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Journal Articles

Development of performance assessment models for glass dissolution

Goto, Takahiro*; Mitsui, Seiichiro; Takase, Hiroyasu*; Kurosawa, Susumu*; Inagaki, Manabu*; Shibata, Masahiro; Ishiguro, Katsuhiko*

MRS Advances (Internet), 1(63-64), p.4239 - 4245, 2016/00

NUMO and JAEA have conducted a joint research since FY2011, which is designed to enhance the methodology of repository design and performance assessment in preliminary investigation stage for deep geological disposal of radioactive waste. As a part of this joint research, we have been developing glass dissolution models which consider various processes in EBS, such as precipitation of Fe-silicates associated with iron overpack corrosion, and Si transport through corrosion products in the cracked overpack. The objectives of the modeling work are to evaluate relative importance of relevant processes and to identify further R&D issues towards development of a convincing safety case. Sensitivity analyses suggested that predicted glass dissolution time ranges from 1$$times$$10$$^3$$ to 1$$times$$10$$^7$$ years or more due to uncertainties in the current understanding of the key processes, namely precipitation of Fe-silicates and transport characteristics of the altered glass layer.

JAEA Reports

Enhancement of the methodology of repository design and post-closure performance assessment for preliminary investigation stage, 3; Progress report on NUMO-JAEA collaborative research in FY2013 (Joint research)

Shibata, Masahiro; Sawada, Atsushi; Tachi, Yukio; Makino, Hitoshi; Wakasugi, Keiichiro; Mitsui, Seiichiro; Kitamura, Akira; Yoshikawa, Hideki; Oda, Chie; Ishidera, Takamitsu; et al.

JAEA-Research 2014-030, 457 Pages, 2015/03

JAEA-Research-2014-030.pdf:199.23MB

JAEA and NUMO have conducted a collaborative research work which is designed to enhance the methodology of repository design and post-closure performance assessment in preliminary investigation stage. With regard to (1) study on rock suitability in terms of hydrology, based on some examples of developing method of hydro-geological structure model, acquired knowledge are arranged using the tree diagram, and model uncertainty and its influence on the evaluation items were discussed. With regard to (2) study on scenario development, the developed approach for "defining conditions" has been reevaluated and improved from practical viewpoints. In addition, the uncertainty evaluation for the effect of use of cementitious material, as well as glass dissolution model, was conducted with analytical evaluation. With regard to (3) study on setting radionuclide migration parameters, based on survey of precedent procedures, multiple-approach for distribution coefficient of rocks was established, and the adequacy of the approach was confirmed though its application to sedimentary rock and granitic rock. Besides, an approach for solubility setting was developed including the procedure of selection of solubility limiting solid phase. The adequacy of the approach was confirmed though its application to key radionuclides.

JAEA Reports

Enhancement of the methodology of repository design and post-closure performance assessment for preliminary investigation stage, 2; Progress report on NUMO-JAEA collaborative research in FY2012 (Joint research)

Shibata, Masahiro; Sawada, Atsushi; Tachi, Yukio; Hayano, Akira; Makino, Hitoshi; Wakasugi, Keiichiro; Mitsui, Seiichiro; Oda, Chie; Kitamura, Akira; Osawa, Hideaki; et al.

JAEA-Research 2013-037, 455 Pages, 2013/12

JAEA-Research-2013-037.pdf:42.0MB

Following FY2011, JAEA and NUMO have conducted a collaborative research work which is designed to enhance the methodology of repository design and performance assessment in preliminary investigation stage. With regard to (1) study on rock suitability in terms of hydrology, the tree diagram of methodology of groundwater travel time has been extended for crystalline rock, in addition, tree diagram for sedimentary rock newly has been organized. With regard to (2) study on scenario development, the existing approach has been improved in terms of a practical task, and applied and tested for near field focusing on the buffer. In addition, the uncertainty of some important processes and its impact on safety functions are discussed though analysis. With regard to (3) study on setting radionuclide migration parameters, the approaches for parameter setting have been developed for sorption for rocks and solubility, and applied and tested through parameter setting exercises for key radionuclides.

