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Journal Articles

Micro- to nano-scale areal heterogeneity in pore structure and mineral compositions of a sub-decimeter-sized Eagle Ford Shale

Wang, Q.*; Hu, Q.*; Zhao, C.*; Yang, X.*; Zhang, T.*; Ilavsky, J.*; Kuzmenko, I.*; Ma, B.*; Tachi, Yukio

International Journal of Coal Geology, 261, p.104093_1 - 104093_15, 2022/09

 Times Cited Count:0 Percentile:0(Energy & Fuels)

Journal Articles

Modelling of the LTDE-SD radionuclide diffusion experiment in crystalline rock at the $"A$sp$"o$ Hard Rock Laboratory (Sweden)

Soler, J. M.*; Meng, S.*; Moreno, L.*; Neretnieks, I.*; Liu, L.*; Kek$"a$l$"a$inen, P.*; Hokr, M.*; $v{R}$$'i$ha, J.*; Vete$v{s}$n$'i$k, A.*; Reimitz, D.*; et al.

Geologica Acta, 20(7), 32 Pages, 2022/07

 Times Cited Count:0 Percentile:0.03(Geology)

Task 9B of the SKB Task Force on Modelling of Groundwater Flow and Transport of Solutes in fractured rock focused on the modelling of experimental results from the LTDE-SD in situ tracer test performed at the $"A$sp$"o$ Hard Rock Laboratory in Sweden. Ten different modelling teams provided results for this exercise, using different concepts and codes. Three main types of modelling approaches were used: (1) analytical solutions to the transport-retention equations, (2) continuum-porous-medium numerical models, and (3) microstructure-based models accounting for small-scale heterogeneity (i.e. mineral grains and microfracture distributions). The modelling by the different teams allowed the comparison of many different model concepts, especially in terms of potential zonations of rock properties (porosity, diffusion, sorption), such as the presence of a disturbed zone at the rock and fracture surface, the potential effects of micro- and cm-scale fractures.

Journal Articles

Evolution of the reaction and alteration of granite with Ordinary Portland cement leachates; Sequential flow experiments and reactive transport modelling

Bateman, K.*; Murayama, Shota*; Hanamachi, Yuji*; Wilson, J.*; Seta, Takamasa*; Amano, Yuki; Kubota, Mitsuru*; Ouchi, Yuji*; Tachi, Yukio

Minerals (Internet), 12(7), p.883_1 - 883_20, 2022/07

 Times Cited Count:0 Percentile:0.03(Geochemistry & Geophysics)

Journal Articles

Predictive modeling of a simple field matrix diffusion experiment addressing radionuclide transport in fractured rock. Is it so straightforward?

Soler, J. M.*; Neretnieks, I.*; Moreno, L.*; Liu, L.*; Meng, S.*; Svensson, U.*; Iraola, A.*; Ebrahimi, K.*; Trinchero, P.*; Molinero, J.*; et al.

Nuclear Technology, 208(6), p.1059 - 1073, 2022/06

 Times Cited Count:1 Percentile:36.81(Nuclear Science & Technology)

The SKB Task Force is an international forum on modelling of groundwater flow and solute transport in fractured rock. The WPDE experiments are matrix diffusion experiments in gneiss performed at the ONKALO underground facility in Finland. Synthetic groundwater containing several conservative and sorbing tracers was injected along a borehole interval. The objective of Task 9A was the predictive modelling of the tracer breakthrough curves from the WPDE experiments. Several teams, using different modelling approaches and codes, participated in this exercise. An important conclusion from this exercise is that the modelling results were very sensitive to the magnitude of dispersion in the borehole opening, which is related to the flow of water. Focusing on the tails of the breakthrough curves, which are more directly related to matrix diffusion and sorption, the results from the different teams were more comparable.

