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Terada, Atsuhiko; Nagaishi, Ryuji
Nuclear Technology, 210(10), p.1871 - 1887, 2024/10
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)In order to understand dispersion of H2 leaked in packed beds of non-porous/porous particles in a partially open space practically, the dispersion of H2 in the particle layers of glass beads and soil was analytically studied using a CFD code to be compared with the experiments and to elucidate the effects of particle layer. H2 flowed out from a single leak point in the particle layer of non-porous glass beads was affected by buoyancy around the leak point, and diffused directly above the leak point in an elliptical shape faster than in the horizontal direction. After that, when it reached the air layer in the head space above the particle layer, H2 spread horizontally, formed a large concentration gradient near the boundary between the particle layer and the air layer, and further diffused in the air layer until the H2 concentration became about 1/3 or less of the concentration near the surface of particle layer. The calculations largely reproduced the experimental concentration distributions. When the particle layer was porous decomposed granite soil, the diffusion behavior of H2 in the particle layer proceeded in the same manner as in the case of glass beads. However, a large concentration gradient was formed near the boundary between the particle layer and the air layer, and then H2 diffused in the air layer until the H2 concentration became below the lower combustion limit. It was suggested through sensitivity analysis that the air permeability coefficient had a large effect on the time course of H2 concentration distribution. Based on the above, we further simulated H2 behavior in the vessel containing the H2 leaked particle layer. By inserting multiple vent pipes without considering H2 generation distribution and particle properties in the particle layer, H2 accumulated from one pipe was discharged by buoyancy without depending on the H2 generation distribution and particle properties in the particle layer, and air flowed in from the other pipe.
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：2 Percentile：13.80(Geochemistry & Geophysics)Yuguchi, Takashi*; Yamazaki, Hayato*; Ishibashi, Kozue*; Sakata, Shuhei*; Yokoyama, Tatsunori; Suzuki, Satoshi*; Ogita, Yasuhiro; Sando, Kazusa*; Imura, Takumi*; Ono, Takeshi*
Journal of Asian Earth Sciences, 226, p.105075_1 - 105075_9, 2022/04
Times Cited Count：6 Percentile：59.00(Geosciences, Multidisciplinary)Simultaneous determination of the U-Pb age of zircon and concentration of titanium in a single analysis spot, using inductively coupled plasma mass spectrometry with laser ablation sample introduction, produces paired age and temperature data of zircon crystallisation, potentially revealing time-temperature (
) histories for evolved magma. The Kurobegawa granite, central Japan, contains abundant mafic magmatic enclaves (MMEs). We applied this method to evaluate MMEs and their host (enclosing) granites. Cooling behaviour common to both MMEs and host rocks was found between 1.5 and 0.5 Ma. Rapid cooling from the zircon crystallisation temperature to the closure temperature of biotite K-Ar system was within 
1 million year. Combining the obtained paths of MMEs and host rocks with petrological information can provide insights into magma chamber processes. This suggests that MME flotation, migration, and spread through the magma chamber ceased at 1.5-0.5 Ma, indicating the emplacement age of the Kurobegawa granitic pluton, as no large-scale reheating episodes have occurred since then.
Nara, Yoshitaka*; Kato, Masaji*; Sato, Tsutomu*; Kono, Masanori*; Sato, Toshinori
Proceedings of 5th ISRM Young Scholars' Symposium on Rock Mechanics and International Symposium on Rock Engineering for Innovative Future (YSRM 2019 and REIF 2019) (USB Flash Drive), 6 Pages, 2019/12
It is important to understand the long-term migration of radionuclides considering carious rock engineering projects such as the geological disposal of radioactive wastes. The network of fractures and pores in a rock mass can play important roles as the pathway of the fluid flow of rock. Usually groundwater contains fine-grained minerals such as clays. It is probable that the accumulation of the fine-grained minerals occurs in a fracture if the groundwater flows in a fracture in a rock. In this study, we have conducted the permeability measurement using water including clays. Specifically, we used a macro-fractured granite as a rock sample, and investigated the change of the permeability under the flow of the water including clays. It was shown that the hydraulic conductivity decreased with elapsed time.
