Through diffusion experiments to study the diffusion and sorption of HTO, Cl, Ba and Cs in crystalline rock

Aromaa, Hanna; Voutilainen, Mikko; Ikonen, Jussi; Yli-Kaila, Maarit; Poteri, Antti; Siitari-Kauppi, Marja

doi:10.1016/j.jconhyd.2019.03.002

Cited by 14 publications

(6 citation statements)

References 43 publications

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“…Thus, understanding the whole system of the bedrock matrix is of importance for the safety considerations of the disposal process. To this end, several key parameters of the crystalline rock in the disposal test sites have been studied extensively: porosity of the rock matrix and fracturation of Olkiluoto rocks (Kuva et al, 2012;Sammaljärvi et al, 2017), advection and flow properties with gas (Kuva, 2016) and in the water phase (Voutilainen et al, 2019), diffusion (Voutilainen et al, 2016(Voutilainen et al, , 2018Aromaa et al, 2019), and sorption (Ervanne et al, 2014;Muuri et al, 2016Muuri et al, , 2017Söderlund et al, 2019). Furthermore, the matrix diffusion (Neretnieks, 2013;Tsang et al, 2015), flow (Liu et al, 2018;Neretnieks and Winberg-Wang, 2019), and advection (Shahkarami et al, 2015) of radionuclides in saturated rock and rock fractures have been reported previously.…”

Section: Introductionmentioning

confidence: 99%

Radium sorption on biotite; surface complexation modeling study

Fabritius

Puhakka

et al. 2022

Applied Geochemistry

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Section: Introductionmentioning

confidence: 99%

Radium sorption on biotite; surface complexation modeling study

Fabritius

Puhakka

et al. 2022

Applied Geochemistry

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“…The distribution coefficients of radionuclides have often been determined using batch sorption experiments on crushed rock. However, recent studies show that the distribution coefficients determined using such experiments overestimate the sorption capacity of the rock due to increased specific surface area [17,18,19,20]. Alternative ways for measuring the distribution coefficients using intact rock has been suggested in these studies and their results show that the results of batch sorption are typically about one order of magnitude larger than the ones determined for intact rock samples.…”

Section: Introductionmentioning

confidence: 99%

“…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%

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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“…Sorption of these nuclides on crystalline rocks has been studied widely using samples from different sites e.g. in Finland (Huitti et al., 1998; Muuri et al., 2017; Aromaa et al., 2019), Sweden (Skagius et al., 1982; Skagius and Neretnieks, 1988), Czech Republic (Videnská et al., 2015), Switzerland (Tachi et al., 2015; Muuri et al., 2016) and Japan (Tachi et al., 2011). These studies include sorption and diffusion of Cs and Sr on various rocks and minerals, including biotite, as a function of their concentration and the results have been modelled in the same way as in this paper.…”

Section: Introductionmentioning

confidence: 99%

Batch sorption experiments of cesium and strontium on crushed rock and biotite for the estimation of distribution coefficients on intact crystalline rock

Lehto

Puukko

Lindberg

et al. 2019

Heliyon

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The distribution coefficient (K d) of radionuclides on bedrock is one of the key parameters used in the safety analysis of spent nuclear fuel repositories. Typically, distribution coefficients have been determined using crushed rock. However, recent studies have shown that crushing of the rock increases considerably the distribution coefficient compared with the values of intact rock. This study aimed to test if batch sorption experiments using different grain sizes (i.e. mean diameter of grains) can be used to evaluate the K d of strontium (Sr) and cesium (Cs) on intact crystalline rock, which would decrease the needed experimental time compared with transport experiments. Here we report the results of the batch sorption experiments with crushed rocks and compare the results with those from a recent study performed using electromigration experiments with intact drill core samples (Puukko et al., 2018). The batch sorption experiments were done for rock samples from Olkiluoto, Finland, as a function of grain size and of Cs and Sr concentration. Furthermore, the specific surface areas of the same rock samples with different grain sizes were determined. It was shown that Cs distribution coefficients correlate with specific surface areas of the studied rocks and biotite, the correlation coefficient being 0.95. The Cs distribution coefficient was highest for biotite at about 0.1 m 3 /kg at 10 À4 M cesium concentration and increased systematically to about 1 m 3 /kg at 10 À8 M. Distribution coefficients for rocks were up to about two orders of magnitude lower, being lowest with the rock with the lowest biotite content (3.3%). The distribution coefficient of Sr varied from 0.04 m 3 /kg to 0.007 m 3 /kg and behaved in a different manner: it remained constant in two out of three studied rocks in the concentration range of 10 À8-10 À4 M and only in the case of one rock a decreasing trend was seen at the higher concentration range. It was also shown that batch sorption experiments overestimate the distribution coefficient in respect to intact rock. The decrease of the distribution coefficient as a function of grain size can be estimated using a power law function. It was also shown that estimation of distribution coefficients of Cs and Sr for intact rock by extrapolation of distribution coefficients determined for different grain sizes is not possible without increasing grain size, but in that case diffusion into the grains would also affect the results. A new method was developed for estimating the fraction of the inner surface area of the total surface area of crushed grains. For the mean grain sizes of 0.25 mm and 0.75 mm the fraction of the inner surface was found to be 35-70% and 60-90%, respectively. The inner specific surface area was highest with biotite at 1.2 m 2 /g and lowest with the rock with lowest biotite content (3.3%) at 0.07 m 2 /g. The surface area analysis revealed that crushing creates and/or allows access to additional inner surface area that is not measured in intact rock. Furthermore, it was demonstr...

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Through diffusion experiments to study the diffusion and sorption of HTO, Cl, Ba and Cs in crystalline rock

Cited by 14 publications

References 43 publications

Radium sorption on biotite; surface complexation modeling study

Radium sorption on biotite; surface complexation modeling study

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

Batch sorption experiments of cesium and strontium on crushed rock and biotite for the estimation of distribution coefficients on intact crystalline rock

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