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Ban Z.,Budapest University of Technology and Economics | Mahler A.,Budapest University of Technology and Economics | Katona T.J.,Paks Nuclear Power Plant | Gyori E.,MTA CSFK GGI Seismological Observatory
Proceedings of the 5th International Conference on Geotechnical and Geophysical Site Characterisation, ISC 2016 | Year: 2016

Empirical liquefaction potential assessment methods are generally based on the result of CPT, SPT or shear wave velocity measurement. In more complex or high risk projects CPT and VS measurement are often performed at the same location commonly in the form of seismic CPT. However, combined use of both in-situ indices in one single empirical method is limited. For this reason the goal of this research was to develop such an empirical method where the result of CPT and VS measurement are used in parallel and can supplement each other. After the accumulation of a case history database where both measurements are available and performing the necessary corrections of the variables, logistic regression was performed to obtain the probability contours of liquefaction occurrence. In this case the graphical representation of the cyclic resistance ratio curve for a given probability can be replaced by a surface. © 2016 Australian Geomechanics Society.


Patzay G.,Budapest University of Technology and Economics | Weiser L.,Budapest University of Technology and Economics | Feil F.,Paks Nuclear Power Plant | Patek G.,Paks Nuclear Power Plant
Desalination | Year: 2013

This paper describes the results of a joint research program of Budapest University of Technology and Economics and the Paks Nuclear Power Plant to modify the radioactive wastewater treatment technology for the evaporator bottom residue contained in tanks in the NPP. The main characteristics of the modified technology were that we first removed all the long life radioactive isotopes with underwater plasma torch reactor (UPTR), micro and ultrafiltration and a cesium selective ion exchanger stable at pH. ~. 12-13. After the separation of precipitated borate crystals, the remaining liquid was released as chemical waste. © 2012 Elsevier B.V.


Katona T.J.,Paks Nuclear Power Plant
Vulnerability, Uncertainty, and Risk: Analysis, Modeling, and Management - Proceedings of the ICVRAM 2011 and ISUMA 2011 Conferences | Year: 2011

In the paper two possible ways are presented for the improvement of the probabilistic seismic safety analysis of nuclear power plants. The fragilities of structures and equipment used in safety analysis are presented as function of peak ground acceleration, although it is not an adequate damage indicator. In the paper an interpretation is given for cumulative absolute velocity as damage indicator. The possibility for derivation of conditional probability of failure for cumulative absolute velocity is also shown. In the paper an attempt is also made for outlining some new options for nuclear power plant seismic fragility development based on the interval and p-box-concept. These theoretical tools might be used in case of large number and variety of types of components, failure modes. The proposed methods can be adopted for simplification of the screening, which requires enormous experience. Copyright © ASCE 2011.


Katona T.J.,Paks Nuclear Power Plant
Computational Materials Science | Year: 2012

Assessment of the safety of the nuclear power plants and evaluation of the plant condition after an earthquake require the knowledge of the fragility of structures and components. In the paper options for improvement of existing methods of the modelling of plant fragilities are outlined based on the interval and p-box theories, use of cumulative absolute velocity as damage indicator and first-passage description the fatigue type failure mode of the components. © 2012 Elsevier B.V. All rights reserved.


Katona T.J.,Paks Nuclear Power Plant
11th International Probabilistic Safety Assessment and Management Conference and the Annual European Safety and Reliability Conference 2012, PSAM11 ESREL 2012 | Year: 2012

In the paper, improvement options for the seismic safety analysis of nuclear power plants (NPP) via utilization of the cumulative absolute velocity (CAV) for independent variable of fragility, and adaptation of the interval and p-box theories for the characterization of the uncertainties are presented. CAV can be used for independent single variable for the fragility, if the failure criteria can be determined via CAV for certain failure modes. For the calculation of the failure rate, the hazard has to be also defined in terms of CAV. CAV can be expressed as a function of the strong motion duration T, and power spectral density (PSD) of the ground motion acceleration. Fatigue damage estimation involves the cycle counting of equivalent stress ranges and accumulation of fatigue damage from each cycle, which requires calculation of the moments of the PSD stress time history. Since the CAV is linked to the PSD of the ground motion acceleration, the moments of the PSD of the stress time-history are correlated to the CAV. The failure criteria of different fatigue theories can be expressed in terms of CAV. In the paper, based on the interval and p-box-concept, options for calculation of the failure rate due to earthquake is outlined. The interval and pbox theories can be useful if the fragility of a particular failure mode of a component is known approximately only, small sample size of damage histories, inconsistency of data, or the modeling of failure component is uncertain. The upper and lower bounds of the distribution functions might be represented by probability boxes specified by a left side and a right side distribution functions. Probability bounds can be calculated for distribution families using only interval estimates for the parameters or having information only on {min, max} or {min, max, mode} etc. of the variable. Upper and lower bounds on parametric values can be provided, typically from expert elicitation. Copyright © (2012) by IAPSAM & ESRA.


