Fujimoto, Shinji*; Tsuchiya, Hiroaki*; Ogawa, Soma*; Iida, Yoshihisa; Taniguchi, Naoki
Materials and Corrosion, 72(1-2), p.333 - 338, 2021/01
The stress corrosion cracking (SCC) of pure copper in bentonite was examined by a slow strain rate test (SSRT). The bentonite was swollen with pure water or aqueous solutions containing NH of 0.05 M and 0.1 M. The thick corrosion films and particulate deposits were formed on copper surface after SSRT. Typical tarnish rupture type SCC occurred on pure copper in swollen bentonite with and without NH. Crack propagation rate was enhanced by NH. It is confirmed thick oxide layer is formed on copper during plastic deformation which resulting in the tarnish crack type SCC. The many particulate deposits observed on the surface might be formed as a results of rapid dissolution of Cu to form porous CuO at locallized deformed sites.
Yamaguchi, Tetsuji; Ohira, Saki; Hemmi, Ko; Barr, L.; Shimada, Asako; Maeda, Toshikatsu; Iida, Yoshihisa
Radiochimica Acta, 108(11), p.873 - 877, 2020/11
Iida, Yoshihisa; Nakadoi, Yasumasa; Yamaguchi, Tetsuji
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 24(1), p.53 - 64, 2017/06
The information on the contaminated water treatment in Fukushima Daiichi Nuclear Power Station announced by Tokyo Electric Power Co., Inc. (TEPCO) were summarized in terms of the management of the secondary wastes, for the purpose of accumulating technical knowledge for long-term storage of the wastes. Concerns for the long-term soundness of waste storage containers were pointed out as follows, corrosion of stainless steel containers exposed to radiation in the presence of chloride ions, corrosion of stainless steel containers under acidic conditions or in the presence of activated carbon, and radiation degradation of the high-performance container (HIC) in which slurry was stored.
Iida, Yoshihisa; Yamaguchi, Tetsuji; Tanaka, Tadao; Hemmi, Ko
Journal of Nuclear Science and Technology, 53(10), p.1573 - 1584, 2016/10
The sorption behavior of thorium (Th) onto granitic rock and its major constituent were investigated by batch sorption experiments. Experiments were carried out under variable pH and carbonate concentrations. Distribution coefficients decreased with increased carbonate concentrations and showed the minimal value at pH 9-10. This sorption tendency was likely due to forming the hydroxide-carbonate complexes of Th in the solutions. The order of sorbability for Th was mica feldspar quartz = granite. The sorption behaviors of Th onto these minerals were analyzed by the triple-layer surface complexation model with the Visual Minteq computer program. The model calculations assuming the inner-sphere surface complexation of Th were able to explain the experimental results reasonably well. It was shown that the sorption behavior of Th onto granite can be explained primarily by the complexation with the surface sites of feldspar.
Iida, Yoshihisa; Barr, L.; Yamaguchi, Tetsuji; Hemmi, Ko
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 23(1), p.3 - 8, 2016/06
Thorium (Th)-229 is one of the important radionuclides for the performance assessment calculations for high-level radioactive waste repositories. The sorption behavior of Th onto montmorillonite and illite were investigated by batch sorption experiments. Experiments were carried out under variable pH and carbonate concentrations. The sorbability of montmorillonite was higher than that of illite. Distribution coefficients, (m kg), decreased with increased carbonate concentrations and showed the minimal value at around pH 10. The sorption behaviors of Th were analyzed by the non-electrostatic surface complex model with PHREEQC computer program. The model calculations were able to explain the experimental results reasonably well. The decreases of was likely due to the stabilization of aqueous species by hydroxo-carbonate complexations in the solutions.
