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Quantifying the Porosity of Crystalline Rocks by In Situ and Laboratory Injection Methods. MINERALS 2021. [DOI: 10.3390/min11101072] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The porosity and pore geometry of rock samples from a coherent granodioritic rock body at the Grimsel Test Site in Switzerland was characterised by different methods using injection techniques. Results from in situ and laboratory techniques are compared by applying innovative in situ resin impregnation techniques as well as rock impregnation and mercury injection under laboratory conditions. In situ resin impregnation of the rock matrix shows an interconnected pore network throughout the rock body, consisting mainly of grain-boundary pores and solution pores in magmatic feldspar, providing an important reservoir for pore water and solutes, accessible by diffusion. Porosity and pore connectivity do not vary as a function of distance to brittle shear zones. In situ porosity was found to be about 0.3 vol.%, which is about half the porosity value that was determined based on rock samples in the laboratory. Samples that were dried and impregnated in the laboratory were affected by artefacts created since core recovery, and thus showed higher porosity values than samples impregnated under in situ conditions. The extrapolation of laboratory measurements to in situ conditions requires great care and may not be feasible in all cases.
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Puhakka E, Li X, Ikonen J, Siitari-Kauppi M. Sorption of selenium species onto phlogopite and calcite surfaces: DFT studies. JOURNAL OF CONTAMINANT HYDROLOGY 2019; 227:103553. [PMID: 31623864 DOI: 10.1016/j.jconhyd.2019.103553] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 09/10/2019] [Accepted: 09/10/2019] [Indexed: 06/10/2023]
Abstract
Sorption of Se(IV) and Se(VI) species onto Mg-rich biotite (phlogopite) and calcite surfaces was investigated using molecular modelling techniques. A CASTEP code implemented into Materials Studio was used to calculate the periodic systems, site densities and site types on the phlogopite and calcite surfaces. According to the results, the Se oxyanions attach to both edge and basal surfaces of phlogopite via an oxygen atom. However, calculated sorption energies indicate that surface complexation reactions via hydrogen bonding happen on the edge surfaces of phlogopite while cation exchange reactions happen on the basal surfaces of phlogopite. These reactions occur on the so-called weak sites according to the PHREEQC modelling. On the calcite surface, only cation exchange reactions are possible, and only for neutral Se species which do not occur in low saline groundwater conditions with pH 8-10. Biotite which is an abundant mineral in crystalline rock works fairly well as a sorbent but calcite which often exists on fracture surfaces of bedrock does not act as a sorbent for Se species.
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Affiliation(s)
- Eini Puhakka
- Department of Chemistry, P.O. Box 55, FI-00014, University of Helsinki, Finland
| | - Xiaodong Li
- Department of Chemistry, P.O. Box 55, FI-00014, University of Helsinki, Finland.
| | - Jussi Ikonen
- Department of Chemistry, P.O. Box 55, FI-00014, University of Helsinki, Finland
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Aromaa H, Helariutta K, Ikonen J, Yli-Kaila M, Koskinen L, Siitari-Kauppi M. Analysis of 3H, 36Cl, 133Ba, 134Cs and 22Na from synthetic granitic groundwater: an in situ through diffusion experiment at ONKALO. J Radioanal Nucl Chem 2018. [DOI: 10.1007/s10967-018-6139-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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4
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Iraola A, Trinchero P, Voutilainen M, Gylling B, Selroos JO, Molinero J, Svensson U, Bosbach D, Deissmann G. Microtomography-based Inter-Granular Network for the simulation of radionuclide diffusion and sorption in a granitic rock. JOURNAL OF CONTAMINANT HYDROLOGY 2017; 207:8-16. [PMID: 29074267 DOI: 10.1016/j.jconhyd.2017.10.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 09/25/2017] [Accepted: 10/16/2017] [Indexed: 06/07/2023]
Abstract
Field investigation studies, conducted in the context of safety analyses of deep geological repositories for nuclear waste, have pointed out that in fractured crystalline rocks sorbing radionuclides can diffuse surprisingly long distances deep into the intact rock matrix; i.e. much longer distances than those predicted by reactive transport models based on a homogeneous description of the properties of the rock matrix. Here, we focus on cesium diffusion and use detailed micro characterisation data, based on micro computed tomography, along with a grain-scale Inter-Granular Network model, to offer a plausible explanation for the anomalously long cesium penetration profiles observed in these in-situ experiments. The sparse distribution of chemically reactive grains (i.e. grains belonging to sorbing mineral phases) is shown to have a strong control on the diffusive patterns of sorbing radionuclides. The computed penetration profiles of cesium agree well with an analytical model based on two parallel diffusive pathways. This agreement, along with visual inspection of the spatial distribution of cesium concentration, indicates that for sorbing radionuclides the medium indeed behaves as a composite system, with most of the mass being retained close to the injection boundary and a non-negligible part diffusing faster along preferential diffusive pathways.
