[en] In this paper,based on the experimental results of power spectrum density of wall pressure fluctuations, the response of pipe vibration caused by orifice plate was calculated with random vibration analysis function of ANSYS code. The effect of correlation between wall pressure fluctuations on the response of pipe vibration was discussed. Furthermore, a simplified method was given, and the calculation result was compared with that of the detailed calculation. It was shown that the simplified method was convenient and efficient. The response of the pipe flow-induced vibration calculated with simplified method was conservative, so it can be used in the engineering evaluation. (authors)

[en] Based on the existing Taitel map and Ulbrich and Mewes map, a new flow pattern map was proposed based on the analysis of the experimental data. According to this map, three typical flow patterns can occur in vertically upward shell-side flow in tube arrays, namely, the bubbly, chum-bubbly and intermittent flows. In different patterns, the typical time-history, power spectral density (PSD) curves and Strouhal numbers associated with the peak PSD of excitation forces working on tube bundle are given. There are obvious effects of flow pattern on the time-history of excitation forces, the shapes and frequency distribution of PSD curves. (authors)

[en] According to the arrangement of the anti-vibration bars (AVBs) and the number of continuous failure of in-plane supports, the in-plane constraint failure analysis of AVBs was classified into several cases. The effects of in-plane constraint failures on the in-plane modes of steam generator heat transfer tubes under different cases were analyzed. The mode damping ratio was calculated by performing a weighted average method based on the mode shape function, and then the effects of different constraints by AVBs on flow-elastic instability of steam generator heat transfer tubes were studied. The analysis results show that with the increase of the continuous failure position of the in-plane support, the first-order modal frequency in the elbow section area decreases continuously, and the more vibration modes appear in the elbow section. The first-order mode in the elbow section is not necessarily the mode in which the maximum flow-elastic instability ratio occurs. The vibration mode with the maximum flow-elastic instability ratio appears almost in the elbow section. With the increase of the continuous failure position of the in-plane support, the flow-elastic instability ratio increases continuously. When three or more in-plane constraints fail continuously, the flow-elastic instability will occur. (authors)

[en] Assuming that all supports were valid, based on the results of fuel rod modal analysis, according to the flow field distribution characteristics of PWR fuel rods, the power spectral density was used to characterize the turbulence excitation. Combining the correlation power spectral density test parameters, the mean square value of the vibration displacement of each mode was found, and the wear depth of dimple position of the fuel rod was calculated based on the ARCHARD wear formula. Due to the manufacturing process, transportation and irradiation, the clamping action of the grid to the fuel rods may relax. Assuming that just one single dimple or spring relaxation is in turn, the effect of grid relaxation on the fuel rod modes, flow-induced vibration and wear were studied. The results show that the relaxation of the grid spring has negligible effect on the natural frequency. The dimple relaxation near the location with larger original amplitude has a significant effect on the natural frequency. The transverse flow velocities at the inlet and outlet of the core are larger and the amplitudes of turbulent excitation at the bottom and top of the fuel rods are larger when all supports are valid. When dimple relaxes in these locations the amplitude of turbulence excitation will obviously increase. The effect of dimple support relaxation in the middle position on amplitude is less. The effect trend of dimple support relaxation on the depth of wear is basically the same as the effect on the maximum amplitude of turbulence excitation. In addition to the amplitude of turbulence excitation, the wear is also related to the natural frequency. The effect of multiplying the top mode and frequency is greater than that of the bottom grid, so the top grid dimple relaxation has the greatest effect on the wear. (authors)

[en] Archard wear formula was used as the theoretical model for fretting wear of PWR fuel rod cladding, and the fretting wear volume between fuel rod cladding and grid would be predicted through this formula, where the significant physical quantities were wear coefficient, contact force between fuel rod and grid, and sliding distance. Wear coefficient was determined by experiment. Contact force between fuel rod and grid was a function varied with assembly burnup, which was determined by experiment or engineering empirical formula. The maximum vibration displacement for all modes would produce relative sliding if the displacement exceeded the threshold which was defined by grid dimple stiffness, contact force between fuel rod and grid, and friction between them, and the sliding distance could be estimated in an infinitesimal time increment. After the three physical quantities were determined, wear formula integral was implemented to obtain the fretting wear volume. According to the wear geometry of cylinder-plane contact, the relationship between wear volume and depth was derived theoretically, then the wear depth could be obtained from the wear volume. Finally comparing the wear depth to the criterion, it was validated that whether the fuel rod could satisfy the requirement on mechanism integrality. (authors)

