No abstract available

[en] The loop installed in the Siloe reactor is described. It is intended for giving data on the phenomena involved in HTR reactors: fission product migration, deposit, and corrosion; and reactor safety (blowdown and water flooding)

[en] This report consists of comparisons of prediction and experiment for German Standard Problem 4a, a blowdown experiment involving structural dynamic response. The comparisons presented herein are of the time histories of displacement, bending stress, and bending axis angle. The reasons for error in the predictions are discussed. The structural model is improved to obtain a better match with the experimental natural frequencies

No abstract available

[en] The efflux of underheated to saturation boiling-up water, containing particles of foamy polystyrene with the density dose to water density and 0.2-0.6 mm in diameter, is studied experimentally. The channel is horizontal, of rectangular cross section 8x10x110 mm³ with transparent walls. Parameters in the experiments varied in the following ranges: pressure at the input to the channel p₀=0.1-0.4 MPa; pressure at the output from the channel p₁=0.1-0.25 MPa; water temperature at the input T=283-353 K; mass part of the particles x=0-10sup(-3). The flow structure was photographed. It is shown that the addition of solid particles to liquid flow intensifies the boiling-up process, increases the dimensions of bubble structure zone, which results in the attaining of efflux crisis at lower flow rate values

[en] This report deals with the structural behaviour of piping systems under earthquake and blowdown conditions. The tests were conducted within the scope of the HDR-safety programme of the BMFT. The applied measuring technique and the evaluation of strains enables a good experimental stress analysis by determining the pressure, axial, bending and torsion loads. Inspite of the extremely low loading which only reached five percent of the material yield point, it was possible to conduct a clear experimental analysis of the structural dynamic response during the earthquake tests under snapback, shaker and explosive excitement. As opposed to this there occurred high pressure and bending peaks exceeding the yield load in steam insulation valve as well as feedwater check valve blowdown tests. The stresses are strongly influenced by the closing characteristic of the valves. (orig.)

[en] The HDR plant has been out of service for several years and is now a test facility for full scale blowdown experiments. The first experimental program was concerned with valves and their dynamic behaviour under blowdown conditions. The pressure waves and the loading of the discharge pipe influenced by the blowdown and the quick closing valves were also observed. A steam isolation valve and a feed water check valve have been tested in this program. The correct operation of these valves is essential in blowdown. For the first tests an original isolation valve which is installed in the steam line of PWR's or BWR's was used. The HDR pressure vessel has a volume of about 66 m³. On the top of this vessel a test blowdown tube with a length of 20 m and an I.D. of 450 mm was constructed. With this facility several tests were conducted with various discharge rates (from nominal rate up to strong blowdown conditions) in the blowdown tube and with a delayed closure so that closing behaviour during two phase flow could also be investigated. In the second part of the valve experiments a quick closing feed water check valve (I.D. 200 mm) was tested with a variation of the damping in order to study the influence on the closing time and on the pressure waves. The pressure amplitudes observed after the valve was closed reached 300 bars in some tests which indicates that it is necessary to consider these severe problems very carefully. (orig.)

[en] The blowdown of a safety valve is defined as the difference between the pressure at which the valve opens and the pressure at which the valve fully closes under certain fluid flow conditions. An extensive series of tests carried out in the EPRI/PWR Utilities Valve Test Program have shown that the blowdown of safety valves can in general be strongly dependent upon the valve geometry and other parameters such as ring adjustments, spring stiffness, back pressure etc. On this study, fluid velocity within safety valve in accordance with ring setting has been investigated

No abstract available

[en] As a part of the HDR program, methods for coupled fluid-structural dynamics are being developed. On the fluid side the 2D finite difference code YAQUI has been modified (it became YAQUIR) and adapted to describe the fluid dynamics in the downcomer of PWR's. On the structural side for determination of the dynamic core barrel response the code CYLDY2 has been developed. In this code the core barrel is treated as a thin cylindrical shell fixed at the upper end and ring stiffened at the lower end. The mass of the lower end ring also simulated a part of the core mass. Both models have been successfully tested. Coupling has been achieved for a simplified structural model proving the correctness of the coupling procedure. The structural model CYLDY2 is based on Fluegge's shell equations and uses variational principles. The solution is a superposition of steady-state and transient eigenfunctions. Results indicate that for the relatively thin-walled core barrel of the HDR-experiments in most cases the local deformations are somewhat higher than the global deformation (beam model). The coupling of YAQUIR and CYLDY2 is performed by imbedding the structural model in the fluid model. Fluid velocities are parallel to the fluid/structure interface. The structure desplacements define the time and space dependent thickness of the two-dimensional fluid layer (2 1/2-dimensional model)