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Affiliation(s)
- Aitor Iraola
- AMPHOS 21 Consulting S.L., Passeig de Garcia i Faria, 49-51, 1-1, Barcelona 08019, Spain
| | - Paolo Trinchero
- AMPHOS 21 Consulting S.L., Passeig de Garcia i Faria, 49-51, 1-1, Barcelona 08019, Spain.
| | - Mikko Voutilainen
- Department of Chemistry, University of Helsinki, P.O. Box 55, Helsinki 00014, Finland
| | - Björn Gylling
- Swedish Nuclear Fuel and Waste Management Company, Box 250, Stockholm 101 24, Sweden
| | - Jan-Olof Selroos
- Swedish Nuclear Fuel and Waste Management Company, Box 250, Stockholm 101 24, Sweden
| | - Jorge Molinero
- AMPHOS 21 Consulting S.L., Passeig de Garcia i Faria, 49-51, 1-1, Barcelona 08019, Spain
| | - Urban Svensson
- Computer-aided Fluid Engineering AB, Frankes väg 3, Lyckeby 371 65, Sweden
| | - Dirk Bosbach
- Institute for Energy and Climate Research: Nuclear Waste Management and Reactor Safety (IEK-6) and JARA-HPC, Forschungszentrum Jülich GmbH, Jülich 52425, Germany
| | - Guido Deissmann
- Institute for Energy and Climate Research: Nuclear Waste Management and Reactor Safety (IEK-6) and JARA-HPC, Forschungszentrum Jülich GmbH, Jülich 52425, Germany
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Kuva J, Sammaljärvi J, Parkkonen J, Siitari-Kauppi M, Lehtonen M, Turpeinen T, Timonen J, Voutilainen M. Imaging connected porosity of crystalline rock by contrast agent-aided X-ray microtomography and scanning electron microscopy. J Microsc 2017; 270:98-109. [PMID: 29071713 DOI: 10.1111/jmi.12661] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Revised: 09/27/2017] [Accepted: 10/02/2017] [Indexed: 11/28/2022]
Abstract
We set out to study connected porosity of crystalline rock using X-ray microtomography and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) with caesium chloride as a contrast agent. Caesium is an important radionuclide regarding the final deposition of nuclear waste and also forms dense phases that can be readily distinguished by X-ray microtomography and SEM-EDS. Six samples from two sites, Olkiluoto (Finland) and Grimsel (Switzerland), where transport properties of crystalline rock are being studied in situ, were investigated using X-ray microtomography and SEM-EDS. The samples were imaged with X-ray microtomography, immersed in a saturated caesium chloride (CsCl) solution for 141, 249 and 365 days and imaged again with X-ray microtomography. CsCl inside the samples was successfully detected with X-ray microtomography and it had completely penetrated all six samples. SEM-EDS elemental mapping was used to study the location of caesium in the samples in detail with quantitative mineral information. Precipitated CsCl was found in the connected pore space in Olkiluoto veined gneiss and in lesser amounts in Grimsel granodiorite. Only a very small amount of precipitated CsCl was observed in the Grimsel granodiorite samples. In Olkiluoto veined gneiss caesium was found in pinitised areas of cordierite grains. In the pinitised areas caesium was found in notable excess compared to chloride, possibly due to the combination of small pore size and negatively charged surfaces. In addition, elevated concentrations of caesium were found in kaolinite and sphalerite phases. The findings concerning the location of CsCl were congruent with X-ray microtomography.
