Kitayama, Ayami; Taniguchi, Naoki; Mitsui, Seiichiro
Materials and Corrosion, 72(1-2), p.211 - 217, 2021/01
Francisco, P. C. M.; Mitsui, Seiichiro; Ishidera, Takamitsu; Tachi, Yukio; Doi, Reisuke; Shiwaku, Hideaki
Geochimica et Cosmochimica Acta, 270, p.1 - 20, 2020/02
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 (CuO) 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.
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
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 110 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 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.
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.
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.
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 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
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.
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.
Yoshikawa, Hideki; Iijima, Kazuki; Sasamoto, Hiroshi; Fujiwara, Kenso; Mitsui, Seiichiro; Kitamura, Akira; Kurikami, Hiroshi; Tokizawa, Takayuki; Yui, Mikazu; Nakayama, Shinichi
Materials Research Society Symposium Proceedings, Vol.1518, p.269 - 275, 2013/10
Following the release of radionuclides into the environment as a result of the accident at Fukushima Daiichi Nuclear Power Plant, Japan Atomic Energy Agency (JAEA) had to develop an immediate and effective method of reducing the dose rate received by students in school facilities. A demonstration of a reducing method was carried out by JAEA at a junior high school ground and kindergarten yard in the center of Fukushima-city. Dose rates of the released radionuclides are largely controlled by the ground level contamination and accumulation of mainly cesium-137 (Cs) and cesium-134 (Cs) in populated areas. An effective means of reducing dose rate was to remove the surface soil and to bury it on-site under fresh uncontaminated soil or soil collected under deep depth at the site for shielding. The dose rate at1 m above ground level was reduced from 2.5 Sv/h to 0.15 Sv/h.
Gin, S.*; Abdelouas, A.*; Criscenti, L.*; Ebert, W.*; Ferrand, K.*; Geisler, T.*; Harrison, M.*; Inagaki, Yaohiro*; Mitsui, Seiichiro; Mueller, K. T.*; et al.
Materials Today, 16(6), p.243 - 248, 2013/06
The nations producing borosilicate glass as a confinement material for high-level waste resulting from spent fuel reprocessing have decided to reinforce scientific collaboration in order to obtain consensus on the mechanisms controlling the long-term dissolution rate of glass. This goal is the most important issue for developing reliable predictive models usable for performance assessment and safety demonstration of geological storage of such materials. This collaboration involves numerous laboratories working either in fundamental or applied research and using all the modern tools available in material science. We present first the situation of the six countries involved in the project regarding their history in nuclear waste vitrification, current policy, and geological disposal project development. This provides an understanding of the common and country specific needs regarding the issue of long-term behavior of glass. Then main proposals and first results are briefly presented.
Yaoshiritsu Rekishi Minzoku Shiryokan Kenkyu Kiyo, (24), p.73 - 80, 2013/03
An ancient iron sword (ca 2,000 year old) was excavated from Ohtake-nishi archaeological site in Yao City, Osaka Prefecture. To understand corrosion state of the sword, we analysed thickness of corrosion layer with a X-ray CT and corrosion products with a portable XRD/XRF. As results, we found that the thickness of corrosion layer on the surface of the sword was generally uniform and identified siderite (FeCO) and goethite (-FeOOH) as corrosion products.
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 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.
Mitsui, Seiichiro; Fujii, Atsuhiro*; Higuchi, Megumi*; Nishimura, Kosuke*
Materials Research Society Symposium Proceedings, Vol.1475, p.545 - 550, 2012/06
An ancient iron sword (ca 2,000 year old) excavated from Ohtake-nishi archaeological site in Osaka Prefecture, is one of the oldest cast iron swords in Japan. Because of a good state of preservation, 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 evaluated from measured corrosion depths was smaller than the probe corrosion rate by two orders of magnitude and identified siderite as a corrosion product. The results suggested that the siderite precipitated on the surface of the iron sword inhibited corrosion reaction.
Inagaki, Yaohiro*; Makigaki, Hikaru; Idemitsu, Kazuya*; Arima, Tatsumi*; Mitsui, Seiichiro; Noshita, Kenji*
Journal of Nuclear Science and Technology, 49(4), p.438 - 449, 2012/04
Dissolution tests were performed for a simulated HLW glass by using a Micro-Channel Flow-Through (MCFT) test to evaluate the initial dissolution rate, , as a function of pH and temperature. The results indicated that the shows a "V-shaped" pH dependence at 25C, which is almost consistent with the previous results measured by using other test methods including Single Pass Flow-Through (SPFT) test. At elevated temperatures, however, the shows a "U-shaped" pH dependence with a flat bottom at neutral pH, which differs from the previous results. The results also indicated that the MCFT provided a higher value of the with a steep slope of pH dependence than the SPFT results at basic pH from 8 to 11 at 90C. With respect to the temperature dependence, the increases with temperature according to an Arrhenius law at any pH, and the apparent activation energy increases with pH, which suggests that the dissolution mechanism can change depending on pH.
Naganoken Maizo Bunkazai Senta Hakkutsu Chosa Hokokusho, 100; Nakanoshi Yanagisawa Iseki, p.139 - 146, 2012/03
Burial environmental conditions of bronze halberds and bells excavated from Yanagisawa archaeological site in Nagano Prefecture were studied. The study indicated that the bronze artifacts were corroded under low oxygen condition in which cuprite is stable. The study results of distribution of chemical components derived from the artifacts revealed that copper and lead transferred at least two meters from the burial pit. On the other hand, tin remained in the vicinity of the artifacts. The tin behavior may explain the long-term corrosion of the bronze artifacts.