Effects of a Gyroscope in Reducing Rocking Motion of a Rigid Vessel Coupled With Inner Structure Subjected to a Base Excitation

2009 ◽  
Author(s):  
Kazuhisa Furuta ◽  
Tomohiro Ito ◽  
Atsuhiko Shintani
Keyword(s):  
Coming Out ◽  
Nuclear Power ◽  
Outer Cylinder ◽  
Rotational Frequency ◽  
Seismic Excitations ◽  
Free Standing ◽  
Worst Case ◽  
Standing Structure ◽  
Rocking Motion ◽  
Active Substances

Many spent fuels coming out of the nuclear power station are planned to be stored in the special site in Japan until they are reprocessed. In this site, the spent fuels are installed in a cylindrical container called canister. The canister, in tern, will be installed in the outer cylinder called cask that is a free-standing structure. When this system is subjected to strong seismic excitations, sliding or rocking motion will be induced. And, in the worst case, the cask may collide to each other or overturn. Therefore, it is very important to reduce sliding and rocking motions of the cask in order to avoid the consequent contamination of radio active substances. The authors have already reported the studies on the sliding and rocking motions of the cask subjected to a seismic excitation that contains a vibration system in it, and clarified the effects of the vibration of the inner canister. It was shown that the inner canister gives very large influences on the sliding and rocking motions of the outer cask. In this study, we applied a gyroscope at the top of the outer cask for reducing rocking motion of the cask. The effects of the gyroscope are studied for various excitation frequencies, excitation amplitudes and the structural dimensions of the gyroscope such as weight and rotational frequency. It is found that the gyroscope is very effective for reducing rocking motions of the cask-canister system subjected to seismic excitations.

Effects of Connecting Damper on Rocking Motion of Multiple Cabinets Subjected to Seismic Excitation

2015 ◽  
Author(s):  
Tomohiro Ito ◽  
Takatsugu Kihara ◽  
Atsuhiko Shintani ◽  
Chihiro Nakagawa
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Thermal Power ◽  
Analytical Models ◽  
Chemical Plants ◽  
Electronic Circuits ◽  
Seismic Excitations ◽  
Free Standing ◽  
Worst Case ◽  
Rocking Motion

In various industrial plants such as thermal power plants, nuclear power plants and chemical plants, numerous cabinets are used for storing the electronic circuits and devices used for controlling the plants. These cabinets are very important for maintaining stable plant operation. Some of these cabinets are simply placed on the floor as free-standing structures, and in many cases, they cannot be connected to the floor using bolts or other means for various reasons. Thus, if these cabinets are subjected to very strong seismic excitations, they will experience very large rocking motions. In the worst case, they will overturn, and the installed electronic circuits or devices will collapse which will cause a loss of plant control and could result in significant accidents. Thus, rocking motion suppression methods have been proposed for these free-standing structures. The authors have also been investigating a method that utilizes a gyro system. Connecting adjacent buildings by damping devices is a well-known architectural mitigation method that is very effective at mitigating their seismic response. The effectiveness of this method was confirmed during the Great East Japan Earthquake in 2011. In this paper, we apply the above-mentioned connecting method to free-standing cabinets in order to suppress rocking motion. There are various types of connecting devices, such as a viscous damper. In this paper, considering the characteristics of these dampers, an elasto-plastic damper is adopted as a connecting device. Analytical models of the rocking motions of control cabinets are established, and the connecting devices are expressed as dampers with a bilinear-type force-displacement characteristic. The rocking motions of the cabinets are analyzed for sinusoidal and seismic excitations by changing the aspect ratio of the cabinets, along with the yield force in the bilinear hysteretic curve. The effects of connecting devices and various parameters are evaluated and discussed in comparison with the rocking motion of a single cabinet. It is found that the proposed connecting method is very effective in suppressing the rocking motion of the free-standing cabinets subjected to base excitations when the hysteretic characteristics are properly adjusted.

