Neutronics-thermal-hydraulics-coupled transient analysis for reactor power change in an inclined offshore floating boiling water reactor

Fukuda, Kodai; Obara, Toru*; Suyama, Kenya

Nuclear Technology, 211(5), p.963 - 973, 2025/05

https://doi.org/10.1080/00295450.2024.2368966

Removal of JMTR secondary cooling system cooling tower and asbestos slate material

Kagi, Takumi; Araki, Daisuke; Yanai, Tomohiro; Kuwabara, Ryota; Sugaya, Naoto; Nishimura, Arashi; Ebisawa, Hiroyuki; Watahiki, Shunsuke; Tanimoto, Masataka

JAEA-Testing 2024-005, 24 Pages, 2025/03

JAEA-Testing-2024-005.pdf:6.92MB

On September 9, 2019, the strong winds of Typhoon No. 15 caused the secondary cooling system cooling tower of the Japan Materials Testing Reactor (JMTR) to collapse. The cooling tower collapsed from east to west, and four secondary cooling system pipes connected to it also pulled down, and all four pipes were damaged at their riser sections. Because the exterior wall slate material (asbestos slate) covering the collapsed cooling tower contained asbestos, it was necessary to ensure the safety of the workers and to minimize the impact of asbestos on the surrounding environment during the removal work. This report describes the work plan devised while complying with the relevant laws and the results of its implementation to ensure worker safety and reduce the environmental impact of asbestos during the removal work, storage management, and transportation of the asbestos slate material from the cooling tower of the secondary cooling system.

Present status of the JAEA-AMS-TONO (2023); Primarily on the cause of the varistor damage

Matsubara, Akihiro*; Fujita, Natsuko; Miyake, Masayasu; Ishii, Masahiro*; Omae, Akiomi*; Maeta, Yusuke; Uno, Sadanori*

Dai-36-Kai Tandemu Kasokuki Oyobi Sono Shuhen Gijutsu No Kenkyukai Hokokushu, p.125 - 129, 2025/03

We will report on the maintenance and management of JAEA-AMS-TONO-5MV (NEC 15SDH-2, maximum terminal voltage 5.0 MV) located at the Toki Geochronology Research Institute, Tono Geoscience Center, Japan Atomic Energy Agency; (1) Regarding damage to varistors in beamline equipment and its causes, (2) Phenomena that suggest a vacuum leak in the accelerator tube of a tandem accelerator and its countermeasures.

Remote alpha/beta measurement system with support vector machine algorithm

Morishita, Yuki; Miyamura, Hiroko; Sato, Yuki; Matsubara, Jun*; Sumali, B.*; Mitsukura, Yasue*

Nuclear Instruments and Methods in Physics Research A, p.170368_1 - 170368_16, 2025/03

https://doi.org/10.1016/j.nima.2025.170368

Decommissioning nuclear reactor sites presents challenges due to the presence of various radionuclides, including alpha emitters (e.g., Pu, Am, Cm) and beta emitters (e.g., Cs, Sr-Y), which pose significant internal exposure risks to workers. Traditional measurement methods require multiple instruments and are time-consuming, particularly in high gamma-ray environments. To address these issues, we developed a remote alpha and beta discrimination measurement system that integrates a stilbene scintillator detector with a silicon photomultiplier, enabling simultaneous detection of both alpha and beta particles. This study further incorporates machine learning techniques, specifically Support Vector Machines (SVM), for automatic discrimination, eliminating the need for user-defined thresholds and ensuring consistent operational conditions. The system was tested with known radiation sources, demonstrating over 96% classification accuracy for alpha and beta particles. Measurements conducted in motion effectively identified contamination sources, confirming the system's capability for real-time analysis. This innovative approach enhances radiation safety and efficiency in nuclear decommissioning operations, making it particularly beneficial in environments where human access is limited.

Validation of crystal surface scattering method for downsizing accelerator mass spectrometry

Jinno, Satoshi; Matsubara, Akihiro*; Fujita, Natsuko; Kimura, Kenji

Nuclear Instruments and Methods in Physics Research B, 557, p.165545_1 - 165545_4, 2024/12

https://doi.org/10.1016/j.nimb.2024.165545

This study introduces the development of a downsized Accelerator Mass Spectrometry (AMS) system aiming to enhance accessibility and cost-effectiveness in radiocarbon analysis. The "crystal surface stripper method" is introduced as a solution to challenges in AMS downsizing, demonstrating effective ion detection with a smaller angular spread compared to conventional gas stripper methods. The experimental results provide insights into charge conversion capabilities, scattering angle broadening, and energy loss associated with surface scattering.

