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Keywords: nuclear power plant, seismic safety, structural control, limit state, numerical methods.

Summary

A numerical procedure for computing the seismic fragility of equipment components in traditional nuclear power plant buildings was proposed in previous research [1,2,3]. The procedure is based on the use of the response surface method for modelling the influence of the selected random variables on the building response; for a linear system the building performance can be described in terms of dynamic amplification. The computation of the probability of exceeding a given amplification factor can be obtained, using Monte Carlo simulation, for all amplification values in the selected range. A procedure for refining the response surfaces has been also proposed.

When the introduction of the isolation system is considered, resulting in a drastic reduction of horizontal peak accelerations inside the building, attention is more focused, in the fragility analysis, on the behaviour of high damping rubber bearing (HDRB) devices. The definition of the limit-state failure, formulated in terms of horizontal and vertical loads acting on the device, will be supported from both analytical and finite element procedures, calibrated on the basis of experimental tests.

Since the behaviour of the HDRB isolators is markedly non linear at the high level of deformation which can be anticipated for the fragility analysis, the hypothesis of linearity of the nuclear steam supply system building response will be removed. This means that the response surface evaluation will be repeated for every value of peak ground acceleration. On the other hand, to evaluate the isolator behaviour the seismic behaviour of the isolated building can be captured by means of a very simple mechanical model.

The procedure for fragility analysis will be applied focusing on the uncertainties related to the isolator behaviour. An example of an application will be shown for both non-isolated and isolated reactor building within the IRIS international project.

References

1: G. Bianchi, L. Corradi, M. Domaneschi, D.C. Mantegazza, F. Perotti, "High Damping Rubber Bearing (HDRB) isolating devices for nuclear power plants: FE modelling and damage characterization", SEWC2011, Cernobbio (CO), Italy, 2011.
2: L. Corradi, M. Domaneschi, C. Guiducci, "Assessing the reliability of seismic base isolators for innovative power plant proposals", Proc. of SMiRT 20, Helsinki, Finland, 2009.
3: S. De Grandis, M. Domaneschi, F. Perotti, "A numerical procedure for computing the fragility of NPP components under random seismic excitation", Nucl. Eng. Des., 239, 2491-2499, 2009. doi:10.1016/j.nucengdes.2009.06.027

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 96 PROCEEDINGS OF THE THIRTEENTH INTERNATIONAL CONFERENCE ON CIVIL, STRUCTURAL AND ENVIRONMENTAL ENGINEERING COMPUTING Edited by: B.H.V. Topping and Y. Tsompanakis Paper 106 Numerical Investigations of a Base Isolation System for Nuclear Power Plants: Safety Domain Definition and Analytical Model Identification G. Bianchi¹, L. Corradi Dell'Acqua², M. Domaneschi¹, D. Mantegazza¹ and F. Perotti¹ ¹Department of Structural Engineering, ²Department of Energy, Politecnico di Milano, Milan, Italy doi:10.4203/ccp.96.106 purchase the full-text of this paper Full Bibliographic Reference for this paper G. Bianchi, L. Corradi Dell'Acqua, M. Domaneschi, D. Mantegazza, F. Perotti, "Numerical Investigations of a Base Isolation System for Nuclear Power Plants: Safety Domain Definition and Analytical Model Identification", in B.H.V. Topping, Y. Tsompanakis, (Editors), "Proceedings of the Thirteenth International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 106, 2011. doi:10.4203/ccp.96.106 Keywords: nuclear power plant, seismic safety, structural control, limit state, numerical methods. Summary A numerical procedure for computing the seismic fragility of equipment components in traditional nuclear power plant buildings was proposed in previous research [1,2,3]. The procedure is based on the use of the response surface method for modelling the influence of the selected random variables on the building response; for a linear system the building performance can be described in terms of dynamic amplification. The computation of the probability of exceeding a given amplification factor can be obtained, using Monte Carlo simulation, for all amplification values in the selected range. A procedure for refining the response surfaces has been also proposed. When the introduction of the isolation system is considered, resulting in a drastic reduction of horizontal peak accelerations inside the building, attention is more focused, in the fragility analysis, on the behaviour of high damping rubber bearing (HDRB) devices. The definition of the limit-state failure, formulated in terms of horizontal and vertical loads acting on the device, will be supported from both analytical and finite element procedures, calibrated on the basis of experimental tests. Since the behaviour of the HDRB isolators is markedly non linear at the high level of deformation which can be anticipated for the fragility analysis, the hypothesis of linearity of the nuclear steam supply system building response will be removed. This means that the response surface evaluation will be repeated for every value of peak ground acceleration. On the other hand, to evaluate the isolator behaviour the seismic behaviour of the isolated building can be captured by means of a very simple mechanical model. The procedure for fragility analysis will be applied focusing on the uncertainties related to the isolator behaviour. An example of an application will be shown for both non-isolated and isolated reactor building within the IRIS international project. References 1 G. Bianchi, L. Corradi, M. Domaneschi, D.C. Mantegazza, F. Perotti, "High Damping Rubber Bearing (HDRB) isolating devices for nuclear power plants: FE modelling and damage characterization", SEWC2011, Cernobbio (CO), Italy, 2011. 2 L. Corradi, M. Domaneschi, C. Guiducci, "Assessing the reliability of seismic base isolators for innovative power plant proposals", Proc. of SMiRT 20, Helsinki, Finland, 2009. 3 S. De Grandis, M. Domaneschi, F. Perotti, "A numerical procedure for computing the fragility of NPP components under random seismic excitation", Nucl. Eng. Des., 239, 2491-2499, 2009. doi:10.1016/j.nucengdes.2009.06.027 purchase the full-text of this paper (price £20) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £130 +P&P)
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