Rail DRAGON: Long-reach Bendable Modularized Rail Structure for Constant Observation inside PCV

Yokomura, Ryota*; Goto, Masataka*; Yoshida, Takehito*; Warisawa, Shinichi*; Hanari, Toshihide; Kawabata, Kuniaki; Fukui, Rui*

IEEE Robotics and Automation Letters (Internet), 9(4), p.3275 - 3282, 2024/04

https://doi.org/10.1109/LRA.2024.3366022

To reduce errors in the remote control of robots during decommissioning, we developed a Rail DRAGON, which enables continuous observation of the work environment. The Rail DRAGON is constructed by assembling and pushing a long rail structure inside the primary containment vessel (PCV), and then repeatedly deploying several monitoring robots on the rails to enable constant observation in a high-radiation environment. In particular, we have developed the following components of Rail DRAGON: bendable rail modules, straight rail modules, a basement unit, and monitoring robots. Concretely, this research proposes and demonstrates a method to realize an ultralong articulated structure with high portability and workability. In addition, it proposes and verifies the feasibility of a method for deploying observation equipment that can be easily deployed and replaced, while considering disposal.

Background radiation monitoring via manned helicopter and development of technology for radiation monitoring via unmanned airplane for application of nuclear emergency response technique in the fiscal year 2022 (Contract research)

Futemma, Akira; Sanada, Yukihisa; Sasaki, Miyuki; Kawasaki, Yoshiharu*; Iwai, Takeyuki*; Hiraga, Shogo*; Haginoya, Masashi*; Matsunaga, Yuki*; Akutsu, Yuichiro*; Arai, Yoshinori*; et al.

JAEA-Technology 2023-026, 161 Pages, 2024/03

JAEA-Technology-2023-026.pdf:14.66MB

By the accident at Tokyo Electric Power Company's (TEPCO's) Fukushima Daiichi Nuclear Power Station (FDNPS), caused by tsunami triggered by the 2011 off the Pacific coast of Tohoku Earthquake, a large amount of radioactive material was released into the surrounding environment. After the accident, Airborne Radiation Monitoring (ARM) via manned helicopter has been utilized as a method to quickly and extensively measure radiation distribution surrounding FDNPS. In order to utilize ARM and to promptly provide the results during a nuclear emergency, information on background radiation levels, topographical features, and controlled airspace surrounding nationwide nuclear facilities have been prepared in advance. In the fiscal year 2022, we conducted ARM around the Mihama Nuclear Power Station of Kansai Electric Power Company (KEPCO), the Tsuruga Power Station of Japan Atomic Power Company (JAPC), and the Ikata Power Station of Shikoku Electric Power Company (YONDEN), and prepared information on background radiation doses and controlled airspace. In addition, we have developed an aerial radiation detection system via unmanned airplane, which is expected to be an alternative to ARM, during a nuclear emergency. This report summarizes the results and technical issues identified.

Results of groundwater pressure and hydro-chemical monitoring as part of environmental monitoring investigation in backfilling of shafts and tunnels of Mizunami Underground Research Laboratory (2022)

Takeuchi, Ryuji; Kokubu, Yoko; Nishio, Kazuhisa*

JAEA-Data/Code 2023-014, 118 Pages, 2024/02

JAEA-Data-Code-2023-014.pdf:4.77MB
JAEA-Data-Code-2023-014-appendix(CD-ROM).zip:249.03MB

The Tono Geoscience Center of Japan Atomic Energy Agency (JAEA) has been conducting the groundwater pressure and hydro-chemical monitoring to confirm the restoration process of the surrounding geological environment associated with the backfilling of shafts and tunnels of Mizunami Underground Research Laboratory (MIU). This report summarizes the data of the groundwater pressure and hydro-chemical monitoring from boreholes and forth at and around the MIU conducted in FY2022. In addition, unreported hydro-chemical monitoring data from the boreholes and forth at the MIU conducted in FY2021 were also compiled.

