Gas Phase Measurements of Porosity, Diffusion Coefficient, and Permeability in Rock Samples from Olkiluoto Bedrock, Finland

Kuva, Jukka; Voutilainen, Mikko; Kekäläinen, Pekka; Siitari-Kauppi, Marja; Timonen, J.; Koskinen, Lasse

doi:10.1007/s11242-014-0432-2

Cited by 26 publications

(16 citation statements)

References 31 publications

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“…In general, the porosities and diffusion coefficients determined from the breakthrough curves of HTO and 36 Cl (see Tables 1 and 2) are in fair agreement with previously determined values for REPRO samples [33,34,37,38] and Olkiluoto samples [9]. However, the variation of previously determined values is relatively large e.g.…”

Section: Discussionsupporting

confidence: 88%

“…The tracer pulse, containing HTO and 36 Cl, was injected into the flow in the beginning of the experiment using an injection valve (9725i, Rheodyne) that contained a injection loop with a volume of 0.5 ml. Previously, [34] performed successfully similar experiments for unsaturated samples in gas phase and [45] have reported preliminary results for the measurement performed for VGN sample.…”

Section: Laboratory Water Phase Diffusion Experimentsmentioning

confidence: 80%

“…The aim of the REPRO-project is to quantify the distribution coefficients, effective diffusion coefficients and connected porosity of the unaltered rock matrix in the repository level stress conditions. The in-situ experiments are performed in drill holes [21,22] while the drill cores from the same sections are used in laboratory experiments [33,34,12,35,36,37,38,20,39].…”

Section: Introductionmentioning

confidence: 99%

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Comparison of water phase diffusion experiments in laboratory and in situ conditions

Voutilainen

Kekäläinen

Poteri

et al. 2019

Journal of Hydrology

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In some countries, the spent nuclear fuel produced by nuclear power plants will be deposited in crystalline granitic rock formations. In Finland, such repository is being built at Olkiluoto. The safety assessment of the repository requires a careful determination of transport properties of the bedrock. Porosity of the rock and effective diffusion coefficient and distribution coefficients of different radionuclides for the bedrock are used as the main parameters in safety assessment calculations. It has been questioned if the parameters determined using laboratory experiments can be used to estimate the parameters in the in-situ conditions. Water Phase Diffusion Experiments (WPDE) performed in the laboratory and in-situ conditions were addressed to resolve this questions. In the experiments, transport of HTO, 36 Cl and 22 Na were studied using similar experimental setups in both conditions. Analytic models were constructed and solved to determine the transport parameters from the measured breakthrough curves. The in-situ WPDE resulted from 12 % to 38 % smaller porosities and from 30 % to 60 % smaller effective diffusion coefficients for HTO and 36 Cl than the laboratory WPDE. It was also shown that anion exclusion reduced the transport parameters of 36 Cl compared with the parameters of HTO in veined gneiss that is the most dominant rock type of Olkiluoto bedrock. Furthermore, the distribution coefficients of 22 Na for veined gneiss were found to be about one order of magnitude smaller in the in-situ conditions than in previous laboratory batch sorption experiments. The effects of the results on the safety assessment were evaluated and discussed.

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Section: Discussionsupporting

confidence: 88%

Section: Laboratory Water Phase Diffusion Experimentsmentioning

confidence: 80%

Section: Introductionmentioning

confidence: 99%

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Comparison of water phase diffusion experiments in laboratory and in situ conditions

Voutilainen

Kekäläinen

Poteri

et al. 2019

Journal of Hydrology

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“…The two rock types are different in their mineralogy and the structure of the pore network, which was seen in the results. Much more significant caesium intrusion was seen in Olkiluoto veined gneiss than Grimsel granodiorite, despite earlier studies showing Grimsel granodiorite to be more conductive than Olkiluoto veined gneiss (Kelokaski et al ., ; Kuva et al ., ). In Olkiluoto veined gneiss there are more areas of high local porosity congruent with cordierites and its alteration product pinite where CsCl was accumulated.…”

Section: Discussionmentioning

confidence: 97%

Imaging connected porosity of crystalline rock by contrast agent‐aided X‐ray microtomography and scanning electron microscopy

Kuva

Sammaljärvi

Parkkonen

et al. 2017

Journal of Microscopy

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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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“…The selected veined gneiss (VGN) and pegmatitic granite (PGR) samples represent the typical rock types of Olkiluoto. Their porosity, mineralogy and transport properties have been widely studied previously [6,8,9,13,17,18,29]. The analyzed samples are collected from the experimental site of the "rock matrix REtention PROperties" (REPRO) project carried out at the underground rock characterization facility of Olkiluoto (ONKALO), at a depth of around 400 m. The project consists of various in situ and laboratory experiments that aim at determining transport properties of the crystalline rock under in situ conditions.…”

Section: Rock Samplesmentioning

confidence: 99%

Grains, grids and mineral surfaces: approaches to grain-scale matrix modeling based on X-ray micro-computed tomography data

Svensson¹,

Trinchero

Ferry³

et al. 2019

SN Appl. Sci.

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X-ray micro-computed tomography (X-μCT) generates 3D mineral distribution maps currently with a resolution of about 10 μm. For tight crystalline rocks, this implies that the mineral grains are well resolved, while micro-fractures, having apertures of less than 10 μm, are not resolved. In this study, we propose a method to analyze the properties (size, volume, surface area) of the mineral grains based on X-μCT data. The numerical approach uses a resolution similar to that of the X-μCT data and hence shares the same limitations. For example, it is clear that a large fraction of the mineral surface area is due to so-called roughness, with scales below 10 μm. In the second part of the study, methods to generate the diffusion-available pore space are discussed. The inter-granular space (distance between grains) is often smaller than 10 μm, and we need to design methods to be able to perform diffusion simulations in the matrix. Three methods, all based on X-μCT, are discussed, and it is demonstrated that models with realistic global properties (mean porosity and effective diffusion coefficient) can be developed based on the suggested techniques.

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Gas Phase Measurements of Porosity, Diffusion Coefficient, and Permeability in Rock Samples from Olkiluoto Bedrock, Finland

Cited by 26 publications

References 31 publications

Comparison of water phase diffusion experiments in laboratory and in situ conditions

Comparison of water phase diffusion experiments in laboratory and in situ conditions

Imaging connected porosity of crystalline rock by contrast agent‐aided X‐ray microtomography and scanning electron microscopy

Grains, grids and mineral surfaces: approaches to grain-scale matrix modeling based on X-ray micro-computed tomography data

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