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Journal Articles

Commissioned research on geological disposal performed by JAEA Safety Research Center

Sawaguchi, Takuma

"Yugai Haikibutsu, Hoshasei Haikibutsu Eno Semento, Konkurito Gijutsu No Tekiyo Kenkyu Iinkai" Hokokusho (CD-ROM), p.165 - 173, 2020/12

no abstracts in English

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:0 Percentile:100(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

Erratum; Effects of OH$$^{-}$$ activity and temperature on the dissolution rate of compacted montmorillonite under highly alkaline conditions [Clay Minerals, vol.51, p.275 (2016), Corrected Fig. 7.]

Sawaguchi, Takuma; Tsukada, Manabu; Yamaguchi, Tetsuji; Mukai, Masayuki

Clay Minerals, 51(5), P. 815, 2016/12

ERRATUM; Effects of OH$$^{-}$$ activity and temperature on the dissolution rate of compacted montmorillonite under highly alkaline conditions [Clay Minerals, vol.51, p.275 (2016), Corrected Fig. 7.]

Journal Articles

Effects of OH$$^{-}$$ activity and temperature on the dissolution rate of compacted montmorillonite under highly alkaline conditions

Sawaguchi, Takuma; Tsukada, Manabu; Yamaguchi, Tetsuji; Mukai, Masayuki

Clay Minerals, 51(2), p.267 - 278, 2016/05

 Times Cited Count:4 Percentile:76.36(Chemistry, Physical)

The dependences of the dissolution rate of compacted montmorillonite on activity of OH$$^{-}$$ (a$$_{rm OH}$$-) and temperature (T) were investigated. The dissolution rate of montmorillonite ($$R_{rm A}$$) in compacted pure montmorillonite, which was formulized as $$R_{rm A}$$ = 10$$^{4.5}$$ (a$$_{rm OH}$$-)$$^{1.3}$$ e$$^{-55000/RT}$$, was higher than that in the compacted sand-bentonite mixtures: $$R_{rm A}$$ = 3500 (a$$_{rm OH}$$-)$$^{1.4}$$ e$$^{-51000/RT}$$. The difference can be explained by considering the decrease in a$$_{rm OH}$$- in the mixtures accompanied by dissolution of accessory minerals such as quartz and chalcedony. The dissolution rate model developed for pure montmorillonite is expected to be applied to bentonite mixtures if quantification of the decrease in a$$_{rm OH}$$- is achieved somehow.

Journal Articles

Mineralogical changes and associated decrease in tritiated water diffusivity after alteration of cement-bentonite interfaces

Yamaguchi, Tetsuji; Sawaguchi, Takuma; Tsukada, Manabu; Hoshino, Seiichi*; Tanaka, Tadao

Clay Minerals, 51(2), p.279 - 287, 2016/02

 Times Cited Count:3 Percentile:82.29(Chemistry, Physical)

Alteration of bentonite-cement interfaces and accompanying changes in diffusivity of tritiated water was experimentally investigated using intact hardened cement specimens. The alteration by carbonate solution was accompanied by mineralogical changes at the interface and a decrease in the diffusivity to 70% of the initial value after 180-day period. Another alteration under silicate system contacting hardened cement and compacted bentonite was accompanied by mineralogical changes at the interface and a decrease in the diffusivity to 71% of the initial value after 600-day period. The changes in the diffusivity were much less than those observed for mixed specimens of granulated hardened cement and bentonite where the diffusivity decreased down to 20% of the initial value over 180 days. The results were extrapolated to 15 years under simple assumptions and showed good agreement with those observed in the cement-argillite interface at Tournemire URL. Such an explanation enhances our confidence in our assessment of alteration of cement-bentonite systems and can be a base for using our data and models in long term assessment of radioactive waste disposal.