Interactive steering on in situ particle-based volume rendering framework

Kawamura, Takuma; Hasegawa, Yuta; Idomura, Yasuhiro

Journal of Visualization, 27(1), p.89 - 107, 2024/02

https://doi.org/10.1007/s12650-023-00945-z

Interactive in-situ steering is an effective tool for debugging, searching for optimal solutions, and analyzing inverse problems in fast and large-scale computational fluid dynamics (CFD) simulations. We propose an interactive in-situ steering framework for large-scale CFD simulations on GPU supercomputers. This framework employs in-situ particle-based volume rendering (PBVR), in-situ data sampling, and a file-based control that enables interactive communication of steering parameters, compressed particle data, and sampled monitoring data between supercomputers and user PCs. The parallelized PBVR is processed on the host CPU to avoid interference with CFD simulations on the GPU. We apply the proposed framework to a real-time plume dispersion analysis code CityLBM on GPU supercomputers. In the numerical experiment, we address an inverse problem to find a pollutant source from the monitoring data, and demonstrate the effectiveness of the human-in-the-loop approach.

Evaluation of the remaining spent extraction solvent in vermiculite after leaching tests via PIXE analysis

Arai, Yoichi; Watanabe, So; Hasegawa, Kenta; Okamura, Nobuo; Watanabe, Masayuki; Takeda, Keisuke*; Fukumoto, Hiroki*; Ago, Tomohiro*; Hagura, Naoto*; Tsukahara, Takehiko*

Nuclear Instruments and Methods in Physics Research B, 542, p.206 - 213, 2023/09

https://doi.org/10.1016/j.nimb.2023.07.003

Atomic reconstruction induced by uniaxial stress in MnP

Kozawa, Tatsuya*; Fujihara, Masayoshi; Uchihara, Takeru*; Mitsuda, Setsuo*; Yano, Shinichiro*; Tamatsukuri, Hiromu; Munakata, Koji*; Nakao, Akiko*

Scientific Reports (Internet), 13, p.13750_1 - 13750_8, 2023/08

https://doi.org/10.1038/s41598-023-40806-1

In condensed matter physics, pressure is frequently used to modify the stability of both electronic states and atomic arrangements. Under isotropic pressure, the intermetallic compound MnP has recently attracted attention for the interplay between pressure-induced superconductivity and complicated magnetic order in the vicinity. By contrast, we use uniaxial stress, a directional type of pressure, to investigate the effect on the magnetism and crystal structure of this compound. An irreversible magnetisation response induced by uniaxial stress is discovered in MnP at uniaxial stress as low as 0.04 GPa. Neutron diffraction experiments reveal that uniaxial stress forms crystal domains that satisfy pseudo-rotational symmetry unique to the MnP-type structure. The structure of the coexisting domains accounts for the stress-induced magnetism. We term this first discovered phenomenon atomic reconstruction (AR) induced by uniaxial stress. Furthermore, our calculation results provide guidelines on the search for AR candidates. AR allows crystal domain engineering to control anisotropic properties of materials, including dielectricity, elasticity, electrical conduction, magnetism and superconductivity. A wide-ranging exploration of potential AR candidates would ensure that crystal domain engineering yields unconventional methods to design functional multi-domain materials for a wide variety of purposes.

Proposition of confirmation items on the borehole sealing for the disposal of radioactive waste

Murakami, Hiroaki; Nishiyama, Nariaki; Takeuchi, Ryuji; Iwatsuki, Teruki

Oyo Chishitsu, 64(2), p.60 - 69, 2023/06

https://doi.org/10.5110/jjseg.64.60

In order to confirm the quality control items for borehole closure in radioactive waste disposal projects, in-situ borehole sealing tests using bentonite material were conducted. As a result, the closure performance was successfully demonstrated by comparing the data of water injection tests conducted before and after the installation of the closure material. However, the breakthrough was observed after closing, probably due to high differential pressure applied to the seal section. Thus, it is important to ascertain throughout the entire operation that the borehole is adequately closed. The placement and specifications of the closure material should be determined according to the hydrogeological structure in the borehole. The confirmation items to use bentonite for sealing material are identified to be: to consider swelling and density loss in the borehole; to place the planned depth using appropriate emplacement technique; to be placed without damage to seals when use some backfilling materials, considering effect of permeability on adjacent seals.

