The thermal-hydraulic system code APROS Version 5.09 [1] is being applied in the European project SCWR-FQT to evaluate the performance of the safety systems for a nuclear test facility operated with supercritical water. In order to validate the commercial code for predictions of transient phenomena, two adequate hydraulic experiments from literature have been simulated.

The experiment of Fujii and Akagawa [2] investigated hydraulic shocks as they will occur in case a pipe, which is stationary passed through by water, is abruptly closed. A simple numerical model with adapted time and space nodalization was able to reproduce the observed physical phenomena, such as the magnitude of the initial pressure wave and reflection time, in detail.

In a second experiment, a test series was performed by Becker et al. [3] and Mathisen [4] in order to examine the natural circulation in a closed loop for different heating rates and system pressures. For a stepwise power increase, the typical mass flow characteristic for boiling channels was recorded until the onset of flow oscillations. In further runs, the effect of different initial conditions on the flow stability was analyzed. This paper compares the numerical predictions with both experimental results. The numerical models could describe the physical phenomena with appropriate accuracy.

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