Journal Articles

Current status of Geological disposal by "all-Japan" activities, 6; Post-closure safety assessment (2)

Tachi, Yukio; Saito, Takumi*; Kirishima, Akira*

Nihon Genshiryoku Gakkai-Shi ATOMO$$Sigma$$, 64(5), p.290 - 295, 2022/05

no abstracts in English

JAEA Reports

Development of JAEA sorption database (JAEA-SDB); Update of sorption/QA data in FY2021

Sugiura, Yuki; Suyama, Tadahiro*; Tachi, Yukio

JAEA-Data/Code 2021-017, 58 Pages, 2022/03

JAEA-Data-Code-2021-017.pdf:1.98MB

Sorption behavior of radionuclides (RNs) in buffer materials (bentonites), rocks and cementitious materials is one of the key processes in a safe geological disposal of radioactive waste because RNs migration in these materials is expected to be retarded by the sorption process. Therefore, it is necessary to understand the sorption process and develop a database compiling reliable data and mechanistic/predictive models so that reliable parameters can be set under a variety of geochemical conditions relevant to a performance assessment (PA). For this purpose, Japan Atomic Energy Agency (JAEA) has developed the database of sorption parameters in bentonites, rocks and cementitious materials. This sorption database (SDB) was firstly developed as an important basis for the H12 PA of a high-level radioactive waste disposal, and have been provided through the Web. JAEA has continued to improve and update the SDB in the view of potential future needs of data focusing on assuring the desired quality level and testing the usefulness of the databases for possible applications to the PA-related parameter setting. This report focuses on updating of the sorption database (JAEA-SDB) as a basis of integrated approach for the PA-related distribution coefficient (Kd) setting and development of mechanistic sorption models. This report also includes an overview of the database structure and contents. Kd data and their quality assurance (QA) results were updated from literature collected with wider ranges. As a result, 8,503 Kd data from 70 references related to the above-mentioned systems were added and the total number of Kd values in JAEA-SDB reached 79,072. The QA/classified Kd data reached about 75.4% for all Kd data in JAEA-SDB. The updated JAEA-SDB is expected to make it possible to give a basis for the next-step PA-related Kd setting.

Journal Articles

Selenide [Se(-II)] immobilization in anoxic, Fe(II)-rich environments; Coprecipitation and behavior during phase transformations

Francisco, P. C. M.; Matsumura, Daiju; Kikuchi, Ryosuke*; Ishidera, Takamitsu; Tachi, Yukio

Environmental Science & Technology, 56(5), p.3011 - 3020, 2022/03

 Times Cited Count:0 Percentile:0(Engineering, Environmental)

Journal Articles

Decrease of radionuclide sorption in hydrated cement systems by organic ligands; Comparative evaluation using experimental data and thermodynamic calculations for ISA/EDTA-actinide-cement systems

Ochs, M.*; Dolder, F.*; Tachi, Yukio

Applied Geochemistry, 136, p.105161_1 - 105161_11, 2022/01

 Times Cited Count:1 Percentile:70.41(Geochemistry & Geophysics)

Various types of radioactive wastes and environments contain organic substances that can stabilize the aqueous complexes with radionuclides and therefore lead to a decrease of sorption. The present study focuses on testing a methodology to quantify sorption reduction factors (SRFs) in the presence of organic ligands for cement systems. Three approaches for the estimation of SRFs; (1) analogy with solubility enhancement factors, (2) radionuclide speciation based on the thermodynamic calculations, and (3) experimental sorption data in ternary systems, were coupled and tested for the representative organic ligands (ISA and EDTA) and selected key radionuclides (actinides). Our approach allows to critically evaluate the dependence of SRFs for various systems on the chosen method of quantification, in accordance with the data availability for a given systems. The reliable SRFs can only be derived from the sorption measurements in ternary systems. SRF often need to be derived in the absence of such direct evidence, and estimations need to be made based on analogies and speciation information. However, such estimates may be subject to substantial uncertainties.

Journal Articles

Uranium (VI) sorption on illite under varying carbonate concentrations; Batch experiments, modeling, and cryogenic time-resolved laser fluorescence spectroscopy study

Mei, H.; Aoyagi, Noboru; Saito, Takumi*; Kozai, Naofumi; Sugiura, Yuki; Tachi, Yukio

Applied Geochemistry, 136, p.105178_1 - 105178_8, 2022/01

 Times Cited Count:0 Percentile:0.01(Geochemistry & Geophysics)

Journal Articles

Evaluation report of Task 9C based on comparisons and analyses of modelling results for the ONKALO REPRO-TDE experiment

Soler, J. M.*; Kek$"a$l$"a$inen, P.*; Pulkkanen, V.-M.*; Moreno, L.*; Iraola, A.*; Trinchero, P.*; Hokr, M.*; $v{R}$$'i$ha, J.*; Havlov$'a$, V.*; Trpko$v{s}$ov$'a$, D.*; et al.

