canisters a year during the operating phase. Considering the overall number of canisters, the annual need for deposition drifts is relatively small. As a result, there is no need to construct the complete underground repository in one go. It is more convenient to construct the facilities in stages according to need. Among other things, this enables the construction cost of the facilities to be distributed over a longer period of time. Figure 4-1 presents the construction of the underground repository planned for a spent nuclear fuel quantity of 9,000 tu, described in Section 3.2 of the previous chapter, divided into ten separate stages. The first stage is the construction phase of ONKALO. It is followed by an excavation stage preparing for the final disposal and eight excavation stages during the operating phase. a) b) Printed out of an electronic original: / OlkiRendSrv Please, check the validity of the document Posiva Oy Approved by: Vuorio Petteri /

92 84 Memo Writer: Timo Kirkkomäki (Fortum Number: POS Power and Heat Oy) Organisation: Development Version: 1 Written: Page(s) 13 (14) Issued: c) d) e) f) g) h) i) j) Figure 4-1. Construction stages for the underground repository, a) ONKALO, b) excavation stage preparing for the final disposal and c) j) excavation stages 1-8. Printed out of an electronic original: / OlkiRendSrv Please, check the validity of the document Posiva Oy Approved by: Vuorio Petteri /