Hemmi, Ko; Yamaguchi, Tetsuji; Iida, Yoshihisa
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 22(1), p.3 - 10, 2015/06
Iodine and tin are important elements in performance assessment of geological disposal of radioactive wastes. Sorption experiments of iodine were carried out under varying nitrate concentration with a range of 0 to 5 mol dm at neutral pH range in order to determine the distribution coefficient of iodine was zero or non-zero value. The experimental results with estimated statistical errors showed non-zero values for tuffaceous sandstone except for NaNO concentration 0.5 mol dm. Non-zero values were also obtained under NaNO concentrations higher than 0.5 mol dm for granodiorite. Sorption experiments of tin were carried out at high pH range in order to check whether the distribution coefficient of tin decreases significantly with pH as a result of formation of anionic hydrolysis species of tin. The distribution coefficients of tin on granodiorite decreased from 9.7910 m kg at pH10.4 to 2.4610 m kg at pH12.4. The distribution coefficient of tin on tuffaceous sandstone was about one order of magnitude higher (about 210 m kg) than that of granodiorite at pH around 12.4.
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 22(1), p.11 - 12, 2015/06
The summary of NUCE session titled "The current status and issues of the contaminated water treatment system at Fukushima Daiichi Nuclear Power Plant" in 2015 AESJ Spring Meeting is reported.
Yamaguchi, Tetsuji; Takeda, Seiji; Nishimura, Yuki; Iida, Yoshihisa; Tanaka, Tadao
Radiochimica Acta, 102(11), p.999 - 1008, 2014/11
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.
Sakamaki, Keiko; Kataoka, Masaharu; Maeda, Toshikatsu; Iida, Yoshihisa; Kamoshida, Michio; Yamaguchi, Tetsuji; Tanaka, Tadao
Corrosion Engineering, Science and Technology, 49(6), p.450 - 454, 2014/09
Corrosion experiments of a carbon steel plate embedded in bentonite mixture were conducted toverify our models assessing Eh evolution induced by corrosion of carbon steel overpack. Theexperimental results showed that the Eh decreased for the first 200 days and was subsequentlystabilised at around -450 mV; corrosion products were identified as magnetite and Fe waspresent mostly as divalent Fe within a 5 mm range from the carbon steel plate. Reactive transportmodelling was performed to assess the Eh evolution in the system using kinetic dissolution modelfor metallic iron and thermodynamic equilibrium models for other chemical reactions and closelyreproduced the experimental results. The models were verified only under the conditionsemployed in this study.
Iida, Yoshihisa; Yamaguchi, Tetsuji; Tanaka, Tadao
Journal of Nuclear Science and Technology, 51(3), p.305 - 322, 2014/03
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.
Sawaguchi, Takuma; Yamaguchi, Tetsuji; Iida, Yoshihisa; Tanaka, Tadao; Kitagawa, Isamu
Clay Minerals, 48(2), p.411 - 422, 2013/05
Diffusive transport of Cs in compacted sand-bentonite mixtures was studied by a through diffusion method. Experiments were performed under variable aqueous compositions. Effective diffusivity () values of 5.2E-10 5.9E-9 m s were obtained. The variation was somewhat large in the values. Apparent diffusivity () values, on the other hand, were 2.0E-12 6.2E-12 m s, which shows small variation. The results indicate that, in applying Fick's 1st law of diffusion, diffusive flux is proportional to the apparent concentration gradient of Cs in the sand-bentonite mixture rather than the gradient of Cs concentration in pore water. Since the apparent concentration gradient in sand-bentonite mixtures is nearly equal to the gradient of adsorbed Cs, diffusion of Cs under adsorbed state would be the main mechanism of diffusion of Cs in sand-bentonite mixtures.
Otsuka, Ichiro*; Iida, Yoshihisa; Yamaguchi, Tetsuji; Kato, Osamu*; Tateishi, Tsuyoshi*; Tanaka, Tadao
Materials Research Society Symposium Proceedings, Vol.1475, p.507 - 512, 2012/06
We conducted corrosion experiments of carbon wires to identify the cathode reaction with overpack corrosion. Carbon steel wires were immersed in selected aqueous solutions of distilled water, sodium hydrogen carbonate solution and sodium sulfate solution sealed in glass ampoules. The ampoules were kept at 60 C for 150 days. Corrosion products, liquid phase and gas phases were analyzed. The results showed that hydrogen gas generation by reduction of hydrogen ions was dominant cathode reaction. Reduction of sulfate and carbonate anions was not observed. Amorphous ferrous hydroxide and/or iron oxides were identified in all the experiments as the corrosion products. Iron carbonate was also identified in the sodium hydrogen carbonate solution. This result indicates that the hydrogen generation reaction might be the dominant cathode reaction under geological disposal environment and that the Eh of the pore water would reach the equilibrium potential of the hydrogen generation reaction.
