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Journal Articles

XAFS analysis of ruthenium in simulated iron phosphate radioactive waste glass

Okamoto, Yoshihiro; Kobayashi, Hidekazu; Shiwaku, Hideaki; Sasage, Kenichi; Hatakeyama, Kiyoshi*; Nagai, Takayuki

Journal of Non-Crystalline Solids, 551, p.120393_1 - 120393_8, 2021/01

The chemical state of ruthenium in simulated iron phosphate radioactive waste glass was investigated by conventional X-ray absorption fine structure (XAFS) and imaging XAFS analyses. The EXAFS analysis suggested that ruthenium was contained as glass phase when content of the waste components was less than 10wt.% in 30 mol%Fe$$_{2}$$O$$_{3}$$-P$$_{2}$$O$$_{5}$$ base glass. In other samples, crystalline RuO$$_{2}$$ was predominant. According to the imaging XAFS analysis, RuO$$_{2}$$ particles in all samples had length smaller than 50$$mu$$m. Aggregations of RuO$$_{2}$$, which are found in nuclear waste borosilicate glass, were not seen in any of the iron phosphate glass samples.

JAEA Reports

Structural investigation of simulated waste glass samples by using XAFS measurement in soft X-ray region (Joint research)

Nagai, Takayuki; Okamoto, Yoshihiro; Yamagishi, Hirona*; Ota, Toshiaki*; Kojima, Kazuo*; Inose, Takehiko*; Sato, Seiichi*; Hatakeyama, Kiyoshi*

JAEA-Research 2020-009, 48 Pages, 2020/09

JAEA-Research-2020-009.pdf:4.67MB

The local structure of glass-forming elements and waste elements in waste glass varies with its chemical composition. In this study, borosilicate glass frit and simulated waste glass samples were prepared and the local structure and chemical state regarding boron (B), oxygen (O), and waste elements of cerium (Ce), cesium (Cs) were estimated by using XAFS measurement in soft X-ray region. Following results were obtained by XAFS measurements of prepared glass frit and simulated waste glass samples: (1) The existence ratio of four coordinate sp$$^{3}$$ structure (BO$$_{4}$$) tends to increase with increasing Na$$_{2}$$O content in glass samples. (2) The height of a pre-edge which appears by K-edge XANES spectrum of O is so high that the Fe content in glass samples. Following results were obtained by XAFS measurements of simulated waste glass samples after immersion test to investigate long chemical stability. (1) The existence ratio of four coordinate sp$$^{3}$$ structure (BO$$_{4}$$) increases by immersion test. (2) Ce which exists in the surface layer is oxidized by immersion test, and much of Cs in surface layer is lost after leach testing. Even if the glass frit form (fiber cartridge or beads) and manufacturing method were changed and a glass sample of the similar chemical composition was prepared, these observed Raman spectra of samples were different.

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

no abstracts in English

JAEA Reports

XAFS measurement of simulated waste glass samples (Joint research)

Nagai, Takayuki; Sasage, Kenichi; Okamoto, Yoshihiro; Shiwaku, Hideaki; Yamagishi, Hirona*; Ota, Toshiaki*; Inose, Takehiko*; Sato, Seiichi*; Hatakeyama, Kiyoshi*; Takahashi, Tomoe*; et al.

JAEA-Research 2019-003, 94 Pages, 2019/09

JAEA-Research-2019-003.pdf:7.92MB

The local structures of glass-forming elements and waste elements would change by the chemical composition of waste glass including those elements. In this study, simulated waste glass samples were prepared from borosilicate glass frit including phosphorus (P) or vanadium (V), and we investigated local structures of boron, sodium, and waste elements in these P glass and V glass samples by using synchrotron XAFS measurements in soft and hard X ray region.

