Structural transformation of zinc in metakaolin-based potassium-geopolymer as revealed by X-ray absorption spectroscopy

Prihutami, P.*; Toda, Kanako*; Chaerun, R. I.; Oya, Yusuke*; Kikuchi, Ryosuke*; Otake, Tsubasa*; Sato, Tsutomu*; Saito, Takumi*

Applied Clay Science, 292, p.108330_1 - 108330_9, 2026/11

https://doi.org/10.1016/j.clay.2026.108330

Limited understanding of zinc (Zn) immobilization in altered geopolymers limits prediction of waste-form durability. This study examined the local structure and retention mechanism of Zn in a metakaolin-based potassium geopolymer by X-ray absorption spectroscopy (XAS). Zn-bearing samples were prepared from metakaolin, zinc chloride (ZnCl) solution, potassium silicate, and potassium hydroxide, cured at 40C and 25C for 48 h, and leached in deionized water for up to 90 days. Zn release was only 0.14%, with limited Al, Si, and Cl release. The main geopolymer framework was preserved after leaching. XAS showed that Zn was initially tetrahedrally coordinated with oxygen and linked to Si or Al tetrahedra. After leaching, Zn changed to octahedral coordination and formed a brucite-like Al-bearing co-precipitate, indicating strong Zn retention despite local structural alteration.

Applications of plastic scintillator fibers for the decommissioning of nuclear facilities

Morishita, Yuki; Abe, Tomohisa; Sasaki, Miyuki; Yamada, Tsutomu*; Nakasone, Takamasa*; Sanada, Yukihisa

Radiation Measurements, 198, p.107772_1 - 107772_11, 2026/11

https://doi.org/10.1016/j.radmeas.2026.107772

Accurate and rapid measurement of beta surface contamination is essential during the decommissioning of nuclear facilities. However, conventional Geiger Muller (GM) survey meters have limited detection areas and cannot measure contamination inside piping, resulting in significant labor and measurement inefficiency. In this study, we developed several plastic scintillation fiber (PSF) based detectors designed for wide-area surface monitoring, in-pipe contamination measurement, and drainage-channel monitoring. The PSF enables radiation detection along its entire length, allowing large-area scanning and insertion into narrow spaces. For surface measurements, a 10-m PSF arranged in a zigzag configuration was mounted under a cart, enabling efficient mapping of beta contamination over asphalt floor surfaces in Fukushima (demonstration up to 5 m 5 m). For piping applications, thin and flexible PSF probes were developed, enabling direct insertion into pipes with an inner diameter of 8 mm and achieving detection limits below the regulatory threshold of 4 Bq/cm; within one minute. Additionally, a waterproof PSF system was developed for monitoring radioactive contamination in drainage channels and successfully detected temporal fluctuations, including rainfall-induced increases in radioactivity. Overall, the developed PSF systems provide practical, versatile, and highly efficient alternatives to conventional survey meters for contamination monitoring in nuclear decommissioning environments.

Bulk modulus and electron density distribution of high-pressure polymorphs of Fe-Ti-O minerals

Yamanaka, Takamitsu*; Hattori, Takanori

Physics and Chemistry of Minerals, 53(3), p.21_1 - 21_11, 2026/09

https://doi.org/10.1007/s00269-026-01350-2

Bulk modulus and electron density distribution of high-pressure polymorphs of Fe-Ti-O minerals (FeO magnetite, FeTiO ulvspinel, FeTiO ilmenite, FeTiO pseudobrokite) are investigated by X-ray and neutron diffraction. The vacant sites in the unit cell have much larger volumes than cation sites in the all structures. Cation site partly occupied by Ti atom shows a smaller than that of only Fe atom and the compressibility of unit cell increases with increasing Ti content. The compressibility of the vacant sites is close to that of unit cells, but are much smaller than that of the cation site. The structure changes such as high-low electron spin transition, Jahn-Teller effect and hybridization in the Fe-O bonds are elucidated by present high-pressure experiments. The hybridization in the octahedral cation site was observed by molecular orbital calculation and it brings the deformation of the octahedral cation site, which triggers structure changes in the high-pressure polymorphs.

