Frustrated random-singlet state with ice-type structural fluctuation in spinel titanates

Hanasaki, Noriaki*; Hattori, Takayuki*; Komoda, Takumi*; Minamoto, Kakuei*; Torigoe, Shuhei*; Yamashita, Satoshi*; Nakazawa, Yasuhiro*; Nakano, Takehito*; Yoshimi, Kohei*; Yashima, Mitsuharu*; et al.

Proceedings of the National Academy of Sciences of the United States of America, 123(1), p.e2517926123_1 - e2517926123_6, 2026/01

https://doi.org/10.1073/pnas.2517926123

Effect of repair welding location and number of welds performed on creep strength of Mod. 9Cr-1Mo steel welded joints

Yamashita, Hayato; Toyota, Kodai; Onizawa, Takashi; Yamamoto, Kenji*; Kubo, Koji*

Nihon Kikai Gakkai Rombunshu (Internet), 13 Pages, 2026/00

https://doi.org/10.1299/transjsme.25-00176

It is planned that Mod.9Cr-1Mo steel will be used as the structural material for the steam generator of the demonstration fast reactor. Creep strength of welded joints of Mod.9Cr-1Mo steel is lower than that of base metal at high temperature and long time. In addition, the creep strength of welded joints of Mod.9Cr-1Mo steel with repair welding is lower than that of without repair welding. In this study, the effects of the location and number of repair welds performed on the creep strength of welded joints of Mod.9Cr-1Mo steel were investigated, and a repair welding method was developed for the construction of the demonstration fast reactor. It was clarified that, regardless of the location and number of repair welds performed, the degradation in creep strength could be greatly reduced by performing the repair welding before post weld heat treatment (PWHT). Furthermore, it was found that the superposition of thermal history and the formation of a heat affected zone (HAZ) on the weld metal promote the coarsening of ferrite grains during creep and cause a slight reduction in creep strength. All repair welding was performed prior to PWHT, and a repair welding method was also developed to minimize thermal history superposition and weld metal HAZ formation.

Feasibility of individual dosimetry using RT-PHITS for patients with SPECT/CT imaging after Lu-DOTATATE peptide receptor radionuclide therapy

Miwa, Kenta*; Kakino, Ryo*; Sato, Tatsuhiko; Furuta, Takuya; Miyaji, Noriaki*; Yamao, Tensho*; Yamashita, Kosuke*; Terauchi, Takashi*

Physical and Engineering Sciences in Medicine, 48(2), p.949 - 957, 2025/06

https://doi.org/10.1007/s13246-025-01551-z

Radiotherapy package based on Particle and Heavy Ion Transport code System (RT-PHITS) enables to calculate the 3-dimensional dose distribution inside patients using their individual SPECT/CT images coupled with the Monte Carlo radiation transport simulation. The objective of this study is to evaluate the feasibility of individual dosimetry based on RT-PHITS for patients after Lu-DOTATATE peptide receptor radionuclide therapy.

Development of time-series point cloud data changes and automatic structure recognition system using Unreal Engine

Kato, Toru*; Takahashi, Hiroki*; Yamashita, Meguru*; Doi, Akio*; Imabuchi, Takashi

Artificial Life and Robotics, 30(1), p.126 - 135, 2025/02

https://doi.org/10.1007/s10015-024-00983-2

R&D status of digital technology on inverse estimation of radioactive source distributions and related source countermeasures; Fast Digital Twin Tech. in Decommissioning Field: 3D-ADRES-Indoor FrontEnd

Machida, Masahiko; Yamada, Susumu; Kim, M.; Tanaka, Satoshi*; Tobita, Yasuhiro*; Iwata, Ayako*; Aoki, Yuto; Aoki, Kazuhisa; Yanagisawa, Kenichi*; Yamaguchi, Takashi; et al.

RIST News, (70), p.3 - 22, 2024/09

Inside the Fukushima Daiichi Nuclear Power Plant (1F), there are many locations with high radiation levels due to contamination by radioactive materials that leaked from the reactor. These pose a significant obstacle to the smooth progress of decommissioning work. To help solve this issue, the Japan Atomic Energy Agency (JAEA), under a subsidy from the Ministry of Economy, Trade, and Industry's decommissioning and contaminated water management project, is conducting research and development on digital technologies to improve the radiation environment inside the decommissioning site. This project, titled "Development of Technology to Improve the Environment Inside Reactor Buildings (Enhancing Digital Technology for Environment and Source Distribution to Reduce Radiation Exposure)," began in April of FY 2023. In this project, the aim is to develop three interconnected systems: FrontEnd, Pro, and BackEnd. The FrontEnd system, based on the previously developed 3D-ADRES-Indoor (prototype) from FY 2021-2022, will be upgraded to a high-speed digital twin technology usable on-site. The Pro system will carry out detailed analysis in rooms such as the new office building at 1F, while the BackEnd system will serve as a database to centrally manage the collected and analyzed data. This report focuses on the FrontEnd system, which will be used on-site. After point cloud measurement, the system will quickly create a 3D mesh model, estimate the radiation source from dose rate measurements, and refine the position and intensity of the estimated source using recalculation techniques (re-observation instructions and re-estimation). The results of verification tests conducted on Unit 5 are also presented. Furthermore, the report briefly discusses the future research and development plans for this project.

