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Journal Articles

Effects of fine-scale surface alterations on tracer retention in a fractured crystalline rock from the Grimsel Test Site

Tachi, Yukio; Ito, Tsuyoshi*; Akagi, Yosuke*; Sato, Hisao*; Martin, A. J.*

Water Resources Research, 54(11), p.9287 - 9305, 2018/11

 Times Cited Count:5 Percentile:37.45(Environmental Sciences)

Effects of fine-scale surface alterations on radionuclide migration in fractured crystalline rocks were investigated by a comprehensive approach coupling a series of laboratory tests, microscopic observations and modelling, using a single fractured granodiorite sample from the Grimsel Test Site, Switzerland. Laboratory tests including through-diffusion, batch sorption and flow-through tests using five tracers indicated that tracer retention was consistently in the sequence of HDO, Se, Cs, Ni, Eu, and as well as showing the existence of a diffusion-resistance layer near the fracture surface, cation excess and anion exclusion effects for diffusion. Microscale heterogeneities in structural properties around the fracture were clarified quantitatively by coupling X-ray CT and EPMA. A three layer model including weathered vermiculite, foliated mica and undisturbed matrix layers, and their properties such as porosity, sorption and diffusion parameters, could provide a reasonable interpretation for breakthrough curves and concentration distributions near fracture surface of all tracers, measured in flow-through tests.

Journal Articles

Characterization of mineralogical controls on ammonium concentrations in deep groundwaters of the Horonobe area, Hokkaido

Sasamoto, Hiroshi; Sato, Hisao*; Arthur, R. C.*

Journal of Geochemical Exploration, 188, p.318 - 325, 2018/05

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

Ammonium is potentially an important constituent of deep groundwater under reducing condition. The retention of cesium by sorption in geological formations may have an important role ensuring the long-term safety of high-level radioactive waste. Cesium sorption will be affected by competing effects due to dissolve cation likely ammonium in groundwater, however. In the present study, a possible reaction to control of ammonium in deep groundwater was evaluated based on the data selected in the Horonobe as a test case in Japan. Results of investigation of mineralogy, thermodynamic evaluation of groundwaters and the Electron Probe Micro Analysis (EPMA) to identify nitrogen distribution on minerals suggest that the clay minerals bearing potassium, particularly smectite, illite and interstratified illite/smectite, appear to control the ammonium concentration in groundwaters by ion exchange reactions. Additionally, the selected groundwaters in the Horonobe seem to resemble to the gas and oil fields groundwater in the screened dataset in Japan in terms of ammonium distribution.

Journal Articles

Localization of cesium on montmorillonite surface investigated by frequency modulation atomic force microscopy

Araki, Yuki*; Sato, Hisao*; Okumura, Masahiko; Onishi, Hiroshi*

Surface Science, 665, p.32 - 36, 2017/11

 Times Cited Count:9 Percentile:49.42(Chemistry, Physical)

no abstracts in English

Journal Articles

Mineralogical, physical and chemical investigation of compacted Kunigel V1 bentonite in contact with a steel heater in the ABM test package 1 experiment, $"A$sp$"o$ Laboratory, Sweden

Sasamoto, Hiroshi; Isogai, Takeshi*; Kikuchi, Hirohito*; Sato, Hisao*; Svensson, D.*

Clay Minerals, 52(1), p.127 - 141, 2017/03

 Times Cited Count:3 Percentile:13.82(Chemistry, Physical)

Compacted bentonite has been considered as a candidate of engineering barrier material in many countries for the safe disposal of high-level radioactive waste. SKB set up an in situ experiment (named ABM project) to compare the stability of different bentonites under the conditions exposed to an iron source and elevated temperature (up to 130$$^{circ}$$C as maximum) at the $"A$sp$"o$ Hard Rock Laboratory, Sweden. Results for the Japanese bentonite (Kunigel V1) are summarized in the present paper. Mineralogical investigation using X-ray diffraction (XRD) and X-ray spectroscopy (SEM-EDX) suggested that no indication of smectite transformation or newly formed clay phases were observed. However, a distinct change of exchangeable cations of smectite was indicated (i.e., from Na type to Fe type) in the bentonite at the vicinity of the steel heater. Physical investigation by measurements of hydraulic conductivity and swelling property suggested that no significant change occur in the bentonite even at the vicinity of the steel heater. Such results might be considered due to the limited portion affected by the iron-bentonite interactions and partially occurred ion exchange reactions. Chemical investigation based on the measurements of methylane blue (MB), cation exchange capacity (CEC) and exchangeable cations showed that the lateral distribution for these parameters were basically constant without the significant gradient.