Iida, Yoshihisa; Yamaguchi, Tetsuji; Tanaka, Tadao
Journal of Nuclear Science and Technology, 48(8), p.1170 - 1183, 2011/08
Effective diffusion coefficients of selenium through bentonite sand mixtures under reducing and anaerobic conditions were obtained by the through-diffusion method. Experiments were carried out under variable bentonite content and porewater salinity. The employed bentonite material was Kunigel V1. The dominant diffusion species were determined to be HSe and SeO under reducing and anaerobic conditions, respectively. The effective diffusion coefficients of selenium species decreased with increasing bentonite content and with decreasing salinity. This tendency is primarily due to anion exclusion which caused by negative surface charge of montmorillonite. A diffusion model for anionic species was developed based on the electric double layer theory and the pore diffusion model, to evaluate diffusion behaviors of HSe and SeO in bentonite porewater. The effective diffusion coefficients of selenium species predicted by this model showed good agreement with experimentally measured ones.
Iida, Yoshihisa; Tanaka, Tadao; Yamaguchi, Tetsuji; Nakayama, Shinichi
Journal of Nuclear Science and Technology, 48(2), p.279 - 291, 2011/02
Batch sorption experiments were carried out to investigate sorption behavior of selenium onto granodiorite, sandy mudstone, tuffaceous sandstone and their major constituent minerals and accessory minerals under reducing conditions. Rocks and groundwater employed in the experiments were sampled with a special care avoiding exposing the rocks and groundwater to the air to minimize their oxidation. The dominant sorbent minerals for selenium were determined to be biotite for granodiorite, and pyrite for sandy mudstone and tuffaceous sandstone at neutral-alkaline pH.
Iida, Yoshihisa; Yamaguchi, Tetsuji; Tanaka, Tadao; Nakayama, Shinichi
Journal of Nuclear Science and Technology, 47(5), p.431 - 438, 2010/05
Solubility experiments for selenium were performed at high ionic strengths (1.0 and 2.0 M NaCl) under anoxic conditions. Dominant aqueous selenium species were identified as hydrogen selenide, HSe, at pH between 5 and 8, and polyselenide, Se at pH between 9 and 13. A solubility-limiting solid was determined to be amorphous selenium at pH between 5 and 8, and crystalline selenium at pH between 9 and 13. The equilibrium constants of Se(am) + H + 2e = HSe, logK = -6.570.15, 4Se(cr) + 2e = Se logK = -16.670.03 and ion interaction coefficients for HSe and Se versus Na, (HSe, Na) = -0.010.10 and (Se, Na) = -0.030.02, were determined by specific ion interaction theory. The standard molar free energy of formation of amorphous selenium and polyselenide species were determined to be G (Se(am)) = 6.02.2 kJ mol, G(Se) = 111.641.61 kJ mol, G(Se) = 98.681.02 kJ mol and G (Se) = 95.140.17 kJ mol, respectively.
Kitamura, Akira; Shibata, Masahiro; Yamaguchi, Tetsuji; Iida, Yoshihisa; Yui, Mikazu
JAEA-Technology 2009-074, 48 Pages, 2010/03
Investigations on systematics of thermodynamic data were performed for performance assessment of geological disposal of high-level and TRU waste. Correlation between standard free energy of formation and standard enthalpy of formation was investigated, and it was shown that estimation of the standard enthalpy of formation from the standard free energy of formation was possible using the correlation. Three models on systematics of formation constant of actinides were compared and the best model was proposed. It was shown that estimation of formation constant for unpublished species was possible using the model. Furthermore, two models for estimation of activity coefficient which was required to estimate solubility of elements of interest and the estimated activity coefficient were compared. It was expected that the obtained results were useful for the performance assessment of geological disposal.
