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Metcalfe, R.*; Benbow, S. J.*; Kawama, Daisuke*; Tachi, Yukio
Science of the Total Environment, 958, p.177690_1 - 177690_17, 2025/01
Uplifting fractured granitic rocks occur in substantial areas of countries such as Japan. A repository site would be selected in such an area only if it is possible to make a safety case, accounting for the changing conditions during uplift. The safety case must include robust arguments that chemical processes in the rocks around the repository will contribute sufficiently to minimise radiological doses to biosphere receptors. To provide confidence in the safety arguments, numerical models need to be sufficiently realistic, but also parameterised conservatively (pessimistically). However, model development is challenging because uplift involves many complex couplings between groundwater flow, chemical reactions between water and rock, and changing rock properties. The couplings would affect radionuclide mobilisation and retardation, by influencing diffusive radionuclide fluxes between groundwater flowing in fractures and effectively immobile porewater in the rock matrix and radionuclide partitioning between water and solid phases, via: (i) mineral precipitation/dissolution; (ii) mineral alteration; and (iii) sorption/desorption. It is difficult to represent all this complexity in numerical models while showing that they are parameterised conservatively. Here we present a modelling approach, illustrated by simulation cases for some exemplar radioelements, to identify realistically conservative process conceptualisations and model parameterisations.
Metcalfe, R.*; Tachi, Yukio; Sasao, Eiji; Kawama, Daisuke*
Science of the Total Environment, 957, p.177375_1 - 177375_17, 2024/12
A safety case for an underground radioactive waste repository must show that groundwater will not in future transport radionuclides from the repository to the near-surface environment (the biosphere) in harmful quantities. Safety cases are developed step-wise throughout a programme to site and develop a repository. At early stages, before a site is selected, safety cases are generic and based on simplified safety assessment models of the disposal system that have conservative parameter values. Later, when site-specific conditions are known, more realistic models are needed for the long-term geo-environmental evolution and their impacts on radionuclide migration/retention. Uplift is one such environmental change, which may be particularly important in countries near active tectonic plate boundaries, such as Japan. Here we review the state of knowledge about how the properties of fractured granitic rocks evolve during uplift, based on studies in Japan. Hence, we present conceptual models and a generic scenario for mass transport and retardation processes in uplifting granitic rocks as a basis for realistic numerical models to underpin safety assessment.
Yoshida, Hidekazu*; Yamamoto, Koshi*; Asahara, Yoshihiro*; Maruyama, Ippei*; Karukaya, Koichi*; Saito, Akane*; Matsui, Hiroya; Mochizuki, Akihito; Jo, Mayumi*; Katsuta, Nagayoshi*; et al.
Communications Engineering (Internet), 3, p.67_1 - 67_10, 2024/05
A capability to permanently seal fluid flow-paths through bedrock, like boreholes or underground tunnels, is needed to ensure the long-term safety and effectiveness of many underground activities e.g. CO storage, hydrocarbon field abandonment, and nuclear waste disposal. Commonly used cementitious seals may not be sufficiently durable due to chemical and physical degradation. Learning from natural calcite (CaCO
) concretion formation, a more durable sealing method was developed using a "concretion-forming solvent". The method was tested by sealing flow-paths next to a tunnel in an underground research laboratory at 350 meters depth. The flow-paths initially sealed rapidly, then resealed after disturbance by earthquakes (M5.4). The treated rock recovered its very low natural permeability, demonstrating permanent sealing that is robust.
