[en] In this contribution, we present the general concept, technical layout, and expected scientific impact of the DR-D experiment, as well as first results from field and related laboratory studies

[en] The time-dependent "2"4"2Pu oxidation state distribution in the presence of Sporomusa sp. cells as a function of pH with or without Na-pyruvate was analyzed. In all cases, the presence of bacterial cells enhanced removal of Pu from solution and accelerated Pu interaction reactions, e.g. biosorption and bioreduction.

[en] Sporomusa sp. MT-2.99 cells displayed a strong pH dependent affinity for Pu. Relatively high maximal Pu loadings as for instance 230 mgPu/g_d_r_y _b_i_o_m_a_s_s for Sporomusa sp. at pH 6.1 were achieved. A much slower abiotic reduction of Pu(VI) was observed at pH 4 compared to pH 6.1. Independent on pH an enrichment of Pu(V) in the supernatant and of Pu(IV)- polymers on the biomass was discovered.

[en] The effects of weathering and decompaction on the Opalinus Clay in northern Switzerland were studied on the basis of a 146 m long drill core profile. Below 6 m of Quaternary sediments, the rock down to 16 m depth is affected by partial or complete dissolution of siderite, calcite, pyrite and organic matter, with goethite as the only identified product. The reduction level of Fe (Fe²⁺/Fe_tot) in the rock increases with depth from 80% in unweathered rock below 24 m. Porosity reaches 0.39 in the shallowest samples before dropping to normal values of around 0.13 below 30 m. Pore-water composition obtained by rock squeezing evolves with depth from fresh water of the Ca-SO₄-HCO₃ type to a 10-12 g/L Na-SO₄-Cl type in unweathered rock below 40 m. Ground-water samples taken in the weathered zone indicate reducing conditions at present and therefore reflect a remaining redox buffering capacity even in the strongly oxidised rock. The interpretation of the rock properties, in conjunction with the chemical and isotopic signatures of ground and pore waters, suggests that substantial weathering occurred primarily during stages with a lower ground-water table in the Pleistocene, providing access to oxygen via gas diffusion across the partially unsaturated zone. Three evolutionary stages can be distinguished: 1) Long-term pyrite oxidation during Pleistocene surface exposure under dry climate and diffusive transport of SO₄^2- into the formation. This explains the higher SO₄^2- pore-water concentrations even in the unweathered rock at depth when compared to regional data from deep boreholes. 2) Build-up of the curved Cl^- and water-isotope diffusion profiles since ∼50-60 ka with a depth penetration of 40-80 m. 3) Holocene rise of the water table, leading to self sealing of fractures and the establishment of a diffusive regime in the weathered zone. Under saturated conditions, the depth penetration of rock oxidation is quite limited, which illustrates the substantial buffering capacity of the Opalinus Clay against external geochemical disturbances. (authors)

[en] In the context of studies on deep geological disposal of radioactive waste, the overpressures whose origin is still debated raise the question of the relevant transport processes to be taken into account in clay media. An anomaly of about 13 bars was identified during the Deep Borehole (DB) experiment at the Mont Terri URL (Switzerland) whose objective was to identify the impact of hydraulic and chemical transient behavior on fluid and solute transfers. The first stage of DB experiment consisted in drilling BDB-1, a 250 m long-inclined borehole across the entire Opalinus Clay (OPA). The second stage of the work aimed at determining the driving forces (pressure, temperature, and salinity gradients) and transport coefficients (diffusion, hydraulic conductivity, chemical and thermal osmotic coefficients) using a multi-packer hydraulic system. The last step of this fully experimental and modelling integrated study was the development of 1D transport models either in fully transient or in pseudo steady state to reproduce the measured pressure and salinity profiles. Pure hydraulic calculations evaluated a Darcy velocity in the order of 10^-14 m s^-1, related to a downward flow. However the best agreement with the data was obtained by introducing osmotic processes. Chemical osmosis slightly increased the advective flow in the same direction, but its effect is minor compared to that of thermo-osmosis which inverts the water movement with a mean Darcy velocity of about 10 ^-13 m s^-1. However, the Peclet number still confirmed the dominance of diffusion with respect to advection at Mont Terri. (authors)

