Seismic Abatement Method for Nuclear Power Plants and Seismic-Isolation Systems for Structural Elements

In Japan, applications of seismic isolation systems to new generation nuclear power plants and fast breeder reactors have been expected in order to enhance seismic safety. However there are lots of restrictions for design of isolation systems, such as strong design seismic wave, deformation of piping between an isolated structure and a non-isolated structure, and so on. In addition combination of horizontal and vertical isolation has possibility to cause rocking motion if a three-dimensional isolation system is applied. Therefore isolation systems should be designed properly. Moreover the design of seismic isolation system has to consider influence on inner equipment and piping. This paper describes investigation regarding required properties and performance of seismic isolation system for nuclear power plants. The investigation is carried out by numerical analysis. In the analysis, various isolation devices such as friction pendulum bearings and so on are applied as well as natural rubber bearings.

Response Analysis of a Seismic Isolated Structure Considering a Probabilistic Approach

10.1115/pvp2014-28596 ◽

2014 ◽

Author(s):

Naoki Akamatsu ◽

Satoshi Fujita ◽

Keisuke Minagawa

Keyword(s):

Sensitivity Analysis ◽

Nuclear Power ◽

Seismic Isolation ◽

Power Plants ◽

Nuclear Power Plants ◽

Large Scale ◽

Probabilistic Approach ◽

Nonlinear Behavior ◽

Response Analysis ◽

Isolation Systems

Japan is one of the most advanced countries in earthquake technology. Isolation systems are widely used in large-scale structures such as hospitals and communication centers. For example, an isolated office building has been used as a hub of recovery from accident by Great East Japan Earthquake in Fukushima nuclear power plant. In the meantime, application of probabilistic risk assessment is used for structure of nuclear power plants. In 2006, Regulatory Guide for Reviewing Seismic Design was revised and according to guideline, it is necessary to consider the residual risk1. In addition, seismic isolation systems are expected to be used for nuclear power plants. Recently, the risk of isolation system’s failure needs to be assessed in case of large ground motion. This paper deals with probabilistic approach on seismic response of an isolated structure. Consequently, sensitivity analysis is carried out. Then, as nonlinear behavior in rubber bearings occurs during huge earthquake, it has to be considered in the sensitivity analysis.

Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities: Part 10 — Evaluation of Seismic Isolator Design

10.1115/pvp2014-29040 ◽

2014 ◽

Cited By ~ 3

Author(s):

Hiroyuki Asano ◽

Tsutomu Hirotani ◽

Takashi Nakayama ◽

Takemi Norimono ◽

Yuji Aikawa ◽

...

Keyword(s):

Nuclear Power ◽

Seismic Isolation ◽

Power Plants ◽

Evaluation Method ◽

Large Diameter ◽

Seismic Isolator ◽

Long Duration ◽

Seismically Isolated ◽

Isolation Systems ◽

This paper provides a part of series of “Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities”. This part shows an evaluation of seismic isolator design established in this project where several methods are newly developed. The major four accomplishments are as follows. One: establishment of design earthquake specially considered for seismically isolated nuclear power facilities. The design earthquakes are made to fit multiple target spectra with different damping factors considering a building, equipment and seismic isolators for more precise response analyses. Two: design and development of a high-performance seismic isolator. Against the large design earthquakes, a seismic isolator is newly developed which has a large diameter lead plug for more damping; the isolators were actually manufactured and tested. Three: seismic response analyses for seismically isolated nuclear power plants. Light water reactors are designed where the structural characteristics of the seismic isolation system is reflected. Four: evaluation of thermal effects on seismic isolators by a long-duration earthquake. Considering a long-duration earthquake, the heat generation phenomenon in the lead plug is analytically evaluated to ensure the lead plug’s damping performance. By introducing these accomplishments, the realistic design of a seismically isolated nuclear power plant is achieved.

Seismic Performance of Piping Systems of Isolated Nuclear Power Plants Determined by Numerical Considerations

Energies ◽

10.3390/en14134028 ◽

2021 ◽

Vol 14 (13) ◽

pp. 4028

Author(s):

Sungjin Chang ◽

Bubgyu Jeon ◽

Shinyoung Kwag ◽

Daegi Hahm ◽

Seunghyun Eem

Keyword(s):

