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Journal Articles

Estimation of creep behavior of thick rubber bearings from 47 years observation in an actual building

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

Journal Articles

Toxicity reduction with total volume control in nuclear waste

Fukaya, Yuji; Ueta, Shohei; Yamamoto, Tomohiko; Chikazawa, Yoshitaka; Yan, X.

Nuclear Technology, 208(2), p.335 - 346, 2022/02

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

When the total volume control on toxicity for nuclear waste management is applied, it becomes a limiting factor for the permittable total operation capacity of nuclear reactors. An alternative conceptual scenario to achieve the control is proposed that aims at toxicity reduction through Partitioning and Transmutation (P&T). Specifically, the electricity generation capacity could be inversely increased up with transmutation of $$^{90}$$Sr-$$^{137}$$Cs. Simultaneously, the cooling time before disposal is reduced to 50 years from the 300 years required by the existing scenarios such as (Accelerator Driven System (ADS). Finally, the scenario is also found feasible in terms of energy balance and cost by the neutron source of Li(d,xn) reaction with the deuteron accelerator for transmutation.

Journal Articles

Comparison of sodium fast reactor core assembly seismic evaluation using the Japanese and French simulation tools

Yamamoto, Tomohiko; Matsubara, Shinichiro*; Harada, Hidenori*; Saunier, P.*; Martin, L.*; Gentet, D.*; Dirat, J.-F.*; Collignon, C.*

Nuclear Engineering and Design, 383, p.111406_1 - 111406_14, 2021/11

 Times Cited Count:0

Japan-France collaboration on ASTRID (Advanced Sodium Technological Reactor for Industrial Demonstration) project is launched in 2014. In this project, Japan-France evaluates core assemblies with interferences on seismic event. The object of this study is to verify the seismic evaluation method on core assemblies between Japan and France by comparing the results. The analysis of this benchmark calculation shows a satisfactory agreement between the Japanese and French tools and the figures show a good behavior of the core in horizontal direction under French seismic condition.

Journal Articles

Study on the predictive evaluation method for loads acting on roof and sidewall of cylindrical tank in nonlinear sloshing based on simplified equations

Ikesue, Shunichi*; Morita, Hideyuki*; Ishii, Hidekazu*; Sago, Hiromi*; Yokoi, Shinobu*; Yamamoto, Tomohiko

Proceedings of ASME 2021 Pressure Vessels and Piping Conference (PVP 2021) (Internet), 8 Pages, 2021/07

In this paper, a new method is proposed for the nonlinear sloshing condition of a cylindrical tank, which can evaluate the vertical load acting on the roof and the horizontal load acting on the sidewall. This method is a combination of simplified equations for the liquid surface level and velocity proposed in the past study and the new pressure model modified from the existing model. A long calculation time as CFD analysis is not needed, because this method is consisted of simplified equations. The validity of this method was confirmed by comparing them with the CFD and the test. And future issues on the improvement of this method were clarified from the result.

Journal Articles

Fundamental study on seismic safety margin for seismic isolated structure using the laminated rubber bearings

Fukasawa, Tsuyoshi*; Miyagawa, Takayuki*; Uchita, Masato*; Yamamoto, Tomohiko; Miyazaki, Masashi; Okamura, Shigeki*; Fujita, Satoshi*

Nihon Kikai Gakkai Rombunshu (Internet), 87(898), p.21-00007_1 - 21-00007_17, 2021/06

This paper describes a fundamental study on the seismic safety margin for the isolated structure using laminated rubber bearings. The variation of the seismic response assumed in the isolated structure will occur under the superposition of "Variations in seismic response due to input ground motions" and "Error with design value accompanying manufacture of the isolation devices ". The seismic response analysis which allows to their conditions is important to assess the seismic safety margin for the isolated structure. This paper clarifies that the seismic safety margin of the isolated structure, which consists of rubber bearings, for Sodium-cooled Fast Reactor (SFR) is ensured against the basis ground motions of Japan Electric Association Guide 4601 (JEAG4601) and SFR through the seismic response analysis considering the variation factors of seismic response. In addition, a relationship between the seismic safety margin and the excess probability of linearity limits is discussed using the results of seismic response analysis.

