Effects of melting and coagulating conditions on the structure of simulated waste glasses

Nagai, Takayuki; Aoyama, Yusuke; Okamoto, Yoshihiro; Hasegawa, Takehiko*; Sato, Seiichi*; Kikuchi, Tetsuya*; Hatakeyama, Kiyoshi*

JAEA-Research 2025-012, 43 Pages, 2026/01

JAEA-Research-2025-012.pdf:6.99MB

In the vitrification process study of high-level radioactive waste liquids, precipitates present in the simulated waste glasses are detected by X-ray diffraction (XRD), but due to the state of the precipitates (fine size, extremely small amount), precipitate peaks cannot be observed in the XRD pattern. We have evaluated the glass structure of simulated waste glasses prepared under different melting and coagulated conditions using Raman spectroscopy and other methods, in this study. The simulated waste glass, which does not show any precipitate peaks in the XRD pattern, was subjected to Raman spectroscopy, and it was confirmed that precipitate particles in the glass phase could be detected. And it was confirmed that in glass preparation, stirring the molten glass and increasing the cooling rate from the molten state are likely to suppress the formation of precipitate particles in the glass phase. The evaluation of the Si-O bridging structure of the glass revealed no difference in the Si-O bridging structure between areas with and without precipitates. The precipitates detected by Raman spectroscopy are not ceria (CeO) or calcium molybdate (CaMoO), but they are presumed to be compounds such as spinel. In experiments using synchrotron radiation, X-ray transmission images of the internal state of glasses were observed, and it was confirmed that stirring molten glass is effective in reducing bubbles present in the glass phase. The XAFS measurements of Mo K-edge, Ce L-edge, and Si K-edge confirmed that stirring the molten glass does not affect the chemical state of Mo, Ce, and Si contained in the glass.

Solidification treatment of simulated decontamination equipment sludge using alkali-activated materials

Matsuzawa, Kazuki*; Yamamoto, Takeshi*; Taniguchi, Takumi; Osugi, Takeshi

Konkurito Kogaku Rombunshu, 36, p.37 - 47, 2025/07

https://doi.org/10.3151/crt.36.37

To dispose the decontamination sludge made from contaminated water in Fukushima Daiichi Nuclear Power Station using alkali-activated materials (AAM), we solidified barium sulfate powder (BS) and potassium hexacyanocobalt(II)-ferrate(II) powder (FCN) with AAM and searched proper compositions corresponding to the standards. At first, we made solidified bodies controlling HO/base ratio, Si/Al molar ratio, and Na/Si molar ratio. When base materials consisted of metakaolin and blast-furnace slag, we found out some proper compositions and two applicable concentrations of solutions to make solidified bodies corresponding to the standards. Secondly, using solutions with the applicable concentrations, we made solidified bodies controlling the amounts of BS, BS+FCN, and HO. The maximum amount of BS+FCN at the proper compositions was larger than that of BS.

Investigation of chemical state of uranium included in simulated waste glass

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

2023-Nendo "Busshitsu, Debaisu Ryoiki Kyodo Kenkyu Kyoten" Kenkyu Seika, Katsudo Hokokusho (Internet), 1 Pages, 2024/07

no abstracts in English

Structural investigation of simulated waste glass surface drained in operation confirmation test of 3rd TVF glass melter

Nagai, Takayuki; Hasegawa, Takehiko*

JAEA-Research 2023-008, 41 Pages, 2023/12

JAEA-Research-2023-008.pdf:7.52MB

To reduce the risks posed by stored the high-level radioactive liquid waste (HAW), Tokai Vitrification Facility (TVF) is working to produce the HAW into vitrified bodies. With the aim of steady vitrification of HAW in TVF, the vitrification technology section has manufactured a new 3rd melter with an improved bottom structure and is working to verify the performance of this melter. In this study, solidified glass samples were taken from simulated vitrified bodies produced by flowing molten glass during the bottom drain-out test in the operation confirmation of the TVF 3rd melter. And the properties of the surface layer and fracture surface of the vitrified bodies were evaluated by using Raman spectroscopy, synchrotron radiation XAFS measurement, and laser ablation inductively coupled plasma atomic emission spectroscopy (LA ICP-AES) analysis. As a result of measuring the surface layer and fracture surface of the solidified samples produced on an actual scale, a slight difference was confirmed between the properties of the surface layer and those of the fracture surface. Since the chemical composition of these simulated vitrified bodies does not contain platinum group elements, it is expected that the glass structure of solidified glass samples is different from that of the actual vitrified body. However, this sample measuring was a valuable opportunity to evaluate samples produced by using the direct energized joule heating method. The properties of cullet used the operation confirmation of the TVF 3rd melter and the cullet of another production lot were measured and analyzed in the same manner under the measuring conditions of solidified glass samples. As a result, it was confirmed that cullet with different producing histories have different glass structures even with the same chemical composition, and that differences in glass structures remain in the glass samples after melting these cullet.

