Speciation of cesium in a radiocesium-bearing microparticle emitted from Unit 1 during the Fukushima nuclear accident by XANES spectroscopy using transition edge sensor

Takahashi, Yoshio*; Miura, Hikaru*; Yamada, Shinya*; Sekizawa, Oki*; Nitta, Kiyofumi*; Hashimoto, Tadashi*; Yomogida, Takumi; Yamaguchi, Akiko; Okada, Shinji*; Itai, Takaaki*; et al.

Journal of Hazardous Materials, 495, p.139031_1 - 139031_19, 2025/09

https://doi.org/10.1016/j.jhazmat.2025.139031

In this presentation, we analyzed the chemical state of cesium in radiocesium-bearing microparticles (CsMPs) released during the 2011 Fukushima Daiichi Nuclear Power Plant accident using high-resolution X-ray absorption spectroscopy (XANES) and micro X-ray fluorescence (-XRF). The results identified two forms of cesium: one dissolved in glass and the other enriched on the surfaces of internal voids. The latter is considered to have originally existed as a gas and became concentrated during the cooling and solidification of the molten glass. These findings are crucial for understanding the formation process of CsMPs during the accident, as well as for future decommissioning and safety assessments.

Removal techniques for contaminated analytical Grove Box with nuclear fuel materials

Yokochi, Masaru; Goto, Yuichi; Kuno, Sorato; Suzuki, Yoshimasa; Yamamoto, Masahiko; Taguchi, Shigeo; Usui, Masato*; Onose, Taku*; Miyamoto, Toshihiko*; Mori, Eito*

Nihon Hozen Gakkai Dai-21-Kai Gakujutsu Koenkai Yoshishu, 4 Pages, 2025/07

Analysis facility in Tokai Reprocessing Plant, which is shifted to decommissioning stage, have been installed about 60 Grove Boxes to handling the nuclear fuel materials. Of these, progressing an aging accompanied by long use for 20 years more than half. This time, removal the special Grove Box that equipped the Thermal Ionization Mass Spectrometry, necessary safeguard analysis for nuclear fuel materials. This report summarized the removal techniques of the special Grove Box, the number of working days, workers and amount of waste generated in this removal work.

Decommissioning report for Wastewater Treatment Facility (Part 2); Chapter on contamination inspection section

Yamamoto, Keisuke; Nakagawa, Takuya; Shimojo, Hiroto; Kijima, Jun; Miura, Daiya; Onose, Yoshihiko*; Namba, Koji*; Uchida, Hiroaki*; Sakamoto, Kazuhiko*; Ono, Chika*; et al.

JAEA-Technology 2024-019, 211 Pages, 2025/02

JAEA-Technology-2024-019.pdf:35.35MB

The uranium enrichment facilities at the Nuclear Fuel Cycle Engineering Laboratories of Japan Atomic Energy Agency (JAEA) were constructed sequentially to develop uranium enrichment technology with centrifugal separation method. The developed technologies were transferred to Japan Nuclear Fuel Limited until 2001. And the original purpose has been achieved. Wastewater Treatment Facility, one of the uranium enrichment facilities, was constructed in 1976 to treat radioactive liquid waste generated at the facilities, and it finished the role in 2008. In accordance with the Medium/Long-Term Management Plan of JAEA Facilities, interior equipment installed in this facility had been dismantled and removed since November 2021 to August 2023. This report summarizes the findings obtained through the work related to the contamination inspection methods cancellation the controlled area of Wastewater Treatment Facility from September 2023 to March 2024.

Research and development of three-dimensional isolation system for sodium cooled fast reactor, 7; Development summary of three-dimensional isolation system

Watakabe, Tomoyoshi; Yamamoto, Tomohiko; Okamura, Shigeki; Miyazaki, Masashi; Miyagawa, Takayuki; Uchita, Masato*; Hirayama, Tomoyuki*; Somaki, Takahiro*; Yukawa, Masaki*; Fukasawa, Tsuyoshi*; et al.

Proceedings of the ASME 2024 Pressure Vessels & Piping Conference (PVP 2024) (Internet), 10 Pages, 2024/07

To secure the seismic safety of the thin-walled mechanical components and piping under a severe design earthquake level, employing a three-dimensional (3D) seismic isolation system has been planned in a sodium-cooled fast reactor. The development results of the 3D isolation system have been reported in previous papers so far. Its update is reported in Part 7 to Part 9. Part 7 describes the overview of the development, the test plan of the isolation system in the assembled state of each element, and the performance of individual isolation elements. In part 8, the performance of the isolation device that each element was assembled into was investigated through loading tests. Part 9 reports analytical studies by an analysis model validated based on the insight of the test results.