JAEA Reports

Enhancement of the methodology of repository design and post-closure performance assessment for preliminary investigation stage; Progress report on NUMO-JAEA collaborative research in FY2011 (Joint research)

Shibata, Masahiro; Sawada, Atsushi; Tachi, Yukio; Makino, Hitoshi; Hayano, Akira; Mitsui, Seiichiro; Taniguchi, Naoki; Oda, Chie; Kitamura, Akira; Osawa, Hideaki; et al.

JAEA-Research 2012-032, 298 Pages, 2012/09

JAEA-Research-2012-032.pdf:33.68MB

JAEA and NUMO have conducted a collaborative research work which is designed to enhance the methodology of repository design and performance assessment in preliminary investigation phase. The topics and the conducted research are follows; (1) Study on selection of host rock: in terms of hydraulic properties, items for assessing rock property, and assessment methodology of groundwater travel time has been organized with interaction from site investigation. (2) Study on development of scenario: the existing approach has been embodied, in addition, the phenomenological understanding regarding dissolution of and nuclide release from vitrified waste, corrosion of the overpack, long-term performance of the buffer are summarized. (3) Study on setting nuclide migration parameters: the approach for parameter setting has been improved for sorption and diffusion coefficient of buffer/rock, and applied and tested for parameter setting of key radionuclides. (4) Study on ensuring quality of knowledge: framework for ensuring quality of knowledge has been studied and examined aimed at the likely disposal facility condition.

Journal Articles

Differences in circadian rhythms of resistance to $$gamma$$-rays and heavy-ion beam in ${it Euglena}$

Bolige, A.*; Sakashita, Tetsuya; Kakizaki, Takehiko*; Funayama, Tomoo; Hamada, Nobuyuki*; Wada, Seiichi*; Kobayashi, Yasuhiko; Goto, Ken*

JAEA-Review 2007-060, JAEA Takasaki Annual Report 2006, P. 117, 2008/03

We report here how these rhythms are related to each other. First, irradiation temperatures influenced neither survival after exposure to UV, $$gamma$$ rays, nor C ions, whereas the incubation at high temperatures (25 $$^{circ}$$C) after irradiation considerably lowered the survival particularly after $$gamma$$ irradiation, but not after UV irradiation at all. Secondly, although the antioxidants $$beta$$ carotene and dimethylsulfoxide (DMSO) increased the survival of the alga at the least resistant phase after UV C and UV B irradiation, respectively, to the level of the most resistant alga, none of these were not so effective for $$gamma$$ or C ion irradiation. Finally, FITC dextran was incorporated into the alga only after C ion irradiation but not $$gamma$$ irradiation, suggesting that C ion may perforate cell membranes to kill the alga.

Journal Articles

Real-time stress measurement in Ge/Si(111)-7$$times$$7 heteroepitaxial growth

Asaoka, Hidehito; Yamazaki, Tatsuya; Shamoto, Shinichi; Arnoldo, A.*; Goto, Seiichi*; Suemitsu, Maki*

Hyomen Kagaku, 28(9), p.500 - 503, 2007/09

Stress evolution during initial stage of Ge nanodot formation on Si(111)-7$$times$$7 has been investigated by using simultaneous measurements of the substrate curvature and the surface morphology. In the beginning of the first bilayer growth of Ge on Si(111)-7$$times$$7, a strong compressive film stress is observed, indicating a formation of a two-dimensional wetting layer. When the layer thickness approaches the critical one for three-dimensional nanodot nucleation, a clear bend in the stress curve is observed, corresponding to a partial relaxation of the lattice planes on the surface of the nanodots. Moreover, a stress transition has been also found to exist in the very early stage of the nanodot formation, which is concurrent with the trench formation around the three-dimensional nanodots.

Journal Articles

Circadian rhythms in resistance to $$gamma$$-irradiation and heavy-ion beam in ${it Euglena}$

Aoen, B.*; Sakashita, Tetsuya; Kakizaki, Takehiko; Funayama, Tomoo; Hamada, Nobuyuki*; Wada, Seiichi*; Kobayashi, Yasuhiko; Goto, Ken*

JAEA-Review 2006-042, JAEA Takasaki Annual Report 2005, P. 120, 2007/02

no abstracts in English

Journal Articles

Photoemission study of the translational energy induced oxidation processes on Cu(111)

Moritani, Kosuke; Okada, Michio*; Sato, Seiichi*; Goto, Seishiro*; Kasai, Toshio*; Yoshigoe, Akitaka; Teraoka, Yuden