Journal Articles

Demonstrative experiments on the migration of radiocesium from buried soil contaminated by the accident at Fukushima Daiichi Nuclear Power Station

Yamaguchi, Tetsuji; Shimada, Taro; Ishibashi, Makoto*; Akagi, Yosuke*; Kurosawa, Mitsuru*; Matsubara, Akiyoshi*; Matsuda, Yuki*; Sato, Shigeyoshi*

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 22(2), p.21 - 27, 2015/12

It is predictable from previous studies that radiocesium hardly migrate into surrounding soils and groundwater from soils contaminated by the Fukushima Daiichi Nuclear Power Plant accident if they are buried and covered with indigenous soils. This study demonstrated the prediction by performing in-situ migration experiments over a year in a public park in Miho, Ibaraki prefecture and in two public parks in Misato, Saitama prefecture. Contaminated soils were buried at a depth range of 0.3 - 1.0 m or at 0.3 - 1.3 m and covered with indigenous soil layer of 0.3 m, and were sprinkled with water to accelerate the radiocesium migration. Migration of radiocesium was not observed from radiometric analyses of boring cores and soil water samples. Laboratory column and sorption experiments revealed that the radiocesium hardly leach out of the soil and even if they leach out from the contaminated soil, radiocesium is sorbed on surrounding soils and hardly migrate through the soli layer. Simulation of Cs-137 migration for 100 years by an advection-diffusion model showed that Cs-137 hardly migrate and decay out in the contaminated soil.

JAEA Reports

Assessment report of research and development on "Nuclear Safety Research" in FY2014 (Post- and pre-review report)

Kudo, Tamotsu; Onizawa, Kunio*; Nakamura, Takehiko

JAEA-Evaluation 2015-011, 209 Pages, 2015/11

JAEA-Evaluation-2015-011.pdf:10.36MB

Japan Atomic Energy Agency (JAEA) consulted an assessment committee, "Evaluation Committee of Research and Development (R&D) Activities for Nuclear Safety", for post- and pre-review assessment of R&D on nuclear safety research. In response to JAEA's request, the Committee assessed mainly the progress of the R&D project according to guidelines, which addressed the rationale behind the R&D project, the relevance of the project outcome and the efficiency of the project implementation during the period of the current and next plan. As a result, the Committee concluded that the progress of the R&D project is satisfactory. This report describes the results of evaluation by the Committee. In addition, the appendix of this report contains presentations used for the evaluation, and responses from JAEA on the comments from the member of the Committee.

Journal Articles

Migration behavior of particulate radioactive cesium species generated at ground surface

Tanaka, Tadao

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 5 Pages, 2015/05

It is necessary to confirm that there is no significant radioactivity remaining on NPP site, for the site release beforehand. Cesium 137 ($$^{137}$$Cs) is the typical radionuclide caused from NPP. In this research, generation of particulate $$^{137}$$Cs species at ground surface and its migration behavior were examined. Migration experiments were carried out by a column method, in which deionized water was fed intermittently at the drying interval for 7 days into a sand layer contaminated with $$^{137}$$Cs. A portion of the $$^{137}$$Cs in the upper surface region, which formed particulate species by sorbing on fine particles, migrated into the deeper layer. Fine particle itself also was generated at the sand surface by weathering. The sand was weathered during the drying period, so that small amount of fine particles including $$^{137}$$Cs was newly dissociated from the sand. Such particulate $$^{137}$$Cs species may be accumulated slowly by repeated cycles of rainfall and drying, during long term.

Journal Articles

Corrosion behavior of simulated high-level waste glass in the presence of calcium ion or metallic iron

Maeda, Toshikatsu; Watanabe, Koichi; Omori, Hiroyuki*; Sakamaki, Keiko; Inagaki, Yaohiro*; Idemitsu, Kazuya*

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 21(2), p.63 - 74, 2014/12

Static leach tests were conducted for simulated HLW glass in CaCl$$_{2}$$/Ca(OH)$$_{2}$$ solutions to investigate the corrosion behavior of HLW glass under calcium-rich environments induced by cement based materials in geological repositories. Another series of leach tests were conducted in deionized water in the presence of iron to investigate the effects of iron over-pack on the glass corrosion. In Ca solutions, corrosion of the glass was inhibited during the test period compared to that in deionized water, while the corrosion was enhanced at the presence of iron. The enhancement of the glass corrosion was assumed to be accompanied with transformation of silica, a glass network former, into iron silicates.