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Affiliation(s)
- J Kuva
- Department of Physics, University of Jyväskylä, Jyväskylä, Finland.,Department of Chemistry, University of Helsinki, Helsinki, Finland
| | - J Sammaljärvi
- Department of Chemistry, University of Helsinki, Helsinki, Finland
| | - J Parkkonen
- Department of Physics, University of Jyväskylä, Jyväskylä, Finland
| | - M Siitari-Kauppi
- Department of Chemistry, University of Helsinki, Helsinki, Finland
| | - M Lehtonen
- Geological Survey of Finland, Espoo, Finland
| | - T Turpeinen
- VTT Technical Research Centre of Finland Ltd, Jyväskylä, Finland
| | - J Timonen
- Department of Physics, University of Jyväskylä, Jyväskylä, Finland
| | - M Voutilainen
- Department of Chemistry, University of Helsinki, Helsinki, Finland
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Muuri E, Siitari-Kauppi M, Matara-aho M, Ikonen J, Lindberg A, Qian L, Koskinen L. Cesium sorption and diffusion on crystalline rock: Olkiluoto case study. J Radioanal Nucl Chem 2016. [DOI: 10.1007/s10967-016-5087-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Ikonen J, Voutilainen M, Söderlund M, Jokelainen L, Siitari-Kauppi M, Martin A. Sorption and diffusion of selenium oxyanions in granitic rock. JOURNAL OF CONTAMINANT HYDROLOGY 2016; 192:203-211. [PMID: 27517514 DOI: 10.1016/j.jconhyd.2016.08.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Revised: 07/16/2016] [Accepted: 08/04/2016] [Indexed: 06/06/2023]
Abstract
The processes controlling diffusion and sorption of radionuclides have been studied extensively in the laboratory, whereas, only a few in-situ experiments have been carried out in order to study in-situ diffusion over the long-term (several years). This is largely due to the fact that in-situ experiments are typically time consuming and cost intensive, and it is commonly accepted that laboratory scale tests are well-established approaches to characterizing the properties of geological media. In order to assess the relevance of laboratory experiments, the Swiss National Cooperative for Disposal of Radioactive Waste (Nagra) have been conducting extensive experiments in the Underground Rock Laboratory (URL) at the Grimsel Test Site (GTS) in order to study radionuclide transport and retention in-situ. One of the elements used in these experiments is non-radioactive selenium, as an analog for the radiotoxic isotope Se-79, which is present in radioactive waste. In this work, two laboratory through-diffusion experiments using selenium as a tracer were carried out in block (decimeter) scale rock specimens to support one of the ongoing radionuclide transport and retention in-situ experiment at the GTS mentioned above. The though-diffusion tests of selenium were performed under atmospheric conditions in both Kuru grey granite (KGG) and Grimsel granodiorite (GG). The decrease of selenium concentration in an inlet hole drilled into each of the rock samples and the breakthrough of selenium into sampling holes drilled around the inlet were analyzed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The effective diffusion (De) and distribution coefficients (Kd) of selenium were then determined from the changes of selenium concentration in the inlet and sampling holes using a Time-Domain Diffusion (TDD) simulations. In addition, Kd of selenium was measured by batch sorption experiments as a function of pH and Se concentration in atmospheric conditions and nitrogen atmosphere. The speciation of selenium was studied by HPLC-ICP-MS in simulated ground waters of each of the rock types. The Kd of selenium was found to be in the range of (6.2-7.0±2.0)×10(-3)m(3)/kg in crushed rock whereas the Kd obtained from block scale through diffusion experiment varied between (1.5±0.3)×10(-3)m(3)/kg and (1.0±0.6)×10(-4)m(3)/kg. The De of selenium was significantly higher for GG; De=(2.5±1.5)×10(-12)m(2)/s than for KGG; De=(7±2)×10(-13)m(2)/s due to the higher permeability of GG compared with KGG.
