No abstract available

[en] This paper is concerned with an attempt to explain some unexpected features which occurred during an investigation into the coupling between an acoustic field in the liquid contained in a shell and the vibrations of the shell itself. This work arose from the development of the Prototype Fast Reactor, in particular the need for ability to estimate the magnitude of vibrations of the primary tank when excited acoustically by the liquid sodium pumps. The vibration modes of a liquid-filled circular cylindrical shell were studied theoretically and experimentally, and reasonable agreement was obtained for the resonant frequencies. However, by experiment it was found that when the liquid was excited in a symmetric (i.e. n=0) mode, the structure vibrated in short-wavelength (n>0) flexural modes, with significant amplitudes in some cases. Since the presence of such waves is not predicted by simple theory, no estimate of the relative amplitudes of the modes could be given. The theory outlined here relates the production of short-wavelength flexural waves in a circular cylindrical shell containing liquid which is excited acoustically, to the initial geometrical distortions present in the shell (e.g. the departures from circularity). The results of some numerical calculations are compared with experimental data. (Auth.)

[en] The theory outlined here relates the production of short-wavelength flexural waves in a circular cylindrical shell containing liquid which is excited acoustically, to the initial geometrical distortions present in the shell (e.g. the departures from circularity). The results of some numerical calculations are compared with experimental measurements

[en] An experimental program has been carried out in order to investigate the excitation of resonant vibration in bent pipe structures by sound in the contained fluid for both air and water filled systems. The work has application to the vibration in coolant circuits of gas and liquid cooled nuclear reactors. It has been found that the low order flexural modes of the pipe cross section and the frequencies above which these modes may exist have a strong influence on the vibration response of such systems. (author)

[en] A candidate technique for detecting incipient blockages in the fuel sub-assemblies of liquid-metal-cooled fast-breeder reactors is the measurement of coolant outlet temperature fluctuations caused by turbulence. A theoretical basis for the method is required, and one model is discussed in this paper. The model requires the paths of individual fluid particles to be traced, allowing their motions to vary randomly, subject to certain constraints of the turbulent motion. It is a Monte Carlo method, already used successfully in predicting the transport of scalar fluctuations. Its advantage is that it allows actual time-dependent temperatures to be computed, and so various methods of analysis (power spectral density, amplitude probability distribution, for example) can be examined. The effect of heat conduction is neglected at present. Computed results show the way in which mean temperature and rms temperature-noise profiles develop in a turbulent flow in a pipe downstream of a plane at which a steady mean profile is maintained. Power spectral densities and amplitude-probability densities are presented, and it is shown how an amplitude-probability density plot distinguishes between a temperature-gradient input profile and a gaussian input profile. Comparisons are given with experimental measurements made in representative heated pin rigs in sodium, with good agreement. Some of the problems associated with extrapolation to real sub-assemblies are discussed. (author)

[en] The Defect Detection Trials were initiated in the post-PISC I era when it was considered essential to determine under controlled conditions the capability of selected ultrasonic techniques to detect and size significant flaws. These trials were not intended to allow a statistical evaluation of either the capability or reliability of a particular team or technique since the number of tests had to be limited. However, useful conclusions relating to the effectiveness of specific ultrasonic techniques under the conditions relevant to the DDT can be drawn, and some guidance can be gained on factors which influence the reliability of inspection. The analysis first considers defect detection and concludes that very high standards were achieved, with all the flaws being reported for DDT Plates 1 and 2 by all the teams. Secondly, the fraction of referable flaws which are correctly classified according to specified criteria is evaluated. In some cases the margin between classifying a flaw as acceptable or referable is extremely small, and tolerances on the sizing data are considered and causes of misclassification are assessed. The contribution made by the tandem and pulse-echo techniques and the degree of redundancy in the detection data re reviewed. (author)

[en] A simplified water model of the region downstream of a fast reactor fuel bundle was built and instrumented. Measurements were made of the mean and fluctuating velocity distributions and turbulent length scales. The progression to fully-developed turbulent flow was observed. By injecting hot water, different fuel bundle outlet temperature profiles were simulated, representing blockages in different regions of the subassembly. Measurements of the mean and fluctuating temperature fields were made. These are being used to validate theoretical models and computer codes. (author)

No abstract available

[en] This paper summarises a study which has been carried out to determine whether a hydroelastic model using water can be built to reproduce realistically combined flow and acoustic induced vibration amplitudes. This problem, is examined in three parts. Firstly the driving forces are considered which are entirely a function of the fluid, and simple mathematical equations are derived which include the geometrical scale, velocity scale and frequency scale. These equations can be simultaneously satisfied and they determine the absolute values of the principal scales. For example the geometrical scale must be 0.392. Later in the paper the detailed effects of departing from these ideal values are considered. Secondly the structure is examined to see how it should be designed to have the correct resonant frequencies. This is most important because some of the driving forces are sinusoidal or narrow band random so that maximum vibration is critically dependent on the coincidence of driving frequency and structural resonance frequency. Thirdly the vibration amplitudes at resonance are checked. There is no freedom to adjust the design at this point since all aspects are determined by the previous arguments. (Auth.)

[en] The feasibility of a hydroelastic model which uses water in place of sodium is proposed as part of the programme of vibration studies for Liquid Metal Fast Breeder Reactors. Vibrations may be excited by local turbulence in the flow, acoustic energy generated by the circulating pump and transmitted through the fluid, or by sloshing wave motions at the free surface of the sodium pool. As a condition for modelling the three driving forces simultaneously, and hence ensuring that any interactive effects are represented, dimensionless groups are derived for amplitude and frequency in each case. It is shown that ideal modelling requires a geometrical scale of 0.392 and that frequency and flow velocity scales are also fixed. The effects of picking a smaller geometrical scale are examined and it is concluded that turbulence and acoustic mechanisms can be precisely simulated but that free surface waves are modelled with reduced accuracy. Structural resonances are examined, both shell flexural and beam swaying modes and the problems of compensating for changed liquid loading discussed. Proposals are made for using steel and brass as modelling material for different components and for adjusting the vibration characteristics by thinning down shell structures. Vibration amplitudes are checked in representative cases and are shown to scale in the same ratio as geometrical scale if vibration damping remains unaltered