Rocking and Sliding Motions of a Freely Standing Structure Coupled With Inner Structure

2008 ◽  
Author(s):  
Kazuhisa Furuta ◽  
Tomohiro Ito ◽  
Atsuhiko Shintani
Keyword(s):  
Coming Out ◽  
Nuclear Power ◽  
Seismic Event ◽  
Outer Cylinder ◽  
Coupled System ◽  
Rigid Bodies ◽  
Free Standing ◽  
Power Stations ◽  
Standing Structure ◽  
Two Degree Of Freedom

Many spent fuels coming out of the nuclear power stations are planned to be stored in the special site in Japan until they are reprocessed. In this site, the spent fuels are installed in a cylindrical container called canister. And the canister is installed in an outer cylinder called cask which is a free-standing structure. Therefore, it is very important to reduce the seismic response of the cask during a seismic event. In this study, the sliding and rocking motions of a cask are evaluated analytically. In an analytical model, the cask and the canister are treated as rigid bodies which are connected by a spring, because the cask and canister system is seen as a two-degree-of-freedom coupled system. The equations are derived for the sliding and rocking motions when the floor is subjected to a horizontal excitation. The displacement and the rocking angle of the cask are evaluated by numerical simulations. The effects of the canister vibration on the cask motion are discussed.

Mitigation of Rocking and Sliding Motion of a Free-Standing Structure Subjected to Base Excitation Using Coaxial Circular Cylinders Containing Highly Viscous Liquid in Annular Spaces

2019 ◽  
Author(s):  
Atsuhiko Shintani ◽  
Tomohiro Ito ◽  
Chihiro Nakagawa
Keyword(s):  
Rigid Body ◽  
Viscous Liquid ◽  
Analytical Model ◽  
Circular Cylinders ◽  
Base Excitation ◽  
Free Standing ◽  
Seismic Input ◽  
Sliding Motion ◽  
Standing Structure ◽  
Rocking Motion

Abstract In this study, the effectiveness of coaxial circular cylinders containing a highly viscous liquid in annular spaces for reduction of rocking motion of a free-standing structure is investigated both analytically and experimentally. First, an analytical model of coupled rocking and sliding motions of a free-standing structure, including the coaxial circular cylinders, subjected to seismic input was derived. The free-standing structure was modeled as a free-standing rigid body. The cylinders were attached to the bottom of the rigid body as a damping device. We then experimentally derived the friction coefficients, inertia moments, and a damping coefficient in the rotating direction. Furthermore, using these parameters, the effectiveness of this system in suppressing the rocking motion is investigated analytically. The proposed method was determined to be very effective in suppressing the rocking motion of a rigid body subjected to a seismic input by the experiment.

Construction of Dynamic Model for Free Standing Spent Fuel Rack Under Seismic Excitations

2015 ◽  
Author(s):  
Shigehiko Kaneko ◽  
Hironao Shirai
Keyword(s):  
Dynamic Model ◽  
Nuclear Power ◽  
Scale Model ◽  
Spent Fuel ◽  
Seismic Excitations ◽  
Power Station ◽  
Free Standing ◽  
Method Of Calculation ◽  
Gap Flow ◽  
Real Size

Free standing rack designed for storing spent fuel at nuclear power station has an advantage to earthquake excitations because both fluid force and friction force can reduce the movement of a rack. However, there are various motions of FS rack such as parallel, rotational and rocking which should be taken into consideration when it is subjected to earthquake excitations. Therefore, the motion of FS rack must be precisely figured out in order to apply FS rack design concept. In this research, to investigate the motion of FS rack, 2-dimensional dynamic model considering pressure loss of gap flow was constructed. In addition, an experiment with a 1/16 scale model was conducted to validate the dynamic model. From numerical results based on the proposed dynamic model, some important features for the design of FS rack were found. Finally, case studies by real size free standing rack under the excitation of actually observed earthquake wave like The Great East Japan earthquake and The Niigata-ken Chuetsu-Oki earthquake were conducted based on the proposed method of calculation.

