The Experts below are selected from a list of 20463 Experts worldwide ranked by ideXlab platform
Guillaume Ricciardi - One of the best experts on this subject based on the ideXlab platform.
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Fluid-structure interaction modelling of a PWR Fuel Assembly subjected to axial flow
Journal of Fluids and Structures, 2016Co-Authors: Guillaume RicciardiAbstract:Nuclear industry needs tools to design reactor cores in case of earthquake. A fluid-structure model simulating the response of the core to a seismic excitation have been developed. Full scale tests considering one Fuel Assembly are performed to identify coefficients (added mass and damping) that will be used as inputs in the models. Tests showed that the axial water flow induced an added stiffness. In the paper, an expression of the model accounting for the fluid in the Fuel Assembly with a porous media model and in the bypasses with a leakage flow model is developed. Numerical simulations are compared to experiments and showed good agreement.
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Measurements of fluid fluctuations around an oscillating nuclear Fuel Assembly
Journal of Fluids and Structures, 2014Co-Authors: Guillaume Ricciardi, Eric BoccaccioAbstract:Abstract In this paper, dynamic measurements of fluid velocity in the by-passes of a test-section representing a nuclear Fuel Assembly are presented. The test-section was designed to identify stiffness, damping and mass coefficients of a Fuel Assembly under axial flow, and previous studies have shown that the by-passes have an influence on the identified coefficients. The results presented in this paper show that the motion of the Fuel Assembly induces fluctuations in the axial fluid velocity in the by-passes. These fluctuations depend on the excitation frequency and position. A delay has been observed between the Fuel Assembly displacement and the fluid velocity fluctuations. The delay decreases when the axial velocity increases which means that it is a convection driven phenomenon.
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Fluid-Structure Interaction in a 3-by-3 Reduced-Scale Fuel Assembly Network
Science and Technology of Nuclear Installations, 2010Co-Authors: Guillaume Ricciardi, Bruno Collard, Sergio Bellizzi, Bruno CochelinAbstract:We present experimental results on 9 reduced-scale Fuel assemblies arranged in a network of 3 by 3, subjected to an axial flow. The objective is to analyse the fluid force induced by the motion of the central Fuel Assembly on the others Fuel assemblies. The displacement of the central Fuel Assembly is imposed, while the others are fixed. Fluid forces acting on Fuel assemblies are measured with force sensors. We observed that the coupling between Fuel assemblies increases with the fluid velocity, and that the coupling in the transverse direction is not negligible compared to the coupling in the direction of excitation. We also observe that the fluid flow induces a stiffening of the central Fuel Assembly.
Yu. M. Semchenkov - One of the best experts on this subject based on the ideXlab platform.
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Measurement of the Absolute Power of a Fuel Assembly and Current by Direct-Charge Detectors on a SK-fiz Critical Test Stand
Atomic Energy, 2002Co-Authors: I. N. Aborina, V. Yu. Aborin, S. S. Gorodkov, Yu. A. Epanechnikov, A. D. Klochkov, Yu. A. Krainov, A. A. Ognev, V. R. Ostrovskii, N. I. Alekseev, Yu. M. SemchenkovAbstract:A series of investigations studying the currents of rhodium sensors in in-reactor monitoring systems and the relation between the currents and the energy release in the Fuel elements in the nearest neighbor environment in a VVÉR-1000 Fuel Assembly model was completed in 2001–2002 at the Russsian Science Center Kurchatov Institute. The experiments were performed on the SK-fiz critical test stand; the calculations were performed using the high precision MCU-REA/2 computer program, implementing the Monte Carlo method. The reference experimental-computational method for determining the relation between the DCD current and the number of fissions in the six neighboring Fuel elements and Fuel Assembly is described, the effects due to the arrangement of the DCDs at the center and in the fourth row of the Fuel Assembly are studied, and the experimental data are compared with the computational results. The possibilities of the only high-flux critical test stand in the industry are demonstrated (the thermal-neutron flux density 10^11 sec^–1·cm^–2, high accuracy of the experimental and computational methods). The SK-fiz stand and the high precision MCU-REA/2 computer program make it possible to perform comprehensive and detailed investigations of the relationship between the DCD current and the local and integral energy release in Fuel assemblies.