SKB TR-21-09, 204 Pages, 2021/11

Journal Articles

A Scaling approach for retention properties of crystalline rock; Case study of the in-situ long-term sorption and diffusion experiment (LTDE-SD) at the $"A$sp$"o$ Hard Rock Laboratory in Sweden

Tachi, Yukio; Ito, Tsuyoshi*; Gylling, B.*

Water Resources Research, 57(11), 20 Pages, 2021/11

 Times Cited Count:1 Percentile:26.22(Environmental Sciences)

This paper focuses on the scaling approach for sorption and diffusion parameters from laboratory to in-situ conditions using the dataset of LTDE-SD experiment performed at the $"A$sp$"o$ HRL. The near-surface heterogeneities at both fracture surface and rock matrix could be evaluated by conceptual model with high porosity and diffusivity, and sorption capacity, and their gradual change at the near-surface zones. The modelling results for non-sorbing Cl-36 and weak-sorbing Na-22 could validate the model concept and the parameter estimation of porosity and diffusivity, by considering the disturbed zone of 5 mm thickness with gradual parameter changes. The De values of these cationic and anionic tracers showed typical cation excess and anion exclusion effects. The modelling results for high sorbing tracers (Cs-137, Ra-226, Ni-63 and Np-237) with different sorption mechanism could confirm the validity of the scaling approaches of Kd values as a function of particle size and their relation to the near-surface disturbances.

Journal Articles

Diffusion of tritiated water, $$^{137}$$Cs$$^{+}$$, and $$^{125}$$I$$^{-}$$ in compacted Ca-montmorillonite; Experimental and modeling approaches

Fukatsu, Yuta; Yotsuji, Kenji*; Okubo, Takahiro*; Tachi, Yukio

Applied Clay Science, 211, p.106176_1 - 106176_10, 2021/09

 Times Cited Count:3 Percentile:50.03(Chemistry, Physical)

Journal Articles

Evolution of the reaction and alteration of mudstone with ordinary Portland cement leachates; Sequential flow experiments and reactive-transport modelling

Bateman, K.; Murayama, Shota*; Hanamachi, Yuji*; Wilson, J.*; Seta, Takamasa*; Amano, Yuki; Kubota, Mitsuru*; Ouchi, Yuji*; Tachi, Yukio

Minerals (Internet), 11(9), p.1026_1 - 1026_23, 2021/09

 Times Cited Count:2 Percentile:52.13(Geochemistry & Geophysics)

Journal Articles

The Impact of cement on argillaceous rocks in radioactive waste disposal systems; A Review focusing on key processes and remaining issues

Wilson, J.*; Bateman, K.; Tachi, Yukio

Applied Geochemistry, 130, p.104979_1 - 104979_19, 2021/07

 Times Cited Count:8 Percentile:75.25(Geochemistry & Geophysics)

The concept of deep geological disposal will include the multiple use of cement-based materials. In the case of argillaceous host rocks, the presence of hyperalkaline cement porefluid results in the destabilization of primary minerals in the argillite, resulting in the development of a zone of alteration at cement-rock interfaces. The process understanding gained from experimental, analogue, and modelling studies has been reviewed, and remaining areas of uncertainty identified. Although there is a reasonably good understanding of the mineral assemblages that are likely to occur due to cement-rock interactions, there are still some areas where a degree of uncertainty remains, in particular: the evolution of cement-argillite interfaces at T $$>$$ 25$$^{circ}$$C; the rates at which secondary minerals form; the extent of pore clogging due to secondary mineral precipitation; the implications of alteration for radionuclide transport.

Journal Articles

Evaluation report of Task 9B based on comparisons and analyses of modelling results for the $"A$sp$"o$ HRL LTDE-SD experiments

Soler, J. M.*; Meng, S.*; Moreno, L.*; Neretnieks, I.*; Liu, L.*; Kek$"a$l$"a$inen, P.*; Hokr, M.*; $v{R}$$'i$ha, J.*; Vete$v{s}$n$'i$k, A.*; Reimitz, D.*; et al.

