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Journal Articles

Characterization of mineralogical controls on ammonium concentrations in deep groundwaters of the Horonobe area, Hokkaido

Sasamoto, Hiroshi; Sato, Hisao*; Arthur, R. C.*

Journal of Geochemical Exploration, 188, p.318 - 325, 2018/05

 Times Cited Count:2 Percentile:16.86(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.

Journal Articles

Polymer model for zeolite thermochemical stability

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:45.47(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.

Journal Articles

Interpretation of undisturbed hydrogeochemical conditions in Neogene sediments of the Horonobe area, Hokkaido, Japan

Sasamoto, Hiroshi; Arthur, R. C.*; Hama, Katsuhiro

Applied Geochemistry, 26(8), p.1464 - 1477, 2011/08

 Times Cited Count:15 Percentile:43.75(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.

Oral presentation

The JAEA thermodynamic database for reactions between groundwater, cement, clay, zeolite and/or rock forming minerals

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.

Oral presentation

Sensitivity analyses of natural tracer profiles in sedimentary rocks of the Horonobe URL, Japan

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.

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