Iida, Yoshihisa; Kimura, Yuichiro*; Yamaguchi, Tetsuji; Ueda, Masato*; Tanaka, Tadao; Nakayama, Shinichi
Genshiryoku Bakkuendo Kenkyu, 15(2), p.57 - 67, 2009/03
Sorption of radionuclides on rocks is an important factor for safety assessments of geologic disposal of radioactive wastes. Batch sorption tests were conducted to investigate effects of concentrations of NaNO and NaCl on sorption distribution coefficients(Kd) of selenium(Se) on a sandy mudstone under reducing environment of underground. The rock and groundwater used in the tests were sampled from depths of 129-156 m with special care minimizing contact with air. Se was spiked as HSe or Se to the test solutions and kept as HSe throughout the test periods by keeping reducing conditions (Eh, pH) of the solutions. Obtained Kd values were in a range of 0.015-0.037 m kg, which were as high as those for a typical sorbing element, Cs.
Iida, Yoshihisa; Yamaguchi, Tetsuji; Tanaka, Tadao; Kitamura, Akira; Nakayama, Shinichi
Proceedings of International Workshop on Mobile Fission and Activation Products in Nuclear Waste Disposal, p.135 - 145, 2009/00
We performed dissolution experiments of iron-selenium compounds from both undersaturation and oversaturation directions to determine the solubility limiting solid of selenium in the presence of iron under anoxic conditions. The solid products was identified to be iron diselenide but the concentration of selenium was 9 orders of magnitude higher than the value calculated from the existing thermodynamic data of FeSe, therefore FeSe was not considered to be the solubility limiting solid. The pH and Eh dependencies of the concentration of selenium were best interpreted as the dissolution reaction of Se(cr), but the concentration of selenium was still 3 orders of magnitude higher than the value calculated from the existing thermodynamic data of Se(cr). Because any selenium compounds other than FeSe was not detected by XRD and the concentration of selenium was higher than the solubility of Se(cr), the solubility limiting solid was considered to be amorphous selenium.
Otsuka, Ichiro; Taki, Hiroshi*; Yamaguchi, Tetsuji; Iida, Yoshihisa; Yamada, Fumika; Inada, Daisuke*; Tanaka, Tadao
JAEA-Research 2008-043, 101 Pages, 2008/03
The influence of carbon steel overpack corrosion on redox potential (h) of bentonite pore water under geological disposal environment was investigated. The thermodynamics data of corrosion products, the corrosion rate of carbon steel, and the information on cathode reactions were acquired by experiments and literature survey. We conducted preliminary analysis of h, ascertained the validity of Phreeq C and identified important points on the analysis. Results were summarized as follows. (1) Thermodynamic data of Fe, FeOH, Fe(OH)(aq), Fe(OH), Fe(OH), Fe, FeS(pyrite), FeCO(siderite),Fe(OH)(s), FeO(magnetite), Fe(cr) were determined by literature survey. The solubility product of FeCO(OH) was determined experimentally, and thermodynamic data were estimated. (2) The corrosion rate of carbon steel was obtained as a function of pH and sulfide ion concentration. (3) After corrosion tests of carbon steel, no CH, HS and HS, the reduction product of CO and SO,were not detected in liquid and gas phases. (4) Preliminary analysis showed that the redox couple changed as HS(aq)/SO, CH(aq)/CO, H(aq)/HO during the evaluation period. After 1000 years, h attained about -500 to -600 mV (vs. NHE) or -750 mV controlled by CH(aq)/CO,or H(aq)/HO, respectively.
Yamaguchi, Tetsuji; Sakamoto, Yoshifumi; Akai, Masanobu; Takazawa, Mayumi; Iida, Yoshihisa; Tanaka, Tadao; Nakayama, Shinichi
Physics and Chemistry of the Earth, 32(1-7), p.298 - 310, 2007/00
Dissolution rate of montmorillonite, diffusivity of hydroxide ion and permeability coefficient in compacted sand-bentonite mixtures were experimentally determined and formulated. A coupled mass-transport/chemical-reaction code was developed to predict variation in permeability of engineered bentonite barrier with alkaline fluid by using the formulae.