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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. Source

Jobbagy V.,Social Organization for Radioecological Cleanliness | Kavasi N.,Social Organization for Radioecological Cleanliness | Somlai J.,University of Pannonia | Dombovari P.,Paks Nuclear Power Plant | And 2 more authors.
Radiation Measurements | Year: 2011

Hungary is rich in underground waters such as thermal, mineral, and spring waters. A survey was carried out to study the naturally occurring alpha emitter radionuclides in popular and regularly consumed spring waters in the Balaton Upland region of Hungary and significant levels of radioactivity were found. Thirty samples were analyzed for gross alpha and beta activity concentrations by the low background gas flow proportional counter. The activity concentrations ranging from 26 to 1749 mBq dm-3 and from 33 to 2015 mBq dm -3 for gross alpha and beta, respectively, were observed in the spring waters. In general, the gross beta activity was higher than the alpha activity concentration. According to the results obtained, elevated level of Total Indicative Dose (TID) might be expected due to spring water consumption. In some cases, total dose might exceed the 100 μSv y-1 reference level recommended by WHO. The data obtained can provide an important information for the consumers and the authorities regarding the preliminary dose exposure risk due to spring water intake. © 2010 Elsevier Ltd. All rights reserved. Source

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. Source

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. Source

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. Source

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