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Journal Articles

Determination of humic substances in deep groundwater from sedimentary formations by the carbon concentration-based DAX-8 resin isolation technique

Terashima, Motoki; Endo, Takashi*; Miyakawa, Kazuya

Journal of Nuclear Science and Technology, 57(4), p.380 - 387, 2020/04

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

JAEA Reports

Synthesis report on the R&D for the Horonobe Underground Research Laboratory; Project carried out during fiscal years 2015-2019

Nakayama, Masashi; Saiga, Atsushi; Kimura, Shun; Mochizuki, Akihito; Aoyagi, Kazuhei; Ono, Hirokazu; Miyakawa, Kazuya; Takeda, Masaki; Hayano, Akira; Matsuoka, Toshiyuki; et al.

JAEA-Research 2019-013, 276 Pages, 2020/03

JAEA-Research-2019-013.pdf:18.72MB

The Horonobe Underground Research Laboratory (URL) Project is being pursued by the Japan Atomic Energy Agency (JAEA) to enhance the reliability of relevant disposal technologies for geological disposal of High-level Radioactive Waste through investigations of the deep geological environment within the host sedimentary rock at Horonobe Town in Hokkaido, north Japan. The investigations will be conducted in three phases, namely "Phase 1: Surface based investigations", "Phase 2: Construction phase" (investigations during construction of the underground facilities) and "Phase 3: Operation phase" (research in the underground facilities). According to the research plan described in the 3rd Mid- and Long- term Plan of JAEA, "Near-field performance study", "Demonstration of repository design option", and "Verification of crustal-movement buffering capacity of sedimentary rocks" are important issues of the Horonobe URL Project, and schedule of future research and backfill plans of the project will be decided by the end of 2019 Fiscal Year. The present report summarizes the research and development activities of these 3 important issues carried out during 3rd Medium to Long-term Research Phase.

JAEA Reports

Data of groundwater chemistry obtained in the Horonobe Underground Research Laboratory Project (FY2017-FY2019)

Miyakawa, Kazuya; Mezawa, Tetsuya*; Mochizuki, Akihito; Sasamoto, Hiroshi

JAEA-Data/Code 2020-001, 41 Pages, 2020/03

JAEA-Data-Code-2020-001.pdf:3.75MB
JAEA-Data-Code-2020-001-appendix(CD-ROM).zip:0.34MB

Development of technologies to investigate properties of deep geological environment and model development of geological environment have been pursued in "Geoscientific Research" in the Horonobe Underground Research Laboratory (Horonobe URL) project. A geochemical model which is a part of geological environment model requires the data of groundwater chemistry around the Horonobe URL for the development. This report summarizes the data obtained for 3 years from the fiscal year 2017 to 2019, especially for the results for measurement of physico-chemical parameters and analysis of groundwater chemistry, in the Horonobe URL project.

Journal Articles

Mudstone redox conditions at the Horonobe Underground Research Laboratory, Hokkaido, Japan; Effects of drift excavation

Mochizuki, Akihito; Ishii, Eiichi; Miyakawa, Kazuya; Sasamoto, Hiroshi

Engineering Geology, 267, p.105496_1 - 105496_11, 2020/03

 Times Cited Count:0 Percentile:100(Engineering, Geological)

The mechanical and hydraulic properties of rocks around mine drifts change significantly during the construction and operation of a radioactive-waste repository, with air intrusion causing the oxidation of rock and groundwater in excavation-damaged zones (EDZ). Redox conditions in such zones associated with niches excavated in mudstone at the Horonobe Underground Research Laboratory (URL), which is believed to be generally representative of conditions that could exist in the EDZ of a repository, were studied with the aim of improving our understanding of factors that control redox conditions in such rock-groundwater systems. Groundwater Eh values around the niches have reducing values of less than -150 mV. The SO$$_{4}$$$$^{2-}$$ concentration, regarded as an oxidation indicator, is consistently as low as 1 $$mu$$mol L$$^{-1}$$. Gas occupies more than 50% of zone volumes, including CH$$_{4}$$ and CO$$_{2}$$ with traces of N$$_{2}$$ and O$$_{2}$$. Cores drilled from host rock around a URL gallery were analyzed, with no pyrite dissolution or precipitation of calcium sulfates being found. It is concluded that oxidizing conditions do not exist in the excavation-damaged zones, which is attributed to the suppression of air intrusion by the release of CH$$_{4}$$ and CO$$_{2}$$ from groundwater as pressures decreased and their accumulation in fractures. The modeling of oxygen diffusion into host rock further indicates that a reducing environment is maintained around the URL drifts.

