Structural change by phosphorus addition to borosilicate glass containing simulated waste components

Okamoto, Yoshihiro; Shiwaku, Hideaki; Shimamura, Keisuke*; Kobayashi, Hidekazu; Nagai, Takayuki; Inose, Takehiko*; Sato, Seiichi*; Hatakeyama, Kiyoshi*

Journal of Nuclear Materials, 570, p.153962_1 - 153962_13, 2022/11

https://doi.org/10.1016/j.jnucmat.2022.153962

Simulated nuclear waste glass samples containing phosphorus, which increase the solubility of molybdenum, were prepared and analyzed using synchrotron X-ray Absorption Fine Structure (XAFS) analysis for some constituent elements and Raman spectroscopic analysis of their complex structure. Changes in local structure and chemical state due to different phosphorus additions and waste loading rates were systematically studied. Consequently, no crystalline phase due to the molybdate compound was observed even at a maximum waste content of 30 wt% (corresponding to 1.87 mol% MoO). Oxidation proceeded when the waste-loading rate was increased, whereas the reduction proceeded when phosphorus was added. In some cases, the effects of oxidation and reduction were offset. The local structure around specific elements can be classified as follows; Zn that is affected mainly by the waste-loading rate, Ce that is affected by both the waste-loading rate and phosphorus addition, and Zr element that is not affected by either of them. From the comparison between the analytical results of Mo and other elements, it was considered that the added phosphorus exists as a free PO structural unit and may deprive the alkali metal coordinated to the molybdate ion.

Structural investigation of borosilicate glasses 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 2021-010, 62 Pages, 2022/01

JAEA-Research-2021-010.pdf:6.05MB

The local structure of glass-forming elements and waste elements in borosilicate glasses 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), silicon(Si) and waste elements of iron(Fe), 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 effect of NaO concentration on B-O coordination structure is greater than that of the waste elements concentration. (2) The height of pre-edge by O K-edge spectrum depends on the concentration of first transition elements such as Fe in glass samples. Following results were obtained by XAFS measurements of simulated waste glass samples after immersion test to investigate the long chemical stability. (1) A new compound was formed on the sample surface after the immersion test, and changes in the surface state were confirmed by Raman spectroscopy. (2) Cs on the sample surface after immersion test dissolves into the leaching solution. The Si K-edge XANES spectra of borosilicate glass frits and simulated waste glass samples included lanthanides oxide were measured, and following was confirmed. (1) As the NaO concentration increases in borosilicate glass frit, the K-edge peak of Si shifts to the low energy side. (2) The peak height of the K-edge of Si differs depending on the kind of lanthanide.

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.

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*

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

https://doi.org/10.3327/taesj.J16.024

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 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). It suggests that stable (Ru,Rh)O 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.

Investigation of the chemical form of ruthenium compounds in the vitrification process, 2; Reactions of sodium ruthenates and raw materials for vitrification such as SiO

Nagai, Takayuki; Sasage, Kenichi; Oyama, Koichi; Sato, Nobuaki*; Inose, Takehiko*; Sato, Seiichi*; Hatakeyama, Kiyoshi*

no journal, , 

no abstracts in English

Investigation of the chemical form of ruthenium compounds in the vitrification process, 3; Reactions of lanthanide nitrates and ruthenium nitrates included in a liquid waste

Nagai, Takayuki; Sasage, Kenichi; Oyama, Koichi; Sato, Nobuaki*; Inose, Takehiko*; Sato, Seiichi*; Hatakeyama, Kiyoshi*

no journal, , 

no abstracts in English

Elemental analysis of borosilicate glass by laser ablation ICP-AES

Inose, Takehiko*; Oyama, Koichi; Miyauchi, Atsushi; Nishizawa, Daiji*; Nagai, Takayuki

no journal, , 

no abstracts in English

Investigation of the chemical form of ruthenium compounds in the vitrification process, 4; RuO generation by reaction with Ru-La-Na mix nitrates and raw materials for vitrification

Nagai, Takayuki; Kobayashi, Hidekazu; Okamoto, Yoshihiro; Sato, Nobuaki*; Inose, Takehiko*; Sato, Seiichi*; Hatakeyama, Kiyoshi*; Seki, Katsumi*

no journal, , 

It is thought that a generated ruthenium compound grows from a high level radioactive liquid waste into RuO crystal by reacting to raw materials for the vitrification process. In this study, the generation reaction to RuO was confirmed by heating Ru-La-Na mix nitrates and the raw materials.

Redox behavior of Ru in NaNO melt

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

no journal, , 

A supplied high level liquid waste into the glass melter is formed to the mixed nitrate salt after the dehydration. In this study, NaNO which is a main ingredient in the waste was selected by the solvent, and NaNO sample including Ru was prepared, and the redox behavior of Ru in NaNO melt was measured by the Cyclic Voltammetry. And valence of Ru included in solidified salt was estimated by the synchrotron XAFS measurement.

Preparation and characterization of simulated waste borosilicate glasses including phosphorus

Nagai, Takayuki; Kobayashi, Hidekazu; Sasage, Kenichi; Oyama, Koichi; Sato, Seiichi*; Inose, Takehiko*; Hatakeyama, Kiyoshi*

no journal, , 

We estimated the long chemical stability of simulated waste borosilicate glass samples reacting with water in a closed case by the immersion test in alkaline solution and confirmed the effect which restrains the elution of molybdenum to the solution from the glass samples made with the frit including phosphorus. After cooling the simulated waste glass samples from melt condition, the crystallization behavior in the glass samples made with the frit including phosphorus was confirmed similar to that of the sample made with a present frit composition.