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Measurement of the Absolute Power of a Fuel Assembly and Current by Direct-Charge Detectors on a SK-fiz Critical Test Stand
Atomic Energy, 2002Co-Authors: I. N. Aborina, V. Yu. Aborin, S. S. Gorodkov, Yu. A. Epanechnikov, A. D. Klochkov, Yu. A. Krainov, A. A. Ognev, V. R. Ostrovskii, N. I. Alekseev, Yu. M. SemchenkovAbstract:A series of investigations studying the currents of rhodium sensors in in-reactor monitoring systems and the relation between the currents and the energy release in the Fuel elements in the nearest neighbor environment in a VVER-1000 Fuel Assembly model was completed in 2001–2002 at the Russsian Science Center Kurchatov Institute. The experiments were performed on the SK-fiz critical test stand; the calculations were performed using the high precision MCU-REA/2 computer program, implementing the Monte Carlo method. The reference experimental-computational method for determining the relation between the DCD current and the number of fissions in the six neighboring Fuel elements and Fuel Assembly is described, the effects due to the arrangement of the DCDs at the center and in the fourth row of the Fuel Assembly are studied, and the experimental data are compared with the computational results.
Vladimír Zeman - One of the best experts on this subject based on the ideXlab platform.
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Impact vibrations of guide thimbles in nuclear Fuel Assembly
Archive of Applied Mechanics, 2017Co-Authors: Vladimír ZemanAbstract:In nuclear Fuel assemblies of pressurized water reactors, guide thimbles (GTs) secure a safe control rod drop. The control rod fall into the GT should be as fast as possible to provide prompt reactor shutdown. The GTs are long thin-walled tubes that are dynamically excited by Fuel Assembly (FA) components motion caused by pressure pulsations of coolant. GTs are embedded in spacer grid cells and sleeve (SL) with radial clearances. Vibration of FA components, caused by the FA support plates motion in the reactor core, possibly generates impact forces between GT and spacer grids. The presented method introduces an original approach to mathematical modelling and simulation analysis of GT nonlinear vibrations respecting impact and friction forces at all the contact points between GT and spacer grids. The dependence of maximal dynamical lateral GT deformations on radial clearances and stiffnesses of spacer grid cells is analysed. The method is applied to GT in the hexagonal-type FA used in the VVER-type reactors.
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Estimation of the nuclear Fuel Assembly eigenfrequencies in the probability sense
Applied and Computational Mechanics, 2014Co-Authors: Vladimír Zeman, Zdeněk HlaváčAbstract:The paper deals with upper and lower limits estimation of the nuclear Fuel Assembly eigenfrequencies, whose design and operation parameters are random variables. Each parameter is defined by its mean value and standard deviation or by a range of values. The gradient and three sigma criterion approach is applied to the calculation of the upper and lower limits of Fuel Assembly eigenfrequencies in the probability sense. Presented analytical approach used for the calculation of eigenfrequencies sensitivity is based on the modal synthesis method and the Fuel Assembly decomposition into six identical revolved Fuel rod segments, centre tube and load-bearing skeleton linked by spacer grids. The method is applied for the Russian TVSA-T Fuel Assembly in the WWER1000/320 type reactor core in the Czech nuclear power plant Temelin.
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Seismic response of nuclear Fuel Assembly
Applied and Computational Mechanics, 2014Co-Authors: Zdeněk Hlaváč, Vladimír ZemanAbstract:The paper deals with mathematical modelling and computer simulation of the seismic response of Fuel Assembly components. The seismic response is investigated by numerical integration method in time domain. The seismic excitation is given by two horizontal and one vertical synthetic accelerograms at the level of the pressure vessel seating. Dynamic response of the hexagonal type nuclear Fuel Assembly is caused by spatial motion of the support plates in the reactor core investigated on the reactor global model. The modal synthesis method with condensation is used for calculation of the Fuel Assembly component displacements and speeds on the level of the spacer grid cells.
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Modelling and modal properties of nuclear Fuel Assembly
Applied and Computational Mechanics, 2011Co-Authors: Vladimír Zeman, Zdeněk HlaváčAbstract:The paper deals with the modelling and modal analysis of the hexagonal type nuclear Fuel Assembly. This very complicated mechanical system is created from the many beam type components shaped into spacer grids. The cyclic and central symmetry of the Fuel rod package and load-bearing skeleton is advantageous for the Fuel Assembly decomposition into six identical revolved Fuel rod segments, centre tube and skeleton linked by several spacer grids in horizontal planes. The derived mathematical model is used for the modal analysis of the Russian TVSA-T Fuel Assembly and validated in terms of experimentally determined natural frequencies, modes and static deformations caused by lateral force and torsional couple of forces. The presented model is the first necessary step for modelling of the nuclear Fuel Assembly vibration caused by different sources of excitation during the nuclear reactor VVER type operation.