Journal Articles

Safety enhancement approach against external hazard on JSFR reactor building

Yamamoto, Tomohiko; Kato, Atsushi; Chikazawa, Yoshitaka; Hara, Hiroyuki*

Nuclear Technology, 206(12), p.1875 - 1890, 2020/12

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

This paper gives a detailed evaluation of the countermeasures for the external hazards and severe accidents that could impact the 2010 JSFR design building by lessons learned from the Fukushima Daiichi Nuclear Power Plant (Fukushima I NPP) accident.

Journal Articles

Comparison of sodium fast reactor core assembly seismic evaluation using the Japanese JAEA/MFBR/MHI and French CEA simulation tools

Yamamoto, Tomohiko; Matsubara, Shinichiro*; Harada, Hidenori*; Saunier, P.*; Martin, L.*; Gentet, D.*; Dirat, J.-F.*; Collignon, C.*

Proceedings of 2019 International Congress on Advances in Nuclear Power Plants (ICAPP 2019) (Internet), 8 Pages, 2019/05

Japan-France collaboration on ASTRID (Advanced Sodium Technological Reactor for Industrial Demonstration) project is launched in 2014. In this project, Japan-France evaluates core assemblies with interferences on seismic event. The object of this study is to verify the seismic evaluation method on core assemblies between Japan and France by comparing the results. The analysis of this benchmark calculation shows a satisfactory agreement between the Japanese and French tools and the figures show a good behavior of the core in horizontal direction under French seismic condition.

Journal Articles

Fast reactor core seismic experiment and analysis under strong excitation

Yamamoto, Tomohiko; Iwasaki, Akihisa*; Kawamura, Kazuki*; Matsubara, Shinichiro*; Harada, Hidenori*

Proceedings of 2018 ASME Pressure Vessels and Piping Conference (PVP 2018), 8 Pages, 2018/07

To design fast reactor (FR) core components, seismic response must be evaluated in order to ensure structural integrity. Thus, a core seismic analysis method has been developed to evaluate 3D core vibration behavior considering fluid structure interaction and vertical displacements (rising). 1/1.5 scale 37 core element mock-ups hexagonal-matrix experiment was performed to validate the core elements vibration analysis code in three dimensions (REVIAN-3D). Based on the test data, the analysis model newly incorporated to respond to strong excitation was verified.

Journal Articles

Core seismic experiment and analysis of full scale single model for fast reactor

Yamamoto, Tomohiko; Kitamura, Seiji; Iwasaki, Akihisa*; Matsubara, Shinichiro*; Okamura, Shigeki*

Proceedings of 2017 ASME Pressure Vessels and Piping Conference (PVP 2017) (CD-ROM), 10 Pages, 2017/07

To design fast reactor (FR) components, seismic response must be evaluated in order to ensure structural integrity. Therefore, a sophisticated analysis method has to be developed to study the seismic response of FR core. The fast reactors are made of several hundred core assemblies in hexagonal arrangement. When a big earthquake occurs, large horizontal displacement and impact force of each core assembly may cause a trouble for control rod insertability and core assembly intensity. Therefore, a seismic analysis method of fast reactor core considering horizontal nonlinear behavior, such as impact, fluid-structure interaction, etc. is needed. Validation of the core assembly vibration analysis code in three dimension (REVIAN-3D) was conducted by a full scale experiment. In this validation, the vertical behavior (raising displacement) and horizontal behavior (Impact force, horizontal response) of the analysis result agreed very well with the experiments.

