Evaluation of hydrogeochemical processes provoked by tunnel excavation and closure based on simulated experiment in a mock-up test drift

Hayashida, Kazuki; Kato, Toshihiro*; Kubota, Mitsuru*; Murakami, Hiroaki; Amano, Yuki; Iwatsuki, Teruki

Chikyu Kagaku, 52(1), p.55 - 71, 2018/03

https://doi.org/10.14934/chikyukagaku.52.55

In this study, the simulated experimental drift was constructed in the granite of 500 m depth at Mizunami Underground Research Laboratory, and the hydrochemical process after the drift closure was observed. The groundwater chemistry around the drift changed with the change of the groundwater flow in the fractures when the gallery was constructed. The redox potential increased due to the infiltration of oxygen from the drift into the rock. After closing the drift, the redox potential of the groundwater plunged due to microbial activity, while the groundwater became alkalized conditon due to the influence of cement material such as shotcrete. The amount of cement material consumed for this alkalization was small, and it was considered that its influence would last long in accordance with the amount of cement used.

Literature survey of redox reactions in the new field

Miki, Takahito*; Sasamoto, Hiroshi; Chiba, Tamotsu*; Inagaki, Manabu*; Yui, Mikazu

JNC TN8400 2000-007, 32 Pages, 2000/01

JNC-TN8400-2000-007.pdf:0.69MB

This report presents a summary of literature survey about geochemical reactions which are important to evaluate the redox conditions in the near field rock mass and buffer. The results of literature survey are summarized as follows; (1)Minerals including ferrous iron and organic materials in the rock mass are important reductants. Initial stage after closure of repository, oxygen will be consumed by pyrite, because the reaction rate between pyrite and oxygen is relatively fast. (2)It is possible to estimate the redox capacity for reductants by rock (mineral)-water iteraction experiment in a laboratory. And it is expected that the ferrous iron-rich rock and higher porosity rock may have bigger redox capacity. (3)It is possible to estimate the oxygen consumption rate by reductants such as minerals including ferrous iron. The rate law and rate constant for the oxidation reaction of ferrous iron in the solution are also determined. As a conclusion, it seems that we can evaluate kinetically the evolution of geochemical conditions in the near field rock mass and buffer by excavation of drifts, based on data derived from these existing literatures.

Development of Thermodynamic Databases for Geochemical Calculations

Oda, Chie; Arthur, R. C,*; Sasamoto, Hiroshi; Shibata, Masahiro; Yui, Mikazu; Neyama, Atsushi*

JNC TN8400 99-079, 287 Pages, 1999/09

JNC-TN8400-99-079.pdf:9.78MB

Two thermodynamic databases for geochemical calculations supporting research and development on geological disposal concepts for high level radioactive waste are described in this report. One, SPRONS.JNC, is compatible with thermodynamic relations comprising the SUPCRT model and software, which permits calculation of the standard molal and partial molal thermodynamic properties of minerals, gases, aqueous species and reactions from 1 to 5000 bars and 0 to 1000C. This database includes standard molal Gibbs free energies and enthalpies of formation, standard molal entropies and volumes, and Maier-Kelly heat capacity coefficients at the reference pressure (1 bar) and temperature (25C) for 195 minerals and 16 gases. It also includes standard partial molal Gibbs free energies and enthalpies of formation, standard partial molal entropies, and Helgeson, Kirkham and Flowers (HKF) equation-of-state coefficients at the reference pressure and temperature for 1147 inorganic and organic aqueous ions and complexes. SPRONS.JNC extends similar databases described elsewhere by incorporating new and revised data published in the peer-reviewed literature since 1991. The other database, PHREEQE.JNC, is compatible with the PHREEQE series of geochemical modeling codes. It includes equilibrium constants at 25C and 1 bar for mineral-dissolution, gas-solubility, aqueous-association and oxidation-reduction reactions. Reaction enthalpies, or coefficients in an empirical log K(T) function, are also included in this database, which permits calculation of equilibrium constants between 0 and 100C at 1 bar. All equilibrium constants, reaction enthalpies, and logK(T) coefficients in PHREEQE.JNC are calculated usig SUPCRT and SPRONS.JNC, which ensures that these two databases are mutually consistent. They are also internally consistent insofar as all the data are compatible with basic thermodynamic definitions and functional relations in the SUPCRT ...

Thermodynamic Date for Predicting Concentrations of AnO and AnO Species in Geologic Environments

Choppin, G. R.*; Bronikowski, M.*; Chen, J.*; Byegard, J.*; Rai, D.*; Yui, Mikazu

JNC TN8400 99-012, 155 Pages, 1999/01

JNC-TN8400-99-012.pdf:5.53MB

This report provides thermodynamic data for predicting concentrations of pentavalent and hexavalent actinide species (AnO and AnO) in geologic environments, and contributes to an integration of the JNC chemical thermodynamic database, JNC-TDB (previously PNC-TDB), for the performance analysis of geological isolation system for high-level radioactive wastes. Thermodynamic data for the formation of complexes or compounds with hydroxide, chloride, fluoride, carbonate, nitrate, sulfate and phosphate are discussed in this report. The estimation of the stability constants by use of the Born equation is included. The Pitzer parameters for AnO and AnO, redox potentials and equilibrium constants of redox reactions for actinides are also included.

None

PNC TJ1150 98-003, 99 Pages, 1998/03

PNC-TJ1150-98-003.pdf:4.39MB

None

None

Yokoi, Koichi*; Yoneda, Yoshihiro*; Takahara, Hiroyuki*; Moriya, Toshifumi*

PNC TJ1380 96-002, 68 Pages, 1996/03

PNC-TJ1380-96-002.pdf:3.16MB

None

Extraction chromatography in the TBP-HNO system, II; Characteristics of the TBP/XAD-4 resin on separation of actinide elements

Kimura, Takaumi

Journal of Radioanalytical and Nuclear Chemistry, 141(2), p.307 - 316, 1990/00

https://doi.org/10.1007/BF02035798

no abstracts in English

None

Gonda, Kozo; *

PNC TN841 79-26, 240 Pages, 1979/02

PNC-TN841-79-26.pdf:5.11MB

no abstracts in English

Redox behavior of RuO particles in borosilicate glass melts

Nagai, Takayuki; Inose, Takehiko*; Sato, Seiichi*; Hatakeyama, Kiyoshi*; Seki, Katsumi*

no journal, , 

no abstracts in English

The Effect of correlation between iron and cerium in borosilicate glass on the structure

Okamoto, Yoshihiro; Nagai, Takayuki; Tsuji, Takuya; Matsumura, Daiju

no journal, , 

Some elements such as chromium, iron, rhodium and cerium have multiple valence in the silicate glass. Among them, iron and cerium are known to show a strong mutual correlation in redox behavior. It is reported that Fe (II) is oxidized by Ce (IV) to produce Ce (III) and Fe (III), resulting in the formation of Ce (III) -O-Fe (III) complex in the silicate glass. It is natural to think that if the valence of a constituent element changes in glass, the local structure around that element also changes. In this study, XAFS analysis of Fe and Ce elements was carried out when the Fe content in borosilicate glass was changed, and the changes in the chemical state and local structure were investigated. It was found that by adding Fe, tetravalent Ce (IV) was reduced and the proportion of trivalent Ce (III) increased, and the local structure around Ce also changed accordingly. It was found that Ce was dispersed in the glass phase regardless of whether it was trivalent or tetravalent. However, when Ce was tetravalent, the structural order of the Ce-O pair was as high as that of crystalline CeO.