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Shimoda, Satoko*; Nakazawa, Toshiyuki*; Kato, Hiroyasu*; Tachi, Yukio; Seida, Yoshimi*
Materials Research Society Symposium Proceedings, Vol.1665, p.179 - 184, 2014/09
The potential effect of alkaline perturbation caused by the cementitious materials must be evaluated in the performance assessment for HLW geological disposal. In this study, sorption of Cs, Ni and Th was investigated using the altered and unaltered samples of sedimentary rock from Horonobe underground research laboratory. The K
values of Cs, Ni and Th measured by batch method using synthetic groundwater changed as a function of degrees of alteration. The K values of Cs increased with increasing degrees of alteration, indicating secondary minerals contributes to the increase in Cs sorption by ion exchange mechanism. On the other hand, the K values of Ni and Th decreased with the increase of degrees of alteration. This change may be caused by dissolution of clay minerals controlling Ni and Th sorption by surface complexation. These results imply that the effect of alkaline perturbation on K values of rocks depend on the surface property of the altered rock and sorption mechanism.
Terashima, Motoki; Nagao, Seiya*; Iwatsuki, Teruki; Fujitake, Nobuhide*; Seida, Yoshimi*; Iijima, Kazuki; Yoshikawa, Hideki
Journal of Nuclear Science and Technology, 49(8), p.804 - 815, 2012/08
Times Cited Count：12 Percentile：66.54(Nuclear Science & Technology)
, I
and HTO in samples of the argillaceous Wakkanai Formation from the Horonobe URL, Japan; Clay-based modeling approachTachi, Yukio; Yotsuji, Kenji; Seida, Yoshimi*; Yui, Mikazu
Geochimica et Cosmochimica Acta, 75(22), p.6742 - 6759, 2011/11
Times Cited Count：58 Percentile：82.25(Geochemistry & Geophysics)Diffusion and sorption behaviors of Cs, I and HTO in samples of the Wakkanai Formation from Horonobe URL were investigated as a function of ionic strength (IS) of synthetic groundwater by through-diffusion and batch sorption experiments. The 
values showed cation excess and anion exclusion effects, which were strongly dependent on IS; for Cs decreased as IS increased, for I showed the opposite dependency and for HTO showed no dependence. The Kd values for Cs determined by through-diffusion and batch experiments were in good agreement and decreased with IS as a result of competitive ion exchange. Diffusion and sorption behaviors were interpreted based on the clay-based modeling approach in assuming the clay components of illite and smectite control diffusion and sorption mechanisms. The model predicted the and Kd trends obtained by the series of experiments reasonably well, implying the key contribution of the clay particle and nano-size pore for ionic migration.
Tachi, Yukio; Nakazawa, Toshiyuki*; Ochs, M.*; Yotsuji, Kenji; Suyama, Tadahiro; Seida, Yoshimi; Yamada, Norikazu*; Yui, Mikazu
Radiochimica Acta, 98(9-11), p.711 - 718, 2010/11
Times Cited Count：25 Percentile：84.21(Chemistry, Inorganic & Nuclear)Diffusion and sorption of radionuclides in compacted bentonite are the key processes in the safe geological disposal. The effects of carbonate and salinity on Np(V) diffusion and sorption in compacted montmorillonite were investigated by experimental and modeling approaches. Effective diffusion coefficients () and distribution coefficients (
) of Np in montmorillonite compacted to dry density of 800 kg/m
were measured under four conditions with different salinities (0.05/0.5 M NaCl) and carbonate concentrations (0/0.01 M NaHCO
). The for carbonate-free conditions decreased as salinity increased, and those for carbonate conditions showed the opposite dependency. The decreased by one order of magnitude under high carbonate condition. Diffusion and sorption behaviors were interpreted by coupling the thermodynamic aqueous speciation, the thermodynamic sorption model based on ion exchange and surface complexation, and the diffusion model based on electrical double layer theory in narrow pores. The mechanistic model could be useful in predicting the sorption and diffusion behavior of complex species in compacted systems.