Fundamental Study on Mitigation of Rocking Motion of a Cask System by a Gyro System

2013 ◽  
Author(s):  
Tomohiro Ito ◽  
Yasumasa Ishikawa ◽  
Atsuhiko Shintani ◽  
Chihiro Nakagawa
Keyword(s):  
Structural Integrity ◽  
Shaking Table ◽  
System Model ◽  
Spent Fuel ◽  
Free Standing ◽  
Fundamental Study ◽  
Worst Case ◽  
Gyro System ◽  
Rocking Motion ◽  
Basic Characteristics

In Japan, ensuring the structural integrity of cask systems during seismic events is becoming increasingly important. Cask systems, which are free-standing cylindrical structures that contain spent fuel assemblies, are believed to exhibit rocking motions under strong seismic excitations. Thus far, analytical studies conducted by the authors have indicated that cask systems subjected to strong seismic motions, undergo large rocking motions, and, in the worst case, may overturn and collapse. Therefore, reducing the rocking motions of casks to avoid overturning and consequent contamination of radioactive substances is critical. To suppress rocking motions for heavy free-standing structures such as cask systems, we propose a rocking motion suppression system that employs a gyro system. This system is installed in the free-standing structure. A previous analytical study showed that this system largely mitigates rocking motion. In the present study, we fabricated a fundamental cask system model and a gyro system. By using the cask system model without a gyro system, free vibration tests and shaking table tests were conducted to understand the basic characteristics of rocking motion and responses under base excitations. Analyses were also conducted to confirm the validity of the analytical model for rocking motion comparing with the experimental data. Moreover, analyses for the cask system with the gyro system were conducted. From these results, we evaluated the ability of the gyro system to mitigate rocking motion.

615 FUNDAMENTAL STUDY ON MITIGATION OF ROCKING MOTION OF A FREE-STANDING STRUCTURE BY A GYRO SYSTEM

2014 ◽  
Vol 2014.89 (0) ◽  
pp. _6-15_
Author(s):  
Yasumasa Ishikawa ◽  
Tomohiro Ito ◽  
Atsuhiko Shintani ◽  
Chihiro Nakagawa
Keyword(s):  
Free Standing ◽  
Fundamental Study ◽  
Gyro System ◽  
Standing Structure ◽  
Rocking Motion

Mitigation of Sliding Motion of a Cask-Canister by Fluid-Structure Interaction in an Annular Region

2011 ◽  
Author(s):  
Tomohiro Ito ◽  
Yoshihiro Fujiwara ◽  
Atsuhiko Shintani ◽  
Chihiro Nakagawa ◽  
Kazuhisa Furuta
Keyword(s):  
Equations Of Motion ◽  
Fluid Structure Interaction ◽  
Shaking Table ◽  
Annular Region ◽  
Test Model ◽  
Free Standing ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Sliding Motion ◽  
Standing Structure

The cask-canister system is a coaxial circular cylindrical structure in which several spent fuels are installed. This system is a free-standing structure thus, it is very important to reduce sliding motion for very large seismic excitations. In this study, we propose a mitigation method for sliding motion. Water is installed in an annular region between a cask and a canister. The equations of motion are derived taking fluid-structure interaction into consideration for nonlinear sliding motion analyses. Based on these equations, mitigation effects of sliding motions are studied analytically. Furthermore, a fundamental test model of a cask-canister system is fabricated and shaking table tests are conducted. From the analytical and test results, sliding motion mitigation effects are investigated.

scholarly journals Highly sensitive pressure sensors employing 3C-SiC nanowires fabricated on a free standing structure

2018 ◽  
Vol 156 ◽  
pp. 16-21 ◽  
Author(s):  
Hoang-Phuong Phan ◽  
Karen M. Dowling ◽  
Tuan Khoa Nguyen ◽  
Toan Dinh ◽  
Debbie G. Senesky ◽  
...  
Keyword(s):  
Pressure Sensors ◽  
Free Standing ◽  
Sic Nanowires ◽  
Highly Sensitive ◽  
Standing Structure ◽  
Sensitive Pressure

