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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:0.01(Chemistry, Inorganic & Nuclear)

Journal Articles

Outline of the OECD/NEA/ARC-F Project

Nakatsuka, Toru; Maeda, Toshikatsu; Sugiyama, Tomoyuki; Maruyama, Yu

Proceedings of 18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18) (USB Flash Drive), p.1650 - 1656, 2019/08

The OECD/NEA is launching a new project named "Analysis of Information from Reactor Buildings and Containment Vessels of Fukushima Daiichi Nuclear Power Station (ARC-F)" Project. This project will serve as the successor to the precedent NEA project, "Benchmark Study of the Accident at the Fukushima Daiichi Nuclear Power Station (BSAF) Phase II" which investigated the accident scenarios, associated fission products behavior in the damaged units and source term to the environment. The ARC-F project comprises three tasks: Task 1: Refinement of analysis for accident scenarios and associated fission product transportation and dispersion; Task 2: Compilation and management of data and information; and Task 3: Discussion for future long-term project. Japan Atomic Energy Agency is the operating agent, responsible to lead all the tasks. Duration of the project is from January 2019 to December 2021 and the final report is planned to be published in 2022.

Journal Articles

Issues for the safety of intermediate depth disposal

Maeda, Toshikatsu

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 25(2), p.119 - 122, 2018/12

no abstracts in English

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

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

Corrosion rate of zircaloy-4 in deoxidized deionized water at 80-120$$^{circ}$$C

Maeda, Toshikatsu; Chiba, Noriaki; Tateishi, Tsuyoshi*; Yamaguchi, Tetsuji

Nihon Genshiryoku Gakkai Wabun Rombunshi, 12(2), p.158 - 164, 2013/06

no abstracts in English

Journal Articles

Glass dissolution mechanism under nearly saturated conditions; Current state and the future

Maeda, Toshikatsu; Yamaguchi, Tetsuji; Bamba, Tsunetaka; Usui, Hideo

Nihon Genshiryoku Gakkai Wabun Rombunshi, 9(3), p.233 - 242, 2010/09

An experimental approach was proposed to understand the mechanism and model for slow dissolution of high-level radioactive waste glass under disposal conditions where silica is nearly saturated in contacting pore water. Based on an extended literature survey covering recent experimental results on glass dissolution, we have reached a hypothesis that the slow dissolution is limited by diffusion of oxonium ions in an altered layer formed on the glass surface. We suggested several experimental methods such as an elaborate and systematic diffusion experiment using thin glass membranes of tens-of-micrometer thickness to validate the hypothesis. Also pointed out was that dissolution model applicable to glass waste form performance evaluation takes into account the surface area evolution and stability of altered region of the waste form.

Journal Articles

A Private remark for the design basis and safety assessment of geological disposal

Maeda, Toshikatsu

Genankyo Dayori, (232), p.3 - 6, 2009/10

no abstracts in English

Journal Articles

Dissolution behavior of slag in cement-equilibrated aqueous solutions

Maeda, Toshikatsu; Bamba, Tsunetaka*; Mizuno, Tsuyoshi*; Terakado, Shogo; Kitagawa, Isamu; Numata, Masami

Haikibutsu Gakkai Rombunshi, 17(4), p.271 - 281, 2006/07

no abstracts in English

JAEA Reports

Melting treatment of incineration ashes of radioactive waste

Ozawa, Tatsuya; Maeda, Toshikatsu; Mizuno, Tsuyoshi; Bamba, Tsunetaka; Nakayama, Shinichi; Hotta, Katsutoshi*

JAEA-Technology 2006-001, 11 Pages, 2006/02

JAEA-Technology-2006-001.pdf:2.2MB

Melting treatment is a candidate solidification technique for nonflammable low-level radioactive wastes including metals, incineration ashes, and glasses. Simulated incineration ashes of a wide range of chemical compositions were molten at 1,600$$^{circ}$$C to produce lab-scale slag form. No visible pores and separated phases were observed in the slag specimens. It was found by optical observation that some precipitates and small voids were uniformly distributed in many of the specimens. The precipitates were identified to be iron oxides by XRD analysis. The present tests indicate that melting treatment is technically capable to produce stable slag from incineration ashes, which is one of representative TRU-cotaminated radioactive wastes.

Journal Articles

Dissolution behavior of slag in the presence of cement

Maeda, Toshikatsu; Bamba, Tsunetaka*; Hotta, Katsutoshi*; Mizuno, Tsuyoshi*; Ozawa, Tatsuya

Nihon Genshiryoku Gakkai Wabun Rombunshi, 4(4), p.242 - 247, 2005/12

no abstracts in English

Journal Articles

Study on dissolution behavior of molten solidified waste

Mizuno, Tsuyoshi*; Maeda, Toshikatsu; Bamba, Tsunetaka*

JAERI-Conf 2005-007, p.225 - 229, 2005/08

no abstracts in English

Journal Articles

Influences of humid substances, alkaline conditions and colloids on radionuclide migration in natural barrier

Mukai, Masayuki; Ueda, Masato; Inada, Daisuke; Yukawa, Kazuhiko; Maeda, Toshikatsu; Iida, Yoshihisa

Proceedings of International Symposium NUCEF 2005, p.219 - 224, 2005/08

For better quantitative understanding of radionuclide migration for safety assessment of geologic disposal, JAERI has been conducting experimental and modeling studies on influences of humic substances, highly alkaline conditions and colloids on sorptive and diffusional behavior of TRU in geologic materials. In the absence of fulvic acid, one of humic substances, diffusion of Am through a tuff sample was not detected. By adding fulvic acid, Am was detected in the downstream cell, which indicates the diffusion through the sample. Highly alkaline conditions arisen from cementitious materials may spread by altering chemical and physical properties of geologic materials. Through-diffusion experiments of alkaline species in granite showed that the effective diffusion coefficient of Ca$$^{2+}$$ and OH$$^{-}$$ in a cement-equilibrated aqueous solution were found to be higher by almost two orders of magnitude than Na$$^{+}$$ and OH$$^{-}$$ in a NaOH solution. Radionuclide migration can be enhanced by colloids, and thus a calculation code describing the effect of colloids on radionuclide migration has been required.

