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JAEA Reports

Hydrochemical investigation at the Mizunami Underground Research Laboratory; Compilation of groundwater chemistry data in the Mizunami group and the Toki granite (fiscal year 2016)

Watanabe, Yusuke; Hayashida, Kazuki; Kato, Toshihiro; Kubota, Mitsuru; Aosai, Daisuke*; Kumamoto, Yoshiharu*; Iwatsuki, Teruki

JAEA-Data/Code 2018-002, 108 Pages, 2018/03

JAEA-Data-Code-2018-002.pdf:6.53MB

Japan Atomic Energy Agency has been investigating groundwater chemistry to understand the effect of excavation and maintenance of underground facilities as part of the Mizunami Underground Research Laboratory (MIU) Project in Mizunami, Gifu, Japan. In this report, we compiled data of groundwater chemistry and microbiology obtained at the MIU in the fiscal year 2016 and 2014 to 2016, respectively. In terms of ensuring traceability of data, basic information (e.g. sampling location, sampling time, sampling method and analytical method) and methodology for quality control are described.

Journal Articles

Evaluation of hydrogeochemical processes provoked by tunnel excavation and closure based on simulated experiment in a mock-up test drift

Hayashida, Kazuki; Kato, Toshihiro*; Kubota, Mitsuru*; Murakami, Hiroaki; Amano, Yuki; Iwatsuki, Teruki

Chikyu Kagaku, 52(1), p.55 - 71, 2018/03

In this study, the simulated experimental drift was constructed in the granite of 500 m depth at Mizunami Underground Research Laboratory, and the hydrochemical process after the drift closure was observed. The groundwater chemistry around the drift changed with the change of the groundwater flow in the fractures when the gallery was constructed. The redox potential increased due to the infiltration of oxygen from the drift into the rock. After closing the drift, the redox potential of the groundwater plunged due to microbial activity, while the groundwater became alkalized conditon due to the influence of cement material such as shotcrete. The amount of cement material consumed for this alkalization was small, and it was considered that its influence would last long in accordance with the amount of cement used.

Journal Articles

Characterization of rare earth elements (REEs) associated with suspended particles in deep granitic groundwater and their post-closure behavior from a simulated underground facility

Iwatsuki, Teruki; Munemoto, Takashi*; Kubota, Mitsuru*; Hayashida, Kazuki; Kato, Toshihiro*

Applied Geochemistry, 82, p.134 - 145, 2017/05

AA2017-0090.pdf:2.35MB

 Times Cited Count:2 Percentile:78.18(Geochemistry & Geophysics)

This study investigated the behavior of rare earth elements (REEs) associated with suspended particles in deep granitic groundwater and in a sealed drift at a depth of 500 m in the Mizunami Underground Research Laboratory (URL) in Japan. Approximately 10%$$sim$$60% of REEs in groundwater are associated with suspended particles. Carbonate particles in groundwater are most likely derived from in situ precipitation of supersaturated carbonate minerals such as calcite. Thermodynamic calculations show that the dissolved REE carbonate complexes in the closed drift decreased in the drift closure period. These complexes may have been absorbed or co-precipitated within the shotcrete on the drift wall. The usage of cement based materials would generate environmental conditions in which REEs are fundamentally immobile in and around the underground facilities.

JAEA Reports

Hydrochemical investigation at the Mizunami Underground Research Laboratory; Compilation of groundwater chemistry data in the Mizunami group and the Toki granite (fiscal year 2015)

Hayashida, Kazuki; Kato, Toshihiro; Munemoto, Takashi; Aosai, Daisuke*; Inui, Michiharu*; Kubota, Mitsuru; Iwatsuki, Teruki

JAEA-Data/Code 2017-008, 52 Pages, 2017/03

JAEA-Data-Code-2017-008.pdf:3.84MB

Japan Atomic Energy Agency has been investigating groundwater chemistry to understand the effect on excavating and maintenance of underground facilities as part of the Mizunami Underground Research Laboratory (MIU) Project in Mizunami, Gifu, Japan. In this report, we compiled data of groundwater chemistry obtained at the MIU in the fiscal year 2015. In terms of ensuring traceability of data, basic information (e.g. sampling location, sampling time, sampling method, analytical method) and methodology for quality control are described.