Ultimate Heat Sink Sizing Requirements on a Month-to-Month Basis

2009 ◽  
Author(s):  
Dong Zheng ◽  
Allen T. Vieira ◽  
Julie M. Jarvis ◽  
George P. Emsurak
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Heat Sink ◽  
Nuclear Power ◽  
Meteorological Data ◽  
Meteorological Condition ◽  
Water Requirement ◽  
Next Generation ◽  
Worst Case ◽  
Automated Methods

The Ultimate Heat Sink (UHS) of a nuclear power plant is a complex cooling water system which serves the plant during normal and accident conditions. For some next generation nuclear plants, the UHS sizing is a major design and licensing analysis task. The analysis involves detailed modeling of the transient heat loads and the selection of worst-case meteorological data for the plant site. The UHS sizing requirements for a representative next generation nuclear power plant are evaluated on a month-to-month basis. This paper assesses the UHS water requirement for each month of year. The UHS analysis for a representative next generation nuclear plant with mechanical draft cooling towers and a water basin is used to determine the maximum evaporation of the basin for the worst-case meteorological data on a month-to-month basis. To size the cooling tower basin, automated methods have been developed which determine the highest evaporative losses from the basin and highest basin temperature over a 30-day design basis accident period. This paper also evaluates the month-to-month basin temperature changes. This assessment is done for a representative next generation nuclear power plant and considers the monthly historical meteorological data over 45 years. The result of this assessment of monthly UHS water requirement is of interest in assessing the margin in the UHS design. This monthly assessment is also useful in demonstrating that the automated methods used to establish the limiting 30-day meteorological condition are indeed accurate. In addition, these results may be useful in helping to plan plant maintenance activities.

Study on Vibration Mitigation of Connected Cabinets Storing Electronics Subjected to Seismic Input Using Elasto-Plastic Damper

2020 ◽  
Author(s):  
Atsuhiko Shintani ◽  
Takuma Yoshida ◽  
Chihiro Nakagawa ◽  
Tomohiro Ito
Keyword(s):  
Rigid Body ◽  
Seismic Wave ◽  
Power Plants ◽  
Rigid Bodies ◽  
Single System ◽  
Maximum Acceleration ◽  
Worst Case ◽  
Seismic Input ◽  
Entire Plant ◽  
Rocking Motion

Abstract This paper deals with the motion of coupled cabinets containing electronics subjected to seismic input. In power plants, chemical plants, etc., several rectangular cabinets containing important electronics are always lined up in the control center. These electronics are necessary for the control of the entire plant; thus, when they are damaged, the entire plant cannot be controlled, and a serious accident may occur. These cabinets are frequently put directly on the floor. Thus, it is perceived that in the worst case, cabinets may turn over by rocking motion during earthquakes and electronics may break. Moreover, even when the cabinets do not overturn, there is a concern about a large acceleration applied to the internal electronics due to the seismic waves. Hence, the need to develop methods that can reduce rocking motion and prevent electronics damage simultaneously. First, we consider the single cabinet with electronics. The cabinet is modeled as a rotating rigid body around its corner. The internal electronics are modeled as a rigid body moving in the translational direction in the cabinet. This system is referred to as single system. We input a seismic wave to the single system and investigate the rocking angle of the cabinet and the acceleration of the electronics in the cabinet. Consequently, we consider the adjacent cabinets connected by an elasto-plastic damper containing electronics. The cabinets are modeled as rotating rigid bodies. The internal electronics are modeled as rigid bodies moving in the translational direction in the cabinets. The whole system is known as a connected system. The elasto-plastic damper has bilinear hysteretic characteristics and can absorb the energy of earthquake inputs. We input the same seismic wave to the connected system to obtain the rocking angle of cabinets and the acceleration of electronics in the connected system. In these simulations, it is assumed that cabinets do not collide with each other. Then, we investigate the effect of the parameters of the elasto-plastic damper suppressing the rocking angle of the cabinets and the acceleration of electronics. Finally, we compare the maximum rocking angle and the maximum acceleration of the single system with that of the connected system and consider an ideal method to reduce the rocking angle and the acceleration simultaneously.

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