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Journal Articles

Use of fracture filling mineral assemblages for characterizing water-rock interactions during exhumation of an accretionary complex; An Example from the Shimanto Belt, southern Kyushu Japan

Ono, Takuya; Yoshida, Hidekazu*; Metcalfe, R.*

Journal of Structural Geology, 87, p.81 - 94, 2016/06

 Times Cited Count:4 Percentile:20.47(Geosciences, Multidisciplinary)

Fracture filling minerals were formed during the development of an accretionary complex. Each mineral formed under favourable geological conditions and can be used to estimate the conditions of accretion. Geological observations and analyses were made on fracture fillings from boreholes of ca. 140 m depth, in the Shimanto Belt of Kyushu. Results revealed that the minerals were formed in 5 stages distinguished by the textural relationships of the minerals. Filling minerals show that the studied rock formation has been subducted to several km depth and the temperature reached was ca. 200 - 300$$^{circ}$$C. After the subduction, the rock formation uplifted and surface acidic water penetrated up to 80 m beneath the present ground surface. The acid water dissolved calcite fillings to form the present groundwater flow-paths. The results shown here imply that filling minerals can be an effective tool to evaluate the environmental changes during accretionary complex formation.

Journal Articles

Effects of $$alpha$$-radiation on a direct disposal system for spent nuclear fuel, 2; Review of research into safety assessments of direct disposal of spent nuclear fuel in Europe and North America

Kitamura, Akira; Takase, Hiroyasu*; Metcalfe, R.*; Penfold, J.*

Journal of Nuclear Science and Technology, 53(1), p.19 - 33, 2016/01

 Times Cited Count:1 Percentile:8.33(Nuclear Science & Technology)

Not only geological disposal of vitrified waste generated by spent fuel (SF) reprocessing, but also the possibility of disposing of SF itself in deep geological strata (hereinafter "direct disposal of SF") may be considered in the Japanese geological disposal program. In the case of direct disposal of SF, the radioactivity of the waste is higher and the potential effects of the radiation are greater. Specific examples of the possible effects of radiation include: increased amounts of canister corrosion; generation of oxidizing chemical species in conjunction with radiation degradation of groundwater and accompanying oxidation of reducing groundwater; and increase in the dissolution rate and the solubility of SF. Therefore, the influences of radiation, which are not expected to be significant in the case of geological disposal of vitrified waste, must be considered in safety assessments for direct disposal of SF. Focusing especially on the effects of $$alpha$$-radiation in safety assessment, this study has reviewed safety assessments in countries other than Japan that are planning direct disposal of SF. The review has identified issues relevant to safety assessment for the direct disposal of SF in Japan.

Journal Articles

Groundwater dating applied for geological disposal of radioactive waste; A Review of methods employed worldwide

Hama, Katsuhiro; Metcalfe, R.*

Nihon Suimon Kagakkai-Shi, 44(1), p.39 - 64, 2014/02

Groundwater dating methods employed in projects aiming to develop deep geological repositories for radioactive wastes have been reviewed. The reviewed projects are being, or have been, undertaken in Japan, Finland, Sweden, Belgium, the UK, Germany, France, Switzerland, Canada and the U.S.A. A wide range of actual and potential repository host rock types are represented by these projects: fractured crystalline igneous and metamorphic rock (Japan, Finland and Sweden); fractured volcanic rock (U.K.); plastic argillaceous rock (Belgium); indurated argillaceous rock (Japan, France, Switzerland); salt (Germany and U.S.A); limestone (Canada); and tuff (U.S.A). Whatever the combinations of methods that have been used in a particular program their results have invariably been interpreted in combination with one another and in the context of other information that is available for the investigated site. That is, a particular groundwater dating method is never applied in isolation.

