Conditions for Prevention of Water Hammers at Start-Up of Emergency Feed-Pumps with a Steam-Driver of Nuclear Power Plants – V. Skalozubov, D. Pirkovskiy, N. Bilous, I. Kozlov, V. Kolyhanov, O. Sedova

The initial event of severe accidents and devastating explosions at Fukushima-Daiichi NPP in 2011 was the complete loss of long-term power supply due to the combined effects of beyond-design tsunamis and an earthquake. Lessons from the Fukushima accident identified the need for further development of safety systems for nuclear power plants that do not require power. A promising approach to managing accidents with complete loss of long-term power supply is the development of emergency feed-pumps with a steam-driver from a steam-generator. The main advantages of this approach in relation to the known systems of passive heat removal with natural circulation are the fundamental possibility of fully compensating for the failure of design safety systems with electric pumps, as well as the absence of the need to remove the safety system elements to a greater height beyond the containment. However, the use of steam-driven emergency pumps requires a deep study of their reliability. One such issue is the qualification of reliability when starting an emergency pump with a steam-driver. An original method for modeling the conditions for the occurrence of a water hammer when starting a steam-driven pump is proposed. The conditions for the prevention of water hammer and pressure amplitudes due to the inertia of the pressure characteristics of emergency feed pumps with a steam-driver from a steam-generator of a nuclear power plant are determined. The pressure amplitude of the water hammer is determined by the conditions for the transition of the kinetic energy of the flow deceleration into the energy of the water hammer pulse. The results obtained can be used in the design of emergency feed pumps with a steam-driver from a steam-generator subject to additional experimental qualifications.

Keywords: emergency feed pump with steam-driver; water hammer; nuclear power plant.