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Mitsui, Seiichiro
NUMO-TR-24-02, p.29 - 31, 2024/06
The Power Reactor and Nuclear Fuel Development Corporation (reorganized into the Nuclear Fuel Cycle Development Agency in 1998, merged with the Japan Atomic Energy Research Institute, and since 2005 has become the Japan Atomic Energy Agency) has been conducting natural analogue studies on the geological disposal system of radioactive waste since JFY1986. Here, we will provide an overview of the natural analogue studies on the long-term behavior of engineered barriers.
Saito, Yuki*; Ishiwata, Tobimaru*; Horiuchi, Misato*; Nishiki, Yuto*; Kikuchi, Ryosuke*; Otake, Tsubasa*; Kawakita, Ryohei; Takayama, Yusuke; Mitsui, Seiichiro; Sato, Tsutomu*
Shigen, Sozai Koenshu (Internet), 11(1), 7 Pages, 2024/03
no abstracts in English
Mitsui, Seiichiro
Kinzoku, 93(3), p.211 - 218, 2023/03
As part of research and development of geological disposal, "natural analogues" have been applied to validate concept of models and evaluation methodologies for performance assessment. By introducing our research results on natural analogues, this paper presents how we have utilized knowledge of excavated archaeological artifacts for geological disposal studies.
Matsubara, Ryuta*; Ishida, Keisuke*; Mitsui, Seiichiro; Inagaki, Yaohiro*; Okubo, Takahiro*
NUMO-TR-22-02, p.65 - 67, 2023/03
no abstracts in English
Nagata, Shuhei*; Ogawa, Yusuke*; Suzuki, Satoru*; Inoue, Hiroyuki*; Watanabe, Yutaka*; Yamamoto, Masahiro*; Abe, Hiroshi*; Mitsui, Seiichiro
NUMO-TR-22-02, p.21 - 22, 2023/03
no abstracts in English
Yanagida, Akinobu*; Ura, Yoko*; Mitsui, Seiichiro; Ishidera, Takamitsu; Kawakita, Ryohei
Nara Bunkazai Kenkyujo Soritsu 70-Shunen Kinen Rombunshu; Bunkazai Ronso 5, p.843 - 856, 2023/03
To investigate chloride salt accumulation inside an iron artifact in soil, non-destructive analysis of three iron artifacts excavated from the Heijo Palace Site was conducted using elemental mapping by X-ray fluorescence analysis, micro-X-ray diffraction analysis, and X-ray computed tomography. Furthermore, the buried environments of the artifacts were presumed based on the previous reports of the environmental investigation at the Heijo Palace site. The results revealed the iron artifact's corrosion behavior was different individually- (1) the iron artifact that was presumed buried under oxidation environments had a goethite/magnetite corrosion layer and contained akageneite inside the corrosion layer. (2) the metal of the other iron artifacts buried under the oxidation environment had eluted absolutely and the artifacts had a rust layer formed by only goethite. (3) the other artifact buried in reduction environments had a rust layer composed of siderite. Accumulation of chloride salts inside an iron artifact was observed only in (1). Because each Cl
concentration measured in underground water observation holes at the Heijo Palace Site showed almost the same level concentrations, it was presumed that the accumulation of chloride salts depended on the environmental factor except for Cl concentration. Based on these results, there was a possibility that the occurrence of local corrosion attributed to the separation of anodic and cathodic regions through the formation of the goethite/magnetite rust layer caused chloride salts accumulation inside an iron artifact.
Ishida, Keisuke*; Mitsui, Seiichiro
Nihon Genshiryoku Gakkai-Shi ATOMO
, 64(4), p.221 - 226, 2022/04
no abstracts in English
Kitayama, Ayami; Taniguchi, Naoki; Mitsui, Seiichiro
Materials and Corrosion, 72(1-2), p.211 - 217, 2021/01
Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)
and Si under anoxic and reducing conditions; Structural characteristics of ferrous silicate co-precipitatesFrancisco, P. C. M.; Mitsui, Seiichiro; Ishidera, Takamitsu; Tachi, Yukio; Doi, Reisuke; Shiwaku, Hideaki
Geochimica et Cosmochimica Acta, 270, p.1 - 20, 2020/02
Times Cited Count：19 Percentile：73.50(Geochemistry & Geophysics)Mitsui, Seiichiro; Murakami, Ryu*; Ueda, Norio*; Hirabayashi, Akira*; Hirota, Kazuho*
Bunkazai Kagaku, (77), p.1 - 14, 2018/10
Well-preserved bronze artifacts comprising five bells and eight halberds from the Yayoi Period were excavated at the Yanagisawa archaeological site in Nakano City, Nagano Prefecture in 2007. Comprehensive analysis of soil and groundwater samples at the site was carried out and geochemical calculations were made to better understand the local conditions that led to the artifacts being so well preserved. Analysis of the soil surface adjacent to the bronze artifacts identified cuprite (Cu
O) as the main corrosion product. Migration behavior of the bronze metal components, copper, tin, and lead, both inside and outside of the burial pit, was also investigated. Copper and lead had migrated 2 m from the burial pit, whereas tin was confined to the immediate vicinity of the bronze artifacts. The difference in migration behavior of these elements can be explained in terms of the chemical stability of the solid phases. The main factor contributing to the well-preserved state of the bronze artifacts was the tin content, which is thought to have formed a protective layer of cassiterite (SnO) on the outer surface of the bronze artifacts.
Mitsui, Seiichiro
Maizo Bunkazai Nyusu, (171), p.10 - 17, 2018/03
As part of research and development of geological disposal, "natural analogues" have been applied to validate concept of models and evaluation methodologies for performance assessment. By introducing domestic and overseas research results on natural analogues, this paper presents how we have utilized knowledge of excavated archaeological artifacts for geological disposal studies.