Journal Articles

Long-term stability of fracture systems and their behaviour as flow paths in uplifting granitic rocks from the Japanese orogenic field

Yoshida, Hidekazu*; Metcalfe, R.*; Ishibashi, Masayuki; Minami, Masayo*

Geofluids, 13(1), p.45 - 55, 2013/02

 Times Cited Count:14 Percentile:63.37(Geochemistry & Geophysics)

In granitic rocks fracture networks provide pathways for groundwater flow and solute transport that need to be understood to assess the long-term performance of deep underground environment. In order to clarify the long-term processes, Japanese plutons of different ages were studied. Detailed investigation of in-situ fracture fillings sampled from a depth of 300 meters was carried out to clarify the fracturing and mineral infilling processes. Different plutons show identical episodes, consisting of: brittle tensile fracturing (Stage I); relatively rapid uplifting accompanied by hydrothermal water circulation that produced fracture fillings (Stage II); and a period of low-temperature meteoric water circulation (Stage III). The paragenesis of carbon isotopic compositions of carbonate minerals show that there were distinct episodes of mineral precipitation. The evolution of fillings identified here enable development of a model of fracturing and persistence of fluid conducting systems.

Journal Articles

Redox front formation in an uplifting sedimentary rock sequence; An Analogue for redox-controlling processes in the geosphere around deep geological repositories for radioactive waste

Yoshida, Hidekazu; Metcalfe, R.*; Yamamoto, Koshi*; Amano, Yuki; Hoshii, Daisuke*; Kanekiyo, Akiko*; Naganuma, Takeshi*; Hayashi, Toru*

Applied Geochemistry, 23(8), p.2364 - 2381, 2008/08

 Times Cited Count:7 Percentile:24.35(Geochemistry & Geophysics)

Subsurface redox fronts control the mobilization and fixation of many trace elements. Any safety assessment for a deep geological repository for radioactive wastes needs to take into account adequately the long-term redox processes in the geosphere surrounding the repository. The water-rock-microbe interactions can be considered analogous to the processes occurring in the redox fronts that would develop around geological repositories for radioactive waste. Once formed, the Fe-ooxyhydroxides within such a front would be preserved even after reducing conditions resume following repository closure.

Journal Articles

Proposal for quality assessment method of groundwater chemistry for hydrochemical investigation

Mizuno, Takashi; Metcalfe, R.*; Iwatsuki, Teruki; Mie, Hideki*

Chikasui Gakkai-Shi, 49(2), p.139 - 152, 2007/05

Hydrochemical studies are generally conducted based on chemical data of groundwater samples. Various methodologies exist for obtaining samples and for assessing the quality of the collected sample. This study is aimed at establishing a methodology for quality assessment of chemical data obtained from groundwater samples using a method known as Evidence Support Logic. In this study, pH data of groundwater obtained from several boreholes were assessed using this method. The results showed that 23 out of 63 samples satisfied the applied quality criteria. When plotted, the data from the 23 samples show a constant value from top to bottom of investigation area when compared to a plot using data from all samples. These results indicate that the quality assessment method demonstrated by this study is applicable to groundwater studies and that by considering the sample quality it will be possible to develop a clearer interpretation of the deep underground geochemical environment.

Journal Articles

An Overview of a natural analogue study of the Tono Uranium Deposit, central Japan

Sasao, Eiji; ; Iwatsuki, Teruki; Niizato, Tadafumi; Arthur, R. C.*; Stenhouse, M. J.*; Zhou, W.*; Metcalfe, R.*; Takase, Hiroyasu; MacKenzie, A. B.*

Geochemistry; Exploration, Environment, Analysis, 6(1), p.5 - 12, 2006/02

The present natural analogue study of the Tono uranium deposit (Tono Natural Analogue Project) was started in 2001 with the main aim of studying a worst case scenario for safety assessment. The project has involved characterising the geology, hydrogeology, geochemistry and microbiology of the deposit and obtaining quantitative information about specific times in the past, as a means for developing, and building confidence in, conceptual and numerical models. Some recent results from site investigations, such as depositional age of the host sedimentary sequence and fault activity, are presented in this paper and in other papers in the series.

