[en] As part of the Swiss high-level radioactive waste disposal programme, the Opalinus Clay, a 95 - 120 m thick Middle Jurassic shale (clay stone) formation is investigated with potential siting areas in Northern Switzerland. Observations in clay pits, and the results of a German research programme focusing on hazardous waste disposal aspects, have demonstrated that the near-surface Opalinus Clay is rather permeable. Hydraulic tests in deeper boreholes, yielded very low hydraulic conductivities (< 10^-12 m/s) even though joints and faults were included in some of the test intervals. These measurements are consistent with hydrogeological information from Opalinus Clay sections of six railway tunnels and four motorway tunnels in the Folded Jura of Northern Switzerland. The hydrogeological dataset presented suggests that radionuclide transport through faults and joints is probably not a critical issue for assessing the suitability of Opalinus Clay as a host rock for a deep geological repository for nuclear waste. (author)

[en] This dossier is the first of a series of eight reports concerning the safety and technical aspects of locations for the disposal of radioactive wastes in Switzerland. It presents an introduction to and a summary of the further seven dossiers on basic geological conditions. Dossier II considers the sediments that can be used along with tectonic considerations, Dossier III takes a look at long-term geological developments and Dossier IV considers the geo-mechanical documentation available. Dossier V looks at hydro-geological considerations. Dossier VI reports on the barrier properties of the proposed host rock sediments and neighbouring rock layers. Dossiers VII takes a look at usage conflicts and Dossier VIII considers the possibilities for the characterisation of the substrates and for the ways in which they can be explored

[en] This paper provides an overview of the geo-scientific basis and the main conclusions concerning the safety case for Project Entsorgungsnachweis (Nagra, 2002a, see first paper). The key geo-scientific input for the safety case is summarised in the following three papers. The data and arguments are discussed in great detail in Nagra (2002b) and in numerous reference reports cited therein. (author)

[en] This article reviews the situation in Switzerland regarding the disposal of radioactive wastes. The development of the Swiss concept for wastes with high, medium and low levels of activity is reviewed, as detailed in the Sectorial Plan for Deep Geological Repositories published in 2008. The three stages involved are described in detail. Further investigations carried out in the Grimsel and Mont Terri underground laboratories are reported on. The state of current work is reviewed. A map is provided of the areas in northern Switzerland which have been selected for further, more intensive research, along with a review of the possible rock formations to be investigated. Data already obtained are reviewed and proposals for further investigations are discussed. In the upcoming stage 3 of the plan, the selection of one site per repository type will be made, leading to the submission of a general licence application

[en] In performance assessment, a sequence of models and supporting submodels is generally used to describe radionuclide release and transport. One important aspect is the quantification of advective groundwater flow using hydrodynamic models. Quantification of groundwater flow involves numerical modelling at various scales, typically at a regional, a local (repository environment) and a block (cavern/emplacement tunnel) scale. (author)

[en] The objectives and rationale behind the design of field tracer tests depend strongly on the type of rock but also on the type of site and on the state of advancement of the waste disposal research programme. Here the objectives and rationale of field tracer tests for two different clays, types of site and different project stages are discussed. Tests have been performed in the Boom Clay at Mol, Belgium and tests planned to be performed in the Opalinus Clay in north-west Switzerland within the framework of the international Mt. Terri Project. (author)

[en] Nagra has completed a study of the feasibility of disposal of spent fuel (SF), HLW and long-lived ILW, based on a concept for a repository at a depth of about 650 m in Opalinus Clay in Northern Switzerland (Nagra 2002). The host rock formation is a Jurassic clay-stone with exceptional isolation properties, including its very low permeability (< 10^-13 m/s) and the absence of water-conducting features. The design concept for the repository is based on emplacement of steel canisters of SF/HLW in small diameter (2.5 m) horizontal tunnels, with bentonite backfill surrounding the canisters (see Figure 1.). An important aspect of the design process is the assessment of thermal considerations for the performance of the various disposal system components, in particular for the bentonite and host rock. The objective of this paper is to examine how thermal considerations affect. repository and EBS design, including what the thermal criteria are and how their appropriateness is evaluated. An important theme is how to approach the design and assessment of the system, given the inevitable uncertainties in evaluating the details of thermal-hydraulic-mechanical-chemical (THMC) processes that are strongly coupled in the early stages after waste emplacement. The methodology used to evaluate thermal aspects of repository design is discussed Section 3. Before outlining this methodology, it is necessary to discuss some of the design constraints and requirements that represent the starting point for the repository design process, focusing in particular on thermal factors. (authors)

[en] There has been recent interest in the shale gas potential of the Opalinus Clay and Posidonia Shale (Middle and Lower Jurassic) below the Swiss Molasse Basin in the light of the future role of domestic gas production within the expected future energy shift of Switzerland and possible conflicts in underground use. The Opalinus Clay of northern Switzerland is a potential host rock for repositories of both high-level and low-to-intermediate level radioactive waste and the exploitation of shale gas resources within or below this formation would represent a serious conflict of use. Well data from northern Switzerland shows that these two formations are unsuitable for future shale gas recovery. They never reached the gas window during their burial history (maturity values are ≤ 0.6% R_o) and as a consequence never generated significant quantities of thermogenic gas. Geochemical data further shows that the average TOC values are in the range of 0.7%, i.e. clearly below accepted values of more than 1.5% for prospective shales. A review of available exploration data for the Opalinus Clay and Posidonia Shale in the deeper and western part of the Swiss Molasse Basin indicate that their shale gas potential may be substantial. The gross Posidonia Shale thickness increases from central Switzerland from less than 10 m to over 100 m in the Yverdon-Geneva area and is characterised by numerous bituminous intervals. A simplified shale gas resource calculation results for a geologically likely scenario in a technically recoverable gas volume of ∼120 billions m³. The current database for such estimates is small and as a consequence, the uncertainties are large. However, these first encouraging results support a more detailed exploration phase with specific geochemical and petrophysical analysis of existing rock and well log data. (authors)

[en] The synthesis of the geological investigations carried out to date as part of the 'Kristallin' programme has indicated that potentially suitable crystalline rock at an appropriate depth can be found in two regions of Northern Switzerland. The most promising siting options are in Canton Aargau, in a strip of land a few kilometers wide to the south of the Rhine river (Area West: Kaisten-Leuggern-Boettstein). A second-priority option is in Canton Schaffhausen (Area East: Siblingen). For the next phase of investigations into the possibility of locating a repository for high-level and long-lived intermediate-level waste in a crystalline formation, it is planned to carry out a 3D seismic survey in the Boettstein-Leuggern region and to drill an array of inclined boreholes at the former deep borehole site at Leuggern (or Boettstein). These two boreholes have already revealed the presence of large sections of low-permeability crystalline basement. (author) 12 figs

[en] Spatial variability of features and parameters relevant for contaminant transport modelling occurs on all scales of interest for the quantification of processes that govern solute migration, typically decimeters to hundreds of meters. Two types of spatial variability are distinguished, namely the internal heterogeneity of each individual water-conducting feature (e.g. the complex architecture of a fault) and the larger-scale heterogeneity that results from the groundwater flow through different types of water-conducting features along the flow-path from the repository to the discharge areas. An up-scaling procedure is required to obtain hydraulic parameters and the properties of the overall flow-path, whereas the heterogeneity of many other geologic features (geometry of flow and matrix porosity, mineralogy, etc.) can be fed directly into coupled codes that quantify radionuclide transport. The procedures needed to derive conceptual models integrating geological and hydraulic field measurements and observations at a given site are illustrated by examples from both crystalline and sedimentary rock formations. (author)