Yoshida, Hidekazu*; Yamamoto, Koshi*; Asahara, Yoshihiro*; Maruyama, Ippei*; Karukaya, Koichi*; Saito, Akane*; Matsui, Hiroya; Mochizuki, Akihito; Katsuta, Nagayoshi*; Metcalfe, R.*
Powering the Energy Transition through Subsurface Collaboration; Proceedings of the 1st Energy Geoscience Conference (Energy Geoscience Conference Series, 1), 20 Pages, 2024/00
A capability to permanently seal fluid flow-paths in bedrock, such as natural faults/fractures, and damaged zones around boreholes/excavations, is needed to ensure the long-term safety and effectiveness of many underground activities. Cementitious materials are commonly used as seals, however these materials unavoidably undergo physical and chemical degradation, therefore potentially decreasing seal durability. In order to solve these problems, a more durable sealing method using concretion-forming resin has been developed by learning from natural calcite (CaCO) concretion formation. The sealing capability of resin was tested by
experiments on bedrock flow-paths in an underground research laboratory (URL), Hokkaido, Japan. The results showed a decrease the permeability rapidly down to 1/1,000 of the initial permeability due to calcite precipitation over a period of one year. During the experiment inland earthquakes occurred with foci below the URL (depths 2-7 km and maximum magnitude 5.4). Due to the earthquakes the hydraulic conductivities of the flow-paths sealed initially by concretion-forming resin increased. However, these flow-paths subsequently resealed rapidly, and within a few months recovered the same hydraulic conductivities as before the earthquakes. This new technique for rapidly producing long-lasting seals against fluid flow through rocks will be applicable to many kinds of underground activities.
Ono, Takuya; Yoshida, Hidekazu*; Metcalfe, R.*
Journal of Structural Geology, 87, p.81 - 94, 2016/06
Times Cited Count:4 Percentile:12.35(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 - 300C. 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.
Kitamura, Akira; Takase, Hiroyasu*; Metcalfe, R.*; Penfold, J.*
Journal of Nuclear Science and Technology, 53(1), p.19 - 33, 2016/01
Times Cited Count:3 Percentile:9.38(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 -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.
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.
Yoshida, Hidekazu*; Metcalfe, R.*; Ishibashi, Masayuki; Minami, Masayo*
Geofluids, 13(1), p.45 - 55, 2013/02
Times Cited Count:14 Percentile:52.02(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.
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:9 Percentile:25.16(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.
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.
Sasao, Eiji; Ota, Kunio; 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.
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.
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.
Metcalfe, R.*; Savage, D.*; Bath, A. H.*; Walker, C.*
JNC TJ7400 2004-013, 148 Pages, 2004/03
This report describes calculations of the solubilities of elements that are relevant to Performance Assessment in the groundwaters of the Tono area.
Takase, Hiroyasu*; Metcalfe, R.*; Inagaki, Manabu*; Noguchi, Toshihide*; Aoyama, Yuji*; Takase, Kyoko*; Tabara, Michiko*
JNC TJ5400 2003-006, 264 Pages, 2004/02
none
Sugita, Kenichiro*; Metcalfe, R.*
JNC TJ7400 2005-073, 181 Pages, 2003/03
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.
Metcalfe, R.*
JNC TJ7400 2003-006, , 2003/03
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.
Metcalfe, R.
JNC TN7440 2002-002, 377 Pages, 2002/02
This report presents work undertaken by Richard Metcalfe, during a JNC International Fellowship, between 1 March1999 and 28 February 2002. During this period, the main purpose of the work was continuous review and appraisal of geochemical studies being done by the Japan Nuclear Cycle Development Institute (JNC) and contribution to a range of specific geochemical sutdies. This involved workng closely with Japanese colleagues at Tono Geoscience Center (TGC). These actvities were very broad in scope and produced a wide range of different outputs. However, a dominant theme was the application of geochemical information to understand past and present grounwater flow. The present report aims to compile those outputs from the Fellowship that deal with this theme.
Ota, Kunio; Nakano, Katsushi; Metcalfe, R.; Ikeda, Koki; ; Amano, Kenji; Takeuchi, Shinji; Hama, Katsuhiro; Matsui, Hiroya
JNC TN7410 99-007, 44 Pages, 1999/08
Mizuno, Takashi; Metcalfe, R.*; Mie, Hideki; Iwatsuki, Teruki
no journal, ,
no abstracts in English