Journal Articles

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

Hama, Katsuhiro; Kunimaru, Takanori; Metcalfe, R.*

Proceedings of 2nd International Meeting on Clays in Natural and Engineered Barriers for Radioactive Waste Confinement, p.399 - 400, 2005/03

The current status of the hydrogeochemical investigations are presented.

Journal Articles

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

Hama, Katsuhiro; Kunimaru, Takanori; Metcalfe, R.*

Proceedings of 2nd International Meeting on Clays in Natural and Engineered Barriers for Radioactive Waste Confinement, p.399 - 400, 2005/03

The current status of the hydrogeochemical study has been presented.

JAEA Reports

Sensitivity analysis to the geochemical parameters of the groundwater

Metcalfe, R.*; Savage, D.*; Bath, A. H.*; Walker, C.*

JNC TJ7400 2004-013, 148 Pages, 2004/03

JNC-TJ7400-2004-013.pdf:6.11MB

This report describes calculations of the solubilities of elements that are relevant to Performance Assessment in the groundwaters of the Tono area.

JAEA Reports

Study on synthesis of geological environment at Horonobe area; A technical review, 2

Takase, Hiroyasu*; Metcalfe, R.*; Inagaki, Manabu*; Noguchi, Toshihide*; Aoyama, Yuji*; Takase, Kyoko*; Tabara, Michiko*

JNC TJ5400 2003-006, 264 Pages, 2004/02

JNC-TJ5400-2003-006(errata).pdf:0.08MB
JNC-TJ5400-2003-006-1.pdf:83.88MB
JNC-TJ5400-2003-006-2.pdf:15.97MB

none

JAEA Reports

Project to develop a coupled geochemical/hydrogeological model of the Tono area

Sugita, Kenichiro*; Metcalfe, R.*

JNC TJ7400 2005-073, 181 Pages, 2003/03

JNC-TJ7400-2005-073.PDF:7.43MB

This document is the report of a project to develop a coupled geochemical/hydrogeological model of the groundwater system in the Tono area of Gifu ken, central Japan. a major outcome of the work has been identify alternative possible origins for the Na-(Ca)-Cl dominated groundwater salinity in the southern part of the study area.

JAEA Reports

A hydrochemical investigation using 36Cl/Cl in groundwaters

Metcalfe, R.*

JNC TJ7400 2003-006, , 2003/03

JNC-TJ7400-2003-006.pdf:2.58MB

This report describes 36Cl studies which were undertaken during the H14 financial year. 6 groundwater samples were collected for 36Cl analysis. The results of this study suggest that 36Cl data could potentially be useful for interpreting groundwater origins and flow paths.

Oral presentation

Development of a method for the classification of groundwater sample quality

Mizuno, Takashi; Metcalfe, R.*; Mie, Hideki; Iwatsuki, Teruki

no journal, , 

no abstracts in English

Oral presentation

Proposal for quality assessment of hydrochemical data

Mizuno, Takashi; Metcalfe, R.*; Iwatsuki, Teruki; Mie, Hideki*

no journal, , 

no abstracts in English

Oral presentation

Spherical concretion formation; Understandings and applications

Yoshida, Hidekazu*; Yamamoto, Koshi*; Maruyama, Ippei*; ASAHARA, Yoshihiro*; Minami, Masayo*; Sirono, Sinichi*; Hasegawa, Hitoshi*; Katsuta, Nagayoshi*; Nishimoto, Shoji*; Muramiya, Yusuke*; et al.

no journal, , 

no abstracts in English

Oral presentation

Evolution of radionuclide transport and retardation processes in uplifting crystalline rocks

Metcalfe, R.*; Kawama, Daisuke*; Benbow, S. J.*; Tachi, Yukio

no journal, , 

17 (Records 1-17 displayed on this page)
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