J101011 Study on Seismic Safety Margin of Large Cylindrical Liquid Storage Tanks in Nuclear Power Plants

2011 ◽  
Vol 2011 (0) ◽  
pp. _J101011-1-_J101011-4
Author(s):  
Akira MAEKAWA ◽  
Tsuneo TAKAHASHI
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Safety Margin ◽  
Storage Tanks ◽  
Seismic Safety ◽  
Liquid Storage

Seismic Safety Margin of Cylindrical Liquid Storage Tanks in Nuclear Power Plants

2011 ◽  
Author(s):  
Akira Maekawa ◽  
Tsuneo Takahashi ◽  
Katsuhisa Fujita
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Large Scale ◽  
Safety Margin ◽  
Buckling Load ◽  
Storage Tanks ◽  
Seismic Safety ◽  
Liquid Storage ◽  
Design Value

In Japanese nuclear power plants, quantitative evaluation for seismic safety margin of the equipment is an important issue. In this study, the seismic safety margin of cylindrical liquid storage tanks used in nuclear power plants was investigated experimentally and analytically using test tanks with water inside. The buckling load of the tanks was examined because buckling was their dominant damage mode. The test tanks were reduced-scale models similar to the large-scale liquid storage tanks used in nuclear power plants. The experimental buckling load was compared with the design value. Furthermore, dynamic and static elastic-plastic buckling simulations by finite element analysis using a three-dimensional model were made and then the simulation results were compared with the experimental and design values. The simulated and experimental results agreed well, showing the values were the nearly-true buckling load, that is, proof stress. The design value was lower than the other values, indicating the difference was the seismic safety margin. The above results illustrated that existing actual tanks would have a bigger seismic safety margin.

Failure Probability of Degraded Pipes Based on Probabilistic Fracture Mechanics for Seismic Safety Margin Assessment on NPP

2010 ◽  
Author(s):  
Yinsheng Li ◽  
Masaki Nakagawa ◽  
Katsumi Ebisawa ◽  
Shinobu Yoshimura ◽  
Hiroyuki Kameda
Keyword(s):  
Failure Probability ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Ground Motions ◽  
Safety Margin ◽  
Mechanical Analysis ◽  
Margin Assessment ◽  
Seismic Safety ◽  
Design Values

The Niigata-ken Chuetsu-oki Earthquake happened in July 2007. Although the observed seismic ground motions of Kashiwazaki-Kariwa nuclear power plants greatly exceeded their design values, the important functions of the plants such as “shutdown”, “cooling”, and “confinement” were successfully ensured. Therefore, assessment of the seismic safety margin of nuclear power plants, both their systems and their components, becomes a very important issue. In this paper, failure probability of cracked pipes in existing nuclear power plants is analyzed by employing an improved probabilistic fracture mechanical analysis code and considering stress corrosion cracking and fatigue. Based on the analysis results of the failure probability and the definitions of the seismic safety margin, the seismic safety margin of degraded pipes in existing nuclear power plants is investigated.

Study on Dynamic Strength Evaluation Method of Mechanical Members Based on Energy Balance

2007 ◽  
Author(s):  
Keisuke Minagawa ◽  
Satoshi Fujita ◽  
Seiji Kitamura ◽  
Shigeki Okamura
Keyword(s):  
Energy Balance ◽  
Experimental Model ◽  
Ultimate Strength ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Dynamic Strength ◽  
Input Energy ◽  
Seismic Safety ◽  
Strength Evaluation

This paper describes the dynamic strength evaluation of piping installed in nuclear power plants from a viewpoint of energy balance. Mechanical structures installed in nuclear power plants such as piping and equipment are usually designed statically in elastic region. Although these mechanical structures have sufficient seismic safety margin, comprehending the ultimate strength is very important in order to improve the seismic safety reliability in unexpected severe earthquakes. In this study, ultimate strength of a simple single-degree-of-freedom model is investigated from a viewpoint of energy balance equation that is one of valid methods for structural calculation. The investigation is implemented by forced vibration experiment. In the experiment, colored random wave having predominant frequency that is similar to natural frequency of the experimental model is input. Stainless steel and carbon steel are selected as material of experimental model. Excitation is continued until the experimental model is damaged, and is carried out with various input levels. As a result of the experiment, it is confirmed that input energy for failure increase with an increase of time for failure. Additionally it is confirmed that input energy for failure depend on the material.

Investigation on Buckling Behavior of Cylindrical Liquid Storage Tanks Under Seismic Excitation: 2nd Report — Investigation on the Nonlinear Ovaling Vibration at the Upper Wall

2003 ◽  
Author(s):  
Hideyuki Morita ◽  
Tomohiro Ito ◽  
Koji Hamada ◽  
Akihisa Sugiyama ◽  
Yoji Kawamoto ◽  
...  
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Pressure Effects ◽  
Storage Tanks ◽  
Response Level ◽  
Vertical Excitation ◽  
Liquid Storage ◽  
Buckling Behavior ◽  
Thin Walled ◽  
Scaled Models

When a thin walled cylindrical liquid storage tank suffers a large seismic base excitation, buckling phenomena such as elephant foot bulge at the bottom portion and nonlinear ovaling vibration at the upper portion shows nonlinearity between the input and response level and suddenly occurs for the excessive input level, thus will be called as “nonlinear ovaling vibration” hereafter in this paper, may be caused. In the 1st report, the elephant foot bulge phenomena and the liquid pressure effects were investigated. In this 2nd report of the series of studies, the effect of nonlinear ovaling vibration phenomena were investigated based on the dynamic buckling tests using scaled models of thin walled cylindrical liquid storage tanks for nuclear power plants. The mechanism and the effect of vertical excitation and liquid sloshing were also studied and discussed.

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