JAEA Reports

Corrosion Behaviour of Carbon Steel in Buffer Material under Anaerobic Condition

Taniguchi, Naoki; Kawasaki, Manabu*; Kawakami, Susumu; Kubota, Mitsuru*

JNC-TN8400 2003-040, 142 Pages, 2004/03

JNC-TN8400-2003-040.pdf:11.15MB

The deep underground environment for geological disposal of HLW will be relativery oxidizing condition at the initial stage of repository, but it will be returned to reducing as the consumption of oxygen by the corrosion of overpack and the reactions with the minerals in buffer material. It is necessarly to understand the corrosion behaviour of carbon steel under such reducing condition for the lifetime prediction of carbon steel overpack. In this study, immersion tests of carbon steel in buffer material were performed in nitrogen atmosphere in which oxygen gas concentration was controlled less than 1 ppm. The corrosion rates of carbon steel were measured by weight loss of the specimens and the corrosion products were analysed by SEM, XRD and EPMA. For investigating the influence of welding of overpack, welded samples by electron-beam welding (EBW) were used for some of the tests. Synthetic sea water (SSW) and aqueous solutions containing bicarbonate ion and chloride ion were chosen as simulated groundwater. According to the experimental results, corrosion products layer contained ferrous carbonate such as FeCO3 and Fe2(OH)2CO3. The average corrosion rates within 1 year were relatively high (0.004-0.018mm/y), but the growths of corrosion after 1 year were decreased rapidly. The increase in average corrosion depths from 1 to 3 (or 4) years was only less than several micro-meters, and the realistic corrosion rates after 1 year were estimated to be less than 0.001m/y in many cases. There was no influence of welding on the corrosion rate of carbon steel up to 3 years of immersion period. The effects of the density of buffer material and the mixing ratio of sand in buffer material on the corrosion rate of carbon steel were also investigated in this study.

Journal Articles

Corrosion Behavior of Carbon Steel in Contact with Bentonite under Anaerobic Condition

Taniguchi, Naoki; Kawasaki, Manabu*; Kawakami, Susumu; Kubota, Mitsuru*

Proceedings of European Corrosion Congress 2004 (EUROCORR 2004), 0 Pages, 2004/00

Long-term immersion tests of carbon steel under anaerobic condition were conducted in bentonite environment. Based on the experimental results, corrosion rate and corrosion products were evaluated.

Journal Articles

Energetic protons from a few-micron metallic foil evaporated by an intense laser pulse

Matsukado, Koji*; Esirkepov, T. Z.; Kinoshita, Kenichi*; Daido, Hiroyuki; Utsumi, Takayuki*; Li, Z.*; Fukumi, Atsushi*; Hayashi, Yukio; Orimo, Satoshi; Nishiuchi, Mamiko; et al.

Physical Review Letters, 91(21), p.215001_1 - 215001_4, 2003/11

 Times Cited Count:131 Percentile:4.3(Physics, Multidisciplinary)

no abstracts in English

JAEA Reports

Physico-chemical characteristics of purified Na-smectite and protonation/deprotonation behavior of smectite surface in NaCl media

; Oda, Chie; ; Shibata, Masahiro; Kohara, Yukitoshi*; Kubota, Mitsuru*

JNC-TN8400 99-066, 75 Pages, 1999/11

JNC-TN8400-99-066.pdf:3.21MB

The physico-chemical characteristics of purified Na-smectite and protonation/deprotonation behavior of smectite surface in different concentrations of NaCl solutions were studied to identify the reaction mechanism of smectite-water interaction for performance assessment of HLW geological disposal system. The Na-smectite was purified from Kunipia F (obtained from Kunimine Industries Co. Ltd. Japan). In this smectite, small amount of quartz was detected as an impurity by X-ray diffraction. As a result of XRD and chemical analysis of the smectite, it was found that exchangeable sites in smectite inter-layer were occupied by Na+. Cation exchange capacity (CEC) was measured as 1.108meq g$$^{-1}$$ by using ammonium acetate. The N$$_{2}$$-BET surface area of smectite was 50$$sim$$58m$$^{2}$$ g$$^{-1}$$. Protonation/deprotonation behavior of smectite was studied for 0.01, 0.1 and 0.5M NaCl by using titration and back titration method. Total amount of H$$^{+}$$ consumption increased with decreasing pH for all NaCl concentrations, and the titration curves in these solutions showed similar trend in the pH range of 6-11. On the other hand, total amount of H$$^{+}$$ consumption increased with decreasing NaCl concentration in the pH range of 2-6. The dominant sorption mechanism of H$$^{+}$$ on smectite was different between pH$$<$$6 and pH$$>$$6, and it can be considered that H$$^{+}$$ was sorbed on the same site as Na$$^{+}$$ for pH$$<$$6 and different site from Na$$^{+}$$ for pH$$>$$6. The prediction of protonation/deprotonation behavior of smectite for 0.01, 0.1 and 0.5M NaCl was carried out based on ion exchange and surface complexation models. The sorption sites were assumed as inter-layer and crystal edge site. The site concentrations for ion exchange and surface complexation were calculated from CEC. The reaction constants were consequently calculated by fitting of experimental results as follows. ...

