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

https://doi.org/10.1016/j.jnoncrysol.2020.120393

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%FeO-PO base glass. In other samples, crystalline RuO was predominant. According to the imaging XAFS analysis, RuO particles in all samples had length smaller than 50m. Aggregations of RuO, which are found in nuclear waste borosilicate glass, were not seen in any of the iron phosphate glass samples.

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 structure (BO) tends to increase with increasing NaO 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 structure (BO) 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.

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

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.

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.

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

Chemical state analysis of simulated corium debris by EXAFS

Okamoto, Yoshihiro; Takano, Masahide

Progress in Nuclear Science and Technology (Internet), 5, p.200 - 203, 2018/11

https://doi.org/10.15669/pnst.5.200

Chemical state of some simulated corium debris samples containing uranium (fuel), zirconium (fuel cladding), iron (structure material), calcium (cement) and lanthanides (fission products) was investigated by synchrotron radiation based extended X-ray absorption fine structure (EXAFS) analysis. The local structure of uranium for the simulated debris was classified into fluorite UO structure and C-type structure (stabilized cubic). The UZrFeCaO sample, which consists of single phase (C-type), shows slightly shorter U-O distance. It can be concluded that the sample contains pentavalent uranium. The local structure of zirconium for U-Zr-O and U-Zr-Fe-O systems was very close to tetragonal ZrO, while that of zirconium changed to CSZ (calcia stabilized cubic) by adding calcium.

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.

Study on Mo structure in simulated dissolved solutions of activated metal waste

Shimada, Asako; Okamoto, Yoshihiro

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

http://pfwww.kek.jp/acr/2017pdf/u_reports/pf17b0191.pdf

no abstracts in English

The Significance of bromide in the Brust-Schiffrin synthesis of thiol protected gold nanoparticles

Booth, S. G.*; Uehara, Akihiro*; Chang, S.-Y.*; La Fontaine, C.*; Fujii, Toshiyuki*; Okamoto, Yoshihiro; Imai, Takahito*; Schroeder, S. L. M.*; Dryfe, R. A. W.*

Chemical Science, 8(12), p.7954 - 7962, 2017/12

https://doi.org/10.1039/C7SC03266H

The two-phase Brust-Schiffrin synthesis of alkane thiol protected metal nanoparticles has been shown to undergo significantly different processes dependent on the precursor species and reactant conditions. In this work X-ray absorption spectroscopy is used in conjunction with liquid/liquid electrochemistry in order to highlight the significance of Br; to the reaction mechanism. We propose that the observed behavior of [AuBr]; species described herein explain a deviation in reported behavior present in the current literature. The reported mechanistic understanding should enable a nanoparticle synthesis with a higher yield and reduce size polydispersity.