Status of geochemical modeling of groundwater evolution at the Tono in-situ tests site, Japan In-situ Tests

Sasamoto, Hiroshi; Yui, Mikazu; Randolph C Arthu*

JNC TN8400 99-074, 84 Pages, 1999/12

JNC-TN8400-99-074.pdf:9.87MB

Hydrochemical investigation of Tertiary sedimentary rocks at JNC's Tono in-situ tests site indicate the groundwaters are: (1)meteoric in origin, (2)chemically reducing at depths greater than a few tens of meters in the sedimentary rock, (3)relatively old [carbon-14 ages of groundwaters collected from the lower part of the sedimentary sequence range from 13,000 to 15,000 years BP (before present)] (4)Ca-Na-HCO type solutions near the surface, changing to Na-HCO type groundwaters with increasing depth. The chemical evolution of the groundwaters is modeled assuming local equilibrium for selected mineral-fluid reactions, taking into account the rainwater origin of these solutions. Results suggest it is possible to interpret approximately the "real" groundwater chemistry (i.e., pH, Eh, total dissolved concentrations of Si, Na, Ca, K, Al, carbonate and sulfate) if the following assumptions are adopted: (1)CO concentration in the gas phase contacting pore solutions in the overlying soil zone = 10 bar, (2)minerals in the rock zone that control the solubility of respective elements in the groundwater include; chalcedony (Si), albite (Na), kaolinite (Al), calcite (Ca and carbonate), muscovite (K) and pyrite (Eh and sulfate). It is noted, however, that the available field data may not be sufficient to adequately constrain parameters in the groundwater evolution model. In particular, more detailed information characterizing certain site properties (e.g., the actual mineralogy of "plagioclase", "clay" and "zeolite") are needed to improve the model. Alternative conceptual models of key reactions may also be necessary. For this reason, a model that accounts for ion-exchange reactions among clay minerals, and which is based on the results of laboratory experiments, has also been evaluated in the present study. Further improvements of model considering ion-exchange reactions are needed in future, however.

Uranium micro-isotopic analysis of weathered rock by a sensitive high resolution ion microprobe (SHRIMPII)

Sato, Tsutomu; Yanase, Nobuyuki; I.S.Williams*; W.Compston*; M.Zaw*; T.E.Payne*; P.L.Airey*

Radiochimica Acta, 82, p.335 - 340, 1998/00

https://doi.org/10.1524/ract.1998.82.special-issue.335

no abstracts in English

Effects of humic acid on the sorption of neptunium(V) on kaolinite

*; Sato, Seichi*; Ohashi, Hiroshi*; Sakamoto, Yoshiaki; Onuki, Toshihiko; Nagao, Seiya; Muraoka, Susumu

Journal of Nuclear Materials, 248, p.328 - 332, 1997/00

https://doi.org/10.1016/S0022-3115(97)00131-1

no abstracts in English

Weathering of chlorite in a quartz-chlorite schist,I; Mineralogical and chemical changes

Murakami, Takashi*; Isobe, Hiroshi; Sato, Tsutomu; Onuki, Toshihiko

Clays and Clay Minerals, 44(2), p.244 - 256, 1996/00

https://doi.org/10.1346/CCMN.1996.0440210

no abstracts in English

Formation of actinide(III)-humate and its influence upon adsorption on kaolinite

Takahashi, Yoshio*; *; Kimura, Takaumi; Meguro, Yoshihiro; *

Materials Research Society Symposium Proceedings, Vol.353, 0, p.189 - 196, 1995/00

no abstracts in English

Study on long term consolidation behavior of buffer materials, 3; Comparison of basic properties of Kunigel V1 and Kaolinite

Takayama, Yusuke; Kikuchi, Hirohito*; Yamamoto, Yoichi*; Goto, Takahiro*

no journal, , 

In this report, permeability, swelling characteristics, and consolidation characteristics of kaolinite were examined and these characteristics of kaolinite were are compared with kunigel V1.