[en] Document available in extended abstract form only. Three different boreholes in the Opalinus Clay formation of the Mont Terri Underground Rock Laboratory (URL Mont Terri) have been investigated in a research project conducted by the Clausthal University of Technology (TUC) in co-operation with the National Cooperative for the Disposal of Radioactive Waste (NAGRA) and the Swiss Federal Institute of Technology Zurich (ETHZ). Aim of the project was to gain a large amount of high quality and significant information that can be used to increase knowledge about and improve understanding of time-dependent load-bearing and deformation behaviour of Opalinus Clay. For this purpose an axial borehole camera and a three-arm calliper have been used. While two of the investigated boreholes (BMB 35, BMB 36) were drilled sub-horizontally with an identical orientation, the longitudinal axis of the third borehole (BRC 3) is dipping into the gallery floor by an angle of 60 degrees. The sub-horizontal boreholes have a length of 10 metres while the third borehole is 25 metres long. The borehole BRC 3 and the sub-horizontal borehole BMB 36 are located in the shaly facies of the URL Mont Terri while the sub-horizontal borehole BMB 35 is located in the sandy facies of the URL Mont Terri. A lot of high quality information on the load-bearing and deformation behaviour of the investigated boreholes was generated by the measurement and monitoring techniques used in the project. Differences regarding load-bearing and deformation behaviour which are very likely due to the different orientation and the different facies the boreholes are located in could be detected during the investigations. The presentation includes a discussion of the results measured by the logging tool as well as the discussion of the borehole-videos that were recorded by the axial borehole camera. A part of the presentation also refers to the comparison of the two different types of information and how they can be correlated. As an example for the information gained with the axial borehole camera the time-dependent development of an exemplarily selected borehole section in borehole BRC 3 is shown. The presentation deals with the visualisation and description of several observed phenomena from the inside of the investigated boreholes like the ones from the examples shown, also including the development of a complete borehole collapse. An example for measurement results recorded with the three-arm calliper is displayed. The demonstrated measurement results are part of the outcome of the logging performed with the three-arm calliper in borehole BRC 3 over the time span between the 27 May and the 17 September 2009. Cautiously interpreted with consideration of the information gained by the use of the axial borehole camera they give an insight into time-dependent deformations as well as into the stability behaviour of the rock mass surrounding the borehole. In addition to measurement results and borehole-videos, results of recent numerical calculations carried out by the TUC are also part of the presentation, since the recorded borehole-videos and gained measurement results are used to adapt and further develop the simulation tool for underground openings in Opalinus Clay and clay-stone rock mass

[en] The sorption of Cs on crushed and intact (non-crushed) Opalinus Clay (OPA) was studied. A Cs sorption isotherm was measured in a synthetic OPA pore water covering an equilibrium concentration (C_Cs,eq) range between 10^-2 M and 10^-9 M. The isotherms measured on crushed (<63 μm) and intact OPA were in excellent agreement indicating that all sorption sites for Cs in intact OPA are available. The isotherms were modelled assuming that illite is the dominating clay mineral responsible for Cs sorption. The model described the results very well at low Cs concentrations, over-predicted the results in the mid-concentration range and under-predicted the data at the highest Cs equilibrium concentrations. Improvements in the mid-concentration range were obtained by lowering the log_K^CsK_c selectivity coefficient of the Type II sites by 0.4 log units. At the highest Cs concentration an improvement can be achieved by considering sorption of Cs on other clay minerals present in OPA. The main result from this study is that in the case of cation exchange processes the exchange sites in the intact material are all available. This corroborates the common practice in performance assessment (PA) of applying batch sorption data obtained on dispersed systems to the intact rock for predicting the retention behaviour of radionuclides.