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

JAEA Reports

Synchrotron radiation based XAFS analysis of the simulated nuclear waste glass samples prepared by bottom drain test in the full-scale mock-up melter (KMOC) (Contract research)

Okamoto, Yoshihiro; Nagai, Takayuki; Shiwaku, Hideaki; Kano, Shigeru; Himeno, Haruyuki*; Kobayashi, Hiroshi*; Nakatani, Mikio*

JAEA-Research 2018-013, 18 Pages, 2019/03

JAEA-Research-2018-013.pdf:1.98MB

The chemical state and local structure of some elements in the simulated nuclear waste glass samples (20 batches) prepared by bottom drain test in the full scale mock-up tests using KMOC melter were investigated by synchrotron radiation based X-ray absorption fine structure (XAFS) analysis. As a result of the analysis of cerium element, it was confirmed that the oxidation proceeds gently as the batch advanced. For manganese, iron, and zinc, there was almost no difference between batches, which seemed to be stabilized by getting into the frame structure of the borosilicate glass. There were no elements that seemed to be clearly crystalline except for platinum group elements. Remarkable precipitation was hardly observed in zirconium and molybdenum with the imaging analysis.

Journal Articles

Contribution to upgrade of vitrification technology by synchrotron radiation analysis; From Chemical state analysis of waste glass to development of structural analysis to prove soundness

Okamoto, Yoshihiro; Nagai, Takayuki; Shiwaku, Hideaki

Yoyuen Oyobi Koon Kogaku, 62(1), p.11 - 17, 2019/01

The vitrified radioactive waste is a multicomponent material containing many kinds of elements. Synchrotron radiation XAFS with element selectivity is suitable for analysis of elements in the waste. From the XAFS analysis, the chemical state and the local structure of each element were clarified. Imaging XAFS technique was used as an analysis based on element distribution in the glass. The imaging XAFS is effective for analysis of elements that are less soluble in the glass like molybdenum and platinum group elements. It was clarified from the simultaneous imaging XAFS analyses of multiple elements that the chemical form of rhodium is strongly dominated by the distribution correlation with ruthenium. We proposed multi - scale structural analyses with wide angle scattering, PDF analysis, small angle scattering in order to evaluate the soundness of the vitrified waste.

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

no abstracts in English

JAEA Reports

Investigation of simulated waste glass samples prepared from borosilicate glass frit including vanadium

Nagai, Takayuki; Okamoto, Yoshihiro; Shiwaku, Hideaki; Inose, Takehiko*; Sato, Seiichi*; Hatakeyama, Kiyoshi*; Hirono, Kazuya*; Homma, Masanobu*; Kobayashi, Hiromi*; Takahashi, Tomoe*; et al.

JAEA-Research 2018-007, 87 Pages, 2018/11

JAEA-Research-2018-007.pdf:61.21MB

To select the chemical composition of a glass frit which can increase the waste content, the simulated waste glass samples prepared from a borosilicate glass frit including vanadium (V) were investigated by using Laser Ablation (LA) ICP-AES analysis, Raman spectrometry, and synchrotron XAFS measurement in this study on foundation business of the Agency for Natural Resources and Energy.

JAEA Reports

XAFS measurement of simulated waste glass samples prepared from borosilicate glass frit including phosphorus pentaoxide (Joint research)

Nagai, Takayuki; Kobayashi, Hidekazu; Shimamura, Keisuke; Oyama, Koichi; Sasage, Kenichi; Okamoto, Yoshihiro; Shiwaku, Hideaki; Yamanaka, Keisuke*; Ota, Toshiaki*

JAEA-Research 2018-005, 72 Pages, 2018/09

JAEA-Research-2018-005.pdf:28.2MB

Addition of radioactive waste to a borosilicate glass frit affects the local structures of glass-forming elements and waste elements in a waste glass produced in a vitrification process. In this study, simulated waste glass samples were prepared from borosilicate glass frit including phosphorus pentaoxide, and we investigated local structures of sodium (Na), boron (B), and waste elements in these glass samples by using synchrotron XAFS measurements in soft and hard X ray region.