JAEA Reports

Nuclear waste glass alteration in silica saturated solution depth profiling by ERDA and ESCA for simulated nuclear waste/ glass

; Kubota, Mitsuru*; *; *

JNC-TN8430 98-001, 12 Pages, 1998/11

JNC-TN8430-98-001.pdf:0.87MB

Leaching experiments were performed with simulated nuclear waste glasses in silica saturated water at 90$$^{circ}$$C for periods of 28 days in order to clarify the alteration mechanism of waste glass under silica saturation. After leaching experiments, the depth profiles of some elements of glass surfaces were measured by ERDA and ESCA. Depth profiles of H and soluble elements, such as B and Na, for the simulated nuclear waste glass after leaching experiments demonstrated the formation of glass hydration layer and the depletion of soluble elements in the glass hydration layer. The results suggest that alteration of nuclear waste glass under silica saturation is attributed to glass hydration and the leaching behaviour of soluble elements depends on the growth of the glass hydration layer.

Journal Articles

Present status and prospects of NUCEF project; Fuel cycle safety engineering research

Takeshita, Isao; Maeda, Mitsuru; Miyoshi, Yoshinori; Oono, Akio; Okazaki, Shuji; Nakajima, Ken; Fujine, Sachio; Kubota, Masumitsu; Muraoka, Susumu; Ara, Katsuyuki; et al.

Genshiryoku Kogyo, 43(9), p.1 - 37, 1997/09

no abstracts in English

Oral presentation

Redox resilience of granitic rock for a large scale underground facility construction and operation

Iwatsuki, Teruki; Hayashida, Kazuki; Kato, Toshihiro; Munemoto, Takashi; Kubota, Mitsuru

no journal, , 

Redox change around drift and MIU facility were observed to estimate redox resilience of granitic rock for facility construction and operation. Redox potential in the vicinity of research gallery and MIU facility heterogeneously changed from -200 to -100 mV in two years according to geological structure.

Oral presentation

Hydrochemical investigation at the Mizunami Underground Research Laboratory; Development of gas-strip techniques of dissolved inorganic carbon for dating groundwater

Kato, Toshihiro; Iwatsuki, Teruki; Munemoto, Takashi; Kubota, Mitsuru; Hayashida, Kazuki; Nakata, Kotaro*; Hasegawa, Takuma*

no journal, , 

no abstracts in English

Oral presentation

Distribution of rare earth elements between deep groundwater and fracture-filling calcite at the Mizunami Underground Research Laboratory

Munemoto, Takashi; Iwatsuki, Teruki; Kato, Toshihiro; Kubota, Mitsuru; Hayashida, Kazuki

no journal, , 

no abstracts in English

Oral presentation

Geosphere stability project, 6; Chronological and chemical analyses of carbonate minerals

Watanabe, Takahiro; Kokubu, Yoko; Murakami, Hiroaki; Yokoyama, Tatsunori; Amamiya, Hiroki; Mizuno, Takashi; Kubota, Mitsuru; Iwatsuki, Teruki

no journal, , 

Chronological and geochemical studies of fracture filling calcite in rocks provide the information for changes in geochemical condition, such as redox potential and pH in geological environments. Because the calcite can be found as common filling minerals in the natural samples, age zoning and spatial distribution of chemical composition in the calcite could be a wide-use indicator to reconstruct the past environmental changes. Radiometric (U-Pb) dating in a micro scale area (less than 10 micrometer) on the filling mineral surface by laser ablation-inductively coupled plasm mass spectrometry system (LA-ICPMS) has been applied to geological samples. Additionally, past redox potential has been estimated by Fe contents in the carbonates, which is based on the distribution coefficient of Fe between calcite deposit and groundwater. In this study, we evaluated the possibility of in-situ radiometric dating for the filling minerals by LA-ICPMS and redox potential reconstruction by the theoretical calculation using the distribution coefficient.

