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Yamaguchi, Tetsuji; Takeda, Seiji; Nishimura, Yuki; Iida, Yoshihisa; Tanaka, Tadao
Radiochimica Acta, 102(11), p.999 - 1008, 2014/11
Times Cited Count：1 Percentile：7.65(Chemistry, Inorganic & Nuclear)An attempt was made to select thermodynamic data with uncertainties and to evaluate the solubility of radioelements with uncertainties considering variation in groundwater chemistry. The thermodynamic data was selected by reviewing the JAEA-TDB released in 2012. Data for Nb, Pd and Pa were revised from the viewpoint of the consistency of the data selection process. Data for Se, U and Pa were revised from the viewpoint of the conservativeness. Up-to-date ternary calcium-metal(IV)-OH complexes were adopted for Zr, Th, U, Np and Pu. A Monte Carlo-based probabilistic calculation code, PA-SOL, was used for probabilistic analysis of the solubility.
) onto iron-containing mineralsIida, Yoshihisa; Yamaguchi, Tetsuji; Tanaka, Tadao
Journal of Nuclear Science and Technology, 51(3), p.305 - 322, 2014/03
Times Cited Count：16 Percentile：69.83(Nuclear Science & Technology)Sorption behaviors of HSe onto iron-containing minerals, magnetite, goethite, ferrous oxide and biotite, were investigated by batch sorption experiments under reducing conditions. The sorption ratios for goethite, as representative examples, show negative dependence on pH and independence of the NaCl concentration. The results indicate that the sorption behavior of HSe is inner sphere surface complexation to ferrol sites. The triple layer model was used in the analysis of the sorption behavior of HSe with Visual Minteq computer program. The intrinsic equilibrium constant was determined by the fitting of model calculations to the experimental results to be 5.5. The value was close to the value of HS (5.3) which is chemically analogous to HSe.
Marin, A.*; Siitari-Kauppi, M.*; Havlov
, V.*; Tachi, Yukio; Miksova, J.*
no journal, ,
Matrix diffusion is very important in the context of the performance assessment of radioactive waste repository in the crystalline rocks. An in-situ long-term diffusion (LTD) project has been performed at the Grimsel Test Site, Switzerland, to realistically evaluate matrix diffusion of radionuclides in crystalline rock with minimal disturbance to in-situ conditions. As part of phase-I, tracers, HTO, Na-22, Cs-134, were continuously circulated through a packed-off borehole and the tracer concentrations in the solution was monitored for 2.5 years. Subsequently, the borehole section was overcored and the tracer profiles in the rock analyzed. These results were analyzed with diffusion-sorption models by different teams. The phase-II plans including experimental design and tracers selection will be discussed.
, I and HTO in compacted sodium montmorillonite as a function of dry densityTachi, Yukio; Yotsuji, Kenji
no journal, ,
Diffusion and sorption of radionuclides in compacted bentonite are key processes in the safe geological disposal. The effects of dry density on diffusion and sorption of Cs, I and HTO in compacted montmorillonite were investigated by experimental and modeling approaches. Effective diffusion coefficients (De) and distribution coefficients (Kd) in montmorillonite compacted to dry density of 0.8, 1.4, 1.8 Mg/m
, and saturated with 0.1 M NaCl solution. Although the De values of HTO and I- decreased as dry density increased, those of Cs were mostly independent of dry density. The Kd values of Cs obtained were independent of dry density and were consistent with batch-derived values. These results were interpreted by the integrated sorption and diffusion (ISD) model coupling the ion exchange model and the EDL diffusion model in narrow pores.
, Na, I and HTO in granodiorite; Laboratory results and their extrapolation to the in-situ conditionTachi, Yukio; Ebina, Takanori*; Takahashi, Hiroaki; Nemoto, Kazuaki; Suyama, Tadahiro*; Martin, A.*
no journal, ,
Matrix diffusion and sorption of radionuclides in crystalline host rocks are key processes controlling safe geological disposal of radioactive waste. Diffusion and sorption parameters for Cs, Na, I and HTO were determined by laboratory experiments using granodiorite samples from the Grimsel Test Site, Switzerland. The De values derived were in the order Cs 
Na HTO I. The capacity factor and Kd values show the same trends. Depth profiles of Cs and Na obtained by abrasing samples after a diffusion period showed typical dual profiles. The results of in-situ long-term diffusion tests at GTS were interpreted by using GoldSim code and transport parameters based on laboratory results and their extrapolations to in-situ conditions. These model calculations could the in-situ LTD results of Cs and Na reasonably well, although it was difficult to interpret HTO results. Key findings from these comparative studies between laboratory experiments and in-situ LTD tests were discussed.
Onuki, Toshihiko; Sakamoto, Fuminori; Kozai, Naofumi; Yamasaki, Shinya
no journal, ,
Chemical states of radioactive Cs deposited in the plants and soil was characterized by the SDA. These results strongly suggest that (1) radioactive Cs at 10
mole L
is more strongly associated with the non-mica minerals than at higher concentrations of 10
and 10
mole L, and (2) the non-mica minerals montmorillonite, mordenite, kaolinite, and MnO
contributed to the irreversible sorption of the radioactive cesium fall-out on Fukushima soil.
Kirishima, Akira*; Kuno, Atsushi*; Amamiya, Hiroki; Murakami, Hiroaki; Amano, Yuki; Iwatsuki, Teruki; Mizuno, Takashi; Kubota, Takumi*; Sasaki, Takayuki*; Sato, Nobuaki*
no journal, ,
For understanding of the migration behavior of minor actinides (MA) in groundwater, the interaction of rare earth elements and suspended matters contained in Horonobe deep groundwater was studied. From this chemical analog study, it is suggested that the migration behavior of MA in the Horonobe groundwater system seems to be regulated by the formation of phosphate precipitation and small percentage of MA would be carried in the groundwater as pseudo colloids like MA-humic substance complex.
Kitamura, Akira
no journal, ,
Some oxidants may be produced in a groundwater by an 
-irradiation released from -emitter contained in high-level radioactive waste (vitrified glass or spent fuel). Effect of oxidants on groundwater redox condition was investigated using thermodynamic calculations. As a result, produced oxidants were consumed around an overpack or a canister and no oxidants will be released to buffer materials and rocks.
Suzuki, Yoshinori*; Saiki, Hiroshi*; Kitamura, Akira; Yoshikawa, Hideki
no journal, ,
We examined the reduction of selenite by a biofilm of 
. After forming a biofilm on cover glasses, selenite solution was contacted to the biofilm and a red precipitate was formed under anaerobilc conditions. It was found that the precipiatate was Se(0) by an X-ray absorption spectroscopy.
