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= 0.01-600
C, 
= 1-3000 bars, 
= 0.35-1.1 g cm
, and 
= 0
Walker, C. S.*; Arthur, R. C.*; Anraku, Sohtaro; Sasamoto, Hiroshi; Mihara, Morihiro
Applied Geochemistry, 175, p.106086_1 - 106086_17, 2024/11
Times Cited Count：0 Percentile：0.00(Geochemistry & Geophysics)The thermodynamic properties and revised Helgeson-Kirkham-Flowers equation of state (r-H-K-F EoS) parameters of the hydrated (Si(OH)
(aq), SiO(OH)
and SiO
(OH)
) and fictive dehydrated (SiO(aq), HSiO and SiO) monomeric silicon species are used extensively to describe the pH, composition, temperature, and pressure dependence of formation/breakdown reactions of all silicon-bearing compounds globally. Experimental log10 equilbrium constant, K values describing the formation reactions of the hydrated and dehydrated monomeric silicon species were therefore compiled from the literature, extrapolated to zero ionic strength by specific ion interaction theory as required and used to derive their thermodynamic properties and r-H-K-F EoS parameters. Consideration of all formation reactions in the same study provides a collective, internally consistent update to the thermodynamic properties and r-H-K-F EoS parameters of the monomeric silicon species that can provide a satisfactory match to the experimental log10 K values at = 0.01-600C, = 1-3000 bars, = 0.35-1.1 g cm, and zero ionic strength. These temperature and pressure limits comfortably bracket t=0.01-100C and P =1-270 bars relecant to the geological disposal of radioactive wastes at depths of up to 1 km.
Sasamoto, Hiroshi; Sato, Hisao*; Arthur, R. C.*
Journal of Geochemical Exploration, 188, p.318 - 325, 2018/05
Times Cited Count：4 Percentile：18.67(Geochemistry & Geophysics)Ammonium is potentially an important constituent of deep groundwater under reducing condition. The retention of cesium by sorption in geological formations may have an important role ensuring the long-term safety of high-level radioactive waste. Cesium sorption will be affected by competing effects due to dissolve cation likely ammonium in groundwater, however. In the present study, a possible reaction to control of ammonium in deep groundwater was evaluated based on the data selected in the Horonobe as a test case in Japan. Results of investigation of mineralogy, thermodynamic evaluation of groundwaters and the Electron Probe Micro Analysis (EPMA) to identify nitrogen distribution on minerals suggest that the clay minerals bearing potassium, particularly smectite, illite and interstratified illite/smectite, appear to control the ammonium concentration in groundwaters by ion exchange reactions. Additionally, the selected groundwaters in the Horonobe seem to resemble to the gas and oil fields groundwater in the screened dataset in Japan in terms of ammonium distribution.
Arthur, R. C.*; Sasamoto, Hiroshi; Walker, C.; Yui, Mikazu
Clays and Clay Minerals, 59(6), p.626 - 639, 2011/11
Times Cited Count：16 Percentile：42.82(Chemistry, Physical)Regarding to geological disposal of high level radioactive waste, long-term evolution of chemical condition in the rock mass by interactions of cementitious grout and rock would be predicted, if the grout is used for reducing the groundwater inflow during construction of drifts. Evolution of chemical condition is important because it could affect the evaluation of radionuclides migration for performance assessment. Zeolite is one of important alteration minerals by interactions of cementitious grout and rock. For evaluation of long-term evolution of chemical condition, it is necessary to develop thermodynamic data for alteration minerals like zeolite. The present paper proposes a revised model to derive more reliable thermodynamic data for zeolite. Additionally, a possibility to apply this revised model on other important alteration minerals is suggested.
Sasamoto, Hiroshi; Arthur, R. C.*; Hama, Katsuhiro
Applied Geochemistry, 26(8), p.1464 - 1477, 2011/08
Times Cited Count：19 Percentile：46.73(Geochemistry & Geophysics)It is important to evaluate the undisturbed hydrochemical conditions in deep underground for considering the initial geochemical setting of performance assessment of high level radioactive waste. In the present study, groundwater data obtained thorough the initial surface-based investigation at the Horonobe URL were used to check the correlation and reliability of data based on empirical, geostatistical and geochemical modeling techniques. Applicability of these techniques were discussed in the present study and the representative undisturbed hydrochemical conditions were estimated.
Walker, C.; Arthur, R. C.*; Wakiya, Arata; Suto, Shunkichi; Sasamoto, Hiroshi; Oda, Chie; Mihara, Morihiro; Honda, Akira
no journal, ,
The JAEA thermodynamic database for reactions between groundwater, cement, clay, zeolite and/or rock forming minerals Summary: Reactions between groundwaters, cement, clay, zeolite and/or rock forming minerals will control the geochemical evolution of a repository built for the geological disposal of radioactive waste in Japan. JAEA has therefore developed a thermodynamic database (TDB) to simulate and assess the impact of these different reactions on the safety and performance of the repository. The thermodynamic properties of all relevant items have been written into formats supporting the geochemical computer programs SUPCRT92, Geochemists Workbenchtextregistered and PHREEQC.
Sasamoto, Hiroshi; Arthur, R. C.*; Alt-Epping, P.*; Tachi, Yukio
no journal, ,
The present study performed an interpretation of natural tracers (non or weakly sorption elements) profiles of groundwater observed in the boreholes drilled from the surface around the Horonobe Underground Laboratory based on the transport processes of advection and diffusion. In the interpretation, due to several uncertainty ranges for transport parameters in initial and boundary conditions, sensitivity analyses considering the relevant model parameters defined uncertainty limits were also conducted to evaluate the plausible parameter sets and conditions to be compatible with observations.