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Affiliation(s)
- Jussi Ikonen
- University of Helsinki, Laboratory of Radiochemistry, Department of Chemistry, P.O. Box 55, FIN-00014 Helsinki, Finland.
| | - Mikko Voutilainen
- University of Helsinki, Laboratory of Radiochemistry, Department of Chemistry, P.O. Box 55, FIN-00014 Helsinki, Finland
| | - Mervi Söderlund
- University of Helsinki, Laboratory of Radiochemistry, Department of Chemistry, P.O. Box 55, FIN-00014 Helsinki, Finland
| | - Lalli Jokelainen
- University of Helsinki, Laboratory of Radiochemistry, Department of Chemistry, P.O. Box 55, FIN-00014 Helsinki, Finland
| | - Marja Siitari-Kauppi
- University of Helsinki, Laboratory of Radiochemistry, Department of Chemistry, P.O. Box 55, FIN-00014 Helsinki, Finland
| | - Andrew Martin
- Nagra (National Cooperative for the Disposal of Radioactive Waste), Wettingen, Switzerland
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Stoll M, Huber FM, Darbha GK, Schill E, Schäfer T. Impact of gravity, collector surface roughness and fracture orientation on colloid retention kinetics in an artificial fracture. J Colloid Interface Sci 2016; 475:171-183. [PMID: 27174623 DOI: 10.1016/j.jcis.2016.04.045] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Revised: 04/27/2016] [Accepted: 04/27/2016] [Indexed: 11/25/2022]
Abstract
The interaction of monodisperse fluorescent carboxylated polystyrene colloids (25nm and 1000nm diameter) with a cut granodiorite surface (Grimsel granodiorite; Switzerland) and with acrylic glass is investigated both experimentally and numerically. Colloid transport experiments are conducted in a parallel plate type fracture flow cell with an aperture of 0.75mm at pH5 under low ionic strength (1mM NaCl) and under laminar flow (7mL/h) conditions. The study focuses on the effect of residence time, colloid size, collector material and fracture orientation on colloid retention. Long colloid residence times are achieved by stop-flow experiments. Using atomic force microscopy and, more specifically, the colloid probe technique surface roughness and force distance information of the collector material (granodiorite or acrylic glass) as a function of probe size (cantilever) are obtained. The experiments are modeled using COMSOL Multiphysics® (2-D numerical simulations). The experimental and the modeled results lead to the conclusion that large colloids (1000nm diameter) undergo sedimentation and deposition on the surface during stop-flow. Collector interaction is not affected by the surface roughness variation. Contrariwise, for the investigated 25nm colloids sedimentation does not play a role under the experimental conditions and collector interaction is triggered by surface inhomogeneities such as surface roughness.
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Affiliation(s)
- M Stoll
- Karlsruhe Institute of Technology (KIT), Institute for Nuclear Waste Disposal (INE), P.O. Box 3640, 76021 Karlsruhe, Germany.
| | - F M Huber
- Karlsruhe Institute of Technology (KIT), Institute for Nuclear Waste Disposal (INE), P.O. Box 3640, 76021 Karlsruhe, Germany
| | - G K Darbha
- Karlsruhe Institute of Technology (KIT), Institute for Nuclear Waste Disposal (INE), P.O. Box 3640, 76021 Karlsruhe, Germany; National Institute of Technology, Tadepalligudem, Andhra Pradesh, 534101, India
| | - E Schill
- Karlsruhe Institute of Technology (KIT), Institute for Nuclear Waste Disposal (INE), P.O. Box 3640, 76021 Karlsruhe, Germany
| | - T Schäfer
- Karlsruhe Institute of Technology (KIT), Institute for Nuclear Waste Disposal (INE), P.O. Box 3640, 76021 Karlsruhe, Germany; Karlsruhe Institute of Technology (KIT), Institute of Applied Geosciences (AGW), Environmental Geology, Karlsruhe, Germany
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9
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The tritiated water and iodine migration in situ in Grimsel granodiorite. Part I: determination of the diffusion profiles. J Radioanal Nucl Chem 2016. [DOI: 10.1007/s10967-016-4890-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Eveliina M, Jussi I, Minja MA, Antero L, Stellan H, Mikko V, Marja SK, Martin A. Behavior of Cs in Grimsel granodiorite: sorption on main minerals and crushed rock. RADIOCHIM ACTA 2016. [DOI: 10.1515/ract-2015-2574] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
In this study the sorption of cesium was investigated on four different minerals; quartz, plagioclase, potassium feldspar and biotite as well as granodiorite obtained from the Grimsel test site in Switzerland. The experiments were conducted in the presence of the weakly saline Grimsel groundwater simulant by determining the distribution coefficients using batch sorption experiments and PHREEQC-modelling across a large concentration range. In addition, the purity of the minerals was measured byXRDand the specific surface areas by BET method using krypton. The distribution coefficients of cesiumwere largest on biotite (0.304±0.005 m3/kg in 10-8 M). Furthermore, the sorption of cesiumon quartzwas found to be negligibly small in all investigated concentrations and the sorption of cesium on potassium feldspar and plagioclase showed similar behavior against a concentration isotherm with distribution coefficients of 0.0368±0.0004 m3/kg and 0.18±0.04 m3/kg in 10-8 M. Finally, cesium sorption behavior on crushed granodiorite followed the trend of one of its most abundant mineral, plagioclase with distribution coefficient values of 0.107±0.003 m3/kg in 10-8 M. At low concentrations (<1.0·10-6 M) cesiumwas sorbed on the frayed edge sites of biotite and once these sites are fully occupied cesium sorbs additionally to the Type II and Planar sites. As a consequence, the sorption of cesium on biotite is decreased at concentrations >1.0·10-6 M. Secondly cesium sorption on potassium feldspar and plagioclase showed similar non-linear behavior with varying concentration. The results were used to assist the interpretation of cesium diffusion process in the 2.5 year in-situ experiment carried out in the underground laboratory at Grimsel test site in Switzerland (2007–2009).