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:88.74(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:100(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

In-situ radioactivity measurement for the site release after decommissioning of nuclear power plants

Tanaka, Tadao; Shimada, Taro; Sukegawa, Takenori

Progress in Nuclear Science and Technology (Internet), 4, p.832 - 835, 2014/04

According to a basic policy of Japan, nuclear power plant sites are allowed to be released from nuclear safety regulations after the plants are decommissioned. It is necessary to confirm that there is no significant radioactivity remaining on the sites, for the site release beforehand. Cobalt 60 is one of the typical radionuclide for nuclear power plants. In the evaluation concept, all of cobalt 60, which is in reality distributed across the area of interest, are assumed to be the single point source located at the furthest position on the surface of the area from a Ge detector. In such a configuration, minimum detectable time was supplied by Monte Carlo calculations, and the minimum detectable time was approximately equal to the actual measurement time of the point source by the Ge detector. These results mean that the proposed evaluation method was reasonable for the conservative evaluation of cobalt 60 remaining in the nuclear power plant sites.

Journal Articles

Alkaline dissolution behavior of montmorillonite under compacted condition

Sawaguchi, Takuma; Kadowaki, Mitsushi*; Yamaguchi, Tetsuji; Mukai, Masayuki; Tanaka, Tadao

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 20(2), p.71 - 78, 2013/12

The dissolution rate for montmorillonite under compacted condition was studied in order to evaluate long-term alteration behavior of bentonite buffer materials by highly alkaline groundwater. The dissolution rate of compacted montmorillonite was found to be larger than that of montmorillonite in compacted sand-bentonite mixtures at 130 $$^{circ}$$C, which revealed that the dissolution of montmorillonite was inhibited by decreasing the activity of hydroxide ions (${it $alpha$$_O$$_H$$^-$}$) in the compacted mixtures including accessory minerals such as silica. In order to provide reliability for the analysis of bentonite-alteration using a formula of dissolution rate of montmorillonite, it is important to quantify the decrease of ${it $alpha$$_O$$_H$$^-$}$ in the compacted mixtures and to formulate the dissolution rate of compacted montmorillonite.

Journal Articles

Changes in hydraulic conductivity of sand-bentonite mixtures accompanied by alkaline alteration

Yamaguchi, Tetsuji; Sawaguchi, Takuma; Tsukada, Manabu; Kadowaki, Mitsushi*; Tanaka, Tadao

Clay Minerals, 48(2), p.403 - 410, 2013/05

 Times Cited Count:5 Percentile:83.63(Chemistry, Physical)

Montmorillonite is the main constituent of bentonite clay buffer materials in radioactive waste repositories. Highly alkaline environments induced by cement based materials are likely to alter montmorillonite, and to deteriorate the physical and/or chemical properties of the buffer materials. The deterioration may cause variation in hydraulic conductivity of the buffer and induce major uncertainties in the radionuclide migration analysis. Empirical data on the variation of hydraulic conductivity are, however, scarce mainly because the alteration of compacted buffer materials, sand-bentonite mixture specimen, is extremely slow. In this study, laboratory experiments were performed to observe changes in hydraulic conductivity of sand-bentonite mixtures accompanied with their alkaline alteration using NaOH based solutions at 80-90 $$^{circ}$$C. Three types of experiments proved that the alkaline alteration of bentonite buffer can increase the hydraulic conductivity. The data obtained in this study are useful for verification of the code that will be used for assessing the alteration.