Seismic Response ◽

Nuclear Power ◽

Seismic Isolation ◽

Power Plants ◽

Nuclear Power Plants ◽

Mesh Size ◽

Seismic Fragility ◽

Response Analysis ◽

Seismic Safety ◽

The interest in the seismic performance of nuclear power plants has increased worldwide since the Fukushima Daiichi Nuclear Power Plant incident. In Korea, interest in the seismic safety of nuclear power plants has increased since the earthquake events in Gyeongju (2016) and Pohang (2017). In Korea, studies have been conducted to apply seismic isolation systems to ensure seismic safety while minimizing the design changes to nuclear power plants. Nuclear power plants with seismic isolation systems may have a higher seismic risk due to the failure of the piping system in the structure after a relatively large displacement. Therefore, it is essential to secure the seismic safety of pipes for the safe operation of nuclear power plants. The seismic safety of pipes is determined by seismic fragility analysis. Seismic fragility analysis requires many seismic response analyses because it is a statistical approach to various random variables. Typical numerical conditions affecting the seismic response analysis of pipes are the convergence conditions and mesh size in numerical analysis. This study examined the change in the seismic safety of piping according to the numerical conditions. The difference in the seismic response analysis results of the piping according to the mesh size was analyzed comparatively. In addition, the change in the seismic fragility curve of the piping according to the convergence conditions was investigated.

Volume 5: High-Pressure Technology; ASME NDE Division; 22nd Scavuzzo Student Paper Symposium and Competition ◽

Effect of Nonlinearity of Rubber Bearing on a Seismic Isolated Structure Considering Their Layout

10.1115/pvp2014-28474 ◽

2014 ◽

Author(s):

Sebastien Chirez ◽

Satoshi Fujita ◽

Keisuke Minagawa

Keyword(s):

Nuclear Power ◽

Seismic Isolation ◽

Power Plants ◽

Response Analysis ◽

Seismic Safety ◽

Rubber Bearing ◽

Isolation Systems ◽

Set Up ◽

Rubber Bearings ◽

In Japan, in order to ensure seismic safety requirements for buildings such as hospitals, nuclear power plants and communication centers for instance, seismic isolation systems have been developed. The most widely used technologies are rubber bearings and oil dampers, which can enhance the protection of equipment or machinery set up in those buildings. However, the isolation performance may face difficulties in case of huge earthquakes because of the nonlinearity of rubber bearings. In a former study of our laboratory, an earthquake response analysis based on the Runge-Kutta-Gill’s method had been carried out in order to assess the behavior of the rubber bearings[1]. In this paper, we use the same method but for further accurate and more realistic simulations, the analytical model has been improved in order to assess the response of rubber bearings depending on their layout when we consider the rocking of the building.

Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities: Part 6 — Scaled Tests to Obtain Basic Characteristics of Lead Rubber Bearing

10.1115/pvp2014-29002 ◽

2014 ◽

Author(s):

Tsutomu Hirotani ◽

Ryota Takahama ◽

Masaki Yukawa ◽

Hiroshi Hibino ◽

Yuji Aikawa ◽

...

Keyword(s):

Nuclear Power ◽

Seismic Isolation ◽

Evaluation Method ◽

Loading Test ◽

Rubber Bearing ◽

Lead Rubber Bearing ◽

Basic Characteristics ◽

Isolation Systems ◽

Seismic Isolation Systems ◽

Hysteresis Characteristics

This paper provides a series comprising the “Development of Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities”. Part 6 presents scaled tests for Lead Rubber Bearing (LRB) newly developed for this project. Following tests are performed to obtain the basic characteristics of LRB,. (1) Horizontal and Vertical Simultaneous Loading Test: LRBs with diameter of 250mm are tested dynamically under simultaneous axial and lateral loading. The hysteresis characteristics is not changed under compressive load although it is changed under tensile load. (2) Basic Break Test: LRBs with a diameter of 800mm are tested statically under various combinations of axial and lateral forces. The hysteresis characteristics model of LRB is determined by this test. It is confirmed that the breaking strain of LRB under compression load exceeds 450%. (3) Horizontal Hardening and Vertical Softening Test: For LRBs with a diameter of 1200 mm, 75% scale of actual LRB are tested statically for horizontal hardening and vertical softening regions. It is confirmed that the hysteresis model which is developed by smaller LRBs is applicable to these large scale models.

Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities: Part 2 — Application of CCFS Method to the Multiply Supported Systems

10.1115/pvp2014-28999 ◽

2014 ◽

Cited By ~ 1

Author(s):

Koichi Tai ◽

Keisuke Sasajima ◽

Shunsuke Fukushima ◽

Noriyuki Takamura ◽

Shigenobu Onishi

Keyword(s):

Power Plant ◽

Nuclear Power ◽

Seismic Isolation ◽

Evaluation Method ◽

Time History ◽

Piping System ◽

History Analysis ◽

Piping Systems ◽

Isolation Systems ◽

This paper provides a part of series of “Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities”. Paper is focused on the seismic evaluation method of the multiply supported systems, as the one of the design methodology adopted in the equipment and piping system of the seismic isolated nuclear power plant in Japan. Many of the piping systems are multiply supported over different floor levels in the reactor building, and some of the piping systems are carried over to the adjacent building. Although Independent Support Motion (ISM) method has been widely applied in such a multiply supported seismic design of nuclear power plant, it is noted that the shortcoming of ignoring correlations between each excitations is frequently misleaded to the over-estimated design. Application of Cross-oscillator, Cross-Floor response Spectrum (CCFS) method, proposed by A. Asfura and A. D. Kiureghian[1] shall be considered to be the excellent solution to the problems as mentioned above. So, we have introduced the algorithm of CCFS method to the FEM program. The seismic responses of the benchmark model of multiply supported piping system are evaluated under various combination methods of ISM and CCFS, comparing to the exact solutions of Time History analysis method. As the result, it is demonstrated that the CCFS method shows excellent agreement to the responses of Time History analysis, and the CCFS method shall be one of the effective and practical design method of multiply supported systems.

Issues in seismic isolation of nuclear power plants

Nuclear Engineering and Design ◽

10.1016/0029-5493(85)90261-4 ◽

1985 ◽

Vol 84 (3) ◽

pp. 433-438 ◽

Cited By ~ 4

Author(s):

A.H. Hadjian ◽

W.S. Tseng

Keyword(s):

Nuclear Power ◽

Seismic Isolation ◽

Power Plants ◽

Nuclear Power Plants

Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities: Part 3 — Seismic Response of Crossover Piping for Seismic Isolation System

10.1115/pvp2014-29012 ◽

2014 ◽

Author(s):

Akihito Otani ◽

Teruyoshi Otoyo ◽

Hideo Hirai ◽

Hirohide Iiizumi ◽

Hiroshi Shimizu ◽

...

Keyword(s):

Seismic Response ◽

Nuclear Power ◽

Seismic Isolation ◽

Evaluation Method ◽

Response Spectrum ◽

Time History ◽

Response Analysis ◽

Isolation System ◽

Isolation Systems ◽

This paper, which is part of the series entitled “Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities”, shows the linear seismic response of crossover piping installed in a seismically isolated plant. The crossover piping, supported by both isolated and non-isolated buildings, deforms with large relative displacement between the two buildings and the seismic response of the crossover piping is caused by two different seismic excitations from the buildings. A flexible and robust structure is needed for the high-pressure crossover piping. In this study, shaking tests on a 1/10 scale piping model and FEM analyses were performed to investigate the seismic response of the crossover piping which was excited and deformed by two different seismic motions under isolated and non-isolated conditions. Specifically, as linear response analysis of the crossover piping, modal time-history analysis and response spectrum analysis with multiple excitations were carried out and the applicability of the analyses was confirmed. Moreover, the seismic response of actual crossover piping was estimated and the feasibility was evaluated.

Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities: Part 4 — Failure Behavior of Crossover Piping for Seismic Isolation System

10.1115/pvp2014-29011 ◽

2014 ◽

Cited By ~ 1

Author(s):

Teruyoshi Otoyo ◽

Akihito Otani ◽

Shunsuke Fukushima ◽

Masakazu Jimbo ◽

Tomofumi Yamamoto ◽

...

Keyword(s):

Nuclear Power ◽

Seismic Isolation ◽

Evaluation Method ◽

Low Cycle Fatigue ◽

Response Analysis ◽

Failure Behavior ◽

Isolation System ◽

Isolation Systems ◽

Seismic Isolation Systems ◽

Failure Location

This paper provides a part of the series titled “Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities”. This part shows the failure behavior of crossover piping installed in a seismic isolated plant. The considered crossover piping is supported on one side by an isolated building and by a non-isolated building on the other side. During an earthquake, the piping structure is deformed due to the large relative displacements between the two buildings and at the same time excited by the different building seismic responses. Therefore, the high-pressure crossover piping structure requires both flexibility and strength. In this study, 1/10 scaled shaking tests and FEM analyses have been performed to investigate the failure behavior of the crossover piping, where both seismic motions and excitations have been taken into account. It was confirmed that the failure occurs at the piping elbow through low cycle fatigue. Moreover, the results of the elastic-plastic response analysis, which simulates an extreme level of excitation corresponding to more than three times the design level, are in good agreement with the test results. The simulation also succeeded in predicting the experimental failure location.