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Affiliation(s)
- Muuri Eveliina
- Department of Chemistry , University of Helsinki , P.O. Box 55, 00014 University of Helsinki, Helsinki, Finland
| | - Ikonen Jussi
- Department of Chemistry , University of Helsinki , P.O. Box 55, 00014 University of Helsinki, Helsinki, Finland
| | - Matara-aho Minja
- Department of Chemistry , University of Helsinki , P.O. Box 55, 00014 University of Helsinki, Helsinki, Finland
| | - Lindberg Antero
- Geological Survey of Finland, Betonimiehenkuja 4, 02151 Espoo, Finland
| | - Holgersson Stellan
- Department of Chemical and Biological Engineering, Nuclear Chemistry , Chalmers University of Technology , Kemivägen 4, SE-41296 Göteborg, Sweden
| | - Voutilainen Mikko
- Department of Chemistry , University of Helsinki , P.O. Box 55, 00014 University of Helsinki, Helsinki, Finland
| | - Siitari-Kauppi Marja
- Department of Chemistry , University of Helsinki , P.O. Box 55, 00014 University of Helsinki, Helsinki, Finland
| | - Andrew Martin
- Nagra (National Cooperative for the Disposal of Radioactive Waste), Wettingen, Switzerland
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Meier DB, Waber HN, Gimmi T, Eichinger F, Diamond LW. Reconstruction of in-situ porosity and porewater compositions of low-permeability crystalline rocks: Magnitude of artefacts induced by drilling and sample recovery. JOURNAL OF CONTAMINANT HYDROLOGY 2015; 183:55-71. [PMID: 26529302 DOI: 10.1016/j.jconhyd.2015.10.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Revised: 10/16/2015] [Accepted: 10/21/2015] [Indexed: 06/05/2023]
Abstract
Geological site characterisation programmes typically rely on drill cores for direct information on subsurface rocks. However, porosity, transport properties and porewater composition measured on drill cores can deviate from in-situ values due to two main artefacts caused by drilling and sample recovery: (1) mechanical disruption that increases porosity and (2) contamination of the porewater by drilling fluid. We investigated the effect and magnitude of these perturbations on large drill core samples (12-20 cm long, 5 cm diameter) of high-grade, granitic gneisses obtained from 350 to 600 m depth in a borehole on Olkiluoto Island (SW Finland). The drilling fluid was traced with sodium-iodide. By combining out-diffusion experiments, gravimetry, UV-microscopy and iodide mass balance calculations, we successfully quantified the magnitudes of the artefacts: 2-6% increase in porosity relative to the bulk connected porosity and 0.9 to 8.9 vol.% contamination by drilling fluid. The spatial distribution of the drilling-induced perturbations was revealed by numerical simulations of 2D diffusion matched to the experimental data. This showed that the rims of the samples have a mechanically disrupted zone 0.04 to 0.22 cm wide, characterised by faster transport properties compared to the undisturbed centre (1.8 to 7.7 times higher pore diffusion coefficient). Chemical contamination was shown to affect an even wider zone in all samples, ranging from 0.15 to 0.60 cm, in which iodide enrichment was up to 180 mg/kg water, compared to 0.5 mg/kg water in the uncontaminated centre. For all samples in the present case study, it turned out that the magnitude of the artefacts caused by drilling and sample recovery is so small that no correction is required for their effects. Therefore, the standard laboratory measurements of porosity, transport properties and porewater composition can be taken as valid in-situ estimates. However, it is clear that the magnitudes strongly depend on site- and drilling-specific factors and therefore our results cannot be transferred simply to other locations. We recommend the approach presented in this study as a route to obtain reliable values in future drilling campaigns aimed at characterising in-situ bedrock properties.