Oral presentation

Measurement of radon concentration and dose evaluation in the galleries at the Mizunami Underground Research Laboratory

Aoki, Katsunori; Ogura, Hideki; Kubota, Mitsuru; Tsurudome, Koji; Ikeda, Koki; Nagasaki, Yasushi; Ogata, Nobuhisa; Furuta, Sadaaki*

no journal, , 

no abstracts in English

Oral presentation

Colloidal solutes transport processes in deep groundwater

Iwatsuki, Teruki; Kubota, Mitsuru; Hayashida, Kazuki; Kato, Toshihiro

no journal, , 

We studied colloidal solutes transport in deep groundwater at depths of 500 m in Mizunami Underground Research Laboratory. Colloidal phases consist of silicate minerals, calcite, iron-hydroxides were observed in groundwater. Those particles possibly transport 10-80 % of metal elements and rare earth elements. In the closed drift, colloidal phases consist of biofilms, ZnS were observed. Since the concentration of rare earth elements are considerably low, rare earth elements with solute and colloidal phases probably absorbed on cementing materials, clay materials in closed drift.

Oral presentation

Areal comparison of the geochemistry of the Todo Porcelain Clay Formation; For reconstruction of paleo-weathering condition in the Neogene period

Hatano, Nozomi*; Yoshida, Koki*; Sasao, Eiji; Kubota, Mitsuru; Adachi, Yoshiko*

no journal, , 

Weathered zone is located between earth surface and geological environment. Understanding of weathered zone is important for safety assessment of HLW geological disposal. Porcelain clay formation, distributed in southeastern Gifu and eastern Aichi prefectures, consists of fine-grained sediment derived from strongly weathered granite. Discussion on relationship between topographic and weathering conditions of basement rock and porcelain clay is needed to understand paleo-environment when porcelain clay was formed. The authors investigate chemical and mineral composition of porcelain clay. Mineral composition varies considerably with location. Si content of porcelain clay is significantly higher than basement rock and PAAS which represents average chemical composition of crust. The result suggests that chemical composition of host rock was altered by strong weathering. Variation of Ti content with location is possibly caused by topographic and weathering condition of provenance.

Oral presentation

Paleoweathering condition in middle Miocene to early Pliocene period in Japanese Island; From paleopedology and chemistry of muddy sediments

Hatano, Nozomi*; Yoshida, Koki*; Sasao, Eiji; Kubota, Mitsuru; Adachi, Yoshiko*

no journal, , 

In Japanese Islands, the middle Miocene to Pliocene fluvial formations include aluminous clayey horizons. These formations can be a useful to reconstruct of weathering conditions. Description of paleosols and geochemical research were carried out in the middle Miocene (10-11 Ma) and the early Pliocene (3-4 Ma) sediments in central Japan in order to illuminate the weathering condition. The major elemental geochemistry shows that the Miocene sediments were supplied from severe weathered sources with CIA values of 80-94. The Pliocene sediments show the CIA values of 72-90 showing the relatively weak weathering condition. The weathering condition in the middle Miocene to Pliocene in Japanese Islands may be affected by the influence of warm water current and initiation of the Eastern Asian monsoon. The middle Miocene period is considered to have been under the intenser weathering condition than one in the early Pliocene period.

Oral presentation

Study on groundwater recovery experiment in Mizunami Underground Research Laboratory, 2; Changes in water chemistry associated with the water recovery around the closure test drift

Hayashida, Kazuki; Kato, Toshihiro; Kubota, Mitsuru; Onoe, Hironori; Iwatsuki, Teruki

no journal, , 

no abstracts in English

Oral presentation

Mizunami Underground Research Laboratory Project; Study on groundwater recovery experiment; Hydrochemical change of groundwater during the water filling of the research gallery

Kubota, Mitsuru; Hayashida, Kazuki; Kato, Toshihiro; Iwatsuki, Teruki

no journal, , 

This poster compiled Hydrochemical change of groundwater during the water filling of the research gallery.

Oral presentation

Geochemical analysis of groundwater chemistry after the drift closure in the granite

Hayashida, Kazuki; Kato, Toshihiro; Kubota, Mitsuru; Iwatsuki, Teruki

no journal, , 

This study aims to understand the hydrogeochemical condition and dominant process after the drift closure. To this aim the drift closure experiment was conducted in the granitic rock of 500 m below ground level of Mizunami Underground Research Laboratory. The groundwater chemistry such as major chemical component, pH and redox condition has been monitored in closed drift for 1 year. Dominant processes on chemical evolution of isolated groundwater in the closed drift were identified as follows; continuous replacement by surround rock water, microbial reduction, water-mineral interactions with evaporite, shotcrete and granite.

21 (Records 1-20 displayed on this page)