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Journal Articles

Effect of calcium on niobium solubility in alkaline solutions

Ohira, Saki; Abe, Takeyasu; Iida, Yoshihisa

Radiochimica Acta, 111(7), p.525 - 531, 2023/07

 Times Cited Count:0 Percentile:0.01(Chemistry, Inorganic & Nuclear)

The solubility of $$^{94}$$Nb in calcium alkaline solutions is one of the important parameters in safety assessment of intermediate-depth disposal which are assumed to use cementitious materials. Nb solubility and solubility-limiting solid phases of Nb in these systems remain unclear. The oversaturation solubility experiments were performed systematically in the 0.001-0.1 M CaCl$$_{2}$$ solutions under alkali conditions, and the characterization of precipitated solid phase controlling Nb solubility was conducted. The negative dependence of Nb solubilities on pH and Ca concentration was observed in solubility experiments, the molar ratio of Nb to Ca of precipitated solid phase was 0.66. The pH and Ca dependence of Nb solubilities was reproduced by the reaction with Nb aqueous species Nb(OH)$$_{6}$$$$^{-}$$ and Ca-Nb oxide with the molar ratio of Nb to Ca 0.66, e.g., Ca$$_{4}$$Nb$$_{6}$$O$$_{19}$$(am).

Journal Articles

Sorption behavior of niobium onto clay minerals in the presence of Ca

Ohira, Saki; Iida, Yoshihisa

Proceedings of Waste Management Symposia 2023 (WM2023) (Internet), 10 Pages, 2023/02

The sorption distribution coefficient (${it K}$d) of niobium-94 (Nb-94) on minerals is one of the important parameters in safety assessment of radioactive waste disposal. In a previous study, the ${it K}$d values of Nb under alkali condition in the presence of Ca, were two orders of magnitude higher than those in the presence of Na. In this study, Nb sorption experiments were performed to reexamine the effect of Ca on Nb sorption on clay minerals, and blank tests were performed to check for precipitation formation. The results showed that the Nb sorption onto montmorillonite and illite, did not depend on the Ca concentration, and ${it K}$d values obtained in the presence of Ca were the same as those in the absence of Ca. A sorption model assuming sorption by complexation on the mineral surface was developed and then calculated using the geochemical calculation code. The model with the surface species X_ONb(OH)$$_{4}$$ and X_ONb(OH)$$_{5}$$$$^{-}$$ represented trends in the data obtained.

Journal Articles

Review of performance assessment for engineered barrier systems to support future RD&D of radioactive waste management in Japan

Abe, Takeyasu; Iida, Yoshihisa

Journal of Advanced Concrete Technology, 20(3), p.236 - 253, 2022/03

 Times Cited Count:0 Percentile:7.33(Construction & Building Technology)

This paper is a state-of-the-art report on the performance assessment of cementitious and related materials as components of engineered barrier systems for radioactive waste management. In this paper, (1) the concept of safety functions is reviewed as the engineering background of discussion, (2) an overview of the postclosure performance assessment for Belgian low- and intermediate-level short-lived radioactive waste disposal is provided, and (3) a modeling methodology for engineered barrier systems is analyzed using the concept of "mandala for durability mechanics". According to these works, authors present technical suggestions for technical stakeholders of Japanese low-level radioactive waste disposal.

Journal Articles

Radiochemical analysis of the drain water sampled at the exhaust stack shared by Units 1 and 2 of the Fukushima Daiichi Nuclear Power Station

Shimada, Asako; Taniguchi, Yoshinori; Kakiuchi, Kazuo; Ohira, Saki; Iida, Yoshihisa; Sugiyama, Tomoyuki; Amaya, Masaki; Maruyama, Yu

Scientific Reports (Internet), 12(1), p.2086_1 - 2086_11, 2022/02

 Times Cited Count:0 Percentile:33.72(Multidisciplinary Sciences)

no abstracts in English

Journal Articles

Stress corrosion cracking of copper in swollen bentonite simulating nuclear waste disposal environment

Fujimoto, Shinji*; Tsuchiya, Hiroaki*; Ogawa, Soma*; Iida, Yoshihisa; Taniguchi, Naoki

Materials and Corrosion, 72(1-2), p.333 - 338, 2021/01

 Times Cited Count:2 Percentile:13.1(Materials Science, Multidisciplinary)

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$$_{3}$$ 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$$_{3}$$. Crack propagation rate was enhanced by NH$$_{3}$$. 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$$^{2+}$$ to form porous CuO at locallized deformed sites.