Regulatory implementation of the occupational equivalent dose limit for the lens of the eye and underlying relevant efforts in Japan

Yokoyama, Sumi*; Hamada, Nobuyuki*; Tsujimura, Norio; Kunugita, Naoki*; Nishida, Kazutaka*; Ezaki, Iwao*; Kato, Masahiro*; Okubo, Hideki*

International Journal of Radiation Biology, 99(4), p.604 - 619, 2023/04

https://doi.org/10.1080/09553002.2022.2115160

In April 2011, the International Commission on Radiological Protection recommended reducing the occupational equivalent dose limit for the lens. Such a new occupational lens dose limit has thus far been implemented in many countries, and there are extensive discussions toward its regulatory implementation in other countries. In Japan, discussions in the Japan Health Physics Society (JHPS) began in April 2013 and in Radiation Council in July 2017, and the new occupational lens dose limit was implemented into regulation in April 2021. To share our experience, we have published a series of papers summarizing situations in Japan: the first paper based on information available by early 2017, and the second paper by early 2019. This paper (our third paper of this series) aims to review updated information available by mid-2022, such as regarding regulatory implementation of the new occupational lens dose limit, recent discussions by relevant ministries based on the opinion from the council, establishment process of safety and health management systems, the JHPS guidelines on lens dose monitoring and radiation safety, voluntary countermeasures of the licensees, development of lens dose calibration method, and recent studies on exposure of the lens in nuclear workers and biological effect on the lens.

Development of bearing units used in the rotating shaft system for power generation in the JAEA-Tokai Tandem accelerator

Otokawa, Yoshinori; Matsuda, Makoto; Abe, Shinichi

JAEA-Technology 2022-037, 23 Pages, 2023/03

JAEA-Technology-2022-037.pdf:5.38MB

Bearing units of rotating shaft system for power generation in the JAEA-Tokai Tandem accelerator had a short operating life from the beginning of the accelerator installation, and even after replacing the bearing unit, early failures often occurred. Therefore, the quantity and frequency of replacement are large, and a lot of time is spent in regular maintenance performed by opening the accelerator pressure vessel, and solving this problem has been a long-standing concern. As a result of considering the cause of this early failure, it was considered that the load caused by parallel, angular, and axial misalignment of the upper and lower bearing units was the cause. In order to solve this problem, we have developed a bearing unit having metal disc-spring couplings in the upper and lower flanges to allow for parallel, angular, and axial misalignment of bearing units. As a result, it is now possible to allow variations in the distance between castings and parallel, angular, and axial misalignment of the upper and lower bearing units. By installing the developed new bearing unit on the rotating shaft system and making improvements while continuing to use it in actual operation, we succeeded in reducing the early failure and extending the operating life by more than double. With this development, the maintenance time has been reduced to one week by reducing the number of replacing the bearing unit. In addition, we have realized one regular maintenance that was carried out about three times a year, and as a benefit, we were able to reduce the amount of sulfur hexafluoride (SF) gas, which is a greenhouse gas, to about 3350% per year. We describe about development of new bearing units and these maintenance status from 2006 to 2020.

Background radiation monitoring via manned helicopter for application of technique of nuclear emergency response in the fiscal year 2021 (Contract research)

Futemma, Akira; Sanada, Yukihisa; Sasaki, Miyuki; Kawasaki, Yoshiharu*; Iwai, Takeyuki*; Hiraga, Shogo*; Haginoya, Masashi*; Matsunaga, Yuki*; Akutsu, Yuichiro*; Hokama, Tomonori; et al.

JAEA-Technology 2022-028, 127 Pages, 2023/02

JAEA-Technology-2022-028.pdf:15.21MB

A large amount of radioactive material was released by the nuclear disaster of Fukushima Daiichi Nuclear Power Station (FDNPS), Tokyo Electric Power Company, caused by the Great East Japan Earthquake and the following tsunami on March 11, 2011. After the nuclear disaster, airborne radiation monitoring via manned helicopter has been utilized to grasp rapidly and widely the distribution of the radioactive materials surrounding FDNPS. We prepare the data of background radiation dose, geomorphic characteristics and the controlled airspace surrounding nuclear facilities of the whole country in order to make effective use of the monitoring technique as a way of emergency radiation monitoring and supply the results during an accident of a facility. This report has summarized the knowledge noted above achieved by the aerial radiation monitoring around Ohi and Takahama nuclear power stations. In addition, the examination's progress aimed at introducing airborne radiation monitoring via an unmanned plane during a nuclear disaster and the technical issues are summarized in this report.