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Watanabe, Kaho; Nishiyama, Yutaka; Kakuta, Masakatsu*; Hayasaka, Toshiro*
JAEA-Testing 2025-003, 52 Pages, 2025/11
JAEA-Testing-2025-003.pdf:5.17MB
There is an emergency response team against nuclear facilities accidents of Japan Atomic Energy Agency (JAEA). The team is managed by the Maintenance and Operation Section for Remote Control Equipment. One of the important tasks of the team is purchasing remote-control robots, the quadrupedal robots (called Spot), were purchased in 2022 and 2023 to prepare for the nuclear disaster in JAEA. This report shows the remote-control manual for the quadrupedal robots (Spot), and it is focused on the necessary operations for the team.
Watanabe, Kaho; Nishiyama, Yutaka; Imahashi, Masaki; Taguchi, Yuji; Iitsuka, Yoshinobu; Ouchi, Takuya; Inoue, Shuichi; Kozawa, Takayuki; Nemoto, Takahiro; Sugaya, Takashi; et al.
JAEA-Testing 2025-001, 56 Pages, 2025/11
JAEA-Testing-2025-001.pdf:2.61MB
There is an emergency response team against 7 nuclear facilities (JRR-3 in Nuclear Science Research Institute, Tokai Reprocessing Plant (TRP) in Nuclear Fuel Cycle Engineering Laboratories, JMTR, HTTR and Joyo in Oarai Research and Development Institute, Prototype Fast Breeder Reactor Monju, Fugen Decommissioning Engineering Center) accidents of Japan Atomic Energy Agency (JAEA). The team is in Naraha Center for Remote Control Technology Development (NARREC). On site surveys which are about the situations and the access entering route of the 7 site emergencies were conducted by the team in 2021. And the results of the surveys made the team get two Spot (quadrupedal robots) in 2022. This is because the team thought using Spot gave operators the less exposure than using crawler robots which had been belonged to the team. After that it was confirmed that the Spot have the ability to respond to the emergency on the route of each facility in 2023. This report shows the results of the Spot's run function (= shooting videos, running oversteps, running up and down stairs, and so on) confirmation about 6 facilities (JRR-3, JMTR, HTTR, Joyo, Monju and Fugen).
Cl
Aoki, So; Abe, Yosuke; Abe, Hiroshi*; Watanabe, Yutaka*; Yamamoto, Masahiro*
Corrosion Science, 255, p.113119_1 - 113119_10, 2025/10
Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)This study aimed to visualise the distribution of chloride in the corroded crevice of stainless steel and to evaluate the chloride content quantitatively. Crevice corrosion tests were carried out using Cl, a radioactive isotope of chloride, as a tracer in NaCl test solutions. After crevice corrosion tests, stainless steel specimens were placed on an imaging plate. The imaging plate was sensitised by 
-ray emitted by Cl adhering to the crevice. As a result, the chloride distribution in the corroded area inside the crevice was visualised. A calibration curve for the amount of Cl was obtained from the relationship between the time of photosensitivity to -ray emitted by Cl and the luminance of the imaging plate. The chloride content in the corroded crevice was quantitatively evaluated based on the calibration curve. These visualisation and quantitative evaluation methods were also applied to tests in which specimens were left in pure water after crevice corrosion tests, and the behaviour of chloride in crevice corrosion was discussed.
Nagata, Shuhei*; Ogawa, Yusuke*; Suzuki, Satoru*; Igarashi, Takahiro; Nagaoka, Toru*; Mitsui, Seiichiro; Watanabe, Yutaka*; Nishikata, Atsushi*
NUMO-TR-25-03, p.46 - 51, 2025/10
no abstracts in English
Otsuka, Takaharu*; Tsunoda, Yusuke*; Shimizu, Noritaka*; Utsuno, Yutaka; Abe, Takashi*; Ueno, Hideki*
European Physical Journal A, 61(5), p.126_1 - 126_45, 2025/05
Times Cited Count：11 Percentile：98.77(Physics, Nuclear)no abstracts in English
Horiguchi, Naoki; Yoshida, Hiroyuki; Kaneko, Akiko*; Abe, Yutaka*
Physics of Fluids, 37(3), p.033333_1 - 033333_20, 2025/03
Times Cited Count：0 Percentile：0.00(Mechanics)In a severe accident, as molten fuel is assumed to behave as a wall-impinging jet in a shallow coolant pool, atomize and accumulate as fuel debris, it is important to reveal the atomization mechanisms of the wall-impinging jet. This study aimed to reveal the atomization mechanisms in the vortex-like flow of a wall-impinging jet in a shallow pool of a liquid-liquid system, focusing on droplet formation as an elementary process of atomization. To quantitatively investigate these mechanisms, we applied quantification methods to three-dimensional interfacial data obtained by a previous experimental study using three-dimensional laser-induced fluorescence with index matching. Detailed observations of the spreading behavior of droplets and vortex-like flow, along with quantitative estimations, found out that the vortex-like flow is the dominant source of droplets on the atomization. Further investigations into the forces acting on the vortex-like flow found out the formation and collapse processes of the vortex-like flow. The accelerations of the normal forces acting on the vortex-like flow can be represented by superficial centrifugal acceleration and gravitational acceleration. Our next analysis focused on investigating droplet formation as the elementary process of atomization. The results showed two droplet formation patterns: liquid-film breaking patterns, wherein droplets directly form from the liquid film, and the surfing pattern, wherein droplets form from interfacial waves on the liquid film. Subsequently, the droplet data were grouped using dimensionless numbers and compared with theoretical lines describing the different droplet formation mechanisms. This comparison revealed the mechanisms of droplet formation within the vortex-like flow.
