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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:1 Percentile:76.68(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:69.4(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.

Oral presentation

Experimental and modelling results of in-situ Long-Term Diffusion test in granodiorite matrix at Grimsel Test Site

Fukatsu, Yuta; Ito, Tsuyoshi*; Tachi, Yukio; Ishida, Keisuke*; Martin, A.*

no journal, , 

no abstracts in English

Oral presentation

Modelling analysis on in situ Long Term Diffusion (LTD-II) test at the Grimsel test site

Fukatsu, Yuta; Ito, Tsuyoshi*; Tachi, Yukio; Ishida, Keisuke*; Martin, A.*

no journal, , 

Oral presentation

An Overview and key results from the long term in situ diffusion project (ltd) at the Grimsel Test Site, Switzerland

Martin, A.*; Fukatsu, Yuta; Tachi, Yukio; Ishida, Keisuke*; Muuri, E.*; Siitari-Kauppi, M.*; Havlova, V.*; Vokal, A.*

no journal, , 

Oral presentation

Relationships between chemical shift and structure of Cs absorbed on clay mineral

Takei, Koyo*; Okubo, Takahiro*; Tachi, Yukio; Fukatsu, Yuta

no journal, , 

Cs adsorption sites on vermiculite clays were investigated by $$^{133}$$Cs magic-angle-spinning nuclear magnetic resonance (MAS NMR) and theoretical $$^{133}$$Cs chemical shift calculations. A partially Cs exchanged vermiculite sample was prepared. Three peaks on $$^{133}$$Cs MAS NMR spectra were experimentally observed. However, Cs absorption sites were not assigned to these peaks. A molecular model of fully Cs exchanged vermiculite was built to obtain $$^{133}$$Cs chemical shift theoretically by GIPAW method. Calculated $$^{133}$$Cs chemical shift ranged 23 to 47 ppm, which corresponds to the peak of the lowest field side. Detailed relationships between structure and $$^{133}$$Cs chemical shifts were investigated from Cs position and vermiculite layer structure.

Oral presentation

Pore connectivity of clay materials implicated in fluid flow and chemical diffusion

Hu, Q.*; Wang, Q.*; Zhao, C.*; Tachi, Yukio; Fukatsu, Yuta

no journal, , 

A low aqueous-phase diffusion in low-permeable clay barrier materials has been accepted as a critical process in the long-term performance evaluation of nuclear waste repository. Low-permeable clay materials whose pores are poorly interconnected are known to have anomalous diffusion properties that strongly impact long-term net diffusion. Related research works with mudrocks of Wakkanai formation of Horonobe URL in Japan, Opalinus clay of Mt. Terri URL in Switzerland, as well as various shale and clay mineral, utilizes a complementary suite of pore structure characterization approaches (e.g., mercury intrusion porosimetry, small angle neutron scattering) and tracer experiments followed with micro-scale mapping with laser ablation-ICP-MS. These results presents the relationship between pore connectivity and anomalous diffusion in clay materials. Pore size is not the major contributor to slow fluid flow and radionuclide transport, the anomalous behavior appears to be caused by low pore connectivity.

Oral presentation

Quantifying isolated pore space in geological barrier materials

Hu, Q.*; Wang, Q.*; Oware, P.*; Tachi, Yukio; Fukatsu, Yuta; Illvsky, J.*; Almer, J.*

no journal, , 

Oral presentation

Realistic modeling approach for tracer migration and retention in fractured crystalline rocks from the Grimsel Test Site

Tachi, Yukio; Ito, Tsuyoshi*; Fukatsu, Yuta; Akagi, Yosuke*; Sato, Hisao*; Hu, Q.*; Martin, A. J.*

no journal, , 

Oral presentation

Diffusion behaviors of Np(V) under coexistence with multiple chemical species in compacted bentonite

Fukatsu, Yuta; Ishidera, Takamitsu; Tachi, Yukio

no journal, , 

no abstracts in English

Oral presentation

Oral presentation

Fluid flow and chemical transport in shallow and deep mudrocks being implicated by pore geometry and connectivity

Hu, Q.*; Wang, Q.*; Zhao, C.*; Zhang, T.*; Tachi, Yukio; Fukatsu, Yuta

no journal, , 

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