Cesium sorption and diffusion on crystalline rock: Olkiluoto case study

Muuri, Eveliina; Siitari-Kauppi, Marja; Matara-aho, Minja; Ikonen, Jussi; Lindberg, Antero; Qian, Lijuan; Koskinen, Lasse

doi:10.1007/s10967-016-5087-8

Cited by 22 publications

(19 citation statements)

References 18 publications

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“…Closer investigation of the microtomographic images showed that in Olkiluoto veined gneiss the CsCl precipitates were found most extensively in cordierite grains and in some extent in pinitised cordierite grains. This is expected as the most pronounced effect is coming from the caesium that is accumulated in the pore space of the rock, because the cation exchange capacity of biotite and studied rock samples is relatively low considering the effect it can have on the local attenuation coefficient (Olin et al ., ; Muuri et al ., , ). In Grimsel granodiorite the density change was smaller and took place relatively evenly in all minerals.…”

Section: Discussionmentioning

confidence: 99%

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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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Section: Discussionmentioning

confidence: 99%

“…). Caesium sorption has been studied in both rock types using lower caesium concentration than here and these studies have shown high sorption on biotite, although clay minerals also contributed to the sorption (Muuri et al ., ; ).…”

Section: Materials and Experimental Methodsmentioning

confidence: 99%

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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“…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%

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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“…The tunnels will be backfilled and the last barrier will be the bedrock itself. Behavior of radionuclides in fractured crystalline rock has been studied for the safety assessment calculations [2,3]. The evaluation of the safety is done for hundreds of thousands of years in the final disposal site [4].…”

Section: Introductionmentioning

confidence: 99%

Analysis of 3H, 36Cl, 133Ba, 134Cs and 22Na from synthetic granitic groundwater: an in situ through diffusion experiment at ONKALO

Aromaa

Helariutta

Ikonen

et al. 2018

J Radioanal Nucl Chem

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A method for analyzing 3 H, 36 Cl, 22 Na, 133 Ba and 134 Cs from simulated groundwater (SGW) samples was introduced. Gamma emitting radionuclides 22 Na, 133 Ba and 134 Cs were measured by using an HPGe-detector. Beta emitting 3 H and 36 Cl were separated 22 from gamma emitting 22 Na, 133 Ba and 134 Cs. AgCl precipitation was used for the separation of 36 Cl from SGW samples with yields of 98 ± 2%. 3 H was separated by distillation with recoveries of 97 ± 3%. This method was used for the determination of activity concentrations of 3 H, 36 Cl, 22 Na, 133 Ba and 134 Cs in SGW samples collected from an in-situ through diffusion experiment (TDE).

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Cesium sorption and diffusion on crystalline rock: Olkiluoto case study

Cited by 22 publications

References 18 publications

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

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

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

Analysis of 3H, 36Cl, 133Ba, 134Cs and 22Na from synthetic granitic groundwater: an in situ through diffusion experiment at ONKALO

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