Specific Issues for Seismic Performance of Power Plant Equipment0 pages
Peter Nawrotzki
nnnnSpecific Issues for Seismic Performance
nnnnof Power Plant Equipment
nnnnPower plant machinery can be dynamically decoupled
nnnnfrom the substructure by the effective use of helical steel
nnnnsprings and viscous dampers. Turbine foundations, coal
nnnnmills, boiler feed pumps and other machine foundations
nnnnbenefit from this type of elastic support systems to miti-
nnnngate the transmission of operational vibration. The appli-
nnnncation of these devices may also be used to protect
nnnnagainst earthquakes and other catastrophic events, i. e.
nnnnairplane crash, of particular importance in nuclear facili-
nnnnties.
nnnnThis article illustrates basic principles of elastic sup-
nnnnport systems and applications on power plant equipment
nnnnand buildings in medium and high seismic areas. Spring-
nnnndamper combinations with special stiffness properties are
nnnnused to reduce seismic acceleration levels of turbine com-
nnnnponents and other safety or non-safety related structures.
nnnnFor turbine buildings, the integration of the turbine sub-
nnnnstructure into the machine building can further reduce
nnnnstress levels in all structural members. The application of
nnnnthis seismic protection strategy for a spent fuel storage
nnnntank in a high seismic area is also discussed.
nnnnSafety in nuclear facilities is of particular importance
nnnnand recent seismic events and the resulting damage in
nnnnthese facilities again brings up the discussion. One of the
nnnnlatest events is the 2007 Chuetsu earthquake in Japan. The
nnnnresulting damage in the Kashiwazaki Kariwa Nuclear
nnnnPower Plant can be found in several reports, e. g. in Ya-
nnnnmashita [1], [2].
nnnn1 Introduction
nnnnSeismic control strategies as described by the introduction
nnnnof PrEN 15129 - Anti-Seismic Devices: "... design of de-
nnnnvices that are provided in structures with the aim of mod-
nnnnifying their response to seismic action [3]. The modifica-
nnnntion ... may be obtained by ...
nnnn- modifying the shape of the fundamental mode
nnnn- increasing the fundamental period
nnnn- increasing the damping.
nnnnUsually, in combination with the modification of the mode
nnnnshape the predominant frequency of the system is re-
nnnnduced. When the response spectrum of recorded or artifi-
nnnncial earthquakes is plotted this strategy can easily be justi-
nnnnfied (Fig. 1 left). Here, the spectrum according to the
nnnnTurkish Standard (Specification for Structures to be Built
nnnnin Disaster Areas) is plotted for the seismic zone 1 and the
nnnnsoil class Zl.
nnnnFlexible structures are usually not in danger of col-
nnnnlapse during an earthquake. Low natural frequencies are
nnnnindicators for a low level of induced seismic energy. Struc-
nnnntures with higher natural frequencies take more energy
nnnnfrom the given base excitation. For the particular example
nnnnaccording to the Turkish regulation the frequency range
nnnnwith the highest acceleration starts at approximately
nnnn3,3 Hz. Up to about 10 Hz an average amplification factor
nnnnof 2,5 must be considered. Here, the peak ground acceler-
nnnn© 2010 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin - Special Kraftwerksbau 67
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