Experimental and theoretical study of steam condensation induced water hammer phenomena

We investigate the steam condensation induced water hammer (CIWH) phenomena and present experimental and theoretical results. The experiments were performed in the PMK-2 facility, which is a full-pressure thermo-hydraulic model of the primary loop of the VVER-440/312 type nuclear power plant and located in the Atomic Energy Research Institute Budapest, Hungary.The present experimental setup is capable to measure CIWH phenomena in a wide range of steam pressure, cold water temperature and mass flow rate at a high level of accuracy. On the theoretical side CIWH is studied and analyzed with the WAHA3 model based on two-phase flow six first-order partial differential equations that present one-dimensional, surface averaged mass, momentum and energy balances. A second order accurate high-resolution shock-capturing numerical scheme was applied with different kind of limiters in the numerical calculations. Our study clearly shows that Relap5 and Cathare which are used in the nuclear industry to simulate nuclear power plant accidents cannot resolve the narrow pressure peaks created during a CIWH event. Only WAHA3 can model CIWH properly. Experimentally measured and theoretically calculated pressure peaks are in good agreement, however simulations always show additional pressure peaks. As a new feature in this study we present calculations without additional unphysical reflections caused by boundary conditions.