I. N. Aborina - One of the best experts on this subject based on the ideXlab platform.
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Measurement of the Absolute Power of a Fuel Assembly and Current by Direct-Charge Detectors on a SK-fiz Critical Test Stand
Atomic Energy, 2002Co-Authors: I. N. Aborina, V. Yu. Aborin, S. S. Gorodkov, Yu. A. Epanechnikov, A. D. Klochkov, Yu. A. Krainov, A. A. Ognev, V. R. Ostrovskii, N. I. Alekseev, Yu. M. SemchenkovAbstract:A series of investigations studying the currents of rhodium sensors in in-reactor monitoring systems and the relation between the currents and the energy release in the Fuel elements in the nearest neighbor environment in a VVÉR-1000 Fuel Assembly model was completed in 2001–2002 at the Russsian Science Center Kurchatov Institute. The experiments were performed on the SK-fiz critical test stand; the calculations were performed using the high precision MCU-REA/2 computer program, implementing the Monte Carlo method. The reference experimental-computational method for determining the relation between the DCD current and the number of fissions in the six neighboring Fuel elements and Fuel Assembly is described, the effects due to the arrangement of the DCDs at the center and in the fourth row of the Fuel Assembly are studied, and the experimental data are compared with the computational results. The possibilities of the only high-flux critical test stand in the industry are demonstrated (the thermal-neutron flux density 10^11 sec^–1·cm^–2, high accuracy of the experimental and computational methods). The SK-fiz stand and the high precision MCU-REA/2 computer program make it possible to perform comprehensive and detailed investigations of the relationship between the DCD current and the local and integral energy release in Fuel assemblies.
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Measurement of the Absolute Power of a Fuel Assembly and Current by Direct-Charge Detectors on a SK-fiz Critical Test Stand
Atomic Energy, 2002Co-Authors: I. N. Aborina, V. Yu. Aborin, S. S. Gorodkov, Yu. A. Epanechnikov, A. D. Klochkov, Yu. A. Krainov, A. A. Ognev, V. R. Ostrovskii, N. I. Alekseev, Yu. M. SemchenkovAbstract:A series of investigations studying the currents of rhodium sensors in in-reactor monitoring systems and the relation between the currents and the energy release in the Fuel elements in the nearest neighbor environment in a VVER-1000 Fuel Assembly model was completed in 2001–2002 at the Russsian Science Center Kurchatov Institute. The experiments were performed on the SK-fiz critical test stand; the calculations were performed using the high precision MCU-REA/2 computer program, implementing the Monte Carlo method. The reference experimental-computational method for determining the relation between the DCD current and the number of fissions in the six neighboring Fuel elements and Fuel Assembly is described, the effects due to the arrangement of the DCDs at the center and in the fourth row of the Fuel Assembly are studied, and the experimental data are compared with the computational results.
V. D. Sorokin - One of the best experts on this subject based on the ideXlab platform.
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Hydrodynamic Features of the Flow Downstream from the Mixing Spacer Grid in a Kvadrat Fuel Assembly in PWRs
Thermal Engineering, 2019Co-Authors: O. B. Samoilov, S. M. Dmitriev, M. A. Legchanov, A A Dobrov, A. S. Noskov, D. L. Shipov, D. V. Doronkov, A. N. Pronin, D. N. Solntsev, V. D. SorokinAbstract:— The experimental investigation of local hydrodynamic characteristics of the coolant flow downstream of a mixing spacer grid (MSG) in characteristic regions of a Kvadrat Fuel Assembly in PWRs was performed. The importance of this investigation is due to the fact that MSGs of interest can enhance heat-and-mass transfer. Finding the best design of the grid is required for corroboration of the thermal engineering reliability and operability of the PWR core. The paper presents a description of the test facility and a model of a Fuel Assembly fragment, the investigation procedure, and discussion of the results. The experiments were performed in the aerodynamic test facility on a scaled model of a fragment of a Kvadrat Fuel Assembly by simulating the water coolant flow using an air flow according to the hydrodynamic similarity theory. Within the scope of the investigation, the transverse velocity fields in the coolant flow were studied in the characteristic cross-sections of the Fuel Assembly. The transverse velocity distribution was measured with a five-channel pneumometric probe that can determine the module and direction of a flow velocity vector at an investigated point. The experimental results are presented in the form of distribution of relative transverse velocity downstream of MSG in the characteristic regions of the Fuel Assembly, such as standard cells, guide channel, and a gap between Fuel rods. Based on the experimental data, the coolant flow features have been revealed, and the regularities in the development of transverse velocity field downstream of the mixing spacer grid under investigation have been determined. These experimental data are required for assessment of the mixing spacer grid effectiveness, verification of 3D CFD-programs, and applicable cell-by-cell codes for calculation of a PWR core with a Kvadrat Fuel Assembly.
