The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform
Juraj Králik - One of the best experts on this subject based on the ideXlab platform.
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Probabilistic Nonlinear Analysis of the NPP Hermetic Cover Failure due to Extreme Pressure and Temperature
Transactions of the VŠB: Technical University of Ostrava Civil Engineering Series, 2017Co-Authors: Juraj KrálikAbstract:Abstract This paper describes the probabilistic nonlinear analysis of the reactor cover under a high Internal Overpressure and temperature. The scenario of the hard accident in NPP and the methodology of the calculation of the fragility curve of the failure Overpressure using the probabilistic safety assessment PSA 2 level is presented. The model and resistance uncertainties were taken into account in the response surface method (RSM).
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Nonlinear Analysis of the Hermetic Postament Safety During Technology Accident in the Nuclear Power Plant
Transactions of the VŠB: Technical University of Ostrava Civil Engineering Series, 2017Co-Authors: Juraj KrálikAbstract:Abstract This paper describes the nonlinear analysis of the nuclear power plant (NPP) postament safety under a high Internal Overpressure and temperature. The scenario of the hard accident in NPP and the methodology of the calculation of the safety of the technology segments are presented. The elastoplastic behavior of steel material dependent on temperature was considered in software ANSYS. The safety analysis of the original and upgraded postament structure is described here.
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Probability and Sensitivity Nonlinear Analysis of the Hermetic Cover of Main Shut-off Valve under Extreme Pressure and Temperature
Transactions of the VŠB: Technical University of Ostrava Civil Engineering Series, 2017Co-Authors: Juraj KrálikAbstract:Abstract This paper describes the probabilistic nonlinear analysis of the containment hermetic cover of main shut-off valve (MSV) under an extreme Internal Overpressure and temperature. The scenario of the hard accident in NPP and the methodology of the calculation of the fragility curve of the failure Overpressure using the probabilistic safety assessment PSA 2 level are presented. The elasto-plastic behavior of steel material dependent on temperature was considered in software ANSYS. The method of central composite design sampling (CCD) of the response surface methodology (RSM) was used to probability and sensitivity analysis of the hermetic cover reliability.
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Experimental and Numerical Analysis of the Hermetic Tightness of NPP Bubble Tower Structure
Procedia Engineering, 2017Co-Authors: Juraj KrálikAbstract:Abstract This paper describes the experience from the experimental testing of the hermetic tightness of bubble tower (BT) of the nuclear power plant (NPP) type VVER 440 under the high Internal Overpressure after 30 years of the performance. The results from the experimental tests were used for the checking of the numerical model of the reinforced concrete structures. There is showed summary of calculation models and calculation methods for the reliability analysis of the structural integrity due to extreme Overpressure. The tightness testing of the steel Internal liner during the NPP performance was realized in accordance of the international standards. The methodology and results of the optical and mechanical measure are presented. On base of the nonlinear analysis the safety and reliability of the concrete structure were considered.
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Nonlinear Probabilistic Analysis of the Failure Pressure of NPP Shielding Plate
Applied Mechanics and Materials, 2016Co-Authors: Juraj Králik, Maroš Klabník, Alzbeta GrmanovaAbstract:This paper describes the nonlinear probabilistic analysis of the failure pressure of the shielding plate of the reactor box of the nuclear power plant under a high Internal Overpressure and temperature. The scenario of the hard accident in Nuclear power plant (NPP) and the methodology of the calculation of the fragility curve of the failure Overpressure using the probabilistic safety assessment PSA 2 level is presented. The fragility curve of the failure pressure was determined using 45 probabilistic simulations using the response surface method (RSM) with the Central Composite Design (CCD) for 106 Monte Carlo simulations for each model and 5 level of the Overpressure.
N. Pelekasis - One of the best experts on this subject based on the ideXlab platform.
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Nonlinear oscillations and collapse of elongated bubbles subject to weak viscous effects: Effect of Internal Overpressure
Physics of Fluids, 2007Co-Authors: Kostas Tsiglifis, N. PelekasisAbstract:The details of nonlinear oscillations and collapse of elongated bubbles, subject to large Internal Overpressure, are studied by a boundary integral method. Weak viscous effects on the liquid side are accounted for by integrating the equations of motion across the boundary layer that is formed adjacent to the interface. For relatively large bubbles with initial radius R0 on the order of millimeters, PSt=PSt′∕(2σ∕R0)∼300 and Oh=μ∕(σR0ρ)1∕2∼200, and an almost spherical initial shape, S∼1, Rayleigh-Taylor instability prevails and the bubble breaks up as a result of growth of higher modes and the development of regions of very small radius of curvature; σ, ρ, μ, and PSt′ denote the surface tension, density, viscosity, and dimensional static pressure in the host liquid while S is the ratio between the length of the minor semiaxis of the bubble, taken as an axisymmetric ellipsoid, and its equivalent radius R0. For finite initial elongations, 0.5⩽S
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nonlinear oscillations and collapse of elongated bubbles subject to weak viscous effects effect of Internal Overpressure
Physics of Fluids, 2007Co-Authors: Kostas Tsiglifis, N. PelekasisAbstract:The details of nonlinear oscillations and collapse of elongated bubbles, subject to large Internal Overpressure, are studied by a boundary integral method. Weak viscous effects on the liquid side are accounted for by integrating the equations of motion across the boundary layer that is formed adjacent to the interface. For relatively large bubbles with initial radius R0 on the order of millimeters, PSt=PSt′∕(2σ∕R0)∼300 and Oh=μ∕(σR0ρ)1∕2∼200, and an almost spherical initial shape, S∼1, Rayleigh-Taylor instability prevails and the bubble breaks up as a result of growth of higher modes and the development of regions of very small radius of curvature; σ, ρ, μ, and PSt′ denote the surface tension, density, viscosity, and dimensional static pressure in the host liquid while S is the ratio between the length of the minor semiaxis of the bubble, taken as an axisymmetric ellipsoid, and its equivalent radius R0. For finite initial elongations, 0.5⩽S<1, the bubble collapses either via two jets that counterpropagate...