Journal Articles

Research and development of thick rubber bearing for SFR; Aging properties tests of semi full-scale thick rubber bearing

Watakabe, Tomoyoshi; Yamamoto, Tomohiko; Fukasawa, Tsuyoshi*; Okamura, Shigeki*; Somaki, Takahiro*; Morobishi, Ryota*; Sakurai, Yu*; Kato, Koji*

Nihon Kikai Gakkai Rombunshu (Internet), 83(850), p.16-00444_1 - 16-00444_14, 2017/06

A seismic isolation system composed of a thick rubber bearing and an oil damper has been developed for Sodium-Cooled Fast Reactor. This paper focused on the aging properties of thick rubber bearings, such as basic mechanical properties and ultimate strength. Aging of the rubber bearings was reproduced using thermal degradation based on Arrhenius law.

Journal Articles

Secondary sodium fire measures in JSFR

Chikazawa, Yoshitaka; Kato, Atsushi*; Yamamoto, Tomohiko; Kubo, Shigenobu; Ohno, Shuji; Iwasaki, Mikinori*; Hara, Hiroyuki*; Shimakawa, Yoshio*; Sakaba, Hiroshi*

Nuclear Technology, 196(1), p.61 - 73, 2016/10

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

JSFR adopts double boundary for all sodium components. However, design measures are investigated for the secondary sodium fire inside the reactor building, which might be assumed as design extension conditions (DECs). Candidates of sodium fire measures in the secondary sodium systems such as sodium drain, nitrogen injection, pressure release valve, catch pan and leak sodium drain system have been compared from the view point of safety. Wide range of sodium fires in the steam generator room and air cooler have been analyzed evaluating performances of the candidate sodium fire measures.

Journal Articles

Development of seismic isolation systems for sodium-cooled fast reactors in Japan

Kawasaki, Nobuchika; Watakabe, Tomoyoshi; Wakai, Takashi; Yamamoto, Tomohiko; Fukasawa, Tsuyoshi*; Okamura, Shigeki*

Proceedings of 2016 ASME Pressure Vessels and Piping Conference (PVP 2016) (Internet), 8 Pages, 2016/07

Sodium-cooled Fast Reactors (SFRs) have components with thinner walls as compared with light water reactors, although Japan is an earthquake-prone country. Thus, seismic isolation systems have been conventionally employed in SFR system design to reduce seismic forces on the systems in Japan. Implementation of seismic design in the reactor core and buckling design in the reactor vessel requires 8 Hz (or less) vertical frequency's isolation system being applied. This paper introduces three isolation concepts to achieve the frequency. The isolation systems, which enable vertical 8 Hz natural frequency, comprise thicker laminated rubber bearings (TRBs). By combining coned disk springs with TRBs, vertical natural frequency is in a range from roughly 3 Hz to 5 Hz. Combining pneumatic springs to RBs and adding the rocking suppression system, vertical natural frequency becomes under 1 Hz. All isolation systems need horizontal damping like oil dampers. A vertical 8 Hz isolation system with TRBs and oil dampers is under development in Japan as a principal isolation concept. The reasons of choosing this system are its simplicity and the number of developing issues. Since TRBs and oil dampers are basic isolation elements, they can be applied to other isolation systems. The response acceleration of 5 Hz vertical isolation is 50% of that of 8 Hz based on the analytical survey. A series of static tests of coned disk springs was carried out to confirm design equations. Based on these knowledge, 5 Hz vertical isolation system with TRBs and the coned disk springs can be designed. The response acceleration of 1 Hz vertical isolation is 10% of that of 8 Hz. A rocking suppression system was studied in the past, and the further simplification of this system is the largest challenge for this concept. These three isolation concepts are isolation candidates for SFRs in Japan. To obtain enough seismic margins for each plant site, these isolation systems need to be developed.