JAEA Reports

Groundwater pressure records by geochemical monitoring system in the 350 m gallery of the Horonobe Underground Research Laboratory (FY 2016-2018)

Mochizuki, Akihito; Miyakawa, Kazuya; Sasamoto, Hiroshi

JAEA-Data/Code 2019-014, 56 Pages, 2020/02

JAEA-Data-Code-2019-014.pdf:6.56MB
JAEA-Data-Code-2019-014-appendix(CD-ROM).zip:5.81MB

Japan Atomic Energy Agency (JAEA) has been conducting "geoscientific study" and "research and development on geological disposal" in the Horonobe Underground Research Laboratory (URL) for safe geological disposal of high-level radioactive waste. Groundwater pressure and geochemical parameters such as pH and oxidation-reduction potential in the deep groundwater have been continuously monitored with monitoring systems which were developed in the Horonobe URL Project. This report presents the data of groundwater pressure which have been obtained by the monitoring systems installed at the 350 m gallery. The data obtained from April 1, 2016 until March 31, 2019 was summarized along with related information such as the specifications of boreholes and the excavation of the URL.

Journal Articles

The Effect of dissolved gas on rock desaturation in artificial openings in geological formations

Miyakawa, Kazuya; Aoyagi, Kazuhei; Sasamoto, Hiroshi; Akaki, Toshifumi*; Yamamoto, Hajime*

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

The construction and operation of geological repositories require excavation and ventilation of galleries, with significant groundwater drainage. Desaturation of rock around galleries is unavoidable and may affect hydraulic properties and redox conditions. This study used numerical modeling to assess the influence of dissolved gas on the degree of saturation of rock surrounding excavated galleries, focusing on siliceous mudstone rock in the 140 m, 250 m, and 350-m-deep galleries of the Horonobe Underground Research Laboratory, Japan. Based on previous $$in situ$$ electrical survey, the degree of saturation in the 250 m gallery was higher than that in the 140 m and 350 m galleries. In the Horonobe area, deep groundwater contains high concentrations of dissolved methane, and exsolution of this methane from pore water can affect desaturation. Simple numerical modeling, including simulation of multiphase flows, was undertaken for each gallery to confirm the effect of dissolved gas and rock permeability on desaturation. A sensitivity analysis was performed by varying dissolved gas contents and permeability. Results indicate that the dissolved gas content affects both the degree of saturation and its spatial extent, whereas rock permeability affects only the latter. Higher dissolved gas concentrations result in lower degrees of saturation with a greater spatial extent of desaturation, and higher permeability leads to greater extents of desaturation. It is therefore likely that gas content, rather than rock permeability, caused the observed variations in the saturation degree.

Journal Articles

Degassing behavior of noble gases from groundwater during groundwater sampling

Nakata, Kotaro*; Hasegawa, Takuma*; Solomon, D. K.*; Miyakawa, Kazuya; Tomioka, Yuichi*; Ota, Tomoko*; Matsumoto, Takuya*; Hama, Katsuhiro; Iwatsuki, Teruki; Ono, Masahiko*; et al.

Applied Geochemistry, 104, p.60 - 70, 2019/05

 Times Cited Count:0 Percentile:100(Geochemistry & Geophysics)

no abstracts in English

Journal Articles

Thermodynamic study of the complexation of humic acid by calorimetry

Kimuro, Shingo; Kirishima, Akira*; Kitatsuji, Yoshihiro; Miyakawa, Kazuya; Akiyama, Daisuke*; Sato, Nobuaki*

Journal of Chemical Thermodynamics, 132, p.352 - 362, 2019/05

 Times Cited Count:3 Percentile:36.1(Thermodynamics)

A combination of potentiometry and calorimetry was used for the determination of the thermodynamic quantities of complexation of generic and groundwater humic acid (HA), which was isolated from deep groundwater at Horonobe, Hokkaido, Japan, with copper (II) ions and uranyl (VI) ions. The apparent complexation constant of Horonobe HA was independent of the pH, whereas that of generic HA was dependent on the pH. This observation indicates that the polyelectrolyte effect of Horonobe HA is negligible because of its small molecular size. In addition, the effect of the heterogeneity of Horonobe HA was not significant. Moreover, the complexation enthalpy of Horonobe HA was consistent with that of homogeneous poly(acrylic acid), which means the complexation of Horonobe HA was not affected by the functional group heterogeneity. Consequently, the characteristic complexation mechanism of Horonobe HA was revealed based on the determined thermodynamic quantities.

