Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Kinoshita, Takahiro*; Okamura, Shigeki*; Nishino, Hiroyuki; Yamano, Hidemasa; Kurisaka, Kenichi; Futagami, Satoshi; Fukasawa, Tsuyoshi*
Transactions of 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.
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.
Uchita, Masato*; Miyagawa, Takayuki*; Dozaki, Koji*; Chikazawa, Yoshitaka; Kubo, Shigenobu; Hayafune, Hiroki; Suzuno, Tetsuji*; Fukasawa, Tsuyoshi*; Kamishima, Yoshio*; Fujita, Satoshi*
Proceedings of 2018 International Congress on Advances in Nuclear Power Plants (ICAPP 2018) (CD-ROM), p.380 - 386, 2018/04
It is well-known that pool-type SFRs are the main streams recently in a field of Generation IV reactors. The pool-type encloses primary pumps and IHXs located around the core barrel in a main vessel. Consequently, the main vessel diameter trends to be larger than that of loop-types. From the viewpoint of commercialization in the future, a target of the vessel diameter and its weight including Sodium coolant will increase further. In this paper, the prospects are described in terms of seismic design and structural integrity for the thermal loadings to prevent buckling of the reactor vessel based on parameter studies with diameters of the vessel. In addition, the seismic isolation device which will be effective as a countermeasure is proposed in order to secure a margin against buckling of a large reactor vessel.
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.
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.
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.
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.
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.
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.
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.
Fukasawa, Tsuyoshi*; Shimoji, Kuniyuki*; Kawamura, Masaya*; Okamura, Shigeki*; Kisohara, Naoyuki; Enuma, Yasuhiro
no journal, ,
no abstracts in English
Sakamoto, Yoshihiko; Fukasawa, Tsuyoshi*; Kawasaki, Nobuchika; Okamura, Shigeki*
no journal, ,
Design study of an FBR demonstration facility is now in progress for the sodium-cooled fast reactor (JSFR). In JSFR, a seismic isolation system is adopted from the viewpoint of reduction in seismic force to major components taking into account the characteristics of the fast reactor. After the 2011 off the Pacific coast of Tohoku Earthquake, a design earthquake was revised for investigation to ensure seismic resistance under a severer seismic condition. Moreover, countermeasures against various external hazards such as tsunami, etc. were investigated for the purpose of establishment of safety design guidelines and enhancement of safety. This presentation introduces the design earthquake and the seismic isolation system concept responding to the external hazards with issues for realization.
Yamamoto, Tomohiko; Kawasaki, Nobuchika; Ishikawa, Nobuyuki; Chikazawa, Yoshitaka; Fukasawa, Tsuyoshi*; Okamura, Shigeki*
no journal, ,
Due to the increase of the seismic condition for JSFR design study, the seismic condition for the design study of components is severer. This report explains the effect of study on reduction of vertical seismic response through the 3-dimensional FEM analysis focusing on study on reduction of vertical seismic response of main components that are critical in seismic feasibility. It also explains the integrity of vertical seismic response of FEM model and the mass model used in design studies with reflecting the vertical seismic response reduction.
Yamamoto, Tomohiko; Watakabe, Tomoyoshi; Okamura, Shigeki*; Fukasawa, Tsuyoshi*
no journal, ,
This paper summarizes the results of each experiment for thicker laminated rubber bearingand shows that the thicker laminated rubber bearing is useful for seismic isolation system for SFR.
Uchita, Masato*; Dozaki, Koji*; Suzuno, Tetsuji*; Fukasawa, Tsuyoshi*; Hayafune, Hiroki; Kato, Atsushi
no journal, ,
Seismic evaluation on the reactor vessel of the pool type sodium-cooled reactor has been conducted using seismic conditions for domestic LWR sites. And parametric design survey when the reactor output is enlarged has also conducted showing available reactor vessel thickness with holizontal seismic isolation system and advanced design with three-dimensional seismic isolation system.
Yamamoto, Tomohiko; Watakabe, Tomoyoshi; Miyagawa, Takayuki*; Okamura, Shigeki*; Fukasawa, Tsuyoshi*; Fujita, Satoshi*
no journal, ,
This report describes that the concepts and specifications of "3-dimensional seismic isolation device" adopting in a Sodium-cooled fast reactor, summary of various tests and analyzes, and shows feasibility of 3-dimensional seismic isolation device for earthquake response reduction effect.
Yamamoto, Tomohiko; Watakabe, Tomoyoshi; Miyagawa, Takayuki*; Fukasawa, Tsuyoshi*; Okamura, Shigeki*; Fujita, Satoshi*
no journal, ,
This report describes that the concepts and specifications of "3-dimensional seismic isolation device" adopting in a Sodium-cooled fast reactor, summary of various tests and analyzes, and shows feasibility of 3-dimensional seismic isolation device for earthquake response reduction effect.
Yamamoto, Tomohiko; Fukasawa, Tsuyoshi*; Somaki, Takahiro*; Hirokawa, Atsushi*; Miyagawa, Takayuki*; Okamura, Shigeki*
no journal, ,
High speed type horizontal oil damper is developed for three dimensional seismic isolation system for SFR. This paper describes the experimental plan of this oil damper.
Okamura, Shigeki*; Kinoshita, Takahiro*; Nishino, Hiroyuki; Yamano, Hidemasa; Kurisaka, Kenichi; Futagami, Satoshi; Fukasawa, Tsuyoshi*
no journal, ,
A Sodium-Cooled Fast Reactor (SFR) has thin-walled structures compared to the LWRs, because its thermal stress due to elevated temperature is much higher and its internal pressure is much lower than that of the LWRs. A seismic isolation system is employed to reduce the seismic force, because the thin-walled structure is strongly affected by severe earthquakes. The thicker laminated rubber bearings are adopted for SFR. The laminated rubber bearing with thickness rubber is adopted for SFR. The characteristic of the laminated rubber bearing has been grasped by the static test with 1/2scale model. The analysis model, which improved non-linear characteristic, has suggested. On the other hand, the earthquake PRA has carried out in the seismic isolation plant of SFR. In this study, the seismic response analysis with the improved analysis model was carried out. The acceleration response in the floor response spectrum was grasped. The damage probability of the reactor with the non-linear characteristic of the laminated rubber bearing is improved.
Okamura, Shigeki*; Fujita, Satoshi*; Uchita, Masato*; Fukasawa, Tsuyoshi*; Yamamoto, Tomohiko
no journal, ,
no abstracts in English