Journal Articles

Transport behavior and deposition kinetics of humic acid under acidic conditions in porous media

Yamashita, Yuji*; Tanaka, Tadao; Adachi, Yasuhisa*

Colloids and Surfaces A; Physicochemical and Engineering Aspects, 417, p.230 - 235, 2013/01

 Times Cited Count:10 Percentile:68.56(Chemistry, Physical)

Transport behavior of humic acid was studied from the aspects of colloidal stability. Deposition kinetics of purified Aldrich humic acid was investigated over a wide range of monovalent and divalent electrolyte concentrations at pH 3.0 by using packed-bed technique. Spherical glass beads with diameters of 0.2 mm were utilized as model collectors. Breakthrough curves of humic acid were measured with UV-VIS spectrophotometer. The values of C/C0 (C and C0 are the effluent and influent concentrations of humic acid, respectively) decreased with increasing electrolyte concentrations. Experimental collision efficiencies were determined from measured single collector efficiencies. The results are presented as stability curves, which is the logarithm of the collision efficiency as a function of the logarithm of salt concentration. Stability curves of humic acid obviously showed favorable and unfavorable regimes and critical deposition concentration in the presence of both electrolytes. As a consequence, it is indicated that transport behavior of humic acid is primarily controlled by electrostatic interaction between humic acids and collectors.

JAEA Reports

Preparation of hydrous titanic acid as an inorganic ion exchanger for Sr recovery

Fujiwara, Takeshi

JAEA-Testing 2012-004, 13 Pages, 2012/11

JAEA-Testing-2012-004.pdf:2.7MB

In the 4-Group partitioning process developed in Japan Atomic Energy Research Institute (presently: Japan Atomic Energy Agency), a heat-generating nuclide group including Sr and Cs is separated by inorganic ion exchangers. Hydrous titanic acid and zeolite are used as the inorganic ion exchangers. The mechanical durability of the particles of hydrous titanic acid used for Sr recovery is not enough in case of mixing with zeolite used for Cs recovery. The method of drying the hydrous titanic acid was improved to provide sufficient mechanical durability to the product of hydrous titanic acid in case of mixing with zeolite. A procedure of producing hydrous titanic acid from the raw material, titanyl sulfate, was established and documented with cares to be taken at each step.

JAEA Reports

Study on experimental models to analyze radionuclide migration behaviors through porous geologic media

Tanaka, Tadao; Mukai, Masayuki

JAEA-Research 2011-053, 41 Pages, 2012/08

JAEA-Research-2011-053.pdf:1.55MB

To understand the migration phenomenon of radionuclide, actual migration data are experimentally acquired by a batch test, a column test and field trial. In the present study, experimental models about the interactions of radionuclide between the solid phase and the liquid phase were discussed systematically to interpret the migration data acquired by the various techniques and conditions. Equilibrium, reversibility, linearity, mechanism and chemistry in the interactions were considered in discussion of the experimental models. A calculation program, which can analyze migration data obtained under various conditions by applying the selected 9 types of experimental models, was maintained. The calculation program makes it be able to predict the migration behavior of radionuclide under various conditions and to decide the important parameter by a fitting analysis of the migration data.

Journal Articles

Functional groups and reactivity of size-fractionated Aldrich humic acid

Tanaka, Tadao

Thermochimica Acta, 532, p.60 - 64, 2012/03

 Times Cited Count:13 Percentile:47.13(Thermodynamics)

The interaction affinity of the Aldrich Chemical humic acid (HA) with Co was examined with respect to molecular size of HA. Correlations between the affinity and the structures of HA were studied. At low HA concentration range, Co was interacted with the HA over 100k Da (HA(100$$<$$)). With increasing HA concentration, the Co was preferentially interacted with the 30k-100k Da of HA (HA(30-100)). HA(100$$<$$) and HA(30-100) were characterized with respect to their FTIR, 13C-NMR spectral analyses and acid-base titration curves. HA(10$$<$$) having aliphatic branched structure, smaller amount of COOH group and large proton exchangeable capacity, seem to show low covalent nature and high ion exchangeability. In addition, steric hindrance may effect on the complexation, by winding up like random coils from the branched structure. HA(30-100) is dominated with the aromatic COOH group and OH group and it preferentially coordinates to Co. These presumptions were supported by XPS analysis, in which the biding energy cobalt-humates was discussed.

105 (Records 1-20 displayed on this page)