Journal Articles

Evaluation of uncertainty of redox potential in deep groundwater; A Case study in the Horonobe area, Hokkaido

Mochizuki, Akihito; Sasamoto, Hiroshi; Mezawa, Tetsuya*; Miyakawa, Kazuya

Chikasui Gakkai-Shi, 61(1), p.3 - 20, 2019/02

Redox potential of deep groundwater in the Horonobe area, Hokkaido, was measured, and uncertainty of the measurement and thermodynamic interpretation was evaluated. The redox potential of groundwater obtained using monitoring units in the Underground Research Laboratory ranged between -250 and -100 mV, and the effect of the excavation of drifts on the redox potential is considered to be small in spite of its temporal variation. The redox potential is controlled by the reaction of chemical pairs of SO$$_{4}$$$$^{2-}$$/FeS$$_{2}$$, SO$$_{4}$$$$^{2-}$$/HS$$^{-}$$ and CO$$_{2}$$(aq)/CH$$_{4}$$(aq). The comparison between the equilibrium potential for these reactions and the measured redox potentials suggests that $$pm$$50 mV of uncertainty for the measurement of the redox potential is appropriate.

Journal Articles

Improvements in drill-core headspace gas analysis for samples from microbially active depths

Miyakawa, Kazuya; Okumura, Fumiaki*

Geofluids, 2018, p.2436814_1 - 2436814_11, 2018/10

 Times Cited Count:1 Percentile:74.64(Geochemistry & Geophysics)

no abstracts in English

Journal Articles

Evaluation of $$delta^{2}$$H and $$delta^{18}$$O of water in pores extracted by compression method; Effects of closed pores and comparison to direct vapor equilibration and laser spectrometry method

Nakata, Kotaro*; Hasegawa, Takuma*; Oyama, Takahiro*; Miyakawa, Kazuya

Journal of Hydrology, 561, p.547 - 556, 2018/06

 Times Cited Count:1 Percentile:80.89(Engineering, Civil)

no abstracts in English

Journal Articles

Status of rock dynamics study in Horonobe Underground Research Laboratory, Japan

Sato, Toshinori; Aoyagi, Kazuhei; Matsuzaki, Yoshiteru; Miyara, Nobukatsu; Miyakawa, Kazuya

Rock Dynamics; Experiments, Theories and Applications, p.575 - 580, 2018/06

Rock dynamics is one of key issue for research and development of techniques for safe geological disposal of high-level radioactive waste. Horonobe Underground Research Laboratory (URL) is off-site URL constructed in soft sedimentary rock to the depth of 350m with three shafts and three level experimental galleries. Earthquake-resistant design of underground openings, observation of seismic records and groundwater pressure change due to earthquakes, and excavation disturbed zone experiment have been performed relating to the study of rock dynamics in URL project. This paper shows current status of Horonobe URL project and results of earthquake-resistant design of shafts, observation of seismic records and groundwater pressure change due to the 2011 off the Pacific coast of Tohoku Earthquake.

Journal Articles

Characterization and thermodynamic study of humic acid in deep groundwater at Horonobe, Hokkaido, Japan

Kimuro, Shingo*; Kirishima, Akira*; Nagao, Seiya*; Saito, Takumi*; Amano, Yuki; Miyakawa, Kazuya; Akiyama, Daisuke*; Sato, Nobuaki*

Journal of Nuclear Science and Technology, 55(5), p.503 - 515, 2018/05

 Times Cited Count:3 Percentile:35.66(Nuclear Science & Technology)

no abstracts in English

JAEA Reports

Records of physico-chemical parameters by geochemical monitoring system in the Horonobe Underground Research Laboratory

Mezawa, Tetsuya; Mochizuki, Akihito; Miyakawa, Kazuya; Sasamoto, Hiroshi

JAEA-Data/Code 2018-001, 55 Pages, 2018/03

JAEA-Data-Code-2018-001.pdf:10.63MB
JAEA-Data-Code-2018-001-appendix(CD-ROM).zip:8.57MB

Japan Atomic Energy Agency has been conducting "geoscientific study" and "research and development on geological disposal" in the Horonobe Underground Research Laboratory (URL) for safe geological disposal of high-level radioactive waste. Geochemical parameters of groundwater pressure, pH, and oxidation-reduction potential in the deep groundwater has been continuously monitored with monitoring systems which were developed in the Horonobe URL Project. This report presents the physico-chemical parameters of groundwater which have been obtained by the monitoring systems installed at the 140 m, 250 m and 350 m gallery. The data obtained until March 31, 2017 was summarized along with related information such as the specifications of boreholes and the excavation of the URL.