Research and development of three-dimensional isolation system for sodium cooled fast reactor, 9; Evaluating seismic isolation performance through seismic response analysis

Fukasawa, Tsuyoshi*; Somaki, Takahiro*; Yukawa, Masaki*; Hirayama, Tomoyuki*; Watakabe, Tomoyoshi; Yamamoto, Tomohiko; Okamura, Shigeki; Miyazaki, Masashi; Uchita, Masato*; Miyagawa, Takayuki; et al.

Proceedings of the ASME 2024 Pressure Vessels & Piping Conference (PVP 2024) (Internet), 10 Pages, 2024/07

https://doi.org/10.1115/PVP2024-121899

Development of seismic isolation system for sodium-cooled fast reactors using high load and high-velocity loading machines

Fukasawa, Tsuyoshi*; Yamamoto, Tomohiko; Uchita, Masato*; Hirayama, Tomoyuki*

Dai-10-Kai Kozobutsu No Anzensei, Shinraisei Ni Kansuru Kokunai Shimpojiumu (JCOSSAR2023) Koen Rombunshu (Internet), p.135 - 142, 2023/10

https://doi.org/10.60316/jcossar.10.0_135

Horizontal seismic isolation systems have been studied for Sodium-Cooled Fast Reactors to improve their seismic resistance. However, challenges arise in reducing seismic forces not only in the horizontal direction but also in the vertical direction. The authors have developed a new three-dimensional seismic isolation system to address this issue. A 1/2-scale test specimen was fabricated, and the force-displacement relationships were examined using static loading tests with a maximum axial force of 8000 kN to evaluate the feasibility of this design. Moreover, a horizontal oil damper was fabricated as a horizontal damping element, and its damping force was assessed through excitation tests with a maximum velocity of 2.7 m/s. This paper reports the findings of these tests.

Evaluation of hydrogen behavior in sodium for sodium-water reaction detection of sodium-cooled fast reactor

Yamamoto, Tomohiko; Kato, Atsushi; Hayakawa, Masato; Shimoyama, Kazuhito; Ara, Kuniaki; Hatakeyama, Nozomu*; Yamauchi, Kanau*; Eda, Yuhei*; Yui, Masahiro*

Proceedings of 2023 International Congress on Advanced in Nuclear Power Plants (ICAPP 2023) (Internet), 6 Pages, 2023/04

Sodium-cooled Fast Reactors

Ohshima, Hiroyuki; Morishita, Masaki*; Aizawa, Kosuke; Ando, Masanori; Ashida, Takashi; Chikazawa, Yoshitaka; Doda, Norihiro; Enuma, Yasuhiro; Ezure, Toshiki; Fukano, Yoshitaka; et al.

Sodium-cooled Fast Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.3, 631 Pages, 2022/07

https://shop.elsevier.com/books/sodium-cooled-fast-reactors/morishita/978-0-12-824076-2

This book is a collection of the past experience of design, construction, and operation of two reactors, the latest knowledge and technology for SFR designs, and the future prospects of SFR development in Japan. It is intended to provide the perspective and the relevant knowledge to enable readers to become more familiar with SFR technology.

Study on vertical restoring force device using disc springs; Examination of optimum combination of disc spring units and identification method of hysteresis loop

Fukasawa, Tsuyoshi*; Somaki, Takahiro*; Miyagawa, Takayuki*; Uchita, Masato*; Yamamoto, Tomohiko; Ishizuka, Futoshi*; Suzuno, Tetsuji*; Okamura, Shigeki*; Fujita, Satoshi*

Kozo Kogaku Rombunshu, B, 68B, p.462 - 475, 2022/04

https://doi.org/10.3130/aijjse.68B.0_462

Development of 3-dimensional seismic isolation system for sodium-cooled fast reactor

Yamamoto, Tomohiko; Fukasawa, Tsuyoshi*; Uchita, Masato*; Okamura, Shigeki*; Fujita, Satoshi*

Proceedings of 17th World Conference on Earthquake Engineering (WCEE-17) (DVD-ROM), 12 Pages, 2021/09

A sodium-cooled fast reactor (SFR) is operated at a high temperature and a low pressure. Components for the SFR have been designed as thin-wall structure to mitigate the thermal stress due to the operation at a high temperature. However, thin wall structures have a disadvantage of the structural integrity for earthquake. To avoid this disadvantage, SFR will adopt seismic isolation system to reduce horizontal seismic loads. Also, it is important to reduce not only the horizontal seismic response but also the vertical seismic response in order to secure the structural integrity of components for the SFR and to realize high power by upsizing of the reactor vessel. To realize these requirements, the 3-dimensional seismic isolation system for the SFR had been studied. This paper describes the concept of the 3-dimensinal seismic isolation system and isolation performance obtained by the seismic response analysis.