Seida, Yoshimi; Terashima, Motoki; Tachi, Yukio; Iijima, Kazuki; Nakazawa, Toshiyuki*; Yamada, Norikazu*; Yui, Mikazu
Radiochimica Acta, 98(9-11), p.703 - 709, 2010/11
Times Cited Count：3 Percentile：24.08(Chemistry, Inorganic & Nuclear)Diffusion and sorption behaviors of Eu in sedimentary rock were investigated in the presence of humic substance in the present study. Sedimentary rock obtained from Horonobe URL test site in Hokkaido, Japan, (accessible pore diameter is around several to several ten nanometer) was used. The Diffusion behaviors of Eu were examined based on reservoir depletion method coupled with analysis of inner distribution of the radioactive elements in the rock. Time sequence of concentration of each radioactive element as well as the humic substance in the reservoir was obtained as a function of concentration and molecular size of humic substance. Coexistence of humic substance reduced the depletion of Eu in the reservoir, indicating complexation between the radioactive elements and the humic substance. On the contrary, obvious decrease of humic substance in the reservoir was not observed in the system. This observation suggests that the radioactive elements became hard to diffuse into the sedimentary rock due to an increase of their size through complexation with the humic substance. The sorption of Eu was reduced with increase of the humic substance although the sorption of the humic substance was not influenced by the existence of Th or Eu. The diffusion and sorption of Eu were found to be reduced in the presence of humic substance.
Ishii, Yasuo; Seida, Yoshimi; Tachi, Yukio; Yoshikawa, Hideki
Materials Research Society Symposium Proceedings, Vol.1265, p.233 - 238, 2010/09
Influence of stagnation of the test tracer solution and diffusion resistance in the filters on data acquisition were measured by Cs and I diffusion experiments and the range of uncertainties of these effects was estimated by calculation of the simulated experimental component. From the ID experiment and the model analysis, it was found that the simultaneous data acquisition of RD and ID methods decreased the residue of retardation parameters effectively.
Tachi, Yukio; Yotsuji, Kenji; Seida, Yoshimi; Yui, Mikazu
Materials Research Society Symposium Proceedings, Vol.1193, p.545 - 552, 2009/05
Diffusion of Cs and I in compacted montmorillonite were examined from the viewpoints of mechanistic understanding of salinity effects. The effective diffusivity and capacity factor for Cs and I were measured in compacted montmorillonite saturated with 0.01, 0.1 and 0.5M NaCl by through-diffusion experiments, coupled with multiple curve analysis including tracer depletion, breakthrough, and depth concentration curves. The De values obtained for Cs decreased as salinity increased, and those for I showed the opposite dependency. The distribution coefficient of Cs decreased as salinity increased. The diffusion and sorption parameters for Cs were also obtained by in-diffusion and batch sorption experiments, showing good agreement with those by the through-diffusion. The diffusion model based on electrical double layer theory predicted the salinity dependence of De reasonably well, the apparent diffusivity which includes sorption effect was also interpreted by the sorption coupled model.
Takahashi, Hiroaki; Seida, Yoshimi; Yui, Mikazu
Diffusion Fundamentals (Internet), 11(89), p.1 - 11, 2009/00
A high-resolution, 3D image of the interior of the sedimentary rock was obtained by means of nano-focus X-ray CT. Using computational methods to analyze the 3D microstructure of the rock, we presented the tortuosity and geometrical constrictivity. We also presented results on the tritiated water (HTO) diffusion tests and a mercury intrusion porosimetry (MIP) test performed on the rock. We have compared these results to understand the dominating parameters that control diffusion of HTO in the present system. These results suggest that the dominating parameters in the present system are not the constrictivity but the tortuosity and the diffusion-accessible porosity. The material considered in this study is the siliceous mudstones sampled from 500 m in depth at the Wakkanai formation around Horonobe underground research center under investigation in Japan to confirm of technical reliability for a deep geological disposal system for radioactive waste.
Tachi, Yukio; Seida, Yoshimi; Doi, Reisuke; Xia, X.*; Yui, Mikazu
Materials Research Society Symposium Proceedings, Vol.1124, p.573 - 579, 2009/00
Seida, Yoshimi; Tachi, Yukio; Kitamura, Akira; Takahashi, Hiroaki; Nakazawa, Toshiyuki*; Yamada, Norikazu*
no journal, ,
no abstracts in English
Takahashi, Hiroaki; Seida, Yoshimi; Miyahara, Kaname; Yui, Mikazu
no journal, ,
no abstracts in English
Tachi, Yukio; Seida, Yoshimi; Doi, Reisuke; Yui, Mikazu
no journal, ,
Sorption and diffusion behaviors of Cs in the Horonobe sedimentary rock were studied by both batch sorption and diffusion experiments from the viewpoints of reliability of experimental evaluation and model prediction. To obtain reliable parameters of sorbing species for intact rock, the through-diffusion experiment coupled with multiple curve analysis including tracer depletion, breakthrough and depth-concentration curves were examined. The Kd values obtained by the diffusion tests using intact rock were consistent with those obtained by the batch tests with crushed rock. The sorption behavior was modeled by considering additive ion-exchange reactions for illite and smectite.