Journal Articles

Consideration on modeling of Nb sorption onto clay minerals

Yamaguchi, Tetsuji; Ohira, Saki; Hemmi, Ko; Barr, L.; Shimada, Asako; Maeda, Toshikatsu; Iida, Yoshihisa

Radiochimica Acta, 108(11), p.873 - 877, 2020/11

 Times Cited Count:7 Percentile:67.5(Chemistry, Inorganic & Nuclear)

Journal Articles

The Survey for the integrity of containers for secondary wastes generated from contaminated water treatment

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.

Journal Articles

Sorption behavior of thorium onto granite and its constituent minerals

Iida, Yoshihisa; Yamaguchi, Tetsuji; Tanaka, Tadao; Hemmi, Ko

Journal of Nuclear Science and Technology, 53(10), p.1573 - 1584, 2016/10

 Times Cited Count:6 Percentile:60.71(Nuclear Science & Technology)

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.

Journal Articles

Sorption behavior of thorium onto montmorillonite and illite

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, $$K_{rm d}$$ (m$$^{3}$$ kg$$^{-1}$$), 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 $$K_{rm d}$$ was likely due to the stabilization of aqueous species by hydroxo-carbonate complexations in the solutions.

Journal Articles

Distribution coefficients of iodine and tin on granodiorite and tuffaceous sandstone specimens

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$$^{-3}$$ 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$$_{3}$$ concentration 0.5 mol dm$$^{-3}$$. Non-zero values were also obtained under NaNO$$_{3}$$ concentrations higher than 0.5 mol dm$$^{-3}$$ 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 9.79$$times$$10$$^{-2}$$ m$$^{3}$$ kg$$^{-1}$$ at pH10.4 to 2.46$$times$$10$$^{-3}$$ m$$^{3}$$ kg$$^{-1}$$ at pH12.4. The distribution coefficient of tin on tuffaceous sandstone was about one order of magnitude higher (about 2$$times$$10$$^{-2}$$ m$$^{3}$$ kg$$^{-1}$$) than that of granodiorite at pH around 12.4.

Journal Articles

Report on the session of the NUCE and water chemistry division in 2015 AESJ Spring Meeting, "The current status and issues of the contaminated water treatment system at Fukushima Daiichi Nuclear Power Plant"

Iida, Yoshihisa

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.

Journal Articles

An Attempt to select thermodynamic data and to evaluate the solubility of radioelements with uncertainty under HLW disposal conditions

Yamaguchi, Tetsuji; Takeda, Seiji; Nishimura, Yuki; Iida, Yoshihisa; Tanaka, Tadao

Radiochimica Acta, 102(11), p.999 - 1008, 2014/11

 Times Cited Count:1 Percentile:8.95(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.

Journal Articles

Experimental verification of models assessing Eh evolution induced by corrosion of carbon steel overpack

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

 Times Cited Count:0 Percentile:0.01(Materials Science, Multidisciplinary)

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.

Journal Articles

Sorption behavior of hydroselenide (HSe$$^{-}$$) onto iron-containing minerals

Iida, Yoshihisa; Yamaguchi, Tetsuji; Tanaka, Tadao

Journal of Nuclear Science and Technology, 51(3), p.305 - 322, 2014/03

 Times Cited Count:10 Percentile:67.72(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$$^{-}$$.