Journal Articles

An Evaluation of the long-term stagnancy of porewater in the neogene sedimentary rocks in northern Japan

Nakata, Kotaro*; Hasegawa, Takuma*; Oyama, Takahiro*; Ishii, Eiichi; Miyakawa, Kazuya; Sasamoto, Hiroshi

Geofluids, 2018, p.7823195_1 - 7823195_21, 2018/01

 Times Cited Count:3 Percentile:42.61(Geochemistry & Geophysics)

A groundwater scenario is one of the scenario for safety assessment of geological disposal of high-level radioactive waste. In the safety assessment for groundwater scenario, the slow groundwater flow for a long-term should be an important factor. In the present study, study on stability of groundwater in the Koetoi and Wakkanai formations of Neogene marine based sedimentary rock at the Horonobe area, Hokkaido was performed by investigating the isotopes of chlorine and helium, and the stable isotopes of water. As the results, the stability of groundwater in deeper part of the Wakkanai formation was suggested due to no direct evidence of meteoric water intrusion during the uplift since ca. 1 Ma. Contrary, the groundwater both in the Koetoi formation and the upper Wakkanai formation would be unstable because the meteoric water intrusion was suggested by paleohydrogeological condition and the results of groundwater dating. Likely the Horonobe area, the accurate dating of groundwater would be difficult due to the complex effects of upward and mixing water derived from diagenesis in the thick sediment formation. However, a comparative procedure using both the results of groundwater dating and paleohydrogeological information would be useful for general evaluation of groundwater flow conditions for the long-term (i.e., check the possibility for long-term stability of groundwater).

Journal Articles

A Proposed method to estimate in situ dissolved gas concentrations in gas-saturated groundwater

Tamamura, Shuji*; Miyakawa, Kazuya; Aramaki, Noritaka*; Igarashi, Toshifumi*; Kaneko, Katsuhiko*

Groundwater, 56(1), p.118 - 130, 2018/01

Groundwater saturated with gas forms bubble under atmospheric pressure, bothering most authorized methods to determine in-situ dissolved gas concentrations. To circumvent this problem, a simple theory to quantify effect of $rm bubble formation on in-situ dissolved gas concentration was developed: Pressure ({it P$_{i},rm original $}$ [bar]) of a gas component "${it i}$" (e.g., CH$$_{4}$$, CO$$_{2}$$ and H$$_{2}$$) in equilibrium with in-situ dissolved concentration (${it C $_{i},rm original $}$ [mol L $$^{-1}$$]) was related to partial pressure of the $rm bubble ({it P $_{i},rm bubble $}$ [bar]) emerged from groundwater in the form: ${it P$_{i},rm original $}$ = ${it P $_{i},rm bubble $}$ + $$Delta$$ ${it P}$ (k${it i}$' ${it P $_{i},rm bubble $}$/($$Sigma$$ ${it j}$k${it j}$' ${it P $_{ j },rm bubble $}$)), where $$Delta$$ ${it P}$ [bar] is groundwater pressure difference before and after the $rm bubble formation, and j refers to all gas components in the system including "{it i.}$" The k${it $_{i}$}$' and k${it $_{j}$}$' corresponds to the Henry's constant [bar L mol$$^{-1}$$] of ${it i}$ (k${it $_{i}$}$) and ${it j}$ (k${it $_{j}$}$), respectively, except for k$$_{CO2}$$', which is pH-dependent function. Dissolved CH$$_{4}$$ concentrations were successfully estimated by the model within the error of $$pm$$ 4.0% from the direct measurements by the sealed sampler method. Similar TIC concentration in the groundwater before and after the rm bubble formation was consistent with the model prediction. The wide application of the model is suggested without selecting sampling locations.

