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Journal Articles

Investigation of chemical state of uranium included in simulated waste glass

Nagai, Takayuki; Akiyama, Daisuke*; Kirishima, Akira*; Sato, Nobuaki*; Okamoto, Yoshihiro

2019-Nendo "Busshitsu, Debaisu Ryoiki Kyodo Kenkyu Kyoten" Oyobi "Hito, Kankyo To Busshitsu O Tsunagu Inobeshion Soshutsu Dainamikku, Araiansu" Kenkyu Seika, Katsudo Hokokusho (CD-ROM), P. 20191107_1, 2020/11

no abstracts in English

Journal Articles

Structural change of borosilicate glass by boron isotope composition

Nagai, Takayuki; Okamoto, Yoshihiro; Akiyama, Daisuke*; Uehara, Akihiro*; Fujii, Toshiyuki*; Sekimoto, Shun*

KURNS Progress Report 2019, P. 257, 2020/08

http://www.rri.kyoto-u.ac.jp/PUB/report/PR/ProgRep2019/ProgressReport2019_online.pdf

To understand the influence of glass structural change by neutron irradiation and boron isotope composition, glass samples were made from enrichment boric acid reagents and neutron irradiation of those samples was carried out in Pn-2 of KUR. The structural change of glass sample after the irradiation will be estimated in 2020FY. Before neutron irradiation test of glass samples, the Si-O bridging structure difference by boron isotope composition compared by using a Raman spectrometry.

Journal Articles

Investigation of chemical state of simulated waste glasses by using XAFS measurement

Nagai, Takayuki; Shimoyama, Iwao; Okamoto, Yoshihiro; Akiyama, Daisuke*; Arima, Tatsumi*

Photon Factory Activity Report 2019 (Internet), 3 Pages, 2020/00

http://pfwww.kek.jp/acr/2019pdf/u_reports/pf19b0042.pdf

no abstracts in English

Journal Articles

Structural change of borosilicate glass by neutron irradiation

Nagai, Takayuki; Kobayashi, Hidekazu; Okamoto, Yoshihiro; Akiyama, Daisuke*; Sato, Nobuaki*; Uehara, Akihiro*; Fujii, Toshiyuki*; Sekimoto, Shun*

KURNS Progress Report 2018, P. 105, 2019/08

http://www.rri.kyoto-u.ac.jp/PUB/report/PR/ProgRep2018/KURNS_Progress_Report2018_web.pdf

To understand this structural change of a borosilicate glass by a neutron irradiation in detail, the irradiation test was carried out in KUR in 2017FY. The glass structure was estimated by using Raman spectrometry in 2018FY. Comparing with the Raman spectra of glass samples before and after irradiation, it could be observed the change of peak height of Si-O bridging structure by the irradiation.

Journal Articles

Investigation of chemical state of uranium included in simulated waste glass

Nagai, Takayuki; Akiyama, Daisuke*; Sato, Nobuaki*; Okamoto, Yoshihiro

"Busshitsu, Debaisu Ryoiki Kyodo Kenkyu Kyoten" Oyobi "Hito, Kankyo To Busshitsu O Tsunagu Inobeshion Soshutsu Danamikku, Araiansu" Kenkyu Seika, Katsudo Hokokusho (Heisei-30-Nendo) (CD-ROM), P. 20181080_1, 2019/06

no abstracts in English

Journal Articles

Evaluation of uranium chemical state in borosilicate glasses by using XAFS measurement

Nagai, Takayuki; Okamoto, Yoshihiro; Akiyama, Daisuke*; Sato, Nobuaki*

Photon Factory Activity Report 2018 (Internet), 2 Pages, 2019/00

http://pfwww.kek.jp/acr/2018pdf/u_reports/pf18b0060.pdf

no abstracts in English

Journal Articles

Investigation of chemical state of uranium included in glass

Nagai, Takayuki; Akiyama, Daisuke*; Sato, Nobuaki*

Busshitsu, Debaisu Ryoiki Kyodo Kenkyu Kyoten Kenkyu Seika Hokokusho (Heisei-29-Nendo) (CD-ROM), 1 Pages, 2018/04

no abstracts in English

Journal Articles

Evaluation of uranium chemical state in borosilicate glasses by using XAFS measurement