Tachi, Yukio; Seida, Yoshimi; Yotsuji, Kenji; Yui, Mikazu
no journal, ,
Ionic diffusion and retardation behaviors in the Horonobe sedimentary rock were studied under different salinity conditions by both diffusion and batch sorption experiments from the viewpoints of reliability of experimental evaluation and model prediction. The De for Cs+ decreased as salinity increased, and those for I- showed the opposite dependency. The Kd of Cs showed a consistent trend for salinity between batch sorption and diffusion tests. Diffusion and sorption behaviors were modeled based on the clay-based approach, assuming clay components of smectite and illite as dominating mineral for diffusion and sorption mechanism. The model predicted the De and Kd values obtained by the series of experiments reasonably well, implying the key contribution of the clay particle and nano-size pore for ionic migration in the rock.
Seida, Yoshimi; Tachi, Yukio; Yoshikawa, Hideki; Yui, Mikazu
no journal, ,
The barrier function of engineering barrier in high-level nuclear waste repository is assessed by retardation parameters of radionuclides. To determine effective diffusion coefficient, De, in compacted clay system, outer reservoirs for diffusion source and drain are needed in diffusion test method with porous thin filters. This experimental configulation causes significant disturbances to De measured on the basis of reservoir concentration. In the present study, influence of boundary condition at reservoir-compacted bentonite boundary on effective diffusion coefficient measurement was examined from an electrochemical point of view. Electric potential difference at the boundary was measured to investigate partition of mobile ions (actual boundary concentration) and its influence on De with theoretical basis as a function of salinity of solution and compaction density of clay.
Terashima, Motoki; Seida, Yoshimi; Iwatsuki, Teruki; Iijima, Kazuki; Yoshikawa, Hideki; Yui, Mikazu; Nagao, Seiya*
no journal, ,
Eu(III) binding abilities of dissolved humic substances (HSs), which were extracted from deep groundwater in the Horonobe Underground Research Center, Hokkaido, Japan, were investigated by fluorescence quenching technique. In the synthetic groundwater condition, the fluorescence quenching due to the binding with Eu(III) was not observed for the groundwater HSs, while that was observed for the Aldrich humic acid (HA). This result indicates that the binding ability of the groundwater HSs are different from that of Aldrich HA. Based on structural characteristics of the groundwater HSs, the differences in the binding ability are discussed.
Takahashi, Hiroaki; Seida, Yoshimi; Yui, Mikazu
no journal, ,
no abstracts in English
Terashima, Motoki; Nagao, Seiya*; Iwatsuki, Teruki; Sasaki, Yoshito; Seida, Yoshimi; Yoshikawa, Hideki
no journal, ,
no abstracts in English
Ishii, Yasuo; Seida, Yoshimi*; Tachi, Yukio; Okazaki, Mitsuhiro*; Kurosawa, Seiichi*
no journal, ,
We developed the Sorption/diffusion data acquisition method for high sorbing nuclides using trivalent actinide Am.
Takahashi, Hiroaki; Seida, Yoshimi*; Yui, Mikazu
no journal, ,
no abstracts in English
Nakazawa, Toshiyuki*; Shimoda, Satoko*; Yamada, Norikazu*; Tachi, Yukio; Seida, Yoshimi*; Yui, Mikazu
no journal, ,
To set reliable parameters for the performance assessment (PA) of geological disposal, it is necessary to establish a reliable method for experimental evaluation and model prediction of sorption and diffusion in compacted bentonites. The through-diffusion and reservoir depletion experiments coupled with multiple curve analyses, including tracer depletion, breakthrough, and depth concentration curves were developed and applied for some systems including key radionuclides and geochemical conditions.
