To effective use of atmospheric dispersion calculations in nuclear emergency response and preparedness; Development of WSPEEDI-DB

Terada, Hiroaki; Tsuzuki, Katsunori; Kadowaki, Masanao; Nagai, Haruyasu

Nihon Genshiryoku Gakkai-Shi ATOMO, 67(2), p.113 - 117, 2025/02

https://doi.org/10.3327/jaesjb.67.2_113

no abstracts in English

Quantitative visualization of a radioactive plume in a nuclear accident

Nagai, Haruyasu; Nakayama, Hiromasa; Satoh, Daiki; Tanimori, Toru*

Dai-52-Kai Kashika Joho Shimpojiumu Koen Rombunshu (Internet), 4 Pages, 2024/07

A novel monitoring method for the quantitative visualization of 3D distribution of a radioactive plume accidentally released from a nuclear facility is proposed, and the feasibility of its analysis method is demonstrated by preliminary test using hypothetical data. The proposed method is the combination of gamma-ray imaging spectroscopy with the electron tracking Compton camera (ETCC) and real-time high-resolution atmospheric dispersion simulation based on 3D wind observation with Doppler lidar. ETCC can acquire the angle distribution images of direct gamma-ray from a specific radionuclide in a target radioactive plume. The 3D distribution of radioactive plume is inversely reconstructed from direct gamma-ray images by several ETCCs located around the target by harmonizing with the air concentration distribution pattern of the plume predicted by real-time atmospheric dispersion simulation. Analysis methods were developed and tested by using hypothetical data generated by numerical simulations of atmospheric dispersion and radiation transport.

Crystallization processes of quartz in a granitic magma; Implications for the magma chamber processes of Okueyama granite, Kyushu, Japan

Yuguchi, Takashi*; Kato, Takenori*; Ogita, Yasuhiro; Watanabe, Minori*; Yamazaki, Hayato*; Kato, Asuka*; Ito, Daichi*; Yokoyama, Tatsunori; Sakata, Shuhei*; Ono, Takeshi*

Journal of Asian Earth Sciences, 265, p.106091_1 - 106091_13, 2024/04

https://doi.org/10.1016/j.jseaes.2024.106091

Assessment of hydrogen embrittlement behavior in Al-Zn-Mg alloy through multi-modal 3D image-based simulation

Fujihara, Hiro*; Toda, Hiroyuki*; Ebihara, Kenichi; Kobayashi, Masakazu*; Mayama, Tsuyoshi*; Hirayama, Kyosuke*; Shimizu, Kazuyuki*; Takeuchi, Akihisa*; Uesugi, Masayuki*

International Journal of Plasticity, 174, p.103897_1 - 103897_22, 2024/03

https://doi.org/10.1016/j.ijplas.2024.103897

Hydrogen(H) embrittlement in high-strength aluminum(Al) alloys is a crucial problem. H accumulation at the interface of precipitates in Al alloy is considered to cause embrittlement. However, there is no quantitative knowledge regarding the interaction between H distribution and stress field near cracks. In this study, using a multi-modal three-dimensional image-based simulation combining the crystal plasticity finite element method and H diffusion analysis, we tried to capture the stress distribution near the crack, its influence on the H distribution, and the probability of crack initiation in the experimental condition. As a result, it was found that grain boundary cracks transition to quasi-cleavage cracks in the region where the cohesive energy of the semi-coherent interface of MgZn precipitates decreases due to H accumulation near the tip. We believe the present simulation method successfully bridges nanoscale delamination and macroscale brittle fracture.