Journal Articles

Development on rubber bearings for sodium-cooled fast reactor, 4; Aging properties of a half scale thick rubber bearings based on breaking test

Watakabe, Tomoyoshi; Yamamoto, Tomohiko; Fukasawa, Tsuyoshi*; Okamura, Shigeki*; Somaki, Takahiro*; Morobishi, Ryota*; Sakurai, Yu*; Kato, Koji*

Proceedings of 2016 ASME Pressure Vessels and Piping Conference (PVP 2016) (Internet), 8 Pages, 2016/07

A seismic isolation system composed of a thick rubber bearing and an oil damper has been developed for Sodium cooled Fast Reactor. One of the advantages of the isolation system is employing the thick rubber bearing in order to realize the longer vertical natural period of a plant, and it leads to mitigation of seismic loads to mechanical components. Rubber bearing technology has progressed based on many past studies, but test data regarding an aging effect is not enough. Also, there is no data of linear strain limit and breaking behavior for the thick rubber bearing after aging. This paper focuses on aging properties of the thick rubber bearing, such as basic mechanical properties and ultimate strength. An aging promote test of the thick rubber bearing was performed by using 1/2 scale and 1/8 scale rubber bearings. Aging of the rubber bearing was reproduced by thermal degradation, where the target aging period was 30 years and 60 years. The load deflection curves of the thick rubber bearing after aging were obtained through the horizontal and vertical static loading tests, and the aging effect was evaluated by comparing with the initial mechanical properties.

Journal Articles

Development on rubber bearings for sodium-cooled fast reactor, 3; Ultimate properties of a half scale thick rubber bearings based on breaking test

Fukasawa, Tsuyoshi*; Okamura, Shigeki*; Yamamoto, Tomohiko; Kawasaki, Nobuchika; Hirotani, Tsutomu*; Moriizumi, Eriko*; Sakurai, Yu*; Masaki, Nobuo*

Proceedings of 2016 ASME Pressure Vessels and Piping Conference (PVP 2016) (Internet), 10 Pages, 2016/07

Half-scale thick rubber bearing to investigate ultimate properties application for a Sodium-cooled-Fast-Reactor. The fundamental restoring-force characteristics of the thick rubber bearings has been already cleared through the static loading tests using a half-scale thick rubber bearing, 800 mm in diameter. However, variations of the restoring force characteristics and ultimate properties have not been obtained yet. The purpose of this paper is to indicate the variation of the stiffness and damping ratio concerning restoring force characteristics and the breaking strain or stress as ultimate properties through static loading tests using the half-scale thick rubber bearings.

Journal Articles

Progress report of Japanese simulation research projects using the high-performance computer system Helios in the International Fusion Energy Research Centre

Ishizawa, Akihiro*; Idomura, Yasuhiro; Imadera, Kenji*; Kasuya, Naohiro*; Kanno, Ryutaro*; Satake, Shinsuke*; Tatsuno, Tomoya*; Nakata, Motoki*; Nunami, Masanori*; Maeyama, Shinya*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 92(3), p.157 - 210, 2016/03

The high-performance computer system Helios which is located at The Computational Simulation Centre (CSC) in The International Fusion Energy Research Centre (IFERC) started its operation in January 2012 under the Broader Approach (BA) agreement between Japan and the EU. The Helios system has been used for magnetised fusion related simulation studies in the EU and Japan and has kept high average usage rate. As a result, the Helios system has contributed to many research products in a wide range of research areas from core plasma physics to reactor material and reactor engineering. This project review gives a short catalogue of domestic simulation research projects. First, we outline the IFERC-CSC project. After that, shown are objectives of the research projects, numerical schemes used in simulation codes, obtained results and necessary computations in future.

Journal Articles

Parametric design study about seismic isolation system for fast reactor JSFR

Kawasaki, Nobuchika; Yamamoto, Tomohiko; Fukasawa, Tsuyoshi*; Okamura, Shigeki*

Proceedings of 2015 ASME Pressure Vessels and Piping Conference (PVP 2015) (Internet), 9 Pages, 2015/07

Japanese seismic conditions are getting severer and natural frequencies of components are getting lower due to the enlargements of components' size, therefore response accelerations and buckling margins of reactor vessels were parametrically surveyed with attention to thicknesses, diameters, and isolation frequencies for reviewing necessary isolation specification. RV installed floor responses and buckling margins were calculated based on this seismic condition. Expansion characteristic of isolation system was evaluated by parametric acceleration response analyses. Japanese seismic design condition may become severer than present one, and a natural frequency of main component may decrease. However based on the buckling margin with present plant specifications and the expansion characteristic of isolation system, the advanced isolation system with 8Hz vertical natural frequency was selected as the isolation system of JSFR at still present occasion.