[en] Document available in extended abstract form only. This Abstract presents the predictive hydro-mechanical (HM) modelling of an excavation performed in Opalinus clay in the Mont Terri underground laboratory. Niche 2 was excavated in the shaly facies of Opalinus clay from gallery 08. The area surrounding the gallery was intensively instrumented. The geology of Mont Terri is described in Thury and Bosssart (1999) and the parameters used in the analysis were taken from Bock (2009). The stress state is derived from Martin and Lanyion (2003). Gallery 08 is horseshoe shaped and has a mean radius of 2.25 m. It was excavated with a road header at a mean velocity of 1 m/day starting on January 30, 2008 (Gallery chainage 43.8) and ending on June 30, 2008 (Gallery chainage 123.8) with a stop from March 18, to April 24, to instrument the area of niche 2. Niche 2 was excavated by successive blastings 1.3 m deep until reaching a distance of 24 m from the gallery 08 wall. Advance was continuous from October 13, to November 7 with the exception of three stops of 3, 5 and 4 days. The niche has an average diameter of 4.5 m and has a slight upward slope of 0.98%. The excavation of gallery 08 from chainage 43.8 to chainage 123.8 and of the niche was simulated by relaxing the normal total stress and water pressure from the value before excavation to 0. The gallery advance rate was simulated in an approximate manner by applying successively the excavation procedure to 9 m long gallery sections. In the case of the niche, the blasting scheme and the application of the shotcrete was closely reproduced. The three dimensional geometry used in the simulation is shown. The coupled hydro-mechanical formulation used for the analysis is based on the simultaneous solution of the balance equation for solid mass, water mass and momentum (equilibrium). In accordance with field observations, it has been assumed that the medium remains saturated throughout. The formulation was completed with a number of constitutive laws that describe the various phenomena under consideration. The density of the solid and the density of the water are dependent on the total mean pressure and the water pressure, respectively and the advective water flux is described by an anisotropic Darcy's law. Finally, the mechanical behaviour is modelled using an anisotropic linear elastic constitutive law that relates the medium deformation with the effective stress (σ'=σ-b.p_w, where σ is total stress, b is the Biot coefficient and p_w the water pressure). The simulated pore water pressure evolution is presented for two points at 1 m from the niche wall, in a transversal section at 16.5 m from the gallery centre (points B1 and B2) for 4 different computations. B1 lies in the direction of the major stress and B2 in the direction of the minor stress. F_an is a 'full' anisotropic computation, considering anisotropy of stress, stiffness and permeability (E₁ = 1.33*E₂ = 4000 MPa). ISO is an isotropic simulation. In E_an and in S_an, all properties are considered isotropic except the mechanical constitutive law (E1 = 2*E2 = 6000 MPa) and the stress state, respectively. Long before the arrival of the gallery, ISO and S_an do not predict significant pore water pressure changes in contrast to the computations that consider an anisotropic constitutive model. The changes are strongest in the case of F_an and are consistent with observations in similar tests performed in Callovo-Oxfordian Clay. After the passage of the shaft, pore water pressure keeps increasing in the minor stress direction whereas it decreases in the major stress direction. A future stage of modelling must incorporate the reduction of stiffness and the increase in permeability cause by rock damage. The result will likely be a lower magnitude of the pore water pressure increments and an acceleration of drainage processes