Journal Articles

Synchrotron radiation based X-ray absorption study for upgrade of nuclear waste vitrification technique

Okamoto, Yoshihiro; Nagai, Takayuki; Shiwaku, Hideaki

Hoshako, 31(4), p.274 - 280, 2018/07

As a method for disposal of nuclear waste, the use of vitrification technique is very promising. In this technique, many kinds of elements should be involved stably in the glass and chemical state of these elements in the glass must be confirmed in order to guarantee stability of the glass. We have used synchrotron based X-ray absorption fine structure (XAFS) technique, in which the element selectivity is utilized, to obtain the chemical state of each element in many kinds of simulated glass samples. In addition, imaging XAFS technique has been used to clarify correlation between constituent elements. We are going to contribute to research and development of the vitrification technique by using synchrotron radiation based XAFS analyses. In this article, we introduce results of the high energy XAFS of high temperature slag samples, the imaging study of high temperature borosilicate glass samples and the imaging XAFS analysis of platinum group metals in the borosilicate glass samples.

Journal Articles

Utilization of the knowledge of excavated archaeological artifacts for research and development of geological disposal

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.

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

no abstracts in English

Journal Articles

Chemical state analysis of rhodium in simulated waste glass by synchrotron-radiation-based XAFS and imaging XAFS techniques

Okamoto, Yoshihiro; Nagai, Takayuki; Shiwaku, Hideaki; Inose, Takehiko*; Sato, Seiichi*

Nippon Genshiryoku Gakkai Wabun Rombunshi, 16(4), p.180 - 190, 2017/12

X-ray absorption fine structure (XAFS) and imaging XAFS analyses were performed to elucidate chemical state of rhodium in the simulated waste glass. The chemical forms of Rh in the glass were evaluated to be 84% RhO$$_{2}$$ and 16% metal/alloy as the result of linear combination analysis of EXAFS data. According to the imaging XAFS analysis, the chemical form of Rh which was located together with Ru was mainly oxide (RhO$$_{2}$$). It suggests that stable (Ru,Rh)O$$_{2}$$ solid solution exists in the simulated glass. On the other hand, that of Rh of which distribution did not accord with Ru in the glass was mainly metallic. In the case of metallic Rh in the glass, it tended to become an aggregation form. It can be concluded that the chemical state of Rh was much affected by the existence and distribution of Ru element.

Journal Articles

Vitrification technology for radioactive wastes

Amamoto, Ippei

Journal of the Society of Inorganic Materials, Japan, 24(391), p.393 - 401, 2017/11

Glass is a non-crystalline solid, as such, it is relatively easy to change its composition to control its characteristics. The borosilicate glass, which is produced by the addition of boron oxide into sodium-lime glass, possesses excellent heat-resistant properties and mechanical strength. It has a wide variety of uses. The borosilicate glass is applied as the vitrified medium for radioactive wastes to immobilize and stabilize them for long term. The glass form which is loaded with high-level radioactive waste is called the vitrified waste. This paper classified the radioactive waste and describes treatment and production methods of vitrified waste, its characteristics, disposal method and also introduces alternative vitrified medium.

JAEA Reports

XAFS measurement of simulated waste borosilicate glass samples (Joint research)

Nagai, Takayuki; Kobayashi, Hidekazu; Sasage, Kenichi; Ayame, Yasuo; Okamoto, Yoshihiro; Shiwaku, Hideaki; Yamanaka, Keisuke*; Ota, Toshiaki*