JAEA Reports

Data of groundwater chemistry obtained in the Horonobe Underground Research Laboratory Project (FY2014-2016)

Miyakawa, Kazuya; Mezawa, Tetsuya; Mochizuki, Akihito; Sasamoto, Hiroshi

JAEA-Data/Code 2017-012, 60 Pages, 2017/10

JAEA-Data-Code-2017-012.pdf:7.94MB
JAEA-Data-Code-2017-012-appendix(CD-ROM).zip:0.09MB

Development of technologies to investigate properties of deep geological environment and model development of geological environment have been pursued in "Geoscientific Research" in the Horonobe Underground Research Laboratory (Horonobe URL) project. A geochemical model which is a part of geological environment model requires the data of groundwater chemistry around the Horonobe URL for the development. This report summarizes the data obtained for 3 years from the fiscal year 2014 to 2016, especially for the results for measurement of physico-chemical parameters and analysis of groundwater chemistry, in the Horonobe URL project.

JAEA Reports

Groundwater pressure records by geochemical monitoring system in the Horonobe Underground Research Laboratory

Mezawa, Tetsuya; Mochizuki, Akihito; Miyakawa, Kazuya; Sasamoto, Hiroshi

JAEA-Data/Code 2017-010, 63 Pages, 2017/06

JAEA-Data-Code-2017-010.pdf:9.66MB
JAEA-Data-Code-2017-010-appendix(CD-ROM).zip:5.08MB

Japan Atomic Energy Agency (JAEA) has been conducting "geoscientific study" and "research and development on geological disposal" in the Horonobe Underground Research Laboratory (URL) for safe geological disposal of high-level radioactive waste. Geochemical parameters of groundwater pressure, pH, and oxidation-reduction potential in the deep groundwater has been continuously monitored by the monitoring system which was developed in the Horonobe URL Project. This report presents the data of groundwater pressure which have been obtained by the monitoring system installed at the 140 m and 350 m gallery. The data obtained until March 31, 2016 was summarized along with related information such as the specifications of boreholes and the excavation of the URL.

Journal Articles

Three-dimensional visualization of methane concentration distribution in tunnels to increase underground safety

Nago, Makito*; Motoshima, Takayuki*; Miyakawa, Kazuya; Kanie, Shunji*; Sanoki, Satoru*

Proceedings of ITA-AITES World Tunnel Congress 2017 (WTC 2017) (USB Flash Drive), 10 Pages, 2017/06

This study presents a new approach to increase construction safety under methane inflow conditions by providing the three-dimensional concentration distribution of methane in underground structures. The study was conducted at the Horonobe Underground Research Laboratory, which is located in Neogene sedimentary rock where groundwater contains dissolved methane. As conventional gas sensors are confined to measurement at a single point in time and space, a new system was developed combining a laser methane detector and a laser range finder to effectively obtain the spatial concentration distribution of methane. This system was tested in tunnel galleries located at a depth of 350 m. The results show that this system is effective for identifying unpredicted methane emissions as well as predicted emission hotspots and for examining the validity of the ventilation scheme, which ensures construction safety.

JAEA Reports

Horonobe Underground Research Laboratory Project; Synthesis of Phase II (Construction Phase) investigations to a depth of 350m

Sato, Toshinori; Sasamoto, Hiroshi; Ishii, Eiichi; Matsuoka, Toshiyuki; Hayano, Akira; Miyakawa, Kazuya; Fujita, Tomoo*; Tanai, Kenji; Nakayama, Masashi; Takeda, Masaki; et al.

JAEA-Research 2016-025, 313 Pages, 2017/03

JAEA-Research-2016-025.pdf:45.1MB

The Horonobe Underground Research Laboratory (URL) Project is being pursued by the Japan Atomic Energy Agency (JAEA) to enhance the reliability of relevant disposal technologies through investigations of the deep geological environment within the host sedimentary formations at Horonobe, northern Hokkaido. This report summarizes the results of the Phase II investigations carried out from April 2005 to June 2014 to a depth of 350m. Integration of work from different disciplines into a "geosynthesis" ensures that the Phase II goals have been successfully achieved and identifies key issues that need to made to be addressed in the Phase II investigations Efforts are made to summarize as many lessons learnt from the Phase II investigations and other technical achievements as possible to form a "knowledge base" that will reinforce the technical basis for both implementation and the formulation of safety regulations.

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