Nagai, Takayuki; Kobayashi, Hidekazu; Okamoto, Yoshihiro; Akiyama, Daisuke*; Sato, Nobuaki*

Photon Factory Activity Report 2017, 2 Pages, 2018/00

http://pfwww.kek.jp/acr/2017pdf/u_reports/pf17b0074.pdf

no abstracts in English

Journal Articles

Chemical behavior of platinum group compounds in the vitrification process condition

Nagai, Takayuki; Akiyama, Daisuke*; Sato, Nobuaki*; Sasage, Kenichi

Busshitsu, Debaisu Ryoiki Kyodo Kenkyu Kyoten Kenkyu Seika Hokokusho (Heisei-28-Nendo) (CD-ROM), 1 Pages, 2017/03

no abstracts in English

Journal Articles

Investigation of ruthenium compounds in the vitrification process condition

Nagai, Takayuki; Sato, Nobuaki*; Sasage, Kenichi

Busshitsu, Debaisu Ryoiki Kyodo Kenkyu Kyoten Kenkyu Seika Hokokusho (Heisei-27-Nendo) (CD-ROM), 2 Pages, 2016/03

no abstracts in English

Journal Articles

Redox equilibrium of the UO$$_2^{2+}$$/UO$$_2^{+}$$ couple in Li$$_{2}$$MoO$$_{4}$$-Na$$_{2}$$MoO$$_{4}$$ eutectic melt at 550$$^{circ}$$C

Nagai, Takayuki; Uehara, Akihiro*; Fujii, Toshiyuki*; Sato, Nobuaki*; Kofuji, Hirohide; Myochin, Munetaka; Yamana, Hajimu*

Journal of Nuclear Materials, 454(1-3), p.159 - 163, 2014/11

https://doi.org/10.1016/j.jnucmat.2014.07.070
 Times Cited Count：0 Percentile：100(Materials Science, Multidisciplinary)

The redox equilibrium of UO$$_2^{2+}$$/UO$$_2^{+}$$ couple was measured in Li$$_{2}$$MoO$$_{4}$$-Na$$_{2}$$MoO$$_{4}$$ eutectic melt at 550$$^{circ}$$C by cyclic voltammetry and absorption spectrophotometry. The standard redox potential of UO$$_2^{2+}$$/UO$$_2^{+}$$ couple was approximately evaluated by cyclic voltammetry. Further, the absorption spectrum and equilibrium potential were measured, repeatedly adding UO$$_2^{2+}$$ source material into the melt containing UO$$_2^{+}$$. From the correlation between the equilibrium potential of the melt and the concentration ratio [UO$$_2^{2+}$$]/[UO$$_2^{+}$$] spectrophotometrically evaluated, the standard redox potential of UO$$_2^{2+}$$/UO$$_2^{+}$$ couple was determined to be -0.847$$pm$$0.010 V vs. O$$_{2}$$/O$$^{2-}$$.

Journal Articles

Absorption spectra and cyclic voltammograms of uranium species in molten lithium molybdate-sodium molybdate eutectic at 550 $$^{circ}$$C

Nagai, Takayuki; Uehara, Akihiro*; Fukushima, Mineo; Myochin, Munetaka; Fujii, Toshiyuki*; Sato, Nobuaki*; Yamana, Hajimu*

Proceedings in Radiochemistry, 1(1), p.151 - 155, 2011/09

http://www.oldenbourg-link.com/doi/abs/10.1524/rcpr.2011.0012

Absorption spectra of dissolved uranium species in molten Li$$_{2}$$MoO$$_{4}$$-Na$$_{2}$$MoO$$_{4}$$ eutectic at 550 $$^{circ}$$C were measured by spectrophotometry, and their redox reactions were also investigated by cyclic voltammetry. Observed absorption spectra of uranium species were similar to those of UO$$_{2}$$$$^{+}$$ in molten chlorides. After purging oxygen into the melt, the absorption peaks of UO$$_{2}$$$$^{+}$$ decreased and UO$$_{2}$$$$^{+}$$ was thought to be oxidized to UO$$_{2}$$$$^{2+}$$. When the uranium species were not contained in the melt, we confirmed that alkali metals deposited at -0.7 V and a small reduction of this melt was observed at -0.3 V. When UO$$_{2}$$ was dissolved into the melt, the reduction of the uranium species was observed at -0.2 V. It was suggested that the dissolved uranium species are recovered as mixed uranium-molybdenum oxides by electrolysis.