JAEA-Research 2017-005, 54 Pages, 2017/06

JAEA-Research-2017-005.pdf:16.17MB

Addition of radioactive waste to a borosilicate frit affects the local structures of boron (B) and waste elements in a waste glass. Synchrotron XAFS measurement was applied to investigate the local structural changes by using simulated waste borosilicate glass samples. Following results were obtained by the B K-edge XAFS analysis. It was confirmed that B K-edge XAFS analysis enables us to discriminate sp$$^{2}$$ type boron (BO$$_{3}$$) from sp$$^{3}$$ type boron (BO$$_{4}$$). Addition of waste elements to a glass frit increases the percentage of BO$$_{3}$$ and decreases that of BO$$_{4}$$. By decreasing the SiO$$_{2}$$/Al$$_{2}$$O$$_{3}$$ ratio or increasing the (SiO$$_{2}$$+B$$_{2}$$O$$_{3}$$)/Al$$_{2}$$O$$_{3}$$ ratio in the glass composition, the BO$$_{3}$$ percentage increases and the BO$$_{4}$$ percentage decreases. Addition of P$$_{2}$$O$$_{5}$$ decreases the BO$$_{3}$$ percentage and increases the BO$$_{4}$$ percentage. Following results were obtained from XAFS measurement of the waste elements. Cerium (Ce) valence is more reduced with the increase of the B$$_{2}$$O$$_{3}$$ content. Addition of P$$_{2}$$O$$_{5}$$ has a tendency to reduce the Ce valence and to enhance deposition of Zr oxide. Deposition of ruthenium compounds separated from glass phase can not be improved by changing the B$$_{2}$$O$$_{3}$$ content. This study was performed as a part of the project, "Improvement of vitrification process of high-level radioactive liquid wastes" on the foundation business of the Agency for Natural Resources and Energy.

Journal Articles

Studies of the setting of engineered barrier configuration utilized in geologic disposal, 1; Dissolution life-time of vitrified waste glass

Oe, Toshiaki*; Wakasugi, Keiichiro

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 24(1), p.27 - 32, 2017/06

The report estimates the life-time of the waste glass dissolution in the geologic disposal environment. The overall safety report on the geologic disposal in Japan showed very short life-time of approximately 70,000 years under pessimistic assumptions ignoring the temperature decrease due to radioactive decay and dissolution rate reduction due to surface shrinkage. These factors are physically established phenomena and may not be excluded. The dissolution models including these factors of temperature and surface area decreases are discussed and used for re-evaluation. Three fracture models are presented for evaluating the surface area decreases; a single plate, monotonic spheres, spheres having power-law distribution. All models have the same initial volume as the waste glass block for mass conservation and the total surface areas are 10 times higher than the initial pristine block because of the fracture development during production. The results indicate the retention time of 50% of initial mass exceed 100,000 years even by different fracture models and the dissolution life-times are expected for 260,000$$sim$$700,000 years depending on models. These results imply more strong isolation capability of the waste glass than that estimated in the overall safety report.

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

JAEA Reports

XAFS measurement of simulated waste glass samples (Borosilicate glass including vanadium)

Nagai, Takayuki; Kobayashi, Hidekazu; Sasage, Kenichi; Ayame, Yasuo; Okamoto, Yoshihiro; Shiwaku, Hideaki; Matsuura, Haruaki*; Uchiyama, Takafumi*; Okada, Yukiko*; Nezu, Atsushi*; et al.

JAEA-Research 2016-015, 52 Pages, 2016/11

JAEA-Research-2016-015.pdf:37.48MB

The local structure of waste elements in simulated waste glasses including V was estimated by using synchrotron XAFS measurement in this study. The results are as follows. (1) V has a high possibility which exists in the glass phase in the case of frit, and V can regard both samples as stable 4 coordination structure. (2) Zn, Ce, Nd, Zr, and Mo exist in the glass phase, and the difference is admitted by the percentage of Ce(III) and Ce(IV) by the composition. (3) Ru is separated from the glass phase as RuO$$_{2}$$ crystalline, both of metal and oxide exist in Rh, and Pd is separated out as metal. (4) It was confirmed that the regularity of the local structure of Zr and Mo in the molten glasses retreats as a result of the XAFS measurement at high temperature. (5) The XAFS measurement of molten glasses were performed at 1200$$^{circ}$$C, so it would be possible to acquire excellent data by improving the shapes of the sample cell.

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

270 (Records 1-20 displayed on this page)