Numerical Investigations of a Base Isolation System for Nuclear Power Plants: Safety Domain Definition and Analytical Model Identification

Author(s):  
G. Bianchi ◽  
L. Corradi Dell'Acqua ◽  
M. Domaneschi ◽  
D. Mantegazza ◽  
F. Perotti
Author(s):  
R. I. Skinner ◽  
R. G. Tyler ◽  
S. B. Hodder

The analysis of one-mass and two-mass models indicates that the earthquake-generated horizontal forces and deformations of the main structures of a nuclear power plant can be reduced by a factor of about ten times by mounting the overall power plant building on a recently developed base-isolation system. The very high forces which the ‘resonant appendage‘ effect may induce in some critical components (such
 as fuel elements, control rods and essential piping) may be reduced by a factor of 40 or more times by the isolation system. The parameters of
 the isolation system have been chosen as appropriate to the level of protection which should be provided for a nuclear plant in a seismically active area. Consideration is given to flexible mounts and dampers suitable for such an isolator.


Author(s):  
Takahiro Shimada ◽  
Junji Suhara ◽  
Kazuhiko Inoue

Three dimensional (3D) seismic isolation devices have been developed to use for the base isolation system of the heavy building like a nuclear reactor building. The developed seismic isolation system is composed of rolling seal type air springs and the hydraulic type springs with rocking suppression system for vertical base isolation device. In horizontal direction, the same laminated rubber bearings are used as horizontal isolation device for these systems. The performances and the applicability have already been evaluated by the technical feasibility tests and performance tests for each system. In this study, it was evaluated that the performance of the 3D base isolation system with rolling seal type air springs combined with hydraulic rocking suppression devices. A 1/7 scaled model of the 3D base isolation devices were manufactured and some performance test were executed for each device. For the rolling seal type air springs, dynamic loading test was executed with a vibration table, and pressure resistant ability test was executed for reinforced air springs. In the dynamic loading test, it is confirmed that the natural period and damping performance were verified. In the pressure resistant ability test, it is confirmed that the air springs had sufficient strength. For the hydraulic rocking suppression system, forced dynamic loading test was carried out in order to measure the frictional and oil flow resistance force on each cylinder. And the vibration table tests were carried out with supported weight of 228 MN in order to evaluate and to confirm the horizontal and vertical isolation performance, rocking suppression performance, and the applicability of the this seismic isolation system as the combined system. 4 rolling seal type air springs and 4 hydraulic load-carrying cylinders with rocking suppression devices supported the weight. As a result, the proposed system was verified that it could be applied to the actual nuclear power plant building to be target.


2019 ◽  
Vol 36 (4) ◽  
pp. 1238-1257 ◽  
Author(s):  
Gangling Hou ◽  
Meng Li ◽  
Sun Hai ◽  
Tianshu Song ◽  
Lingshu Wu ◽  
...  

Purpose Seismic isolation, as an effective risk mitigation strategy of building/bridge structures, is incorporated into AP1000 nuclear power plants (NPPs) to alleviate the seismic damage that may occur to traditional structures of NPPs during their service. This is to promote the passive safety concept in the structural design of AP1000 NPPs against earthquakes. Design/methodology/approach In conjunction with seismic isolation, tuned-mass-damping (TMD) is integrated into the seismic resistance system of AP1000 NPPs to satisfy the multi-functional purposes. The proposed base-isolation-tuned-mass-damper (BIS-TMD) is studied by comparing the seismic performance of NPPs with four different design configurations (i.e. without BIS, BIS, BIS-TMD and TMD) with the design parameters of the TMD subsystem optimized. Findings Such a new seismic protection system (BIS-TMD) is proved to be promising because the advantages of BIS and TMD can be fully used. The benefits of the new structure include effective energy dissipation (i.e. wide vibration absorption band and a stable damping effect), which results in the high performance of NPPs subject to earthquakes with various intensity levels and spectra features. Originality/value Parametric studies are performed to demonstrate the seismic robustness (e.g. consistent performance against the changing mass of the water in the gravity liquid tank and mechanical properties) which further ensures that seismic safety requirements of NPPs can be satisfied through the use of BIS-TMD.


Author(s):  
Timothy M. Adams ◽  
Eun Woo Ahn ◽  
Sungjune Kim ◽  
Sookyum Kim ◽  
Deasoo Kim

KEPCO Engineering and Construction is developing a Nuclear Power Plant Design that places the Nuclear Island on a base isolation system while the remaining plant structures are on standard structural foundations. When subjected to seismic (earthquake) loading, this will result in large differential displacements between the nuclear island and the adjacent buildings. Critical piping systems, which must remain functional during and after the seismic event, must withstand the large displacements. This paper summarizes the studies conducted to develop design methods for such piping systems. Also presented are the recommended approaches to be used in the design of such piping systems.


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