Real-time inversion of radioactive source distribution using air dose rate measurements via least absolute shrinkage and selection operator method

Shi, W.*; Machida, Masahiko; Okamoto, Koji*; Luo, X.*; Feng, W.*; Liu, X.*

Reliability Engineering & System Safety, 272, Part1, p.112538_1 - 112538_18, 2026/08

http://doi.org/10.1016/j.ress.2026.112538

The reliability of emergency response in severe nuclear accidents critically depends on robust real-time monitoring of radioactive source distributions. However, this safety function is challenged by physical constraints that create monitoring blind spots and by the inadequacy of static methods in tracking dynamic releases. To enhance the reliability and robustness of source term estimation, this study proposes a dynamic reconstruction framework based on LASSO regression with temporal regularization. A sliding-window time-penalty mechanism is introduced, imposing -norm constraints on inter-step source variations to ensure physical continuity. The contribution matrix and measurement vector are normalized to counteract biases from radiation shielding and time-varying intensities. Validation using a two-room model with internal shielding, with PHITS Monte Carlo simulation, demonstrates accurate reconstruction of dynamic sources from remote measurements. Temporal regularization enhances situational awareness by suppressing spatial aliasing: at sliding-window width (no regularization), hotspot locations fluctuate significantly, with quantitative mean absolute error fluctuations at around , whereas yields improved spatial consistency and the fluctuation quantities decrease to the range. Comparative analysis identifies as optimal in balancing accuracy and computational cost. This work establishes a more reliable pathway for dynamic hazard assessment, enabling accurate localization and intensity tracking under challenging conditions. The proposed framework provides a decision-support tool enhancing the resilience and safety of emergency management in nuclear facilities.

Data-driven on-site diagnostic technology: Predicting microbiologically influenced corrosion risk for ensuring long-term integrity (Contract research); FY2024 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Japan Agency for Marine-Earth Science and Technology*

JAEA-Review 2026-013, 86 Pages, 2026/07

JAEA-Review-2026-013.pdf:5.3MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), has been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") from FY2019. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station (1F), Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2024, this report summarizes the research results of the "Data-driven on-site diagnostic technology: predicting microbiologically influenced corrosion risk for ensuring long-term integrity" conducted in FY2024. The present study aims to establish an innovative on-site diagnostic protocol capable of predicting microbiologically influenced corrosion (MIC) risks with high accuracy. To achieve this, we combined high-throughput analytical methods, simulated field experiments, and data-driven statistical analyses. Environmental samples were collected in Fukushima Prefecture to characterize microbial community structures and to develop key technologies for on-site genetic diagnostics. Using these samples, we evaluated the iron-corroding potential under various culture conditions and designed experimental systems simulating 1F environment. A high-throughput testing framework was validated for its ability to measure actual iron corrosion. In parallel, statistical approaches integrating microbial community profiles with MIC activity data were applied, yielding useful insights into both their applicability and limitations. Further, fixation methods for microbial observation in corrosion samples were examined, and optimal conditions were identified. Overall, the project provided valuable information on environmental microbial communities, cultivation of corrosion-associated microorganisms, and data-driven statistical approaches. These results lay the groundwork for the development of biomarker-based, ubiquitous diagnostic technologies for MIC applicable to diverse field environments, including those around 1F site.

Development of a radiation resistant laser scanner and 3D modeling method using AI and image processing (Contract research); FY2024 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; The University of Osaka*

JAEA-Review 2026-009, 81 Pages, 2026/07

JAEA-Review-2026-009.pdf:5.42MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), has been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") from FY2019. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2024, this report summarizes the research results of the "Development of a radiation resistant laser scanner and 3D modeling method using AI and image processing" conducted in FY2024. This research focuses on developing a radiation-resistant 3D laser scanner and technologies to enhance the quality of point cloud data. A new scanner system was designed with a laser scanning head composed only of radiation-tolerant electrical and mechanical components, excluding semiconductors, and a control unit placed remotely in a low-radiation zone. The system aims to enable stable scanning in high-radiation environments. Its performance will be evaluated in comparison with commercial scanners. To address the sparsity of acquired point clouds, we are developing two complementary systems: one uses machine learning to complete and enhance point clouds through processes such as denoising, normalization, and interpolation; the other uses photogrammetry to reconstruct 3D data from image sets and integrate it with scanner-derived data. In FY2024, (1) Optical and electronic circuits were designed and assembled, and waveform collection and analysis software was developed to prepare for scanner detection efficiency evaluation. (2) A point cloud completion system incorporating AI was implemented, and methods for point cloud densification and completion were investigated. (3) A processing environment and workflow were established to integrate point clouds with photogrammetry, and 3D surface models were constructed. (4) Efficient scanning strategies under high-radiation conditions were analyzed, and a methodology for accuracy evaluation was studied. (5) The project was advanced through close coordination among research components and related institutions.