Nohara, Tsuyoshi; Uno, Masaoki*; Tsuchiya, Noriyoshi*
Geofluids, 2019, p.6053815_1 - 6053815_16, 2019/08
Times Cited Count：3 Percentile：27.59(Geochemistry & Geophysics)Amphibole-plagioclase thermometry was applied to estimate the temperature of a glassy vein as approximately 700. The results of observations of the rock core revealed that of supercritical fluid flow was microfracture filling with hornblende and plagioclase. The current high permeability was recognized to be microfracture network. A high-angle fracture of chlorite filling in combination with an open fracture was recognized as characteristics of a high-permeability type.
Nara, Yoshitaka*; Kuwatani, Ryuta*; Kono, Masanori*; Sato, Toshinori; Kashiwaya, Koki*
Zairyo, 67(7), p.730 - 737, 2018/07
Information of confining ability of rock is important for the geological disposal of radioactive wastes. To maintain or improve the confining ability of rocks, it is important to seal pores and cracks. In this study, we investigated the precipitation of minerals on the rock surface. As rock samples, we used Berea sandstone and Toki granite in this study. It was shown that precipitation occurred on the surface of rock specimens kept in calcium hydroxide solution for 1 month if the concentration was high. Specifically, if the concentration of calcium hydroxide solution was higher than 300 mg/l, the precipitation occurred obviously. After keeping rock specimens in calcium hydroxide solution, the weight of the rock samples increased and the concentration of calcium ion decreased by the precipitation. It is considered that the calcium ion in water was used for the precipitation on rock surfaces. Since the precipitation has been recognized for rock surfaces, it is possible to seal pores and cracks in rocks. Therefore, it is also possible to keep or decrease the permeability of rocks by the precipitation of calcium compounds.
Kato, Masaji*; Nara, Yoshitaka*; Okazaki, Yuki*; Kono, Masanori*; Sato, Toshinori; Sato, Tsutomu*; Takahashi, Manabu*
Zairyo, 67(3), p.318 - 323, 2018/03
To ensure the safe geological disposal of radioactive wastes, it is important to determine the permeability of clays. The transient pulse test is suitable to apply to the low permeability materials, because it takes relatively short term to determine the permeability. Usually we increase the upstream pore pressure in the measurement with the transient pulse test. However, it is impossible to determine the permeability of clay in this procedure because of the increase of pore pressure. Therefore, the transient pulse test has never been applied to the determination of permeability of clays. In this study, we tried to apply the transient pulse test to a clay obtained in Mizunami Underground Research Laboratory to determine the permeability with decreasing the downstream pore pressure. It was clarified that the transient pulse test with decreasing downstream pore pressure is appropriate from the measurements of granite and sandstone. It was shown that the permeability of a clay was determined by the transient pulse test with decreasing the downstream pore pressure, which agreed with the permeability determined from the falling head test. The measurement time of the transient pulse test is much shorter than that of the falling head test. It is concluded that the transient pulse test is appropriate for the determination of the permeability of clays.
Soler, J. M.*; Landa, J.*; Havlov
, V.*; Tachi, Yukio; Ebina, Takanori*; Sardini, P.*; Siitari-Kauppi, M.*; Eikenberg, J.*; Martin, A. J.*
Journal of Contaminant Hydrology, 179, p.89 - 101, 2015/08
Times Cited Count：41 Percentile：82.37(Environmental Sciences)Matrix diffusion is a key process for radionuclide retention in crystalline rocks. An in-situ diffusion experiment in granite matrix was performed at the Grimsel Test Site (Switzerland). Several tracers (HTO, Na
, Cs) were circulated through a borehole and the decrease in tracer concentrations was monitored for 2.5 years. Then, the borehole section was overcored and the tracer profiles in the rock were analyzed. Transport distances in the rock were 20 cm for HTO, 10 cm for Na and 1 cm for Cs. The dataset was analyzed with diffusion-sorption models by different teams using different codes, with the goal of obtaining effective diffusivities (De) and rock capacity factors. There was a rather good agreement between the values from different teams, implied that De and capacity factors in the borehole damaged zone are larger than those in the bulk rock. However, HTO seems to display large discrepancies between measured and modeled results.