Structural investigation of borosilicate glasses by using XAFS measurement in soft X-ray region, 3 (Joint research)

Nagai, Takayuki; Okamoto, Yoshihiro; Yamagishi, Hirona*; Shibata, Daisuke*; Kojima, Kazuo*; Hasegawa, Takehiko*; Sato, Seiichi*; Fukaya, Akane*; Hatakeyama, Kiyoshi*

JAEA-Research 2023-004, 45 Pages, 2023/09

JAEA-Research-2023-004.pdf:6.07MB

The local structure of glass-forming elements and waste elements in borosilicate glasses varies with its chemical composition. In this study, simulated waste glass samples were prepared and the chemical state regarding boron (B), silicon (Si) and waste elements of iron (Fe), cesium (Cs) were estimated by using XAFS measurement in soft X-ray region. To understand the chemical stability of simulated waste glasses, XANES spectra of B K-edge, Fe L, L-edge, and Cs M, M-edge were measured on the glass surface exposed to the leachate. As a result, it was found that the glass surface exposed to the leachate was changed and it was difficult to obtain a clear XANES spectrum. From the B K-edge XANES spectra on glass surfaces exposed to the leachate, an increase in three-coordination of B-O (BO) and a decrease in four-coordination of B-O (BO) were observed compared to the glass surfaces before immersion. The XANES spectra of Fe L, L-edge, and Cs M, M-edge show that as the exposure time in the leachate increases, the Cs present on the glass surface dissolves into the leachate. The XANES spectra of Si K-edge were measured on simulated waste glass surfaces before immersion, and it was confirmed that the change in XANES spectra given by NaO concentration had a larger effect than the waste component concentration.

Structural evaluation of coagulated surface of simulated waste glass by using Raman spectroscopy

Nagai, Takayuki

JAEA-Research 2022-014, 84 Pages, 2023/02

JAEA-Research-2022-014.pdf:22.26MB

Most of the simulated waste glasses used for physical property evaluation are processed into a shape suitable for the measurement method from glass gob obtained by slowly cooling molten glass to room temperature. However, the actual vitrified waste glass material is obtained by cooling and being coagulated the glass drained from the bottom of glass melter into the canister. In this study, Raman spectroscopy was performed on the coagulated surface of molten simulated waste glass in the depth direction to evaluate the state of the Si-O bridging structure near the coagulated glass surface. The Raman spectra measured from the surface to the depth direction near the surface of the glasses produced by several melting and coagulation conditions of molten simulated waste glass cullet in the air atmosphere, and it was confirmed that there were changes in these spectra. On the other hand, the raw material glass cullet and the surface of the glass solidified in argon gas atmosphere showed little change in the spectrum in the depth direction, and the Si-O bridging structure near the glass surface was similar. It was also confirmed that the spectrum change in the depth direction measurement was small for the cut surface of the glass, and that the change in the spectrum for the broken glass fracture surface was also small. For glasses with a large change in Raman spectra in the depth direction near the coagulated surface, the molten glass was cooled from the molten state to room temperature in a muffle furnace with air atmosphere. That is, the magnitude of the spectral change with respect to the depth direction depends on the time from the molten state to coagulation. In order to confirm the reason why the number of bridging oxygen in the Si-O bridging structure is small on the coagulated surface of glass, the XANES spectra of Si-K edge and Ce-L3 edge were measured by XAFS on the coagulated surface and the cutting face. As a result, the Si-K edge peak on the coagulated surface is

Cement solidification technology for waste

Haga, Kazuko*; Shibuya, Kazutoshi*; Osugi, Takeshi; Yamada, Kazuo*

Haikibutsu Shigen Junkan Gakkai-Shi, 33(6), p.435 - 447, 2022/11

https://doi.org/10.3985/mcwmr.33.435

Cement solidification technology has been widely applied to waste stabilization and treatment because cement is not only relatively stable in physical and chemical properties after hardening, but also an inexpensive and easy-to-handle solidification material and treatment facilities are simple and economical. As the current status of cement solidification treatment technologies for wastes, this paper describes a study on cement solidification of wastes from the Fukushima Daiichi Nuclear Power Plant accident, the current status of cement solidification treatment of low-level radioactive wastes, and cement solidification technology for incinerated ash, and review previous research results on immobilization and leaching mechanisms of heavy metals in cement solidified products.

Structural investigation of borosilicate glasses by using XAFS measurement in soft X-ray region, 2 (Joint research)

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

JAEA-Research 2022-008, 37 Pages, 2022/10

JAEA-Research-2022-008.pdf:5.27MB

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 chemical state regarding boron (B), 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 simulated waste glass surfaces after immersion test to investigate the long chemical stability. (1) As the leaching time of glass samples in immersion test passed, the Cs M, M-edge XANES spectra disappeared and the Fe L, L-edge spectra changed. (2) A new compound was formed on the sample surface after the immersion test, and these changes in the surface state were confirmed by Raman spectroscopy. However, it became difficult to obtain a clear B K-edge XANES spectrum by forming a compound on glass surfaces. The Si K-edge XANES spectra of borosilicate glass frits with different NaO content 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 intensity of the Si K-edge peak is maximum when the NaO content in glass frits was about 7wt%.

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.

Investigation of chemical state of uranium included in simulated waste glass

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

2020-Nendo "Busshitsu, Debaisu Ryoiki Kyodo Kenkyu Kyoten" Oyobi "Hito, Kankyo To Busshitsu O Tsunagu Inobeshion Soshutsu Dainamikku, Araiansu" Kenkyu Seika, Katsudo Hokokusho (CD-ROM), 1 Pages, 2021/11

no abstracts in English