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.

Effect evaluation of partial termination of local sampling system in Hot Laboratory at Oarai Nuclear Engineering Institute; Airflow analysis on diffusion of radioactive material

Fukui, Makoto; Chizuwa, Shingo*; Kikuchi, Norihiro; Tanaka, Masaaki; Hashimoto, Makoto

JAEA-Review 2025-045, 42 Pages, 2025/12

JAEA-Review-2025-045.pdf:2.95MB

Hot laboratory (HL) at Oarai Nuclear Engineering Institute is a facility that conducts post-irradiation testing of fuel samples and reactor materials in hot cells. A set of local sampling system (LSS) is installed as a radiation control equipment to monitor the concentration of radioactive materials in the air in work environment. The LSS of HL equipped 23 sampling points, which are called as local sampling ends (LSE). It was recognized that air sampling had not operated at some of the LSE, and the concentration of radioactive materials in the air was not measured as prescribed. In this report, we evaluated the effect of partial termination of the LSS and the resulting increase in sampling intervals on the control of radioactive material concentrations in the air using airflow analysis assuming the diffusion of radioactive materials from hot cells in the controlled area of HL. The Service Area of the HL, where 10 LSEs were set in a wide area, was selected as an evaluation area. Airflow analysis including the diffusion of virtual contaminant particles was conducted on the evaluation area. Diffusion of virtual contaminants from hot cells and sampling of virtual contaminants at LSEs are simulated in the case of LSS in fully working and LSS with termination of 4 LSEs. The evaluation results showed that the effect of the partial termination of LSS and the resulting increase in sampling intervals on the control of the concentration of radioactive materials in the air are small.

Structural investigation of borosilicate glasses by using XAFS measurement in soft X-ray region, 5 (Joint research)

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.

Compliance measures at the Radioactive Waste Treatment Facilities at the Nuclear Science Research Institute; Aseismic reinforcement of the Radioactive Waste Treatment Facility No. 3, Waste Size Reduction and Storage Facility, and Waste Volume Reduction Facility

Iketani, Shotaro; Suzuki, Takeshi; Yokobori, Tomohiko; Sugawara, Satoshi; Yokota, Akira; Kikuchi, Genta; Muraguchi, Yoshinori; Kitahara, Masaru; Seya, Manato; Kurosawa, Tsuyoshi; et al.

JAEA-Technology 2025-001, 169 Pages, 2025/08

JAEA-Technology-2025-001.pdf:14.22MB

The radioactive waste treatment facilities at the Nuclear Science Research Institute includes the Radioactive Waste Treatment Facility No. 3, Waste Size Reduction and Storage Facility, and Waste Volume Reduction Facility. These three facilities come under the purview of the Act on the Regulation of Nuclear Source Material, Nuclear Fuel Material and Reactors, and are included under Class C of the act based on the seismic requirements specified in the Act. We assessed the seismic capacity of these three radioactive waste treatment facilities based on the current Building Standards Act, to verify whether they comply with the new regulatory requirements enforced by the Nuclear Regulation Authority (NRA) in the aftermath of the 2011 nuclear accident at the Fukushima Daiichi Nuclear Power Station operated by the Tokyo Electric Power Company. We found that the allowable stress of a few structural members used in the construction of the facilities did not meet the regulatory requirements. After studying the approval granted by the NRA for the construction plans, including the design and construction methods (design and construction plans) of the three facilities on March 5, 2021, we made aseismic reinforcement at these facilities between 2021 and 2022. This report presents an overview of the seismic design of these facilities and an outline of the aseismic reinforcement conducted, management system existing, safety measures adopted, and the preoperational inspections conducted at these facilities.

Annual report on the effluent control of low level liquid waste in Nuclear Fuel Cycle Engineering Laboratories FY2023

Kokubun, Yuji; Hosomi, Kenji; Seya, Natsumi; Nagaoka, Mika; Inoue, Kazumi; Koike, Yuko; Hasegawa, Ryo; Kubota, Tomohiro; Hirao, Moe; Iizawa, Shogo; et al.