Okita, Shoichiro; Abe, Yutaka*; Tasaki, Seiji*; Fukaya, Yuji
Radioisotopes, 73(3), p.233 - 240, 2024/11
Sato, Nobuaki*; Kameo, Yutaka; Sato, Soichi; Kumagai, Yuta; Sato, Tomonori; Yamamoto, Masahiro*; Watanabe, Yutaka*; Nagai, Takayuki; Niibori, Yuichi*; Watanabe, Masayuki; et al.
Introduction to Dismantling and Decommissioning Chemistry, 251 Pages, 2024/09
This book focuses on the dismantling and decommissioning of nuclear facilities and reactors that have suffered severe accidents. In Part 1, we introduce basic aspects ranging from fuel chemistry, analytical chemistry, radiation chemistry, corrosion, and decontamination chemistry to waste treatment and disposal. Then, Part 2 covers the chemistry involved in the decommissioning of various nuclear facilities, and discusses what chemical approaches are necessary and possible for the decommissioning of TEPCO's Fukushima Daiichi Nuclear Power Plants, how decommissioning should be carried out, and what kind of research and development and also human resource development are required for this.
Be and 
Al under direct muon-induced spallation in granite quartz and its implications for past high-energy cosmic ray fluxesSakurai, Hirohisa*; Kurebayashi, Yutaka*; Suzuki, Soichiro*; Horiuchi, Kazuho*; Takahashi, Yui*; Doshita, Norihiro*; Kikuchi, Satoshi*; Tokanai, Fuyuki*; Iwata, Naoyoshi*; Tajima, Yasushi*; et al.
Physical Review D, 109(10), p.102005_1 - 102005_18, 2024/05
Times Cited Count：0 Percentile：0.00(Astronomy & Astrophysics)Secular variations of galactic cosmic rays (GCRs) are inseparably associated with the galactic activities and should reflect the environments of the local galactic magnetic field, interstellar clouds, and nearby supernova remnants. The high-energy muons produced in the atmosphere by high-energy GCRs can penetrate deep underground and generate radioisotopes in the rock. As long lived radionuclides such as Be and Al have been accumulating in these rocks, concentrations of Be and Al can be used to estimate the long-term variations in high-energy muon yields, corresponding to those in the high-energy GCRs over a few million years. This study measured the production cross sections for muon induced Be and Al by irradiating positive muons with the momentum of 160 GeV/c on the synthetic silica plates and the granite core at the COMPASS experiment line in CERN SPS. In addition, it the contributions of the direct muon spallation reaction and the nuclear reactions by muon-induced particles on the production of long lived radionuclides in the rocks were clarified.
Kaneko, Koji; Tabata, Chihiro; Hagihara, Masato; Yamauchi, Hiroki; Oba, Yojiro; Kumada, Takayuki; Kubota, Masato; Kojima, Yuki*; Nabatame, Nozomi; Sasaki, Miki; et al.
JPS Conference Proceedings (Internet), 41, p.011015_1 - 011015_6, 2024/03
Kutsukake, Kenichi; Matsuda, Makoto; Nakamura, Masahiko; Ishizaki, Nobuhiro; Kabumoto, Hiroshi; Otokawa, Yoshinori; Asozu, Takuhiro; Matsui, Yutaka; Nakagawa, Sohei; Abe, Shinichi
Proceedings of 20th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1080 - 1084, 2023/11
no abstracts in English
Horiguchi, Naoki; Yoshida, Hiroyuki; Kaneko, Akiko*; Abe, Yutaka*
Nihon Kikai Gakkai Kanto Shibu Dai-29-Ki Sokai, Koenkai Koen Rombunshu (Internet), 5 Pages, 2023/10
To elucidate the behavior of molten fuels as a liquid jet in a shallow pool, which is assumed in a core meltdown accident of an LWR, and develop the evaluation method, we investigated the behavior of the vortical liquid film of the simulated wall-impinging liquid jet using 3-dimensional interface shape data obtained by the experiment in a liquid-liquid system.