Journal Articles

Influence of humic substances on the $$^{63}$$Ni migration through crushed rock media

Tanaka, Tadao; Sakamoto, Yoshiaki; Mukai, Masayuki; Maeda, Toshikatsu; Nakayama, Shinichi

Radiochimica Acta, 92(9-11), p.725 - 729, 2004/12

 Times Cited Count:1 Percentile:10.52(Chemistry, Inorganic & Nuclear)

Migration experiments of $$^{63}$$Ni for crushed rocks, granite and tuff, were performed under the coexistent condition with a humic acid and a fulvic acid of 0-30 mg/l in concentration, which are Nordic humic substances supplied from International Humic Substance Society. Migration experiments of Ni had been performed by a column system, to investigate migration behavior of Ni through a column packed crushed rock. The Ni concentration in the effluent passed through the column was corresponding to the fractional percentage of Ni complexing with humic substance in influent solution. This result suggests that the Ni complexing with humic substance in influent solution was flowed out from the column without any effective interactions with the rock media. The migration behavior of Ni could be expressed by a migration model taking account of the complexation kinetics of Ni with humic substance in the aqueous phase.

Journal Articles

Status of studies on HLW glass performance for confirming its validity in assessment

Inagaki, Yaohiro*; Mitsui, Seiichiro*; Makino, Hitoshi*; Ishiguro, Katsuhiko*; Kamei, Gento*; Kawamura, Kazuhiro*; Maeda, Toshikatsu; Ueno, Kenichi*; Bamba, Tsunetaka*; Yui, Mikazu*

Genshiryoku Bakkuendo Kenkyu, 10(1-2), p.69 - 83, 2004/03

no abstracts in English

Journal Articles

Effects of basicity and leachant pH on the dissolution rates of molten slag

Maeda, Toshikatsu; Bamba, Tsunetaka*; Mizuno, Tsuyoshi*

Haikibutsu Gakkai Rombunshi, 15(1), p.45 - 51, 2004/01

no abstracts in English

JAEA Reports

Status of Studies on HLW Glass Performance for Increasing Its Validity in Assessment

Inagaki, Yaohiro*; Mitsui, Seiichiro; Makino, Hitoshi; Ishiguro, Katsuhiko; Kamei, Gento; Kawamura, Kazuhiro; Maeda, Toshikatsu*

JNC TN8400 2003-036, 53 Pages, 2003/12

JNC-TN8400-2003-036.pdf:0.51MB

Obtain of sufficient data for the performance of high-level radioactive waste(HLW) glass and verification of a model for the radionuclide release from the HLW glass in the disposal condition are required in order to show the objective reliability. In this paper, some reports about performance assessment of HLW glass are reviewed and we clarify the problems to raise reliability comparing these reports.

Journal Articles

Field tests on migration of TRU-nuclide, 1; General introduction

Ogawa, Hiromichi; Tanaka, Tadao; Mukai, Masayuki; Maeda, Toshikatsu; Munakata, Masahiro; Matsumoto, Junko; Bamba, Tsunetaka; Li, S.*; Wang, Z.*; Li, Z.*; et al.

Nihon Genshiryoku Gakkai Wabun Rombunshi, 2(3), p.332 - 335, 2003/09

The filed migration test using TRU nuclide was carried out as a cooperative research project between JAERI and CIRP (China Institute for Radiation Protection). This report introduced the outline of the filed migration test and described the outline of the special number of Field Test on Migration of TRU-nuclide and main results as a summary report.

Journal Articles

Field tests on migration of TRU-nuclide, 2; Migration test for engineered barrier materials in aerated soil

Maeda, Toshikatsu; Tanaka, Tadao; Mukai, Masayuki; Ogawa, Hiromichi; Yamaguchi, Tetsuji; Munakata, Masahiro; Matsumoto, Junko; Kozai, Naofumi; Bamba, Tsunetaka; Fan, Z.*; et al.

Nihon Genshiryoku Gakkai Wabun Rombunshi, 2(3), p.336 - 341, 2003/09

no abstracts in English

Journal Articles

Field tests on migration of TRU-nuclide, 4; Radionuclide migration test in aquifer soil layer

Tanaka, Tadao; Mukai, Masayuki; Munakata, Masahiro; Maeda, Toshikatsu; Ogawa, Hiromichi; Wang, Z.*; Li, S.*; Yang, Y.*; Zhao, Y.*

Nihon Genshiryoku Gakkai Wabun Rombunshi, 2(3), p.350 - 360, 2003/09

Migration data of $$^{90}$$Sr,$$^{237}$$Np and $$^{238}$$Pu in natural aquifer were collected by a field test, which was performed in an aquifer at 30 m under ground surface of the field test site. Migration parameters for analysis of the results obtained the field test were measured by laboratory column tests and batch tests. Diffusion coefficient corresponding to water velocity was determined from the relationship between water velocity and diffusion length, which obtained from the column tests. Distribution coefficient was determined by considering confident ability of data, test conditions, and environmental conditions. One dimensional migration behavior of the radionuclides in aquifer, calculated by using the migration parameters obtained from the batch and column tests, agreed with the results obtained from the field test. It was confirmed that the migration behavior of alpha-nuclides could be evaluated by applying the conventional equation for evaluating the radionuclide migration and the migration parameters obtained from laboratory tests.

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