JAEA Reports

Construction of a car-borne survey system for measurement of dose rates in air; KURAMA-II, and its application

Tsuda, Shuichi; Yoshida, Tadayoshi; Nakahara, Yukio; Sato, Tetsuro; Seki, Akiyuki; Matsuda, Norihiro; Ando, Masaki; Takemiya, Hiroshi; Tanigaki, Minoru*; Takamiya, Koichi*; et al.

JAEA-Technology 2013-037, 54 Pages, 2013/10

JAEA-Technology-2013-037.pdf:4.94MB

JAEA has been performing dose rate mapping in air using a car-borne survey system KURAMA-II. The KURAMA system is a GPS-aided mobile radiation monitoring system that has been newly developed by Kyoto University Research Reactor Institute in response to the nuclear disaster. The KURAMA system is composed of an energy-compensated scintillation survey meter for measuring dose rate, electric device for controlling both the dose rates and the position data from a GPS module, a computer server for processing and analyzing data from KURAMA, and client PCs for providing for end users. The KURAMA-II has been improved in small-packaging, durability, and automated data transmission. In consequence, dose rate mapping in wide area has become possible in shorter period of time. This report describes the construction of KURAMA-II, its application and a suggestion of how to manage a large number of KURAMA-II.

JAEA Reports

Experimental study of alteration of bentonite coexisting iron material

Sasamoto, Hiroshi; Ishii, Tomoko*; Sato, Hisao*; Sazarashi, Masami

JAEA-Research 2010-030, 64 Pages, 2010/09

JAEA-Research-2010-030.pdf:15.41MB

It is necessary to evaluate the alteration behavior of buffer material by interactions of overpack (iron) and buffer (bentonite) materials for geological disposal of high level radioactive waste. In the present study, laboratory experiments were carried out for the better understanding of phenomena caused by iron-bentonite (smectite) interactions. Before conducting the experiments, literature survey was performed to summarize the existing knowledge about iron-bentonite interactions and to identify the dominant factors affecting the alteration behavior. As the results of experiment, experimental conditions caused remarkable alteration, secondary minerals suggested as alteration product, different behavior of alteration between batch and compacted systems etc. were revealed.

Journal Articles

Measurement of interaction forces between montmorillonite particles in NaCl solutions using a colloidal probe atomic force microscopy

Kurosawa, Susumu; Mizukami, Masashi*; Sato, Hisao*; Nozawa, Jun*; Tsujimoto, Keiichi*; Kurihara, Kazue*

Nihon Genshiryoku Gakkai Wabun Rombunshi, 5(3), p.251 - 256, 2006/09

no abstracts in English

Oral presentation

Experimental studies of iron-bentonite interactions under high temperature condition

Sasamoto, Hiroshi; Sazarashi, Masami; Ishii, Tomoko*; Sato, Hisao*; Kato, Hiroyasu*

no journal, , 

To investigate bentonite-iron interaction under high temperature condition, alteration experiments considering several factors (smectite composition, solution chemistry, iron-bentonite ratio) which were believed to affect on bentonite alteration were conducted with different experimental conditions. As the results, it was suggested that the factors considered in this study could also significantly affect on bentonite alteration in addition to temperature condition.

Oral presentation

Experimental investigation of iron-bentonite interactions under high temperature condition

Sasamoto, Hiroshi; Sazarashi, Masami; Ishii, Tomoko*; Sato, Hisao*; Kato, Hiroyasu*

no journal, , 

To investigate bentonite-iron interaction under high temperature condition, alteration experiments considering several factors (smectite composition, solution chemistry, iron-bentonite ratio) which were believed to affect on bentonite alteration were conducted with different experimental conditions. As the results, it was suggested that the factors considered in this study could also significantly affect on bentonite alteration in addition to temperature condition.