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Affiliation(s)
- D B Meier
- Rock-Water Interaction, Institute of Geological Sciences, University of Bern, Baltzerstrasse 3, 3012, Bern, Switzerland.
| | - H N Waber
- Rock-Water Interaction, Institute of Geological Sciences, University of Bern, Baltzerstrasse 3, 3012, Bern, Switzerland.
| | - T Gimmi
- Rock-Water Interaction, Institute of Geological Sciences, University of Bern, Baltzerstrasse 3, 3012, Bern, Switzerland; Paul Scherrer Institut PSI, 5232 Villigen, Switzerland.
| | - F Eichinger
- Hydroisotop GmbH, Woelkestrasse 9, 85301 Schweitenkirchen, Germany.
| | - L W Diamond
- Rock-Water Interaction, Institute of Geological Sciences, University of Bern, Baltzerstrasse 3, 3012, Bern, Switzerland.
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Soler JM, Landa J, Havlova V, Tachi Y, Ebina T, Sardini P, Siitari-Kauppi M, Eikenberg J, Martin AJ. Comparative modeling of an in situ diffusion experiment in granite at the Grimsel Test Site. JOURNAL OF CONTAMINANT HYDROLOGY 2015; 179:89-101. [PMID: 26074058 DOI: 10.1016/j.jconhyd.2015.06.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Revised: 05/28/2015] [Accepted: 06/01/2015] [Indexed: 06/04/2023]
Abstract
An in situ diffusion experiment was performed at the Grimsel Test Site (Switzerland). Several tracers ((3)H as HTO, (22)Na(+), (134)Cs(+), (131)I(-) with stable I(-) as carrier) were continuously circulated through a packed-off borehole and the decrease in tracer concentrations in the liquid phase was monitored for a period of about 2years. Subsequently, the borehole section was overcored and the tracer profiles in the rock analyzed ((3)H, (22)Na(+), (134)Cs(+)). (3)H and (22)Na(+) showed a similar decrease in activity in the circulation system (slightly larger drop for (3)H). The drop in activity for (134)Cs(+) was much more pronounced. Transport distances in the rock were about 20cm for (3)H, 10cm for (22)Na(+), and 1cm for (134)Cs(+). The dataset (except for (131)I(-) because of complete decay at the end of the experiment) was analyzed with different diffusion-sorption models by different teams (IDAEA-CSIC, UJV-Rez, JAEA) using different codes, with the goal of obtaining effective diffusion coefficients (De) and porosity (ϕ) or rock capacity (α) values. From the activity measurements in the rock, it was observed that it was not possible to recover the full tracer activity in the rock (no activity balance when adding the activities in the rock and in the fluid circulation system). A Borehole Disturbed Zone (BDZ) had to be taken into account to fit the experimental observations. The extension of the BDZ (1-2mm) is about the same magnitude than the mean grain size of the quartz and feldspar grains. IDAEA-CSIC and UJV-Rez tried directly to match the results of the in situ experiment, without forcing any laboratory-based parameter values into the models. JAEA conducted a predictive modeling based on laboratory diffusion data and their scaling to in situ conditions. The results from the different codes have been compared, also with results from small-scale laboratory experiments. Outstanding issues to be resolved are the need for a very large capacity factor in the BDZ for (3)H and the difference between apparent diffusion coefficients (Da) from the in situ experiment and out-leaching laboratory tests.