Development of time-series point cloud data changes and automatic structure recognition system using Unreal Engine

Kato, Toru*; Takahashi, Hiroki*; Yamashita, Meguru*; Doi, Akio*; Imabuchi, Takashi

Proceedings of 29th International Symposium on Artificial Life and Robotics (AROB 29th 2024) (Internet), p.1097 - 1100, 2024/01

Summary report in FY2022 of subsidy program for the Project of Decommissioning and Contaminated Water Management "Development of Analysis and Estimation Technology for Characterization of Fuel Debris (Development of Technologies for Enhanced Analysis Accuracy, Thermal behavior Estimation, and Simplified Analysis of Fuel Debris)" started in FY2021

Koyama, Shinichi; Ikeuchi, Hirotomo; Mitsugi, Takeshi; Maeda, Koji; Sasaki, Shinji; Onishi, Takashi; Tsai, T.-H.; Takano, Masahide; Fukaya, Hiroyuki; Nakamura, Satoshi; et al.

Hairo, Osensui, Shorisui Taisaku Jigyo Jimukyoku Homu Peji (Internet), 216 Pages, 2023/11

https://en.dccc-program.jp/wp-content/uploads/20231117_JAEA.pdf

In FY 2021 and 2022, JAEA perfomed the subsidy program for "the Project of Decommissioning and Contaminated Water Management (Development of Analysis and Estimation Technology for Characterization of Fuel Debris (Development of Technologies for Enhanced Analysis Accuracy, Thermal Behavior Estimation, and Abbreviated Analysis))" started in FY 2021. This presentation material summarized the results of the project, which will be available shortly on the website of Management Office for the Project of Decommissioning, Contaminated Water and Treated Water Management.

Improvement of nano-polycrystalline diamond anvil cells with Zr-based bulk metallic glass cylinder for higher pressures; Application to Laue-TOF diffractometer

Yamashita, Keishiro*; Komatsu, Kazuki*; Ohara, Takashi; Munakata, Koji*; Irifune, Tetsuo*; Shimmei, Toru*; Sugiyama, Kazumasa*; Kawamata, Toru*; Kagi, Hiroyuki*

High Pressure Research, 42(1), p.121 - 135, 2022/03

https://doi.org/10.1080/08957959.2022.2045982

Summary results of subsidy program for the "Project of Decommissioning and Contaminated Water Management (Development of Analysis and Estimation Technology for Characterization of Fuel Debris (Development of Technologies for Enhanced Analysis Accuracy and Thermal Behavior Estimation of Fuel Debris))"

Koyama, Shinichi; Nakagiri, Toshio; Osaka, Masahiko; Yoshida, Hiroyuki; Kurata, Masaki; Ikeuchi, Hirotomo; Maeda, Koji; Sasaki, Shinji; Onishi, Takashi; Takano, Masahide; et al.

Hairo, Osensui Taisaku jigyo jimukyoku Homu Peji (Internet), 144 Pages, 2021/08

https://dccc-program.jp/3797

JAEA performed the subsidy program for the "Project of Decommissioning and Contaminated Water Management (Development of Analysis and Estimation Technology for Characterization of Fuel Debris (Development of Technologies for Enhanced Analysis Accuracy and Thermal Behavior Estimation of Fuel Debris))" in 2020JFY. This presentation summarized briefly the results of the project, which will be available shortly on the website of Management Office for the Project of Decommissioning and Contaminated Water Management.

GPU acceleration of multigrid preconditioned conjugate gradient solver on block-structured Cartesian grid

Onodera, Naoyuki; Idomura, Yasuhiro; Hasegawa, Yuta; Yamashita, Susumu; Shimokawabe, Takashi*; Aoki, Takayuki*

Proceedings of International Conference on High Performance Computing in Asia-Pacific Region (HPC Asia 2021) (Internet), p.120 - 128, 2021/01

https://doi.org/10.1145/3432261.3432273

We develop a multigrid preconditioned conjugate gradient (MG-CG) solver for the pressure Poisson equation in a two-phase flow CFD code JUPITER. The MG preconditioner is constructed based on the geometric MG method with a three-stage V-cycle, and a RB-SOR smoother and its variant with cache-reuse optimization (CR-SOR) are applied at each stage. The numerical experiments are conducted for two-phase flows in a fuel bundle of a nuclear reactor. The MG-CG solvers with the RB-SOR and CR-SOR smoothers reduce the number of iterations to less than 15% and 9% of the original preconditioned CG method, leading to 3.1- and 5.9-times speedups, respectively. The obtained performance indicates that the MG-CG solver designed for the block-structured grid is highly efficient and enables large-scale simulations of two-phase flows on GPU based supercomputers.