Horie, Hiroki*; Yukumatsu, Kazuki*; Mishima, Fumihito*; Akiyama, Yoko*; Nishijima, Shigehiro*; Sekiyama, Tomio*; Mitsui, Seiichiro; Kato, Mitsugu
Journal of Physics; Conference Series, 871, p.012102_1 - 012102_7, 2017/07
Times Cited Count：2 Percentile：65.83(Physics, Applied)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
10
to 110
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.
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.
Mitsui, Seiichiro
Koeki Zaidan Hojin Tottoriken Kyoiku Bunka Zaidanhen 2014 "Yoshida Nakamichi Iseki" Tottoriken Kyoiku Iinkai, p.221 - 230, 2015/03
An ancient socketed iron axe was excavated from Yoshida Nakamichi site in Tottori City, Tottori Prefecture. To understand reasons of corrosion state of the axe, we studied relationship between burial environment and corrosion. As environmental conditions, we investigated groundwater chemistry and corrosion rate with iron probe monitor, etc. As for corrosion state, we analysed corrosion depths with a X-ray CT and corrosion products with a portable XRD/XRF. As results, we found that the redox potential and dissolved oxygen level as environmental conditions were very low, and that the maximum corrosion rate (210
mm/y) evaluated from measured corrosion depths was smaller than the probe corrosion rate (510
mm/y) by two orders of magnitude and identified siderite (FeCO
) as a corrosion product. The results suggested that the siderite precipitated on the surface of the iron sword inhibited corrosion reaction.
Mitsui, Seiichiro
Mukibanda Iseki Hakkutsu Chosa Kenkyu Nempo 2014, p.27 - 44, 2015/03
A number of ancient iron artifacts were excavated from Mukibanda archaeological remains in Tottori Prefecture. To obtain detailed information on corrosion state of the iron artifacts, we analysed corrosion depths with a X-ray Computer Tomography (X-ray CT) and corrosion products with a portable X-ray diffractometer equipped with X-ray fluorescence spectrometer (XRD/XRF). As reference information for relationship between corrosion and environmental conditions, we also measured some environmental parameters. As results, we found that the maximum corrosion rates evaluated from measured corrosion depths was smaller than the probe corrosion rate by one to two orders of magnitude. The results suggested that the corrosion products precipitated on the surface of the iron artifacts inhibited corrosion reaction.
Mitsui, Seiichiro
Ippan Zaidan Hojin Yonagoshi Bunkazaidan Maizo Bunkazai Hakkutsu Chosa Hokokusho, 6; Ippan Kokudo 180-Go (Nambu Baipasu) Doro Kairyo Koji Ni Tomonau Maizo Bunkazai Hakkutsu Chosa Hokokusho V; Tottoriken Saihakugun Nambucho; Sakaiyaishi Iseki, 2, p.35 - 48, 2015/00
A number of ancient iron artifacts in apparently well-preserved state were excavated from Sakai-Yaishi archaeological site in Nambu Town, Tottori Prefecture. To obtain detailed information on corrosion state of the iron artifacts, we analysed corrosion depths with a X-ray Computer Tomography (X-ray CT) and corrosion products with a portable X-ray diffractometer equipped with X-ray fluorescence spectrometer (XRD/XRF). For comparison, a poor-preserved iron artifact excavated from Bakurou-Machi archaeological site in Bakurou Town also analysed. The results imply that the difference in the corrosion states of the iron artifacts between Sakai-Yaishi and Bakurou-Machi archaeological sites reflects a difference in locations between both archaeological sites, that is a difference in burial environmental conditions between a hillside and a beachside.
Kihara, Shinji; Amazawa, Hiroya; Sakai, Akihiro; Nakata, Hisakazu; Kugo, Teruhiko; Matsuda, Norihiro; Oizumi, Akito; Sasamoto, Hiroshi; Mitsui, Seiichiro; Miyahara, Kaname
JAEA-Research 2013-033, 320 Pages, 2014/07
JAEA-Research-2013-033.pdf:119.17MB
JAEA performed decontamination experiments at two test sites that combined a range of buildings and different types of land use, located in Date and Minami Soma municipalities as field pilot projects in order to accumulate knowledge and data for full-scale decontamination activities performed by local governments. In the pilot projects, we established its plan using practical decontamination methods that can be easily implemented, according to decontamination targets (e.g., forests, agricultural land, residential house and roads) at each site. As a result of the decontamination, the average air dose rates were reduced to approximately one half of the values before decontamination.
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.
Mitsui, Seiichiro
Ippan Kokudo 9-Go (Tottori Nishi Doro) No Kaichiku Nitomonau Maizo Bunkazai Hakkutsu Chosa Hokokusho, 8; Motodaka Yuminoki Iseki (5-Ku) I, 3, p.241 - 258, 2013/10
An ancient iron plowshare (ca 1,700 year old) was excavated from Motodaka Yuminoki archaeological site in Tottori Prefecture. We analysed corrosion state with a X-ray CT and corrosion products with a portable XRD/XRF. For comparison, we also analysed iron knife excavated from Miyadani ancient tomb No. 26 and iron adze excavated from Yoshida Nakamichi archaeological site. As results of analyses of the plowshare and the adze, we identified siderite as a corrosion product and confirmed the existence of metal iron in the artifacts. Previous experimental study suggested inhibition of corrosion reaction associated with siderite formation. Good state of preservation of the plowshare and the adze could be attributed to the formation of siderite on the surface of the artifacts.