Horiguchi, Naoki; Yoshida, Hiroyuki; Kaneko, Akiko*; Abe, Yutaka*
Physics of Fluids, 35(7), p.073309_1 - 073309_17, 2023/07
Times Cited Count：3 Percentile：29.39(Mechanics)The atomization of a liquid jet in an immiscible liquid-liquid system is significant for the safety in the nuclear industry field. The Japan Atomic Energy Agency has developed an evaluation method of a melt fuel behavior as a liquid jet in an immiscible liquid-liquid system for subsequence using mechanistic numerical simulation and has investigated liquid jet behavior in a shallow pool through numerical simulations and experiments. The paper clarifies the atomization mechanism in the wall-impinging liquid jet. Herein, the atomization behavior in the wall-impinging liquid jet in a shallow pool in an immiscible liquid-liquid system was studied in terms of droplet formation and flow field using numerical simulation and the dispersed-phase tracking method. The results show that the droplet formation in the liquid film flow of the wall-impinging liquid jet had the three patterns, and we obtained the droplet properties immediately after droplet formation and developed the theoretical criterion regions using the dimensionless numbers for droplet formation. We characterized the patterns by comparing them with the regions and elucidated the droplet formation mechanisms depending on their sources. Moreover, we elucidated that the relationship between droplet formation as the local behaviors of the jet and atomization as the whole behavior.
Urakawa, Yutaka*; Egusa, Daisuke*; Itakura, Mitsuhiro; Abe, Eiji*
Materials Transactions, 64(5), p.1065 - 1071, 2023/05
Times Cited Count：2 Percentile：15.19(Materials Science, Multidisciplinary)Hata, Kuniki; Kimura, Atsushi*; Taguchi, Mitsumasa*; Sato, Tomonori; Kato, Chiaki; Watanabe, Yutaka*
Zairyo To Kankyo, 72(4), p.126 - 130, 2023/04
Gamma-radiolysis experiments with gas-liquid coexistent samples were carried out to investigate effects of gas-phase radiolysis on corrosive environment for materials in solutions under irradiation. After gamma-ray irradiation, hydrogen peroxide, nitrate ion, nitrite ion were detected in the liquid phase. The production yields of nitrate ion and nitrite ion increased with increasing gas-phase volume and oxygen concentration. This result indicated that chemical reactions including oxygen and nitrogen in the gas phase were required for the production of nitrate ion and nitrite ion. To magnify the effects of gas-phase radiolysis in the gas-liquid coexistent samples, absorption dose rate in the liquid phase was reduced by one-hundredth using lead shield. The concentration of hydrogen peroxide and the pH in the shielded liquid phase were similar to those in the irradiated pure water, which did not contact with gas phase. This result indicated that the effects of nitrate ion and nitrite ion dissolved in the liquid phase on water radiolysis were not important in the current experimental system, in which the effects of gas-phase radiolysis were increased by 100-times.
Ishizaki, Nobuhiro; Matsuda, Makoto; Nakamura, Masahiko; Kabumoto, Hiroshi; Kutsukake, Kenichi; Otokawa, Yoshinori; Asozu, Takuhiro; Matsui, Yutaka; Abe, Shinichi
JAEA-Conf 2022-002, p.5 - 10, 2023/03
no abstracts in English
Nagata, Shuhei*; Ogawa, Yusuke*; Suzuki, Satoru*; Inoue, Hiroyuki*; Watanabe, Yutaka*; Yamamoto, Masahiro*; Abe, Hiroshi*; Mitsui, Seiichiro
NUMO-TR-22-02, p.21 - 22, 2023/03
no abstracts in English
Iwamoto, Osamu; Iwamoto, Nobuyuki; Kunieda, Satoshi; Minato, Futoshi; Nakayama, Shinsuke; Abe, Yutaka*; Tsubakihara, Kosuke*; Okumura, Shin*; Ishizuka, Chikako*; Yoshida, Tadashi*; et al.
Journal of Nuclear Science and Technology, 60(1), p.1 - 60, 2023/01
Times Cited Count：318 Percentile：99.99(Nuclear Science & Technology)Kabumoto, Hiroshi; Matsuda, Makoto; Nakamura, Masahiko; Ishizaki, Nobuhiro; Kutsukake, Kenichi; Otokawa, Yoshinori; Asozu, Takuhiro; Matsui, Yutaka; Nakagawa, Sohei; Abe, Shinichi
Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1109 - 1113, 2023/01
no abstracts in English
Ichihara, Akira; Abe, Yutaka*
JAEA-Conf 2022-001, p.175 - 180, 2022/11
Thermal neutron scattering law data were calculated for the heavy water molecule toward the fifth version of the Japanese evaluated nuclear data library, JENDL-5. The scattering laws for deuterium and oxygen atoms were computed using the molecular dynamics simulations. The simulations have been performed in the temperature range from 283.6 K to 600 K. The scattering law data have been evaluated in the neutron incident energies between 0.01 meV and 10 eV. With the obtained scattering laws, we calculated the cross sections for the heavy water molecule, and confirmed that the experimental data at room temperature were well reproduced. Moreover, in the computed temperature range, the cross sections were almost consistent with the ENDF/B-VIII.0 evaluations.
