Stable hydrogen and oxygen isotope analyses of geological samples using a thermal conversion elemental analyzer-isotope ratio mass spectrometer at Tono Geoscience Center

Yamamoto, Yusuke*; Watanabe, Takahiro; Niwa, Masakazu; Shimada, Koji

JAEA-Testing 2023-003, 67 Pages, 2024/02

JAEA-Testing-2023-003.pdf:4.63MB

A long-term geosphere stability for geological disposal is evaluated by the past geological environmental changes and modern conditions. Stable hydrogen and oxygen isotope ratios (D, O) of geological samples are useful information to estimate the past environmental changes and modern conditions. Recently, the thermal conversion elemental analyzer and isotope ratio mass spectrometer (TC-EA/IRMS) were installed in the Tono Geoscience Center for D and O measurements of geological samples. In this study, we reported analytical methods of D and O using international standard reference materials. In addition, evaluation tests of uncertainty by repeated analyses of the standards were performed using the TC-EA/IRMS. Furthermore, the D and O analyses by the TC- EA/IRMS were also applied to fault rock samples.

Sorption of Eu on montmorillonite studied by time-resolved laser fluorescence spectroscopy and surface complexation modeling

Sasaki, Takayuki*; Ueda, Kenyo*; Saito, Takumi*; Aoyagi, Noboru; Kobayashi, Taishi*; Takagi, Ikuji*; Kimura, Takaumi; Tachi, Yukio

no journal, , 

The influence of pH, ionic strength, and the concentrations of Eu and nitrate salts on the sorption of Eu on Na-montmorillonite was investigated by batch sorption measurements. The distribution coefficient (Kd) indicated that the cation exchange reaction is significant in pH 4-7 at low ionic strength, and the formation of surface complexation is related to the pH dependence of Kd at high ionic strength. The Eu surface species were investigated using time-resolved laser fluorescence spectroscopy (TRLFS) with parallel factor analysis (PARAFAC). The PARAFAC modeling indicated two surface species, the outer-sphere (factor A) and inner-sphere (factor B) Eu complexes. Factor B was dominant at high pH and ionic strength, which was determined to be a Eu colloidal species formed at high Eu concentrations. A cation exchange model combined with a one-site non-electrostatic surface complexation model was applied to the measured Kd data, using the results of the TRLFS-PARAFAC analyses.