Journal Articles

Electrochemical behavior and electronic absorption spectra of uranium trivalent ions in molten LiCl-CsCl mixtures

Nagai, Takayuki; Uehara, Akihiro*; Fujii, Toshiyuki*; Sato, Nobuaki*; Yamana, Hajimu*

Journal of Nuclear Materials, 414(2), p.226 - 231, 2011/07

https://doi.org/10.1016/j.jnucmat.2011.03.048
 Times Cited Count：6 Percentile：49.18(Materials Science, Multidisciplinary)

Journal Articles

${it Ex-situ}$ and ${it in-situ}$ X-ray diffractions of corrosion products freshly formed on the surface of an iron-silicon alloy

Suzuki, Shigeru*; Matsubara, Eiichiro*; Komatsu, Takuya*; Okamoto, Yoshinori*; Kanie, Kiyoshi*; Muramatsu, Atsushi*; Konishi, Hiroyuki; Mizuki, Junichiro; Waseda, Yoshio*

Corrosion Science, 49(3), p.1081 - 1096, 2007/03

https://doi.org/10.1016/j.corsci.2006.06.029
 Times Cited Count：28 Percentile：18.59(Materials Science, Multidisciplinary)

${it Ex-situ}$ X-ray diffraction measurements of a small amount of samples extracted from wet corrosion products freshly formed on a pure iron and iron-2 mass% silicon surfaces have been conducted using synchrotron radiation. The results showed that $$gamma$$-FeOOH was formed on the outer side of wet corrosion products formed on the pure iron by sodium chloride solution, while $$gamma$$-FeOOH, $$alpha$$-FeOOH, Fe$$_{3}$$O$$_{4}$$, and green rusts were formed on the inner side. In comparison to the case of the pure iron, a significant formation of $$beta$$-FeOOH was observed in the iron-silicon alloy. Furthermore, in-situ diffraction measurements by a conventional X-ray source were conducted for analyzing corrosion products formed on the pure iron and iron-silicon alloy surfaces by cyclic exposure to wet and dry atmospheres. The results obtained by the ${it in-situ}$ diffraction and ${it ex-situ}$ diffraction measurements on the corrosion products were consistent.

Journal Articles

Growth kinetics of very thin oxide on Si and Ti surfaces studied by real-time surface analytical methods

Takakuwa, Yuji*; Ogawa, Shuichi*; Ishizuka, Shinji*; Yoshigoe, Akitaka; Teraoka, Yuden

Journal of Surface Analysis, 13(1), p.36 - 84, 2006/04

no abstracts in English

Oral presentation

Real-time monitoring of interfacial strained Si layers during oxidation on Si(001) surface by XPS using high brightness synchrotron radiation

Ogawa, Shuichi*; Yoshigoe, Akitaka; Ishizuka, Shinji*; Teraoka, Yuden; Takakuwa, Yuji*

no journal, , 

High resolution O1s and Si2p photoelectron spectroscopy using synchrotron radiation was employed to clarify layer-by-layer oxidation reaction mechanisms at an Si(001) surface from a viewpoint of point-defect generation due to oxidation-induced strain at SiO$$_{2}$$/Si interface. Beta- and alpha-Si components in Si2p$$_{3/2}$$ spectra, which are assigned to the first and second strained Si layers, show significant decrease during step-by-step temperature increase. Because of the band bending measured by O1s peak position, the observed decrease of beta-Si and alpha-Si components is assigned to not only by a structural relaxation of SiO$$_{2}$$ network due to thermal annealing effects, but also due to point-defect generation at SiO$$_{2}$$/Si interface.