SKB TR-20-17, 71 Pages, 2021/07

Task 9B of the SKB Task Force on Modelling of Groundwater Flow and Transport of Solutes in fractured rock focused on the modelling of experimental results from the LTDE-SD in situ tracer test performed at the $"A$sp$"o$ Hard Rock Laboratory in Sweden. Ten different modelling teams provided results for this exercise, using different concepts and codes. Three main types of modelling approaches were used: (1) analytical solutions to the transport-retention equations, (2) continuum-porous-medium numerical models, and (3) microstructure-based models accounting for small-scale heterogeneity (i.e. mineral grains and microfracture distributions). The modelling by the different teams allowed the comparison of many different model concepts, especially in terms of potential zonations of rock properties (porosity, diffusion, sorption), such as the presence of a disturbed zone at the rock and fracture surface, the potential effects of micro- and cm-scale fractures.

Journal Articles

Reaction and alteration of mudstone with Ordinary Portland Cement and Low Alkali Cement pore fluids

Bateman, K.; Amano, Yuki; Kubota, Mitsuru*; Ouchi, Yuji*; Tachi, Yukio

Minerals (Internet), 11(6), p.588_1 - 588_19, 2021/06

 Times Cited Count:4 Percentile:77.35(Geochemistry & Geophysics)

Journal Articles

Effect of interlayer cations on montmorillonite swelling; Comparison between molecular dynamic simulations and experiments

Yotsuji, Kenji*; Tachi, Yukio; Sakuma, Hiroshi*; Kawamura, Katsuyuki*

Applied Clay Science, 204, p.106034_1 - 106034_13, 2021/04

 Times Cited Count:23 Percentile:99.3(Chemistry, Physical)

Journal Articles

Development of evaluation method for diffusion and filtration behavior of colloid in compacted bentonites using dendrimers

Endo, Takashi*; Tachi, Yukio; Ishidera, Takamitsu; Terashima, Motoki

Nihon Genshiryoku Gakkai Wabun Rombunshi, 20(1), p.9 - 22, 2021/03

Evaluation method of colloid diffusion and filtration in compacted bentonites was developed using dendrimers. Diffusion and filtration behavior of PAMAM dendrimers with the size of 5.7$$sim$$7.2nm was investigated by the through-diffusion experiment in bentonite compacted to 0.8 Mg/m$$^{3}$$ and saturated with 0.005$$sim$$0.5mol/L NaCl. Effective diffusivities (De) and filtration ratios (Rf) of dendrimers were determined from the breakthrough curves and the depth profiles in compacted bentonite, respectively. The De values of negatively charged dendrimer increased when porewater salinity increased and dendrimer size decreased as influenced by anion exclusion effect in negatively charged clay surfaces. The Rf values increased when porewater salinity decreased and dendrimer size increased, demonstrating significant fractions of dendrimer were filtered by narrow pores in complex pore networks. These trends consistent with the previous studies emphasize the validity of the evaluation method using dendrimer.

Journal Articles

Surface complexation of Ca and competitive sorption of divalent cations on montmorillonite under alkaline conditions

Sugiura, Yuki; Ishidera, Takamitsu; Tachi, Yukio

Applied Clay Science, 200, p.105910_1 - 105910_10, 2021/01

 Times Cited Count:4 Percentile:76.73(Chemistry, Physical)

Journal Articles

Pore distribution of compacted Ca-montmorillonite using NMR relaxometry and cryoporometry; Comparison with Na-montmorillonite

Okubo, Takahiro*; Yamazaki, Akio*; Fukatsu, Yuta; Tachi, Yukio

Microporous and Mesoporous Materials, 313, p.110841_1 - 110841_11, 2021/01

 Times Cited Count:1 Percentile:19.44(Chemistry, Applied)

Pore distributions in water-saturated Ca-montmorillonite were investigated using $$^{1}$$H NMR measurements under various dry densities (0.8 - 1.6 g/cm$$^{3}$$) and porewater salinity conditions (deionized water, 0.1 and 1 M CaCl$$_{2}$$), at the temperature range of 233 - 303 K. The volume fractions of the interlayer pore including two and three hydrated layers and the non-interlayer pore in compacted Ca-montmorillonite were quantified by NMR relaxometry including $$T1$$ and $$T1/T2$$ distribution analysis, and were compared with NMR cryoporometry and X-ray diffractometry. These analysis provided consistent pictures on the pore distributions in compacted Ca-montmorillonite, in contrast to Na-montmorillonite. The main factor affecting the pore distribution in compacted Ca- and Na-montmorillonite is the density, whereas the effect of porewater salinity is relatively smaller. The effect of interlayer cations is also relatively smaller at higher density, although the differences in the pore structures are significant at low density.

248 (Records 1-20 displayed on this page)