[en] Document available in extended abstract form only. With the objective of understanding the gas flow processes through argillaceous rocks in schemes of radioactive waste disposal, the HG-A in situ experiment was planned. The modelling of the experiment will permit to improve the design and the action to be taken, to better understand of the responses, to confirm hypothesis of mechanisms and processes and to learn in order to design future experiments. The experiment and modelling activities are included in the project FORGE (FP7). The in situ test HG-A is to be performed by NAGRA at the Mont Terri underground research laboratory. A micro-tunnel of 1 m diameter was excavated in Opalinus Clay departing from a niche in the 2004 gallery. The drilling was performed parallel to the bedding planes, which have a dipping angle of 50 deg. to SE. The aim of the test is to monitor the creation and evolution of the excavation damage zone around the micro-tunnel, to asses the variations in the hydro-mechanical behaviour of Opalinus Clay, with especial focus on its flow properties, and to observe its impact in the gas migration properties during gas injection phase. The experiment main stages are: tunnel excavation; tunnel backfill and emplacement of instrumentation; packer inflation and backfill saturation; gas injection tests; and a second campaign of hydraulic tests. A cross section model of the test is being developed. The modelled section corresponds to the gas injection interval (backfilled section) and is perpendicular to the tunnel axis and the bedding. The constitutive model considers the hydro-mechanical anisotropy of argillaceous rocks. A composite mechanical law for argillaceous rocks allows taking into account the elastoplastic response of the clay matrix and the damage behaviour for the bonding material of Opalinus Clay. The elastic law is a cross anisotropic linear elastic model that includes the bedding orientation. Increases in permeability can be obtained by increase of rock damage and deformation due to excavation and also due to wetting-drying cycles during open tunnel phase. An embedded fracture permeability model can be adopted for the hydraulic problem in order to include the process of bedding opening due to unloading or fluid injection. In this model, permeability and retention curve depend on strains through a fracture aperture. Both hydraulic and mechanical parts are coherently linked trough the bedding orientation. The following test stages are foreseen to be included in different modelling stages: the formation of the EDZ due to the tunnel excavation and its evolution due to the ventilation process taking place during the open tunnel period prior to the backfilling and installation of the so-called mega-packer. The simulation results will be compared to the experimental data once the model is reliable. The backfilling and saturation/ water injection stages will be also included in the simulation. Finally a scoping calculation of the gas injection test will be carried out considering different gas injection techniques. First the replacement of the backfill pore-water by gas is considered prior to the gas injection stage. In the second case the possibility of gas injection directly into the saturated backfill is simulated. (authors)

[en] Document available in extended abstract form only. Shrinkage structures in the Opalinus Clay, related to seasonal changes in temperature and humidity, are observed on the tunnel walls of the Mont Terri Rock Laboratory. The structures open in winter, when relative humidity in the tunnel decreases to 65%. In summer the cracks close again because of the increase in the clay volume when higher humidity causes rock swelling. Shrinkage structures are monitored in the Mont Terri Rock Laboratory at two different sites within the undisturbed rock matrix and a major fault zone. The relative movements of the rock on both sides of the cracks are monitored in three directions and compared to the fluctuations in ambient relative humidity and temperature. The cyclic deformations (CD) experiment aims to quantify the variations in crack opening in relation to the evolution of climatic conditions and to identify the processes underlying these swell and shrinkage cycles. It consists of the following tasks: - Measuring and quantifying the long-term (now up to three yearly cycles) opening and closing and, if present, the associated shear displacements of selected shrinkage cracks along an undisturbed bedding plane as well as within a major fault zone ('Main Fault'). The measurements are accompanied by temperature and humidity records as well as by a long-term monitoring of tunnel convergence. - Analysing at the micro-scale the surfaces of the crack planes to identify potential relative movements, changes in the rock fabric on the crack surfaces and the formation of fault gouge material as observed in closed cracks. - Processing and analysing measured fluctuations of crack apertures and rock deformation in the time series as well as in the hydro-meteorological variables, in particular relative humidity Hr(t) and air temperature. - Studying and reconstructing the opening cycles on a drill-core sample under well-known laboratory conditions and observing potential propagation of the cracks with evolving number of climatic cycles. The experiment is running since July 2006 and data acquisition of displacements and climate in the rock in the rock laboratory are still going on. The resolution of the installed crack- and joint meters allows the identification of the opening cycles in the field. The existing time series over thee years clearly indicates the correlation between climate and differential movement with a minor lag time. A negative trend within the displacement data is observed even though the relative difference between the crack opening and closure remains at the same level. Shear movement between the blocks has not been identified yet, and the investigation of crack surfaces will give additional evidence of the potential fault gouge formation at the surfaces or disturbances of the crack surfaces. First results of the in situ measurements, statistical analysis as well as hypotheses of the underlying processes are presented and compared. (authors)