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Okamura, Shigeki; Nakashima, Risako*; Hirayama, Tomoyuki*; Yukawa, Masaki*; Watanabe, Shotaro*; Fujita, Satoshi*; Yamaguchi, Akira*
Journal of Nuclear Science and Technology, 63(10), p.1209 - 1217, 2026/10
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Masaki, Nobuo*; Murota, Nobuo*; Kato, Koji*; Okamura, Shigeki; Yamamoto, Tomohiko; Uchita, Masato*; Fujita, Satoshi*
Nihon Kenchiku Gakkai Gijutsu Hokokushu, 31(78), p.687 - 692, 2025/06
Creep characteristic of the thick laminated rubber bearing made of natural rubber installed in the actual vibration isolation building for 55.2 years could be estimated by using existing measurement data and newly measurement data. Creep measurement data sets were examined by simple regression equation of recommended by JIS K6410-2. Regression analysis showed that the average creep displacement characteristics could be described by a power law. Average creep displacement of the thick laminated rubber bearings installed the building for 60 years was estimated 3.4 mm by the regression equation. The method of JIS K6410-2 is useful for forecasting creep displacement.
Yamamoto, Tomohiko; Okamura, Shigeki; Hirayama, Tomoyuki*; Morobishi, Ryota*; Endo, Naoki*; Adachi, Yoshihiko*
Yukuatsu Gijutsu, 63(12), p.22 - 26, 2024/11
JAEA is currently conducting research and development of a three-dimensional seismic isolation system as a measure to improve earthquake resistance in the research and development for the practical application of sodium-cooled fast reactors in the future. This paper presents an overview of the high-velocity oil damper, one of the components of the three-dimensional seismic isolation system that is currently being researched and developed.
Kinoshita, Takahiro*; Okamura, Shigeki; Nishino, Hiroyuki; Yamano, Hidemasa; Kurisaka, Kenichi; Futagami, Satoshi; Fukasawa, Tsuyoshi*
International Journal of Pressure Vessels and Piping, 211, p.105299_1 - 105299_5, 2024/10
Times Cited Count：1 Percentile：13.24(Engineering, Multidisciplinary)The seismic evaluation of key components such as reactor vessel is important for the Seismic Probabilistic Risk Assessment (S-PRA) in a Sodium-Cooled Fast Reactor (SFR). Many components were fractured by integrated damage like fatigue damage during seismic ground motion. In this paper, failure probability evaluation method with integrated energy was developed by comparing the energy with vibration tests and fatigue tests. Vibration tests were performed to evaluate integrated vibration energy at failure by energy balance equation, and fatigue tests were performed to evaluate integrated vibration energy at failure based on experimental results. As results, it is shown that integrated energy at failure time by vibration tests were estimated and its values were in range the energy based on results of fatigue tests.
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
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.
Somaki, Takahiro*; Yukawa, Masaki*; Fukasawa, Tsuyoshi*; Hirayama, Tomoyuki*; Uchita, Masato*; Miyagawa, Takayuki; Okamura, Shigeki; Yamamoto, Tomohiko; Watakabe, Tomoyoshi; Miyazaki, Masashi; et al.
Proceedings of the ASME 2024 Pressure Vessels & Piping Conference (PVP 2024) (Internet), 9 Pages, 2024/07
Murota, Nobuo*; Kato, Koji*; Takeuchi, Sadamitsu*; Masaki, Nobuo*; Fujita, Satoshi*; Okamura, Shigeki; Yamamoto, Tomohiko; Ahmadi, H.*; Picken, R.*; Kingston, J.*
Proceedings of 18th World Conference on Earthquake Engineering (WCEE2024) (Internet), 12 Pages, 2024/06
Yamamoto, Tomohiko; Watakabe, Tomoyoshi; Miyazaki, Masashi; Okamura, Shigeki; Miyagawa, Takayuki; Yokoi, Shinobu*; Fukasawa, Tsuyoshi*; Fujita, Satoshi*
Mechanical Engineering Journal (Internet), 11(2), p.23-00393_1 - 23-00393_21, 2024/04
Yamamoto, Tomohiko; Okamura, Shigeki; Hirayama, Tomoyuki*; Somaki, Takahiro*
Haikan Gijutsu, 65(13), p.1 - 4, 2023/11
The authors are conducting research and development on three-dimensional seismic isolation devices to improve the earthquake resistance of future sodium-cooled fast reactors. This paper introduces an overview of the device and how to use it.