J. Botija - One of the best experts on this subject based on the ideXlab platform.
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Assembly and final dimensional inspection at factory of the JT-60SA Cryostat Vessel Body Cylindrical Section
Fusion Engineering and Design, 2019Co-Authors: J. Botija, Javier A. Alonso, P. Fernández, M. Medrano, Francisco Ramos, Esther Rincon, Alfonso Soleto, Santiago Cabrera, Antonino Cardella, Kei MasakiAbstract:Abstract The superconducting tokamak JT-60SA is currently being assembled at the QST laboratories in Naka (Japan). Within the European contribution in the framework of the Broader Approach, Spain has been responsible for providing JT-60SA cryostat. The cryostat is a large vacuum vessel made up of 304 stainless steel which encloses the tokamak providing the vacuum environment to reduce thermal loads on the components at cryogenic temperature. It must withstand the external atmospheric pressure during normal operation and the Internal Overpressure in case of an accident. Due to functional purposes, the cryostat has been divided in three assemblies: the Cryostat Base (CB), the Cryostat Vessel Body Cylindrical Section (CVBCS) and the Top Lid. For transport and assembly reasons the cryostat is made up of 20 main parts: 7 making up the CB and 13 making up the CVBCS (including the top lid). The joints between them rely on bolted flanges together with light seal welds, non-structural fillet welds performed from inside and/or outside of the cryostat. The single wall is externally reinforced with ribs to support the weight of all the ports and port plugs and also to withstand the vacuum pressure. The material is SS 304 (Co
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Manufacturing of the JT-60SA cryostat vessel body cylindrical section
Fusion Engineering and Design, 2017Co-Authors: J. Botija, Javier A. Alonso, P. Fernández, M. Medrano, Francisco Ramos, Esther Rincon, Alfonso Soleto, Santiago Cabrera, Antonino Cardella, Kei MasakiAbstract:Abstract The JT-60SA cryostat is a large vacuum vessel made up of 304 stainless steel which encloses the tokamak providing the vacuum environment to reduce thermal loads on the components at cryogenic temperature. It must withstand the external atmospheric pressure during normal operation and the Internal Overpressure in case of an accident. Due to functional purposes, the cryostat has been divided in three large assemblies: the Cryostat Base (CB), the Cryostat Vessel Body Cylindrical Section (CVBCS) and the Top Lid. The CB was manufactured in Spain and assembled in-situ in 2013, while the CVBC is currently under manufacturing also by a Spanish company and it is expected to be delivered in Naka next year 2017. This paper gives an overview of the manufacturing process and present status of the CVBCS. The manufacturing includes the assembly and testing at the manufacturer workshop as well as the packaging of the component. The reference code being used for the manufacturing is ASME 2007 Section VIII Div.2.
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Structural analysis of the JT-60SA cryostat vessel body
Fusion Engineering and Design, 2013Co-Authors: J. Botija, Javier A. Alonso, P. Fernández, M. Medrano, Francisco Ramos, Esther Rincon, Alfonso Soleto, S. Davis, Enrico Di Pietro, V. TomarchioAbstract:Abstract The JT-60SA cryostat is a stainless steel vacuum vessel (14 m diameter, 16 m height) which encloses the Tokamak providing the vacuum environment (10 −3 Pa) necessary to limit the transmission of thermal loads to the components at cryogenic temperature. It must withstand both external atmospheric pressure during normal operation and Internal Overpressure in case of an accident. The paper summarizes the structural analyses performed in order to validate the JT-60SA cryostat vessel body design. It comprises several analyses: a buckling analysis to demonstrate stability under the external pressure; an elastic and an elastic–plastic stress analysis according to ASME VIII rules, to evaluate resistance to plastic collapse including localized stress concentrations; and, finally, a detailed analysis with bolted fasteners in order to evaluate the behavior of the flanges, assuring the integrity of the vacuum sealing welds of the cryostat vessel body.