None

Matsubara, Ryuta*; Ueno, Fuga*; Iwata, Hajime; Inagaki, Yaohiro*; Okubo, Takahiro*

NUMO-TR-24-03, p.55 - 61, 2024/10

https://www.numo.or.jp/technology/technical_report/pdf/NUMO-TR-24-03.pdf

no abstracts in English

Survey of asbestos in piping insulation in specified facilities of JMTR

Kuwabara, Ryota; Yanai, Tomohiro; Kagi, Takumi; Tanimoto, Masataka

JAEA-Review 2024-036, 43 Pages, 2024/09

JAEA-Review-2024-036.pdf:4.18MB

The Japan Materials Testing Reactor (JMTR) has a main facility and a specified facility, and construction began in 1967. Therefore, there is concern that asbestos was used in various parts of the facility since it was built before asbestos was regulated. Asbestos has very good properties such as durability, heat resistance, chemical resistance, and electrical insulation, and there is a high probability that asbestos was contained in components and building materials at that time. Therefore, the investigation was focused on specified facilities outside the controlled areas, and an investigation was conducted on heat insulators wrapped around piping installed in the facilities. Of the various systems of piping installed in the facilities, we investigated the presence or absence of asbestos in the heat insulators, especially in piping that had been installed for a long period of time. Inhalation of asbestos can cause diseases such as lung cancer and mesothelioma, so when buildings are demolished or renovated, there is a legal requirement to conduct a preliminary investigation to determine the presence of asbestos. Therefore, it is important to understand the status of asbestos usage within the facility in advance, and we believe that it can also be applied to the formulation of plans for the dismantling and removal of equipment and devices during future decommissioning. As a result of the investigations, asbestos was found in the thermal insulation, especially in the elbow where the piping is bent. The results of these investigations are presented in this report.

A Cause and the measures that the expansion joint of the steam plumbing for Reprocessing Plants damaged

Nishino, Shohei; Nishida, Tetsuro; Kawasaki, Ichio; Motohashi, Masahiro; Kambara, Takashi*; Suzuki, Takaichi*; Kinoshita, Masato*

Nihon Hozen Gakkai Dai-20-Kai Gakujutsu Koenkai Yoshishu, p.14 - 21, 2024/08

Steam is used to a process and air conditioning in Nuclear fuel Cycle engineering Laboratories (NCL). The steam is used mainly in Reprocessing Plant, and it is supplied by two steam plumbing. A leak occurred from the steam plumbing in November, 2022. As a result of cause investigation, I estimated that it had leaked by a water hammer caused for the trouble of the steam trap.

Evaluation of the effects of bentonite colloids

Matsubara, Ryuta*; Hamamoto, Takafumi*; Ishidera, Takamitsu

NUMO-TR-24-01, p.91 - 94, 2024/05

no abstracts in English

Generality assessment of a model considering heterogeneous cancer cells for predicting tumor control probability for stereotactic body radiation therapy against non-small cell lung cancer

Saga, Ryo*; Matsuya, Yusuke; Obara, Hideki*; Komai, Fumio*; Yoshino, Hironori*; Aoki, Masahiko*; Hosokawa, Yoichiro*

Advances in Radiation Oncology (Internet), 9(4), p.101437_1 - 101437_5, 2024/04

https://doi.org/10.1016/j.adro.2023.101437

The curative effects after radiotherapy are evaluated by the index of tumor control probability (TCP), and the treatment regimen has been determined empirically based on clinical experiences. In recent years, in order to determine TCP for any treatment regimens based on cell experiments, it is necessary to consider the existence of radioresistant cancer stem cells, which are included in tumors at from a few to several tens of percent. Our previous study has proposed an integrated microdosimetric-kinetic (IMK) model that explicitly considers cancer stem cells, and successfully reproduced cancer cell death obtained from cell experiments and clinical TCP. However, the verification so far has been limited to comparison with the clinical data of Hirosaki University Hospital, and comparative verification with clinical data of other facilities has not been performed. In this study, we focused on the stereotactic radiotherapy against non-small cell lung cancer that prescribes a large dose at once, and compared the public data collected by meta-analysis with the IMK model. As a result, it was found that the IMK model considering cancer stem cells well reproduced the clinical TCP regardless of the observed facility type. This work would contribute to the development of technology for predicting curative effects of radiotherapy with high precision.