Fukasawa, Tsuyoshi*; Hirayama, Tomoyuki*; Yokoi, Shinobu*; Hirota, Akihiko*; Somaki, Takahiro*; Yukawa, Masaki*; Miyagawa, Takayuki; Uchita, Masato*; Yamamoto, Tomohiko; Miyazaki, Masashi; et al.
Nihon Kikai Gakkai Rombunshu (Internet), 89(924), p.23-00023_1 - 23-00023_17, 2023/08
no abstracts in English
Yamamoto, Tomohiko; Watakabe, Tomoyoshi; Miyazaki, Masashi; Miyagawa, Takayuki*; Yokoi, Shinobu*; Okamura, Shigeki*; Fukasawa, Tsuyoshi*; Fujita, Satoshi*
Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 7 Pages, 2023/05
Kinoshita, Takahiro*; Okamura, Shigeki*; Nishino, Hiroyuki; Yamano, Hidemasa; Kurisaka, Kenichi; Futagami, Satoshi; Fukasawa, Tsuyoshi*
Transactions of the 26th International Conference on Structural Mechanics in Reactor Technology (SMiRT-26) (Internet), 7 Pages, 2022/07
The seismic evaluation of key components such as reactor vessel is important for the Seismic Probabilistic Risk Assessment (S-PRA) in a Sodium-Cooled Fast Reactor (SFR). Many components were damaged by cumulative damage like fatigue damage during seismic ground motion. However, general evaluation method for key components under seismic ground motion has been based on static loads and elastic region of materials. More accurate evaluation method for S-PRA, which can evaluate the failure of key components such as reactor vessels, has been actually required. In this study, failure probability evaluation method with integrated energy was developed by comparing the energy with vibration tests and fatigue tests. Vibration tests were performed to evaluate integrated vibration energy at failure by energy balance equation and fatigue tests were performed to evaluate integrated vibration energy at failure based on experimental results of fatigue tests.
Yamano, Hidemasa; Okamura, Shigeki*
Transactions of the 26th International Conference on Structural Mechanics in Reactor Technology (SMiRT-26) (Internet), 9 Pages, 2022/07
Seismic response analyses were conducted for the pipe with and without the seismic isolation system based on the response waveforms. This study performed a fragility analysis by setting uncertainty parameters on the basis of existing studies. The comparison results showed that the seismic isolation technology is effective for the pipe to prevent cliff-edge effects. In other words, the seismic margin for the seismically isolated plant is 1.2 times larger than that of the non-isolated plant. To evaluate the response reduction effect, this study focused on response coefficients of components as uncertainty parameters, which were specified within a physically possible range. Even if the uncertainty is considered, the HCLPF for the isolated plant is nearly twice as high as the non-isolated plant, namely the response reduction effect is still significant for the isolated plant. Therefore, the isolation technology is effective to avoid cliff-edge effects.
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
Masaki, Nobuo*; Kato, Koji*; Yamamoto, Tomohiko; Miyagawa, Takayuki*; Fujita, Satoshi*; Okamura, Shigeki*
Nihon Kenchiku Gakkai Gijutsu Hokokushu, 28(68), p.81 - 84, 2022/02
no abstracts in English
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.
Furuya, Osamu*; Fujita, Satoshi*; Muta, Hitoshi*; Otori, Yasuki*; Itoi, Tatsuya*; Okamura, Shigeki*; Minagawa, Keisuke*; Nakamura, Izumi*; Fujimoto, Shigeru*; Otani, Akihito*; et al.
Proceedings of ASME 2021 Pressure Vessels and Piping Conference (PVP 2021) (Internet), 6 Pages, 2021/07
Since the Fukushima accident, with the higher safety requirements of nuclear facilities in Japan, suppliers, manufacturers and academic societies have been actively considering the reconstruction of the safety of nuclear facilities from various perspectives. The Nuclear Regulation Authority has formulated new regulatory standards and is in operation. The new regulatory standards are based on defense in depth, and have significantly raised the levels of natural hazards and have requested to strengthen the countermeasures from the perspective of preventing the simultaneous loss of safety functions due to common factors. Facilities for dealing with specific serious accidents are required to have robustness to ensure functions against earthquakes that exceed the design standards to a certain extent. In addition, since the probabilistic risk assessment (PRA) and the safety margin evaluation are performed to include the range beyond the design assumption in the safety improvement evaluation, it is very important to extent the special knowledge in the strength of important equipment for seismic safety. This paper summarizes the research and examination results of specialized knowledge on the concept of maintaining the functions of important seismic facilities and the damage index to be considered by severe earthquakes. In the other paper, the study on reliability of seismic capacity analysis for important equipment in nuclear facilities will be reported.
