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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

Remarks on accepting young best presentation award for the meeting of Japanese association of groundwater hydrology

Mochizuki, Akihito

Chikasui Gakkai-Shi, 61(4), P. 346, 2019/11

no abstracts in English

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

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.

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.

Oral presentation

The Redox condition of rocks in the excavation damaged zone of galleries in the Horonobe Underground Research Laboratory

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

no journal, , 

no abstracts in English

Oral presentation

A Case study for evaluation of uncertainty of redox potential in deep groundwater

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

no journal, , 

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 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.

Oral presentation

Sorption behavior of uranium ion on Neogene sedimentary rocks in the presence of carbonate

Haruki, Kazuto*; Sasaki, Takayuki*; Kirishima, Akira*; Sasamoto, Hiroshi; Mochizuki, Akihito; Miyakawa, Kazuya

no journal, , 

no abstracts in English

Oral presentation

Characterization of dissolved organic matter in deep groundwater by convenient analytical methods

Mochizuki, Akihito; Sasamoto, Hiroshi; Ikigaki, Kayoko*

no journal, , 

Convenient characterization methods available to small volume of samples were applied to groundwater and surface water in the Horonobe area, Hokkaido, to characterize dissolved organic matter (DOM) including humic substances. 3D-fluorescense spectrum obtained from small volume of groundwater was similar to those from isolated humic substances, and showed little variation with depth. However, the peak position of spectrum for surface water was different from those for groundwater. Gel permeation chromatography showed that DOM in groundwater mainly consists of humic substances with molecule weight of approximately 1,200$$sim$$2,000 Da, and that the molecule weight decreases with depth. These results were consistent with the characteristics of isolated humic substances. Ion chromatography revealed that low molecule weight organic matter was minor component of DOM in the groundwater, which was consistent with the result of gel permeation chromatography.

Oral presentation

Characterization of dissolved organic matter in deep groundwater by simple analytical methods; A Case study in Horonobe area, Hokkaido

Mochizuki, Akihito; Sasamoto, Hiroshi; Ikigaki, Kayoko*

no journal, , 

Simple characterization methods available to small volume of samples were applied to groundwater and surface water in the Horonobe area, Hokkaido, to characterize dissolved organic matter (DOM) including humic substances. The results indicate that the methods applied in this study are useful for the characterization of DOM in groundwater using a small sample volume.

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