Katona T.J.,Paks Nuclear Power Plant
Proceedings of the 8th International Conference on Structural Dynamics, EURODYN 2011 | Year: 2011

Assessment of seismic safety of nuclear power plants requires convolution of plant fragilities with seismic hazard curves. Plant level fragility versus peak ground acceleration is obtained by combining component fragilities according to the Boolean-expression of the sequence leading to core damage. An improvement of the fragility modelling can be achieved via description of the fragility as a function of cumulative absolute velocity of ground motion instead of peak ground acceleration. In the paper the physical meaning of the cumulative absolute velocity is discussed and its dependence on strong motion parameters is also analysed. The reason why the cumulative absolute velocity is an appropriate damage indicator is demonstrated regarding fatigue type failure mode.


Katona T.J.,Paks Nuclear Power Plant
Proceedings of the 13th International Conference on Civil, Structural and Environmental Engineering Computing | Year: 2011

Assessment of seismic safety of nuclear power plants requires convolution of plant fragilities with seismic hazard curves. In the paper, an option for representing the uncertainty of seismic fragility is outlined based on the interval and p-box concept. The conditional probability of failure is developed as a function of the cumulative absolute velocity. The dependence of the cumulative absolute velocity on the strong motion parameters is analysed. It is demonstrated that the cumulative absolute velocity is an appropriate damage indicator for fatigue failure mode. Relation between cumulative absolute velocity of failure and various failure theories is established in the paper. © Civil-Comp Press, 2011.


Katona T.J.,Paks Nuclear Power Plant | Ratkai S.,Paks Nuclear Power Plant | Pammer Z.,PaB Co.
Nuclear Engineering and Design | Year: 2011

The WWER-440/213 type units of Paks Nuclear Power Plant in Hungary were designed, manufactured in accordance with the Soviet codes and standards valid in late sixties and seventies. Design lifetime of the units was 30 years, and the operational licence had been limited to that term. A very important aspect of justification of safe operation beyond this term is the review and validation of the time-limited ageing analyses. In the specific case of Paks Nuclear Power Plant (NPP) the designer made time-limited ageing analyses that are partly missing, partly inadequate because of the lack of proper documentation or obsolete. For the solution of this issue the necessary analyses (stress calculations, pressurized thermal shock, fatigue, etc.) have to be performed using state-of-the-art methods, which involves also verification of strength calculations of most important structures and components. The goal of this paper is to describe the specific aspects of reconstituting the time-limited ageing analyses and verification of strength calculations for Paks NPP WWER-440/213 units. The paper will focus on the scope of the time-limited ageing analyses, the methodology and peculiarities of the adaptation of ASME BPVC will also be considered in the paper. © 2010 Elsevier B.V. All rights reserved.


Katona T.J.,Paks Nuclear Power Plant | Toth L.,Hungarian Academy of Sciences | Toth L.,GeoRisk Earthquake Engineering Ltd.
Acta Geodaetica et Geophysica | Year: 2013

After an earthquake, the condition of industrial systems, structures and equipment, especially at nuclear power plants has to be assessed since this information is needed for accident management and for the decision on the continuation of the operation. The damaging potential of the earthquake can be characterized by maximum horizontal acceleration of the ground motion, response spectra, cumulative absolute velocity and different instrumental intensity values. These quantities can be correlated with the earthquake characteristics, magnitude, distance, etc. Some of the indices are selective to damage mechanism and can be correlated to load-bearing features of the structures. Different indicators of damaging potential of earthquakes are analyzed in the paper from the point of view of applicability for post-event condition assessment at nuclear power plants and for using as criteria for restart of the operation. © 2013 Akadémiai Kiadó, Budapest, Hungary.


Katona T.,Paks Nuclear Power Plant
Pollack Periodica | Year: 2011

Assessment of seismic safety of nuclear power plants requires convolution of plant fragilities with seismic hazard curves. Plant level fragility versus peak ground acceleration is obtained by combining component fragilities according to the Boolean-expression of the sequence leading to core damage. An improvement of the fragility modeling can be achieved via description of the fragility as a function of cumulative absolute velocity of ground motion instead of peak ground acceleration. In the paper the physical meaning and dependence on strong motion parameters is also discussed. The reason why the cumulative absolute velocity is an appropriate damage indicator is analyzed.

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