Oral presentation

Experimental and modeling studies on iron-bentonite interactions

Sasamoto, Hiroshi; Wilson, J.*; Sato, Hisao*; Sazarashi, Masami

no journal, , 

The proposed repository design for high-level radioactive waste in Japan includes iron containers surrounded by a bentonite buffer. Interactions of iron-bentonite (I/B) materials may lead to the adverse transformation of smectite to phases with a limited capacity to swell. Batch experiments that included native iron powder and bentonite and column experiments whereby compacted bentonites were reacted with embedded iron coupons were conducted in order to evaluate the effects of environmental parameters on I/B interactions. Additionally, several model simulations have been produced in order to evaluate the factors influencing the nature of bentonite alteration in the presence of iron. The dominant process of interest over performance assessment timescales was estimated as the results of variant simulations.

Oral presentation

Radionuclide migration in single fracture of granodiorite at the Grimsel Test Site, 2; Mineral and pore investigations

Sato, Hisao*; Akagi, Yosuke*; Tachi, Yukio; Matsumoto, Kazuhiro

no journal, , 

To validate radionuclide migration model in single fracture in crystalline rocks, the granodiorite sample with single fracture from the Grimsel Test Site in Switzerland was investigated focusing on the minerals and pores distributions. Mineral distributions from fracture surface to matrix were evaluated by X-ray CT, and were validated by comparing the elemental mapping measured by EPMA. Based on these results, the qualitative analysis methods for aperture and connectivity in fracture, and minerals distribution near fracture surface were developed.

Oral presentation

Investigations of mineral alteration in Kunigel V1 samples contacted with iron obtained from long-term in-situ experiments

Ishidera, Takamitsu; Sasamoto, Hiroshi; Sato, Hisao*

no journal, , 

no abstracts in English

Oral presentation

Investigations of mineral alteration in Kunigel V1 samples contacted with iron obtained from long-term in-situ experiments

Ishidera, Takamitsu; Sasamoto, Hiroshi; Sato, Hisao*

no journal, , 

Compacted bentonite (Kunigel V1) retrieved from the in-situ experiments in the ABM project was investigated to identify the mineralogical alteration of montmorillonite by iron-bentonite interaction in compacted bentonite. Berthierine, Fe-saponite and Fe-chlorite were found as the most possible alteration minerals of montmorillonite. Gypsum and calcite were identified at the contact surface between iron heater and compacted bentonite. These minerals were considered to be formed by the concentrating of salinity in the pore water of compacted bentonite due to the temperature gradient from iron heater.

Oral presentation

Effects of heterogeneity at fracture surface for tracer migration in a fractured crystalline rock from the Grimsel Test Site

Tachi, Yukio; Ito, Tsuyoshi; Akagi, Yosuke*; Sato, Hisao*; Martin, A. J.*

no journal, , 

The effects of heterogeneity at fracture surface on radionuclides migration in fractured crystalline rocks was investigated by laboratory migration experiments, microscopic observations and detailed modelling, using a single fractured granodiorite sample from the Grimsel Test Site (GTS), Switzerland. The tracer migration behaviors in fracture and matrix parts were evaluated by series of laboratory experiments including through-diffusion and flow-through experiments. Mineral distributions from fracture surface to matrix were evaluated by X-ray CT, and were validated by comparing the elemental mapping measured by EPMA. Based on the microscopic observations by X-ray CT and EPMA, the aperture and connectivity in fracture and minerals distribution near fracture surface were quantitatively evaluated. The heterogeneous multi-layered model assuming a weathered vermiculite zone, a foliated mica zone and rock matrix was possible to provide a reasonable interpretation for measured breakthrough curves of all tracers.

Oral presentation

Modelling of radionuclide migration in Grimsel granodiorite with microscale heterogeneities

Ota, Ryosuke*; Mitsuyama, Kazuaki*; Tachi, Yukio; Yotsuji, Kenji*; Sato, Tomofumi*; Sato, Hisao*; Martin, A.*

no journal, , 

The radionuclide migration model representing heterogeneities in distributions of minerals and pores was developed for Grimsel granodiorite. This model was applied to quantify the impact of heterogeneities on radionuclide migration and was validated by comparing with the measured data.

Oral presentation

In situ interactions of concretes with mudstones from Horonobe URL

Anraku, Sohtaro; Sato, Hisao*; Walker, C.*; Amano, Yuki; Sakurai, Akitaka; Nakayama, Masashi; Tachi, Yukio

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

Realistic modeling approach for radionuclide transport in heterogeneous fractured crystalline rocks

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

no journal, , 

18 (Records 1-18 displayed on this page)
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