Mukai, Masayuki; Ueda, Masato; Inada, Daisuke; Yukawa, Kazuhiko; Maeda, Toshikatsu; Iida, Yoshihisa
Proceedings of International Symposium NUCEF 2005, p.219 - 224, 2005/08
For better quantitative understanding of radionuclide migration for safety assessment of geologic disposal, JAERI has been conducting experimental and modeling studies on influences of humic substances, highly alkaline conditions and colloids on sorptive and diffusional behavior of TRU in geologic materials. In the absence of fulvic acid, one of humic substances, diffusion of Am through a tuff sample was not detected. By adding fulvic acid, Am was detected in the downstream cell, which indicates the diffusion through the sample. Highly alkaline conditions arisen from cementitious materials may spread by altering chemical and physical properties of geologic materials. Through-diffusion experiments of alkaline species in granite showed that the effective diffusion coefficient of Ca
and OH
in a cement-equilibrated aqueous solution were found to be higher by almost two orders of magnitude than Na and OH in a NaOH solution. Radionuclide migration can be enhanced by colloids, and thus a calculation code describing the effect of colloids on radionuclide migration has been required.
in granite matrixYamaguchi, Tetsuji; Nakayama, Shinichi; Kawada, Chiharu*
Genshiryoku Bakkuendo Kenkyu, 9(1), p.61 - 66, 2002/09
The effective diffusivity (
) and distribution ratio (
) of 
Ba in Inada granite have been determined by the through-diffusion method. Experiments were performed in triplicate for 10
, 1 and 10 mol m
BaCl
solutions at 25
C. The value obtained at a BaCl concentration of 10 mol m, agreed to the estimated value based on the pore diffusion model. The lower BaCl concentrations yielded higher values and higher values. The variation in was neither due to the speciation of barium in the solutions nor due to variation in physical properties of the pore structure in the rock. Contribution of diffusion in sorbed state should be responsible for the variation in .
Nagano, Tetsushi; Isobe, Hiroshi*; Nakashima, Satoru*; Ashizaki, Midori*
Applied Spectroscopy, 56(5), p.651 - 657, 2002/05
Times Cited Count：11 Percentile：52.73(Instruments & Instrumentation)no abstracts in English
Yamaguchi, Tetsuji; Nakayama, Shinichi
JAERI-Conf 2002-004, p.325 - 332, 2002/03
When long-lived radionuclides are transported by groundwater through fractures in the rock mass surrounding a radioactive waste repository, their diffusion into pores in the rock matrix and ensuing sorption onto mineral surfaces are expected to retard their transport along the pathways. We have characterized the pore structure of the Japanese Inada biotite granite and confirmed that Fick's diffusion law can be applied to the transport of aqueous species in granite. Effective diffusivity was determined by the through-diffusion method for cationic, anionic and actinide complex species to explore the mechanism of diffusion of the aqueous species. The results of this study enable us to provide a scientifically sound basis for radionuclide diffusion in granite for performance assessment of geological disposal. Future studies should emphasize understanding the diffusion mechanisms in low-permeability engineered barrier materials, data acquisition on long-term degradation of the materials and quantifying uncertainties associated with long-term mass transport analysis.
; ;
Oyo Chishitsu, 32(2), p.55 - 63, 1991/06
no abstracts in English
; ; Nagano, Tetsushi;
Kozan Chishitsu, 39(6), p.349 - 354, 1989/00
no abstracts in English
; ; ;
Journal of Nuclear Science and Technology, 22(10), p.833 - 840, 1985/00
Times Cited Count：3 Percentile：46.93(Nuclear Science & Technology)no abstracts in English
Nohara, Tsuyoshi; Tsuchiya, Noriyoshi*
no journal, ,
A trace of a high-temperature fluid in the Toki granite is investigated using pre-existing boring core of MIU. Fractures filled with secondary formed biotite and pores filled with quarts are recognized. It is considered that these filling minerals are traces of a high-temperature fluid in the past.
Nohara, Tsuyoshi; Takeuchi, Ryuji; Sakai, Toshihiro
no journal, ,
Focusing on the characteristics of the faults and fractures of the MIU, based on analysis of existing data and on geological investigations, we examined the geological and hydrological features of the deep underground granitic rocks in the site scale. As a result, main permeable structures of granitic rocks can be associated with the old structures formed with the faulting and/or hydrothermal activity in geological times. Furthermore, we examined the distribution of the major permeable structures, based on the distribution of the geological structures.