Journal of Vacuum Science and Technology A, 22(4), p.1625 - 1630, 2004/08

 Times Cited Count:18 Percentile:40.92(Materials Science, Coatings & Films)

We studied the oxidation of Cu{111} surface with a hyperthermal O$$_{2}$$ molecular beam (HOMB) using X-ray photoemission spectroscopy (XPS) in conjunction with a synchrotron radiation (SR) source. The efficiency of oxidation with 0.6-eV-HOMB is higher thab that with 2.3-eV-HOMB under $$theta$$ $$leq$$ 0.5ML. Ont the other hand, further oxidation occurs rather inefficiency under $$theta$$ $$geq$$ 0.5ML. In this region, efficiency of oxidation with 2.3-eV-HOMB is higher than 0.6-eV-HOMB. We found that such slow oxidation process of Cu can be interpreted in terms of a collision-induced-adsorption mechanism. These results suggest that we can control the oxidation process of Cu by using HOMB.

Journal Articles

Progress in physics and technology developments for the modification of JT-60

Tamai, Hiroshi; Matsukawa, Makoto; Kurita, Genichi; Hayashi, Nobuhiko; Urata, Kazuhiro*; Miura, Yushi; Kizu, Kaname; Tsuchiya, Katsuhiko; Morioka, Atsuhiko; Kudo, Yusuke; et al.

Plasma Science and Technology, 6(1), p.2141 - 2150, 2004/02

 Times Cited Count:2 Percentile:92.83(Physics, Fluids & Plasmas)

The dominant issue for the the modification program of JT-60 (JT-60SC) is to demonstrate the steady state reactor relevant plasma operation. Physics design on plasma parameters, operation scenarios, and the plasma control method are investigated for the achievement of high-$$beta$$. Engineering design and the R&D on the superconducting magnet coils, radiation shield, and vacuum vessel are performed. Recent progress in such physics and technology developments is presented.

Journal Articles

Objectives and design of the JT-60 superconducting tokamak

Ishida, Shinichi; Abe, Katsunori*; Ando, Akira*; Chujo, T.*; Fujii, Tsuneyuki; Fujita, Takaaki; Goto, Seiichi*; Hanada, Kazuaki*; Hatayama, Akiyoshi*; Hino, Tomoaki*; et al.

Nuclear Fusion, 43(7), p.606 - 613, 2003/07

no abstracts in English

Journal Articles

Objectives and design of the JT-60 superconducting tokamak

Ishida, Shinichi; Abe, Katsunori*; Ando, Akira*; Cho, T.*; Fujii, Tsuneyuki; Fujita, Takaaki; Goto, Seiichi*; Hanada, Kazuaki*; Hatayama, Akiyoshi*; Hino, Tomoaki*; et al.

Nuclear Fusion, 43(7), p.606 - 613, 2003/07

 Times Cited Count:33 Percentile:27.31(Physics, Fluids & Plasmas)

no abstracts in English

Oral presentation

Circadian rhythms of resistance to heavy ion beam in Euglena

Aoen, B.*; Sakashita, Tetsuya; Kakizaki, Takehiko; Funayama, Tomoo; Hamada, Nobuyuki*; Wada, Seiichi*; Kobayashi, Yasuhiko; Goto, Ken*

no journal, , 

no abstracts in English

Oral presentation

Circadian rhythm of radiation resistance in ${it Euglena gracilis}$ Z

Aoen, B.*; Sakashita, Tetsuya; Kakizaki, Takehiko; Funayama, Tomoo; Hamada, Nobuyuki*; Wada, Seiichi*; Kobayashi, Yasuhiko; Goto, Ken*

no journal, , 

no abstracts in English

Oral presentation

Real time SR-XPS on initial oxidation process at Si(110)-16$$times$$2 surface

Yamamoto, Yoshihisa*; Togashi, Hideaki*; Kato, Atsushi*; Hasegawa, Satoshi*; Goto, Seiichi*; Nakano, Takuya*; Suemitsu, Maki*; Narita, Yuzuru*; Yoshigoe, Akitaka; Teraoka, Yuden

no journal, , 

We have investigated the initial oxidation process on an Si(110)-16$$times$$2 surface by real time synchrotron radiation photoemission spectroscopy (SR-XPS). As a result, a rapid initial oxidation regime was found to exist on this surface, which is not present on other crystal orientations. Analyses of the O1s spectra suggest insertion of oxygen atoms at the Si-Si bonds as the predominant process during initial oxidation. The rapid initial oxidation is accompanied by decrease of the Si2p subpeak that is related to Si(110)-16$$times$$2 reconstruction, indicating the preferential oxidation at the pentagon pair.

