抄録
Mechanical loadings on pipe systems caused by water hammer with phase changes make calculation of final forces difficult in nuclear power plants. The common procedure in Sweden is to calculate the water hammer loadings, according to the classical one-dimensional theory of liquid transient flow in a pipeline, and then transfer the results to strength analyses of pipeline structure. This procedure assumes that there is quasi-steady response of the pipeline structure to pressure surges - no dynamic interaction between the fluid and the pipeline construction. The hydraulic loadings are calculated with 1-D so-called "network" programs. Commonly used in Sweden are Relap5 (Mod3.2.2 and higher) and Drako. As a third party accredited inspection body INSPECTA NUCLEAR AB reviews calculations of water hammer loadings. An important question for the reviewer (and also for the users) is knowledge about their ability to calculate the dynamic loadings. While the ability of Relap5 and DRAKO to calculate water hammer without phase changes is relatively well investigated the skills of the programs when phase changes are present need some more attention. The presented work shall be seen as an attempt to illustrate ability of Relap5, and Drako programs to calculate the water hammer loadings with phase changes. A special attention was paid to using of Relap5 for calculation of water hammer pressure surges (including some aspects of influence of discretisation of space on the calculation results). The calculations are compared with experimental results. The experiments have been conducted at a test rig designed and constructed at the Szewalski Institute of Fluid-Flow Machinery of the Polish Academy of Sciences (IMP PAN) in Gdansk, Poland. The comparison of calculated and measured pressures shows some differences, only the first pressure peak, occurring before evaporation is calculated quite exactly. All next coming pressure peaks differ slightly from the measured with respect to amplitude and frequency.