Oral presentation

Photoelectron spectroscopic observation of Si(001) surface oxidation processes using high brilliance synchrotron radiation

Ogawa, Shuichi*; Yoshigoe, Akitaka; Ishizuka, Shinji*; Teraoka, Yuden; Takakuwa, Yuji*

no journal, , 

no abstracts in English

Oral presentation

Role of the emitted Si atom due to oxidation-induced strain during very thin oxide decomposition on Si(001) studied by RHEED combined with AES

Ogawa, Shuichi*; Yoshigoe, Akitaka; Ishizuka, Shinji*; Teraoka, Yuden; Takakuwa, Yuji*

no journal, , 

To verify the unified model of Si oxidation reactions mediated by point defects generation (emitted Si atoms + vacancies) due to oxidation-induced strain, which is also applicable to void nucleation reactions during oxide decomposition, RHEED combined with AES was employed to monitor simultaneously the oxide coverage and interfacial roughness during void nucleation and growth in the oxide decomposition on Si(001). By the RHEED-AES measurements, not only the void nucleation time but also the void growth time by the complete oxide removal are considerably elongated as the second oxide layer coverage increases. From these results, it is found that the oxide decomposition by emitted Si atoms due to the oxidation-induced strain at SiO$$_{2}$$/Si interface, which is a rate-limiting reaction of void nucleation, takes place frequently even after void nucleation.

Oral presentation

Real-time photoelectron spectroscopy study on the oxidation-induced strained Si atom at SiO$$_{2}$$/Si(001) interface; Dependence on oxidation temperature

Ogawa, Shuichi*; Yoshigoe, Akitaka; Ishizuka, Shinji*; Teraoka, Yuden; Takakuwa, Yuji*

no journal, , 

To verify experimentally the unified model of Si oxidation reactions mediated by point defects generation (emitted Si atoms + vacancies) due to oxidation-induced strain, real-time photoelectron spectroscopy using synchrotron radiation was employed to monitor the oxidation-induced strained Si atom at SiO$$_{2}$$/Si interface, oxidation states, and the oxide thickness simultaneously during oxidation on n-type Si(001) surfaces with O$$_{2}$$ gas. Upon introducing O$$_{2}$$ gas at 300$$^{circ}$$C, both Si$$alpha$$ and Si$$beta$$ increase with time and then Si$$beta$$ decreases gradually at first oxide layer, while Si$$alpha$$ continues to increase, but with a decreased rate. It is found that the amount of Si$$beta$$ and Si$$alpha$$ at the completion of first oxide layer growth decrease gradually with raising temperature from 300 to 600$$^{circ}$$C, where oxide grows in the Langmuir-type adsorption manner. These results indicate that the oxidation-induced strain decreases with surface temperature.

Oral presentation

Experimental verification of the unified Si oxidation reaction model, 2; O$$_{2}$$ pressure dependence of interfacial oxidation rate

Ogawa, Shuichi*; Yoshigoe, Akitaka; Ishizuka, Shinji*; Teraoka, Yuden; Takakuwa, Yuji*

no journal, , 

In this study, real-time XPS was applied to investigating the effect of the rapid O$$_{2}$$ pressure increase on the interfacial oxidation rate in connection with the changes in stress (strain) at the SiO$$_{2}$$/Si(001) interface. The oxidation experiments were performed using the surface reaction analysis apparatus placed at the BL23SU of SPring-8. The photoelectron spectroscopy measurement of O1s and Si2p was performed during oxidation of a p-type Si(001) surface. When the Si surface was completely covered by the oxide, the O$$_{2}$$ pressure was increased to enhance the interfacial oxidation. The O$$_{2}$$ pressure and initial rate of interfacial reaction after O$$_{2}$$ pressure increase shows the linear correlation and its gradient is obtained as 0.5. It is found that the O$$_{2}$$ supply is not the limiting reaction of SiO$$_{2}$$/Si interface oxidation. Based on these results, an interfacial reaction model of oxygen and Si atoms is proposed.

43 (Records 1-20 displayed on this page)