Oral presentation

Synchrotron radiation photoemission spectroscopy for initial oxidation processes at Si(110)-16$$times$$2 surface

Togashi, Hideaki*; Yamamoto, Yoshihisa*; Goto, Seiichi*; Takahashi, Yuya*; Nakano, Takuya*; Kato, Atsushi*; Hasegawa, Satoshi*; Konno, Atsushi*; Suemitsu, Maki*; Asaoka, Hidehito; et al.

no journal, , 

no abstracts in English

Oral presentation

SR-XPS study on the RT-adsorption of water on Si(110)-16$$times$$2

Nakano, Takuya*; Hasegawa, Satoshi*; Togashi, Hideaki*; Kato, Atsushi*; Goto, Seiichi*; Teraoka, Yuden; Yoshigoe, Akitaka; Suemitsu, Maki*

no journal, , 

no abstracts in English

Oral presentation

Structural formation on semiconductor surfaces

Asaoka, Hidehito; Yamada, Yoichi; Yamazaki, Tatsuya; Girard, A.*; Yamamoto, Hiroyuki; Shamoto, Shinichi; Arnoldo, A.*; Goto, Seiichi*; Suemitsu, Maki*

no journal, , 

We reports the recent progress about structural formation on semiconductor surface: real-time stress analysis of Ge nanodot growth on Si(111)-7$$times$$7 surfaces, and preparation of the single-domained Si(110)-16$$times$$2 surface.

Oral presentation

Rapid initial oxidation of Si(110)-16$$times$$2 surface and surface reconstruction

Togashi, Hideaki*; Yamamoto, Yoshihisa*; Goto, Seiichi*; Takahashi, Yuya*; Nakano, Takuya*; Konno, Atsushi*; Suemitsu, Maki*; Asaoka, Hidehito; Yoshigoe, Akitaka; Teraoka, Yuden

no journal, , 

Initial oxidaion processes at Si(110)-16$$times$$2 clean surface with O$$_{2}$$ mokecules have been observed by real-time SR-XPS and STM methods. SR-XPS experiments were performed at BL23SU in SPring-8 and STM experiments were performed in JAEA Tokai research center. From comparison of oxygen uptake curves of Si(110)-16$$times$$2 with Si(001)-2$$times$$1, following conclusions were obtained. Rapid initial oxidation occured at the Si(110) surface and layer-by-layer oxidation was also took place. In-situ observation with STM revealed that the rapid initial oxidation was due to oxygen adsorption at pentagon-pair Si atoms on the topmost surface, at least 4 kinds of oxygen-adsorbed states, and the DD site was a condensed oxidation state.

Oral presentation

Direct determination of surface stress during Ge/Si hetero-growth

Asaoka, Hidehito; Yamazaki, Tatsuya; Shamoto, Shinichi; Alguno, A.*; Goto, Seiichi*; Suemitsu, Maki*

no journal, , 

no abstracts in English

Oral presentation

Metastable chemisorption state of oxygen on Si(110)-16$$times$$2 surface observed by SR-PES

Yamamoto, Yoshihisa*; Togashi, Hideaki*; Kato, Atsushi*; Hasegawa, Satoshi*; Nakano, Takuya*; Goto, Seiichi*; Teraoka, Yuden; Yoshigoe, Akitaka; Suemitsu, Maki*

no journal, , 

In this study, we have investigated adsorption of oxygen molecules on Si(110)-16$$times$$2 clean surface at room temperature by synchrotron radiation photoemission spectros (SR-PES). The SR-PES experiments were conducted at the surface chemistry end-station of BL23SU in the SPring-8. The photon energy was 334 eV. Samples were B-doped p-type Si(110) wafers, and were flash-annealed in an UHV ambient prior to the exposure to oxygen gas at room temperature at the gas pressure of 6.7$$times$$10$$^{-6}$$ Pa. By observing a structural change after a mild annealing, we have confirmed presence of a metastable state of oxidation on this RT-oxidized Si(110) surface.

26 (Records 1-20 displayed on this page)