Journal Articles

Development on rubber bearings for sodium-cooled fast reactor, 1; Examination plan

Yamamoto, Tomohiko; Kawasaki, Nobuchika; Fukasawa, Tsuyoshi*; Okamura, Shigeki*; Somaki, Takahiro*; Samejima, Yusuke*; Masaki, Nobuo*

Proceedings of 2015 ASME Pressure Vessels and Piping Conference (PVP 2015) (Internet), 7 Pages, 2015/07

Since a SFR (Sodium-cooled Fast Reactor) has thin-walled component structures, a seismic isolation system is employed to mitigate the seismic force. Seismic isolation system for applying the SFR consists of the laminated rubber bearing considering characteristics of SFR structures. This paper describes a basic mechanical characteristic examination with a 1/8 scale model and a characterization examination plan of half-scale laminated rubber.

Journal Articles

Development on rubber bearings for sodium-cooled fast reactor, 2; Fundamental characteristics of half-scale rubber bearings based on static test

Fukasawa, Tsuyoshi*; Okamura, Shigeki*; Yamamoto, Tomohiko; Kawasaki, Nobuchika; Somaki, Takahiro*; Sakurai, Yu*; Masaki, Nobuo*

Proceedings of 2015 ASME Pressure Vessels and Piping Conference (PVP 2015) (Internet), 10 Pages, 2015/07

This paper described the results of static loading tests using a half-scale rubber bearing model to investigate the fundamental characteristics such as restoring force of a rubber bearing applied to a Sodium-Cooled-Fast-Reactor (SFR). Since the SFR has thin-walled structures, a seismic isolation system is employed to mitigate the seismic force. The static loading tests were performed using the half-scale rubber bearing with a diameter of 800 mm in the range which exceeds a linear limit of horizontal direction and a yield stress of vertical direction to investigate the horizontal and vertical of each stiffness and damping ratio. The fundamental characteristic of rubber bearing employed to the SFR and the validity of a design formula became clear through the static tests.

Journal Articles

Performance evaluation on secondary sodium fire measures in JSFR

Chikazawa, Yoshitaka; Kato, Atsushi; Yamamoto, Tomohiko; Kubo, Shigenobu; Iwasaki, Mikinori*; Hara, Hiroyuki*; Shimakawa, Yoshio*; Sakaba, Hiroshi*

Proceedings of 2014 International Congress on the Advances in Nuclear Power Plants (ICAPP 2014) (CD-ROM), p.523 - 530, 2014/04

JSFR adopts double boundary for all sodium components. However, design measures are investigated for the secondary sodium fire inside the reactor building, which might be assumed as design extension conditions (DECs). Candidates of sodium fire measures in the secondary sodium systems such as sodium drain, nitrogen injection, pressure release valve, catch pan and leak sodium drain system have been compared from the view point of safety. Wide range of sodium fires in the steam generator room have been analyzed evaluating performances of the candidate sodium fire measures.

Journal Articles

Three-dimensional tsunami analysis for the plot plan of a sodium-cooled fast reactor plant

Hayakawa, Satoshi*; Watanabe, Osamu*; Ito, Kei; Yamamoto, Tomohiko

Nihon Kikai Gakkai Rombunshu, B, 79(808), p.2645 - 2649, 2013/12

As the practical evaluation method of the effect of tsunami on buildings, the formula of tsunami force has been used. However, it cannot be applied to complex geometry of buildings. In this study, to analyze the effect of tsunami on the buildings of sodium-cooled fast reactor plant more accurately, three-dimensional tsunami analysis was performed. In the analysis, VOF (Volume of Fluid) method was used to capture free surface of tsunami. At the beginning, it was confirmed that the tsunami experiment results was reproduced by VOF method accurately. Next, the three-dimensional tsunami analysis was performed with VOF method to evaluate the flow field around the buildings of the plant from the beginning of the tsunami until the backwash of that.

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