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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.
Nagai, Takayuki; Aoyama, Yusuke; Okamoto, Yoshihiro; Shibata, Daisuke*; Asakura, Kiyotaka*; Hasegawa, Takehiko*; Sato, Seiichi*; Fukaya, Akane*; Kikuchi, Tetsuya*; Hatakeyama, Kiyoshi*
JAEA-Research 2025-009, 122 Pages, 2025/11
JAEA-Research-2025-009.pdf:20.77MB
XAFS measurements in the soft X-ray region are suitable for evaluating the chemical state of the surface layer of a measurement sample because the X-ray transmittance is low. This study measured the K-edges of the glass-forming elements boron (B), oxygen (O), sodium (Na), and silicon (Si), as well as the L-edge of the waste component cerium (Ce), to verify the differences between the coagulated layer and the inside of simulated waste glasses made from raw glass compositions with increased alumina concentration. As a result, from the B K-edge XANES spectra, the proportion of B-O tetracoordinate sp
structures (BO) on the surface layer of the coagulated glass samples was higher than that on the cut surface inside the glass samples. On the other hand, the O K-edge XANES spectra showed differences by measuring points for each glass sample, but the trends of those differences varied between the glass samples. The reason is that the molten raw glass with increased alumina concentration has a high viscosity, making it impossible to produce waste glasses with a uniform composition. The Na and Si K-edge spectra showed no differences between the coagulated layer and the inside of glass samples. In addition, the Ce L-edge XANES spectra confirmed that the Ce valence in the coagulated layer of glass samples was more oxidized compared to that in the inside of glass samples.
Asahi, Yoshimitsu; Fukuda, Shigeki; Shiramizu, Daiki; Miyata, Koshi; Tone, Masaya; Katsuoka, Nanako; Maeda, Yuta; Aoyama, Yusuke; Niitsuma, Koichi; Kobayashi, Hidekazu; et al.
JAEA-Technology 2024-024, 271 Pages, 2025/03
JAEA-Technology-2024-024.pdf:33.98MB
JAEA-Technology-2024-024-hyperlink.zip:31.96MB
A glass melter for the vitrification process of highly active liquid waste in the Tokai Reprocessing Plant, TVF's 3rd melter, was built, and the glass of 18 vitrified waste canisters in weight was melted and poured through a cold test operation. The molten glass surface was covered by a cold cap from feeding fiberglass cartridges saturated with non-radioactive simulant liquid waste as raw material, whose components are equivalent to actual waste. Differences in inherent characteristics of the thermal behavior between the 2nd and the 3rd melter due to the difference in design were considered to establish the procedure to control the new melter. The melter's condition was stabilized at a higher glass temperature and the cooling of 1 kW less in each of the two main electrodes, compared to the 2nd one. Under 39 kW joule heating of the main electrodes with 26 Nm3/h coolant flow rate, it showed the capability to finish heating the bottom furnace in 5 hours before pouring, 2 hours shorter than the 2nd melter. Measurements of the temperature distributions in molten glass and casing surface yielded data that is efficient for developing a simulation model. After Platinum Group Elements (PGE) concentration saturates in the molten glass, feeding raw material and discharging glass were suspended to examine a holding state, indicating PGE settling could retard. During the holding test, observation of the melting process of the cold cap declared that the surface was covered by a thin layer with almost non-fluidity. It will be a reason for choosing the no-slip condition of a fluid calculation, even in the hot-top condition. The investigation of PGE discharging behavior by analyzing the elemental composition of poured glass showed the accumulated PGE amount in the 3rd melter is small compared to the 2nd melter. Inspection of the melter inside after draining out concluded that there were neither significant residual glass nor refractory fragments.
Gd
MnO
Ishii, Yuta*; Sakakura, Terutoshi*; Ishikawa, Yoshihisa*; Kiyanagi, Ryoji; Lustikova, J.*; Aoyama, Takuya*; Ogushi, Kenya*; Wakabayashi, Yusuke*; Kimura, Hiroyuki*; Noda, Yukio*
Physical Review B, 110(18), p.184404_1 - 184404_7, 2024/11
Times Cited Count：0 Percentile：3.43(Materials Science, Multidisciplinary)Aoyama, Yusuke; Katsuoka, Nanako; Nagai, Takayuki; Okamoto, Yoshihiro; Akiyama, Daisuke*; Kirishima, Akira*
no journal, ,
no abstracts in English
Aoyama, Yusuke; Tone, Masaya; Shiramizu, Daiki; Katsuoka, Nanako; Miyata, Koshi; Fukuda, Shigeki; Otaka, Hikaru; Kobayashi, Hidekazu; Kodaka, Akira
no journal, ,
In the new glass melter (the 3rd melter) at the Tokai Vitrification Facility (TVF), the bottom shape of the melter was changed from the square pyramid of the existing melter (the 2nd melter) to a cone to improve ability to discharge platinum group elements. To confirm the effect of the improvement, operational test using non-radioactive simulant of liquid waste containing platinum group elements was carried out. Discharging behavior of platinum group elements was evaluated in comparison with the 2nd melter.
Tone, Masaya; Shiramizu, Daiki; Katsuoka, Nanako; Aoyama, Yusuke; Miyata, Koshi; Fukuda, Shigeki; Otaka, Hikaru; Kobayashi, Hidekazu; Kodaka, Akira
no journal, ,
The replacement of existing 2nd glass melter with the 3rd glass melter is scheduled from 2025 to 2026 in Tokai Vitrification Facility, TVF. The bottom shape of 3rd melter was changed from the square pyramid of 2nd melter to a cone to improve ability to discharge platinum group elements. Therefore, it is necessary to confirm operational parameters appropriate for the 3rd melter with cone shaped bottom. Operational test using non-radioactive simulant of liquid waste was carried out to ensure the appropriate operational parameters that accommodate key control values such as glass temperature.