Development of core technologies for a wireless communication chipset with radiation tolerance (RF analog circuit development) (Contract research); FY2024 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Institute of Science Tokyo*

JAEA-Review 2026-005, 51 Pages, 2026/07

JAEA-Review-2026-005.pdf:3.06MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), has been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") from FY2019. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station (1F), Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2024, this report summarizes the research results of the "Development of core technologies for a wireless communication chipset with radiation tolerance (RF analog circuit development)" conducted in FY2024. The present study aims to establish a wireless communication system operable inside the reactor containment vessel and the reactor pressure vessel of 1F, and to develop key circuit technologies with radiation tolerance. The elemental developments will be carried out through the collaboration of two subthemes: RF analog circuit development and baseband circuit development. In this research, we are responsible for the RF analog circuit development, designing and implementing various circuits using radiation-tolerant silicon CMOS integrated circuit technology as well as diamond semiconductor devices. For silicon CMOS high-frequency analog circuits, RF analog signal processing circuits such as power amplifiers, low-noise amplifiers, mixers, and variable-gain amplifiers will be developed. For diamond semiconductor technology, device-level development of power amplifiers and power management circuits will be conducted. Ultimately, this project aims to realize prototype components of a wireless communication chipset capable of achieving a data rate of 2.5 Mbps or higher while withstanding a total ionizing dose exceeding 1 MGy.

Assessment report on research and development activities in FY2025 Activity; Research and development related to the accident at TEPCO's Fukushima Daiichi Nuclear Power Station (Mid-term Evaluations)

Fukushima Research and Engineering Institute*

JAEA-Evaluation 2026-004, 29 Pages, 2026/07

JAEA-Evaluation-2026-004.pdf:1.05MB
JAEA-Evaluation-2026-004-appendix(CD-ROM).zip:174.35MB

Japan Atomic Energy Agency (hereinafter referred to as "JAEA") consulted an assessment committee, "Evaluation Committee of Research and Development related to the Accident at TEPCO's Fukushima Daiichi Nuclear Power Station" (hereinafter referred to as "Committee") for ex-ante evaluations of "Research and Development Related to the Accident at TEPCO's Fukushima Daiichi Nuclear Power Station" in accordance with "General Guideline for the Evaluation of Government Research and Development (R&D) Activities" by Cabinet Office, Government of Japan, "Guideline for Evaluation of R&D in Ministry of Education, Culture, Sports, Science and Technology" and "Regulation on Conduct for Evaluation of R&D Activities" by JAEA. Based on a request from JAEA, the committee conducted a mid-evaluation of research and development activities in the current phase (April 2022 to March 2026). This report summarizes the results of the assessment by the Committee.

Reactive-transport model of fracture-matrix alteration by hyperalkaline fluid interactions; Influence of boundary conditions on sealing behavior

Sasamoto, Hiroshi; Arthur, R. C.*

Environmental Earth Sciences, 85(13), p.300_1 - 300_16, 2026/07

https://doi.org/10.1007/s12665-026-13029-6

Development of an electron spin resonance spectroscopy code for measuring carbonate radicals in tooth enamel and verification of its practicality using irradiated Japanese macaque teeth

Yamashita, Takuma*; Hayashi, Teppei*; Mitsuyasu, Yusuke*; Ono, Kenta*; Iwami, Satone*; Kino, Yasushi*; Sekine, Tsutomu*; Oka, Toshitaka; Takahashi, Atsushi*; Shimizu, Yoshinaka*; et al.

International Journal of Radiation Biology, 102(7), p.880 - 887, 2026/07

https://doi.org/10.1080/09553002.2025.2510676

no abstracts in English