METHODOLOGY TO INVESTIGATE VIBRATION PHENOMENA CAUSED BY THE STEAM CONDENSATION AT SUB-ATMOSPHERIC CONDITION

The phenomenon of steam-water direct contact condensation (DCC) was widely investigated in the past because of conventional and nuclear engineering applications, like in the safety suppression system of BWRs. When steam is injected into a sub cooled water, different condensation regimes can be observed, such as chugging, condensation oscillation, bubbling condensation oscillation etc. (these have been identified during the experimental campaign on condensation of steam injected into water at sub-atmospheric conditions carried out at Lab. B. Guerrini of DICI- University of Pisa). According to the thermal hydraulic conditions of the condensing jet plume, vibrations may arise. This paper so deals with the analysis of vibration phenomena that originate during the steam-water direct contact condensation at sub-atmospheric conditions, not treated till today. Numerical investigations (by proper FEM code) as well as experimental activity will be presented and discussed in order to evaluate if vibrations are capable to jeopardise this safety suppression system, which is designed to protect Vacuum Vessel of ITER from pressurizing accidents.