[en] There are many tube bundles subjected to two-phase cross flow in heat exchangers, such as steam generators. For calculating the vibration response of tube bundles caused by two-phase flow turbulence, the power spectrum density (PSD) of buffeting forces should be obtained firstly. Since there is no generally accepted method for normalizing the buffeting forces, the acknowledged upper bound of buffeting forces caused by two-phase flow is absent. By modifying the definition of mixture velocity used in the de Langre's nondimensional normalizing procedure, a new set of upper bound of buffeting forces caused by two-phase flows was obtained. The new upper bound was compared with the one based on single-phase flow and de Langre's upper bound. Through a sample of steam generator tube subjected nonuniform two-phase cross flow, the random vibration responses were calculated with the three types of upper bounds. The results show that the upper bound based on single-phase flow is not conservative as the input for calculating the vibration response excited by two-phase cross flow, and the new upper bound reduces the excessive conservatism of de Langre's bound in the premise of ensuring the safety. (authors)

[en] With the experimental data of buffeting force in tube bundles subjected to air-water two-phase flow, the characteristics of buffeting force associated with two-phase flow were determined, and the effect of mixture velocity and bubble size on buffeting force was analyzed. The results show that the buffeting force increases linearly with the interfacial velocity, mixture density and kinematical viscosity, and the buffeting force in the bubbly flow regime increases linearly with the bubble size. It is discovered that the dominant frequency of buffeting force of two phase flow is correlative with the bubble number rate. Based on the characteristics of buffeting force, a normalized expression for the buffeting force is given for engineering application. A better normalized effect is obtained with this expression. (authors)

[en] The flying of missile will severely jeopardize the structural integrity in control rod ejection accident. In order to analyze the strength of a new type of shield plate under control rod drive mechanism (CRDM) impact, this article develops the simulation model and conducts the nonlinear response analysis of the missile under 4 cases. In addition, the stress analysis and evaluation of protection shield plate at the most dangerous case are performed. The computed results are validated via empirical formula. The motion analysis of CRDM missile indicates that the fracture at trapezoid thread place is more dangerous than the fracture occurs at cold fitting place. Moreover, the impact at the rim of the shield by the CRDM rod travelling housing is more dangerous than at the center. Therefore, the fracture at trapezoid thread place as well as the shield plate rim under impact should be examined when performing the stress evaluation of the shield plate. Under this circumstance, the maximum stress intensity of the shield plate will exceed the yielding stress and thereby local plasticity will occur. Strain analysis shows that compared with the extension ratio at structural failure, the computed strain still has quite amount of margin to ensure the shield plate will not be penetrated. Hence, this new type of the protection shield plate is capable to prevent the damage of other components by the flying of CRDM missile.

[en] Through reasonable simplification and equivalence finish, a detailed nonlinear finite element model of steam generator (SG) of a domestic 3rd generation nuclear power plant (NPP) is established. This model is then connected with the reactor coolant loop (RCL) to carry out the analysis of dynamic response for SG LOCA shaking. By calculation, the maximum absolute stresses of SG heat transfer tube bundles and its variation with tube diameter and reacting forces of upper supports are obtained. In order to study the effect of SG decoupling from the RCL on the shaking dynamic response, a comparative study of decoupling/coupling methods is developed. Results show that SG decoupling has a significant impact on the calculation result, and the calculation method of coupling is more closer to the real situation and should be recommended. (authors)

[en] The process of fuel assembly dynamic analysis for accident condition was studied. Method of axial and lateral dynamic modeling was developed. The axial and lateral dynamic response calculation method was established, and then the grid impact force and guide thimble stress calculation were carried out. Based on ANSYS APDL and UIDL language, introducing the idea of parameterization and modularization, the fuel assembly dynamic analysis program (program-developed) for accident condition was developed. Compared validation was carried out using program-developed and software-specific respectively for a certain type of fuel assembly. Comparison results show that the difference was small, and in the range of engineering permissible error. The program developed can be used to analyze the fuel assembly accident instead of software-specific. Analysis ability of the program developed was stronger and calculation efficiency was higher than that of the specific software. Selecting a nuclear power plant as the analysis object, the program developed is used to do the dynamic calculation of fuel assembly for accident condition, and the analysis results meet the requirements of the code. (authors)