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Affiliation(s)
- Josep M Soler
- IDAEA-CSIC, Jordi Girona 18-26, 08034 Barcelona, Catalonia, Spain.
| | - Jiri Landa
- UJV-Rez, Rez 130, 250 68, Czech Republic
| | | | - Yukio Tachi
- JAEA, 4-33 Muramatsu, Tokai-mura, Naka-gun, Ibaraki 319-1194, Japan.
| | - Takanori Ebina
- JAEA, 4-33 Muramatsu, Tokai-mura, Naka-gun, Ibaraki 319-1194, Japan
| | - Paul Sardini
- Université de Poitiers, HYDRASA/IC2MP 4, rue Michel Brunet - TSA 51106, 86073 Poitiers Cedex 9, France.
| | - Marja Siitari-Kauppi
- Laboratory of Radiochemistry, Department of Chemistry, A.I.Virtasen Aukio 1, FIN-00014 University of Helsinki, Helsinki, Finland.
| | - Jost Eikenberg
- Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
| | - Andrew J Martin
- NAGRA, Hardstrasse 73, Postfach 280, CH-5430 Wettingen, Switzerland.
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13
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Tachi Y, Ebina T, Takeda C, Saito T, Takahashi H, Ohuchi Y, Martin AJ. Matrix diffusion and sorption of Cs+, Na+, I- and HTO in granodiorite: Laboratory-scale results and their extrapolation to the in situ condition. JOURNAL OF CONTAMINANT HYDROLOGY 2015; 179:10-24. [PMID: 26024950 DOI: 10.1016/j.jconhyd.2015.05.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Revised: 04/17/2015] [Accepted: 05/07/2015] [Indexed: 06/04/2023]
Abstract
Matrix diffusion and sorption are important processes controlling radionuclide transport in crystalline rocks. Such processes are typically studied in the laboratory using borehole core samples however there is still much uncertainty on the changes to rock transport properties during coring and decompression. It is therefore important to show how such laboratory-based results compare with in situ conditions. This paper focuses on laboratory-scale mechanistic understanding and how this can be extrapolated to in situ conditions as part of the Long Term Diffusion (LTD) project at the Grimsel Test Site, Switzerland. Diffusion and sorption of (137)Cs(+), (22)Na(+), (125)I(-) and tritiated water (HTO) in Grimsel granodiorite were studied using through-diffusion and batch sorption experiments. Effective diffusivities (De) of these tracers showed typical cation excess and anion exclusion effects and their salinity dependence, although the extent of these effects varied due to the heterogeneous pore networks in the crystalline rock samples. Rock capacity factors (α) and distribution coefficients (Kd) for Cs(+) and Na(+) were found to be sensitive to porewater salinity. Through-diffusion experiments indicated dual depth profiles for Cs(+) and Na(+) which could be explained by a near-surface Kd increment. A microscopic analysis indicated that this is caused by high porosity and sorption capacities in disturbed biotite minerals on the surface of the samples. The Kd values derived from the dual profiles are likely to correspond to Kd dependence on the grain sizes of crushed samples in the batch sorption experiments. The results of the in situ LTD experiments were interpreted reasonably well by using transport parameters derived from laboratory data and extrapolating them to in situ conditions. These comparative experimental and modelling studies provided a way to extrapolate from laboratory scale to in situ condition. It is well known that the difference in porosity between laboratory and in situ conditions is a key factor to scale laboratory-derived De to in situ conditions. We also show that cation excess diffusion is likely to be a key mechanism in crystalline rocks and that high Kd in the disturbed surfaces is critically important to evaluate transport in both laboratory and in situ tests.
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Affiliation(s)
- Yukio Tachi
- Japan Atomic Energy Agency, Muramatsu 4-33, Tokai, Ibaraki, 319-1194, Japan.
| | - Takanori Ebina
- NESI Inc., Muramatsu 4-33, Tokai, Ibaraki, 319-1112, Japan
| | - Chizuko Takeda
- Tokyo Nuclear Service Inc., Midorigahara 4-19-2, Tsukuba, Ibaraki, 300-2646, Japan
| | - Toshihiko Saito
- Tokyo Nuclear Service Inc., Midorigahara 4-19-2, Tsukuba, Ibaraki, 300-2646, Japan
| | - Hiroaki Takahashi
- Japan Atomic Energy Agency, Muramatsu 4-33, Tokai, Ibaraki, 319-1194, Japan
| | - Yuji Ohuchi
- Inspction Development Co. Ltd., Muramatsu 4-33, Tokai, Ibaraki, 319-1112, Japan
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