Kei Masaki - One of the best experts on this subject based on the ideXlab platform.
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Assembly and final dimensional inspection at factory of the JT-60SA Cryostat Vessel Body Cylindrical Section
Fusion Engineering and Design, 2019Co-Authors: J. Botija, Javier A. Alonso, P. Fernández, M. Medrano, Francisco Ramos, Esther Rincon, Alfonso Soleto, Santiago Cabrera, Antonino Cardella, Kei MasakiAbstract:Abstract The superconducting tokamak JT-60SA is currently being assembled at the QST laboratories in Naka (Japan). Within the European contribution in the framework of the Broader Approach, Spain has been responsible for providing JT-60SA cryostat. The cryostat is a large vacuum vessel made up of 304 stainless steel which encloses the tokamak providing the vacuum environment to reduce thermal loads on the components at cryogenic temperature. It must withstand the external atmospheric pressure during normal operation and the Internal Overpressure in case of an accident. Due to functional purposes, the cryostat has been divided in three assemblies: the Cryostat Base (CB), the Cryostat Vessel Body Cylindrical Section (CVBCS) and the Top Lid. For transport and assembly reasons the cryostat is made up of 20 main parts: 7 making up the CB and 13 making up the CVBCS (including the top lid). The joints between them rely on bolted flanges together with light seal welds, non-structural fillet welds performed from inside and/or outside of the cryostat. The single wall is externally reinforced with ribs to support the weight of all the ports and port plugs and also to withstand the vacuum pressure. The material is SS 304 (Co
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Manufacturing of the JT-60SA cryostat vessel body cylindrical section
Fusion Engineering and Design, 2017Co-Authors: J. Botija, Javier A. Alonso, P. Fernández, M. Medrano, Francisco Ramos, Esther Rincon, Alfonso Soleto, Santiago Cabrera, Antonino Cardella, Kei MasakiAbstract:Abstract The JT-60SA cryostat is a large vacuum vessel made up of 304 stainless steel which encloses the tokamak providing the vacuum environment to reduce thermal loads on the components at cryogenic temperature. It must withstand the external atmospheric pressure during normal operation and the Internal Overpressure in case of an accident. Due to functional purposes, the cryostat has been divided in three large assemblies: the Cryostat Base (CB), the Cryostat Vessel Body Cylindrical Section (CVBCS) and the Top Lid. The CB was manufactured in Spain and assembled in-situ in 2013, while the CVBC is currently under manufacturing also by a Spanish company and it is expected to be delivered in Naka next year 2017. This paper gives an overview of the manufacturing process and present status of the CVBCS. The manufacturing includes the assembly and testing at the manufacturer workshop as well as the packaging of the component. The reference code being used for the manufacturing is ASME 2007 Section VIII Div.2.
Laurent Ricciardi - One of the best experts on this subject based on the ideXlab platform.
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reduced scale study of transient flows inside mechanically ventilated buildings subjected to wind and Internal Overpressure effects
Building and Environment, 2013Co-Authors: Nicolas Le Roux, Xavier Faure, Christian Inard, Sandrine Soares, Laurent RicciardiAbstract:Abstract To study transient mass transfers inside buildings equipped with ventilation systems, reduced-scale experiments have been performed by applying the scaling down methodology developed for studying isothermal airflows in a steady or a transient state [1] . Transient tests have been carried out both on simplified cases considered for the validation of the methodology and on two reference industrial configurations representative of real industrial facilities. In this article, focus is made on transient results obtained on simplified and reference industrial cases subjected to wind and Internal Overpressure effects. The main objectives are firstly to identify the Internal transient airflow behaviour, compared with Helmholtz oscillated phenomena underlined from natural ventilation studies, secondly to analyse the pollutant containment of reference industrial configurations subjected to wind and/or Internal Overpressure effects due to an accident, and finally to check the ability of the SYLVIA code to model these transient phenomena.
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Reduced-scale study of wind influence on mean airflows inside buildings equipped with ventilation systems
Building and Environment, 2012Co-Authors: Nicolas Le Roux, Xavier Faure, Christian Inard, Sandrine Soares, Laurent RicciardiAbstract:Abstract To study mass transfers inside buildings equipped with ventilation systems, a methodology has been developed to carry out reduced-scale experiments for studying isothermal flows in a steady or a transient state. This methodology has been numerically and experimentally validated on simple configurations and applied to two reference configurations representative of nuclear facilities. The wind influence on mass transfers inside these configurations, in nominal, damaged (ventilation stopped) or accidental (Internal Overpressure) situations, has been studied by carrying out wind tunnel experiments. The objectives of this article are to present the scaling-down methodology and the main experimental results concerning the influence of wind on steady-state airflows inside the reduced-scale models. It is notably shown that wind effects can lead to a partial or a total loss of the pollutant containment inside buildings. The reliability of the zonal code SYLVIA, which is used to support safety assessments in nuclear facilities, has then been analysed from these experimental results.