The hydrogeochemistry of argillaceous rock formations at the Horonobe URL site, Japan

Hama, Katsuhiro; Kunimaru, Takanori; Metcalfe, Richard; Martin, Alan J.

doi:10.1016/j.pce.2005.12.008

Cited by 80 publications

(42 citation statements)

References 5 publications

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“…In Japan, salt water is often found underground [14][15][16]. Thus, considering the condition of groundwater in Japan, the HSULPC specimen was kept in simulated seawater inside a plastic bottle.…”

Section: Observation Methodsmentioning

confidence: 99%

Investigation of self-sealing in high-strength and ultra-low-permeability concrete in water using micro-focus X-ray CT

Fukuda

Nara

Kobayashi

et al. 2012

Cement and Concrete Research

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High-strength and ultra-low-permeability concrete (HSULPC) is thought to be useful as a radioactive waste package. Thus, a high confining ability is desirable.For cementitious materials, sealing of cracks may occur in water due to the precipitation of calcium compounds. This can affect the confining ability. In this study, the sealing of a crack in HSULPC in water was investigated using microfocus X-ray computed tomography (CT). The sealing by precipitation occurred only around the end of the specimen. Sealed regions of the crack were identified using three-dimensional image registration and CT image subtraction of images obtained for the specimen before and after it was immersed in water to evaluate temporal changes of the sealing deposits in the crack. The sealing deposits increased as the HSULPC specimen was kept in water longer. It was concluded that cracks in HSULPC in water are sealed by precipitation.

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Section: Observation Methodsmentioning

confidence: 99%

Investigation of self-sealing in high-strength and ultra-low-permeability concrete in water using micro-focus X-ray CT

Fukuda

Nara

Kobayashi

et al. 2012

Cement and Concrete Research

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“…The age of the HSULPC specimen used in this study was approximately two years. Because salt water is often found underground (Mizukami et al 1977;Iwatsuki et al 2005;Hama et al 2007), the HSULPC specimen was kept in simulated seawater based on the groundwater conditions in Japan (chemical composition in Table 2). The sealing of the macro-fracture was observed using micro-focus X-rayCT (Fukuda et al 2012).…”

Section: Sample Preparationmentioning

confidence: 99%

Observation of fracture sealing in high-strength and ultra-low-permeability concrete by micro-focus X-ray CT and SEM/EDX

et al. 2014

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Fracture sealing by precipitation is known to occur in high-strength and ultra-lowpermeability concrete (HSULPC) immersed in water. Because a high ability to retard radionuclide migration is required for HSULPC, understanding both the sealing process and the composition of sealing deposits is important to identify optimum conditions for significant sealing. In this study, sealing of a macro-fractured HSULPC specimen with initial aperture of approximately 0.1 mm was investigated in simulated seawater over 49 days. The composition of sealing deposits at 49 days after immersion was clarified by scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM/EDX), and the progress of sealing during the 49 days was clarified by image analysis with micro-focus X-ray computed tomography (X-rayCT). Both the SEM/EDX and X-rayCT results showed that significant sealing was attained only near the outermost part of the specimen. The SEM/EDX results showed that a thin brucite layer formed on the entire specimen surface over which significant precipitation of calcium carbonate occurred and sealed the macro-fracture only near the outermost part of the specimen. The X-rayCT results indicated that the amount of sealing deposits in the macro-fracture (P seal ) reached 70 % in the mostly sealed region at 49 days and the rate of change in P seal became maximum (3.7 % day -1 ) during 7-21 days after immersion, then decreased. In conclusion, Revised_Manuscript Click here to download Manuscript: IJF_manuscript_FRAC_Rev1.doc Click here to view linked References 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 2 the findings in this study represent an important clue in the search for optimum conditions to achieve fracture sealing in HSUPLC.

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“…Hama et al (2007) have investigated the in-situ chemical conditions and the residence time of groundwater in that area, showing the Na-Cl dominated water chemistry at the depths lower than 250 m. They concluded that the vertical and lateral salinity gradients can be used to test groundwater flow models. Kurikami et al (2008) investigated the heterogeneity in hydraulic conductivity of both the Wakkanai and Koetoi formations.…”

Section: Methodsmentioning

confidence: 99%

An axisymmetric diffusion experiment for the determination of diffusion and sorption coefficients of rock samples

Takeda¹,

Hiratsuka²,

Ito³

et al. 2011

Journal of Contaminant Hydrology

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Diffusion anisotropy is a critical property in predicting migration of substances in sedimentary formations with very low permeability. The diffusion anisotropy of sedimentary rocks has been evaluated mainly from laboratory diffusion experiments, in which the directional diffusivities are separately estimated by through-diffusion experiments using different rock samples, or concurrently by in-diffusion experiments in which only the tracer profile in a rock block is measured.To estimate the diffusion anisotropy from a single rock sample, this study proposes an axisymmetric diffusion test, in which tracer diffuses between a cylindrical rock sample and a surrounding solution reservoir. The tracer diffusion between the sample and reservoir can be monitored from the reservoir tracer concentrations, and the tracer profile could also be obtained after dismantling the sample. Semi-analytical solutions are derived for tracer concentrations in both the reservoir and sample, accounting for an anisotropic diffusion tensor of rank two as well as the dilution effects from sampling and replacement of reservoir solution.The transient and steady-state analyses were examined experimentally and numerically for different experimental configurations, but without the need for tracer profiling. These experimental configurations are tested for in-and out-diffusion experiments using Koetoi and Wakkanai mudstones and Shirahama sandstone, and are scrutinized by a numerical approach to identify favorable conditions for parameter estimation. Page 2 of 31The analysis reveals the difficulty in estimating diffusion anisotropy; test configurations are proposed for enhanced identifiability of diffusion anisotropy. Moreover, it is demonstrated that the axisymmetric diffusion test is efficient in obtaining the sorption parameter from both steady-state and transient data, and in determining the effective diffusion coefficient if isotropic diffusion is assumed. Moreover, measuring reservoir concentrations in an axisymmetric diffusion experiment coupled with tracer profiling may be a promising approach to estimate of diffusion anisotropy of sedimentary rocks.

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The hydrogeochemistry of argillaceous rock formations at the Horonobe URL site, Japan

Cited by 80 publications

References 5 publications

Investigation of self-sealing in high-strength and ultra-low-permeability concrete in water using micro-focus X-ray CT

Investigation of self-sealing in high-strength and ultra-low-permeability concrete in water using micro-focus X-ray CT

Observation of fracture sealing in high-strength and ultra-low-permeability concrete by micro-focus X-ray CT and SEM/EDX

An axisymmetric diffusion experiment for the determination of diffusion and sorption coefficients of rock samples

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