IAEA support for nuclear facilities in Ukraine during Russia's invasion

Kobayashi, Naoki

Dai-44-Kai Nihon Kaku Busshitsu Kanri Gakkai Nenji Taikai Kaigi Rombunshu (Internet), 5 Pages, 2023/11

no abstracts in English

Multi-modal 3D image-based simulation of hydrogen embrittlement crack initiation in Al-Zn-Mg alloy

Higa, Ryota*; Fujihara, Hiro*; Toda, Hiroyuki*; Kobayashi, Masakazu*; Ebihara, Kenichi; Takeuchi, Akihisa*

Keikinzoku, 73(11), p.530 - 536, 2023/11

https://doi.org/10.2464/jilm.73.530

In Al-Zn-Mg alloys, suppression of hydrogen embrittlement is necessary to improve their strength. In this study, the distribution of stress, strain, and hydrogen concentration in the actual fracture region was investigated using the crystal plasticity finite element method and hydrogen diffusion analysis based on a model derived from three-dimensional polycrystalline microstructural data obtained by X-ray CT. In addition, the distributions of stress, strain, and hydrogen concentration were compared with the actual crack initiation behavior by combining in-situ observation of tensile tests using X-ray CT and simulation. The results show that stress loading perpendicular to the grain boundary due to crystal plasticity dominates grain boundary crack initiation. It was also found that internal hydrogen accumulation due to crystal plasticity has little effect on crack initiation.

7.2 Source term

Terada, Hiroaki

Ten Hasseigen Karano Mesosukeru Kakusan Shumireshon; Fukushima Daiichi Genshiryoku Hatsudensho Jiko O Fumaete (Kisho Kenkyu Noto Dai-248-Go), p.115 - 121, 2023/09

no abstracts in English

Nuclear disaster prevention based on lessons learned from the Fukushima Daiichi Nuclear Power Station accident

Shimada, Kazumasa; Nagai, Haruyasu; Hashimoto, Makoto; Iimoto, Takeshi*

Nihon Genshiryoku Gakkai-Shi ATOMO, 65(5), P. 290, 2023/05

https://doi.org/10.3327/jaesjb.65.5_290

This article is part of the special feature article "What should be done from now on after the 1F accident and what should be conveyed to the next generation after the 1F accident?" of the Atomic Energy Society of Japan, which summarizes the discussions and future proposals on nuclear disaster prevention in which the members of the Health Physics and Environment Science Subcommittee have been involved. In view of the recommendations of the Accident Investigation Committee of the Atomic Energy Society of Japan and the Meteorological Society of Japan, the behavior of radioactive plumes and the prediction of residents' evacuation behavior should be studied to support decision-making on evacuation and other protective measures for residents in and outside the UPZ. Furthermore, decision-making on protective measures and practical risk communication to residents based on radiation health risks to residents and ethical aspects are newly proposed.

The Tenth Review Conference of the Parties to the Treaty on the Non-Proliferation of Nuclear Weapons (NPT); Key issues and why the final document could not be adopted

Tazaki, Makiko

Nihon Genshiryoku Gakkai-Shi ATOMO, 65(3), p.183 - 186, 2023/03

https://doi.org/10.3327/jaesjb.65.3_183

no abstracts in English

Statistical analysis of simulated oceanic dispersion of dissolved radionuclide hypothetically released from the Fukushima Dai-ichi Nuclear Power Plant using long-term oceanographic reanalysis data

Ikenoue, Tsubasa; Kawamura, Hideyuki; Kamidaira, Yuki

Journal of Nuclear Science and Technology, 60(1), p.61 - 71, 2023/01

https://doi.org/10.1080/00223131.2022.2079569

We conducted numerical simulations on the oceanic dispersion of dissolved radionuclide hypothetically released from the Fukushima Dai-ichi Nuclear Power Plant using long-term oceanographic reanalysis data. We evaluated the characteristics and trends of dissolved radionuclide behavior in the ocean using statistical analysis based on the simulation results. The surface meridional current at the release point in the Fukushima coastal ocean and the Kuroshio Extension significantly affected the north-south transport of the surface radionuclide in the Fukushima coastal ocean and the eastward transport of the offshore surface radionuclide, respectively. Because the surface kinetic energy in the coastal to the offshore area was larger, the range of the dispersed surface radionuclide tended to be larger. In summer (July-September), the increased frequency radionuclide entrainment by the Kuroshio Extension because of the surface southward radionuclide transport in the Fukushima coastal ocean and the large surface kinetic energy caused a large dispersed surface radionuclide. In winter (January-March), the decreased frequency radionuclide entrainment by the Kuroshio Extension because of the surface northward radionuclide transport in the Fukushima coastal ocean and the small surface kinetic energy caused a small dispersed surface radionuclide.