Journal Articles

Diffusion of Cs, Np, Am and Co in compacted sand-bentonite mixtures; Evidence for surface diffusion of Cs cations

Sawaguchi, Takuma; Yamaguchi, Tetsuji; Iida, Yoshihisa; Tanaka, Tadao; Kitagawa, Isamu

Clay Minerals, 48(2), p.411 - 422, 2013/05

 Times Cited Count:2 Percentile:6.55(Chemistry, Physical)

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 ($$D$$$$_{e}$$) values of 5.2E-10$$ sim$$ 5.9E-9 m$$^{2}$$ s$$^{-1}$$ were obtained. The variation was somewhat large in the $$D$$$$_{e}$$ values. Apparent diffusivity ($$D$$$$_{a}$$) values, on the other hand, were 2.0E-12 $$sim$$ 6.2E-12 m$$^{2}$$ s$$^{-1}$$, 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.

Journal Articles

Identification of the cathode reaction accompanied with overpack corrosion

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 $$^{circ}$$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.

Journal Articles

Experimental and modeling study on diffusion of selenium under variable bentonite content and porewater salinity

Iida, Yoshihisa; Yamaguchi, Tetsuji; Tanaka, Tadao

Journal of Nuclear Science and Technology, 48(8), p.1170 - 1183, 2011/08

 Times Cited Count:19 Percentile:80.33(Nuclear Science & Technology)

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$$_{3}$$$$^{2-}$$ 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$$_{3}$$$$^{2-}$$ in bentonite porewater. The effective diffusion coefficients of selenium species predicted by this model showed good agreement with experimentally measured ones.

Journal Articles

Sorption behavior of selenium(-II) on rocks under reducing conditions

Iida, Yoshihisa; Tanaka, Tadao; Yamaguchi, Tetsuji; Nakayama, Shinichi

Journal of Nuclear Science and Technology, 48(2), p.279 - 291, 2011/02

 Times Cited Count:11 Percentile:66.95(Nuclear Science & Technology)

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.

Journal Articles

Solubility of selenium at high ionic strength under anoxic conditions

Iida, Yoshihisa; Yamaguchi, Tetsuji; Tanaka, Tadao; Nakayama, Shinichi

Journal of Nuclear Science and Technology, 47(5), p.431 - 438, 2010/05

 Times Cited Count:17 Percentile:77.6(Nuclear Science & Technology)

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$$_{4}$$$$^{2-}$$ 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$$^{0}$$ = -6.57$$pm$$0.15, 4Se(cr) + 2e$$^{-}$$ = Se$$_{4}$$$$^{2-}$$ logK$$^{0}$$ = -16.67$$pm$$0.03 and ion interaction coefficients for HSe$$^{-}$$ and Se$$_{4}$$$$^{2-}$$ versus Na$$^{+}$$, $$varepsilon$$(HSe$$^{-}$$, Na$$^{+}$$) = -0.01$$pm$$0.10 and $$varepsilon$$(Se$$_{4}$$$$^{2-}$$, Na$$^{+}$$) = -0.03$$pm$$0.02, were determined by specific ion interaction theory. The standard molar free energy of formation of amorphous selenium and polyselenide species were determined to be $$Delta$$$$_{f}$$G$$_{m}$$$$^{0}$$ (Se(am)) = 6.0$$pm$$2.2 kJ mol$$^{-1}$$, $$Delta$$$$_{f}$$G$$_{m}$$$$^{0}$$(Se$$_{2}$$$$^{2-}$$) = 111.64$$pm$$1.61 kJ mol$$^{-1}$$, $$Delta$$$$_{f}$$G$$_{m}$$$$^{0}$$(Se$$_{3}$$$$^{2-}$$) = 98.68$$pm$$1.02 kJ mol$$^{-1}$$ and $$Delta$$$$_{f}$$G$$_{m}$$$$^{0}$$ (Se$$_{4}$$$$^{2-}$$) = 95.14$$pm$$0.17 kJ mol$$^{-1}$$, respectively.

JAEA Reports

Investigations on systematics of thermodynamic data and comparison of estimation of solubility values among different activity coefficient models for development of thermodynamic database

Kitamura, Akira; Shibata, Masahiro; Yamaguchi, Tetsuji; Iida, Yoshihisa; Yui, Mikazu

JAEA-Technology 2009-074, 48 Pages, 2010/03

JAEA-Technology-2009-074.pdf:7.33MB

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.

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