JAEA-Review 2024-053, 116 Pages, 2025/03

JAEA-Review-2024-053.pdf:3.26MB

Based on the regulations (the safety regulation of Tokai Reprocessing Plant, the safety regulation of nuclear fuel material usage facilities, the radiation safety rule, the regulation about prevention from radiation hazards due to radioisotopes, which are related with the nuclear regulatory acts, the local agreement concerning with safety and environment conservation around nuclear facilities, the water pollution prevention act, and by law of Ibaraki Prefecture), the effluent control of liquid waste discharged from the Nuclear Fuel Cycle Engineering Laboratories of Japan Atomic Energy Agency has been performed. This report describes the effluent control results of the liquid waste in the fiscal year 2023. In this period, the concentrations and the quantities of the radioactivity in liquid waste discharged from the reprocessing plant, the plutonium fuel fabrication facilities, and the other nuclear fuel material usage facilities were much lower than the limits authorized by the above regulations.

Neutron flux and energy resolution of direct-geometry disk-chopper spectrometer AMATERAS at J-PARC

Nirei, Masami; Kofu, Maiko; Nakajima, Kenji; Kikuchi, Tatsuya*; Kawamura, Seiko; Murai, Naoki; Harada, Masahide; Inamura, Yasuhiro

Journal of Neutron Research, 26(2-3), p.75 - 82, 2024/09

https://doi.org/10.3233/JNR-230013

Multistep kinetics of the thermal dehydration/decomposition of metakaolin-based geopolymer paste

Shindo, Manami*; Ueoku, Aya*; Okamura, Wakana*; Kikuchi, Shin; Yamazaki, Atsushi*; Koga, Nobuyoshi*

Thermochimica Acta, 738, p.179801_1 - 179801_12, 2024/08

https://doi.org/10.1016/j.tca.2024.179801

Development of safety design technologies for sodium-cooled fast reactor coupled to thermal energy storage system with sodium-molten salt heat exchanger, 3; Reaction on sodium-nitrate molten salt

Kikuchi, Shin; Sato, Rika; Kondo, Toshiki; Umeda, Ryota; Yamano, Hidemasa

Dai-28-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu (Internet), 4 Pages, 2024/06

no abstracts in English

Development of a design optimization framework for sodium-cooled fast reactors, 3; Development of a prototype with user interface

Doda, Norihiro; Nakamine, Yoshiaki*; Yoshimura, Kazuo; Kuwagaki, Kazuki; Hamase, Erina; Yokoyama, Kenji; Kikuchi, Norihiro; Mori, Takero; Hashidate, Ryuta; Tanaka, Masaaki

Keisan Kogaku Koenkai Rombunshu (CD-ROM), 29, 6 Pages, 2024/06

As a part of the development of the "Advanced Reactor Knowledge- and AI-aided Design Integration Approach through the whole plant lifecycle (ARKADIA)" to utilize the knowledge obtained through the sodium-cooled fast reactors (SFRs) and combine the latest numerical simulation technologies, ARKADIA-Design is being developed to support the optimization of SFRs in the conceptual design stage. ARKADIA-Design consists of three systems of Virtual Plant Life System (VLS), Enhanced and AI-aided optimization System (EAS), and Knowledge Management System (KMS). A design optimization framework controls the linkage among the three systems through the interfaces in each system. In this study, we have developed a prototype of the framework for core design optimization using the coupled analysis functions in VLS and optimization control function in the linkage of EAS and VLS to investigate the applicability of the framework to the SFR design optimization process.

Annual report on the effluent control of low level liquid waste in Nuclear Fuel Cycle Engineering Laboratories FY2022

Kokubun, Yuji; Nakada, Akira; Seya, Natsumi; Nagaoka, Mika; Koike, Yuko; Kubota, Tomohiro; Hirao, Moe; Yoshii, Hideki*; Otani, Kazunori*; Hiyama, Yoshinori*; et al.

JAEA-Review 2023-052, 118 Pages, 2024/03

JAEA-Review-2023-052.pdf:3.67MB

Based on the regulations (the safety regulation of Tokai Reprocessing Plant, the safety regulation of nuclear fuel material usage facilities, the radiation safety rule, the regulation about prevention from radiation hazards due to radioisotopes, which are related with the nuclear regulatory acts, the local agreement concerning with safety and environment conservation around nuclear facilities, the water pollution control law, and by law of Ibaraki Prefecture), the effluent control of liquid waste discharged from the Nuclear Fuel Cycle Engineering Laboratories of Japan Atomic Energy Agency has been performed. This report describes the effluent control results of the liquid waste in the fiscal year 2022. In this period, the concentrations and the quantities of the radioactivity in liquid waste discharged from the reprocessing plant, the plutonium fuel fabrication facilities, and the other nuclear fuel material usage facilities were much lower than the limits authorized by the above regulations.